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Research involving Lowell Observatory staff 2015
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Years: 2015 Bottom


  1. Rebull, L., Stauffer, J., Cody, A., et al., (including Covey, K.), 2015, AJ, 150, 175, YSOVAR: Mid-infrared Variability in NGC 1333
    As part of the Young Stellar Object VARiability (YSOVAR) program, we monitored NGC 1333 for 35 days at 3.6 and 4.5 m using the Spitzer Space Telescope. We report here on the mid-infrared variability of the point sources in the 10 20 area centered on 03:29:06, +31:19:30 (J2000). Out of 701 light curves in either channel, we find 78 variables over the YSOVAR campaign. About half of the members are variable. The variable fraction for the most embedded spectral energy distributions (SEDs) (Class I, flat) is higher than that for less embedded SEDs (Class II), which is in turn higher than the star-like SEDs (Class III). A few objects have amplitudes (10-90th percentile brightness) in [3.6] or [4.5] > 0.2 mag; a more typical amplitude is 0.1-0.15 mag. The largest color change is >0.2 mag. There are 24 periodic objects, with 40% of them being flat SED class. This may mean that the periodic signal is primarily from the disk, not the photosphere, in those cases. We find 9 variables likely to be dippers, where texture in the disk occults the central star, and 11 likely to be bursters, where accretion instabilities create brightness bursts. There are 39 objects that have significant trends in [3.6]-[4.5] color over the campaign, about evenly divided between redder-when-fainter (consistent with extinction variations) and bluer-when-fainter. About a third of the 17 Class 0 and/or jet-driving sources from the literature are variable over the YSOVAR campaign, and a larger fraction (half) are variable between the YSOVAR campaign and the cryogenic-era Spitzer observations (6-7 years), perhaps because it takes time for the envelope to respond to changes in the central source. The NGC 1333 brown dwarfs do not stand out from the stellar light curves in any way except there is a much larger fraction of periodic objects (60% of variable brown dwarfs are periodic, compared to 30% of the variables overall).
  2. Dalle Ore, C., Cruikshank, D., Stern, A., et al., (including Grundy, W.), 2015, AGUFM, 2015, P41E-02, Charon as Seen by New Horizons in the Infrared
    Charon, the largest satellite of Pluto, is a gray-colored icy world covered mostly in H2O ice, with spectral evidence for NH3, as previously reported (Cook et al. 2007, Astrophys. J. 663, 1406-1419; Merlin, et al. 2010, Icarus, 210, 930; Cook, et al. 2014, AAS/Division for Planetary Sciences Meeting Abstracts, 46, #401.04). Images from the New Horizons spacecraft reveal a surface with terrains of widely different ages and a moderate degree of localized coloration. New Horizons observed Charon at high spatial resolution (better than 10 km/px) with the LEISA imaging spectrometer. LEISA is part of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Science Reviews, 140, 129) and affords a spectral resolving power of 240 in the wavelength range 1.25-2.5 m, and 560 in the range 2.1-2.25 m. We present results obtained from the analysis of high spatial resolution data obtained close to flyby.
  3. Buie, M., Stern, A., Young, L., et al., (including Grundy, W.), 2015, AGUFM, 2015, P41E-03, Comparisons Between New Horizons Results and Long-Term Monitoring of Pluto
    The New Horizons encounter data have revealed a diverse and complicated surface and atmosphere for Pluto showing strong correlations between geologic features and the albedo and compositional units known from ground- and HST-based observations over the decades prior. This presentation will delve into detailed comparisons between the long time base and low spatial resolution data and the new high resolution snapshot of Pluto from the flyby. Special emphasis will be placed on the albedo and near-infrared spectral evolution over time. We will compare the albedo maps from the late 1980's built on mutual event data and two epochs of HST observations against the New Horizons images, after correcting for viewing geometry. Also included will be a discussion of the evolutionary trends in the hemispherically averaged spectral properties from Lowell Observatory and IRTF data against the resolved compositional and spectral maps from New Horizons. The combination of these data sets now permits an unprecedented ability to constrain time-variability on the surface from apparent changes due to viewing geometry and surface inhomogeneities. These comparisons require a reconcilliation of surface scattering properties that are enabled by the firm determination of the size of Pluto.
  4. Singer, K., Schenk, P., McKinnon, W., et al., (including Grundy, W.), 2015, AGUFM, 2015, P41E-07, Craters on Pluto and Charon: The Influence of Low Gravities, Low Impact Speeds, and Unique Ices
    The surfaces of Pluto and Charon display a wide variety of crater landforms. Pluto and Charon present a unique regime to investigate cratering physics due to a combination of circumstances: 1) their relatively low gravitiesPluto's gravity (~0.66 m s-2) falls between those of the large icy satellites of Jupiter and their mid-sized saturnian cousins, while Charon's gravity (0.28 m s-2) is more similar to the latter, 2) the low primary impact velocities onto Pluto and Charon's surfaces (average ~2 km s-1), and 3) the mix of surface ices likely present (e.g., N2, CO, CH4, H2O). We use available images from both the Long Range Reconnaissance Imager (LORRI; Cheng et al., 2008, SSR 140, 189-215) and data from the Ralph (Reuter et al., 2008, SSR 140, 129-154) color/composition instruments to characterize crater morphologies and ejecta characteristics. This presentation will focus on understanding formation of craters on Pluto and Charon (with reference to deformation/degradation processes described in other presentations) and will include comparison to icy satellites. We will also discuss what inferences can be drawn about impactor characteristics.
  5. Killen, R., Bida, T., 2015, AGUFM, 2015, P41F-01, Observations of the minor species Al, Fe and Ca+ in Mercury's exosphere
    We report here on the first observational evidence of Al and Fe in the exosphere of Mercury, based on measurements of 4-5- resolved emission lines of these metals made with Keck-1/HIRES. AlI emission was observed on two separate runs, in 2008 and 2013, with tangent column densities of 2.4 and 3.0e+07 Al atoms cm-2 at altitudes of 1300 and 1850 km (1.1 and 1.5 RM), respectively. FeI emission has been observed once, yielding a tangent column of 6.2e+08 cm-2 at an altitude of 950 km (1.4 RM) in 2009. We also present observations of 3.5- CaII emission features near Mercury's equatorial anti-solar limb in 2011, from which a stringent column abundance upper limit of 4.0e+06 cm-2 is derived for the Ca ion. A simple model for zenith column abundances of the neutral species yields 2.0e+07 Al cm-2, and 8.2e+08 Fe cm-2. The observations appear to be consistent with production of these species by impact vaporization, with a large fraction of the Al ejecta in molecular form, and that for Fe in mixed atomic and molecular forms. The scale height of the Al gas is consistent with a kinetic temperature of 4800-8200 K while that of Fe is 5000-13000 K. The apparent high temperature and low density of the Al gas would suggest that it may be produced by dissociation of molecules. A large fraction of both Al and Fe appear to condense in a vapor cloud at low altitudes.
  6. Parker, A., Weaver, H., Porter, S., et al., (including Grundy, W.), 2015, AGUFM, 2015, P51A-2033, Pluto's small satellites in the context of the Kuiper Belt
    New Horizons is now beyond Pluto and flying deeper into the Kuiper Belt. The small satellites in the Pluto system are the closest analogues to typical Kuiper Belt Objects yet observed at close-range by the spacecraft, and we will review these observations in the greater context of the Kuiper Belt and as they pertain to New Horizons' exploration of a similarly-sized classical Kuiper Belt target in late 2018 or early 2019. Finally, we will summarize the current state-of-knowledge regarding the potential long-range and close-range Kuiper Belt targets.
  7. Umurhan, O., Moore, J., Howard, A., et al., (including Grundy, W.), 2015, AGUFM, 2015, P51A-2040, N2 glacial flow on and onto Sputnik Planum
    Sputnik Planum (SP)[1,2] is the high albedo crater-free western portion of Tombaugh Regio imaged in July by the New Horizons LORRI instrument. The relatively high resolution (400 m/pix) LORRI mosaics of the northern portions of the planum bordered by the Cousteau Rupes (CR) scarp reveal surface patterns highly suggestive of viscous flow dynamics. Spectroscopic measurements of SP taken by the New Horizons LEISA instrument also indicate that SP is a region containing (among others) a significant amount of N2 [2]. Taken together these observations suggest the possibility that the high albedo material on SP is glacial N2 ice atop a bedrock-like substrate and the notable lack of craters on SP means that these processes are acting on relatively fast geologic timescales. Using the known properties of N2 ice in the temperature range of interest, we formulate and implement a numerical landform evolution model in order to examine a number of hypothetical evolutionary scenarios for SP and its environs. [1] All place names on Pluto and Charon are informally known as such as of the writing of this abstract. [2] Stern, S. A et al. 2015 Science.
  8. Spencer, J., Stern, A., Weaver, H., et al., (including Grundy, W.), 2015, AGUFM, 2015, P51A-2042, Understanding Pluto's Surface: Correlations between Geology and Composition
    New Horizons has revealed that Pluto's surface is composed of a remarkable variety of terrains that differ strikingly in their landforms, color, and near-infrared spectral characteristics. Strong correlations are seen between the morphology revealed by high-resolution imaging from the Long Range Reconnaissance Imager (LORRI), and the surface composition inferred from the spacecraft's color camera and near-infrared spectrometer, which are both included in the Ralph instrument. These correlations provide the potential for a much deeper understanding of the processes that have shaped Pluto's complex surface that was possible for Pluto's sibling Triton, for which Voyager did not provide compositional maps. We will discuss how the full suite of New Horizons remote sensing instruments reveal a surface modified by the interplay of insolation variations, meteorology, and endogenic processes.
  9. Bosh, A., Pasachoff, J., Babcock, B., et al., (including Levine, S.), 2015, AGUFM, 2015, P51A-2048, Ground-based Light Curves Two Pluto Days Before the New Horizons Passage
    We observed the occultation of a 12th magnitude star, one of the two brightest occultation stars ever in our dozen years of continual monitoring of Pluto's atmosphere through such studies, on 29 June 2015 UTC. At Canterbury University's Mt. John University Observatory on the south island of New Zealand, in clear sky, we used our POETS frame-transfer CCD at 10 Hz with GPS timing on the 1-m McLellan telescope as well as an infrared camera on an 0.6-m telescope and three-color photometry at a slower cadence on a second 0.6-m telescope. The light curves show a central flash, indicating that we were close to the center of the occultation path, and allowing us to explore Pluto's atmosphere lower than usual. The light curves show that Pluto's atmosphere remained robust. Observations from 0.5- and 0.4-m telescopes at the Auckland Observatory gave the first half of the occultation before clouds came in. We coordinated our observations with aircraft observations with NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) and its High Speed Imaging Photometer for Occultations (HIPO). Our ground-based and airborne stellar-occultation effort came only just over two weeks of Earth days and two Pluto days (based on Pluto's rotational period) before the flyby of NASA's New Horizons spacecraft, meaning that the mission's exquisite snapshot of Pluto's atmosphere can be placed in the context of our series of ground-based occultation observations carried out on a regular basis since 2002 following a first Pluto occultation observed in 1988 from aloft. Our observations were supported by NASA Planetary Astronomy grants NNX12AJ29G to Williams College, NNX15AJ82G to Lowell Observatory, and NNX10AB27G to MIT, and by the National Research Foundation of South Africa. We thank Alan Gilmore, Pam Kilmartin, Robert Lucas, Paul Tristam, and Carolle Varughese for assistance at Mt. John.
  10. Olkin, C., Reuter, D., Stern, S., et al., (including Grundy, W.), 2015, AGUFM, 2015, P54A-01, Color and Composition of Pluto and Its Moons from the New Horizons Mission
    NASA's New Horizons mission has goals of providing maps of the color and composition of Pluto and its largest moon Charon. When the small moons of Pluto were discovered, the New Horizons science team added investigations on the color and composition of Nix and Hydra and also color of Styx and Kerberos and near-infrared spectra of Kerberos. Color observations taken by Ralph/MVIC, the Multispectral Visible Imaging Camera have revealed diverse terrain units across Pluto. By constructing an enhanced color composite image of Pluto from the Blue, Red and NIR filter images of Pluto, we can see that the informally named, Tombaugh Regio (the large heart-shaped region on Pluto), is clearly two different colors with a clear demarcation down the center of Tombaugh Regio. From infrared spectroscopic data taken by Ralph/LEISA, Linear Etalon Imaging Spectral Array, early analysis has shown that in the less blue region of Tombaugh Regio there is a concentration of CO ice. This paper will present selected highlights of results from the color and composition investigations of the New Horizons mission.
  11. Binzel, R., Stern, A., Weaver, H., et al., (including Grundy, W.), 2015, AGUFM, 2015, P54A-02, Pluto's Global Color Variability as Seen by the New Horizons Multispectral Visible Imaging Camera
    While variability in Pluto's albedo, color, and methane distribution had been previously discerned from ground-based and Hubble Space Telescope observations [e.g. 1,2], the sharp juxtaposition of contrasting units forms one of the greatest surprises returned (to date) from the New Horizons mission. Here we present a global analysis of the color distribution of Pluto's surface factoring in both seasonal and large scale geologic processes. We will also explore the possible role of long-term (million year) precession cycles [3] in shaping the surface morphology and the distribution of volatiles. We utilize data returned by the New Horizons Multispectral Visible Imaging Camera (MVIC) operating as part of the Ralph instrument [4]. MVIC captures images over five wavelength bands from blue to the near-infrared, including a broad panchromatic band and a narrow band centered on the 0.89-micron methane absorption feature. References: [1] Young, E. F., Binzel, R. P., Crane, K. 2001; Astron. J. 121, 552-561. [2] Grundy, W.M., Olkin, C.B., Young, L.A., Buie, M. W., Young, E. F. 2013; Icarus 223, 710-721. [3] Earle, A. M., Binzel, R. P. 2015; Icarus 250, 405-412. [4] Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008; Space Science Reviews, 140, 129-154.
  12. Olkin, C., Howett, C., Grundy, W., et al., 2015, AGUFM, 2015, P54A-03, Charon's Color: A view from New Horizon Ralph/Multispectral Visible Imaging Camera
    The Multispectral Visible Imaging Camera (MVIC; Reuter et al., 2008) is part of Ralph, an instrument on NASA's New Horizons spacecraft. MVIC is the color 'eyes' of New Horizons, observing objects using five bands from blue to infrared wavelengths. MVIC's images of Charon show it to be an intriguing place, a far cry from the grey heavily cratered world once postulated. Rather Charon is observed to have large surface areas free of craters, and a northern polar region that is much redder than its surroundings. This talk will describe these initial results in more detail, along with Charon's global geological color variations to put these results into their wider context. Finally possible surface coloration mechanisms due to global processes and/or seasonal cycles will be discussed.
  13. Bosh, A., Person, M., Zuluaga, C., et al., (including Levine, S., Dunham, E., Bida, T., Bright, L., Collins, P.), 2015, AGUFM, 2015, P54A-07, Occultation Evidence for Haze in Pluto's Atmosphere in 2015 at the New Horizons Encounter
    On UT 29 June 2015, the occultation by Pluto of a bright star (r'=11.9) was observed from the Stratospheric Observatory for Infrared Astronomy (SOFIA) as well as several ground-based stations in New Zealand and Australia. Pre-event astrometry allowed for an in-flight update to the SOFIA team with the result that SOFIA was deep within the central flash zone. Combined analysis of the data sets leads to the result that Pluto's middle atmosphere is essentially unchanged from 2011 and 2013 (Person et al. 2013; Bosh et al. 2015); there has been no significant expansion or contraction of the atmosphere. Additionally, we find that a haze component in the atmosphere is required to reproduce the light curves obtained. This haze scenario has implications for understanding the photochemistry of Pluto's atmosphere. This work was supported by NASA grants NNX15AJ82G (Lowell Observatory), NNX10AB27G (MIT), and NNX12AJ29G (Williams), and by the National Research Foundation of South Africa. Co-authors were visiting observers on SOFIA, at the Keck Observatory, the Magellan Observatory, the SARA-CT Observatory, the Mt. John University Observatory, and the Auckland Observatory.
  14. Cochran, A., Levasseur-Regourd, A., Cordiner, M., et al., (including Schleicher, D.), 2015, SSRv, 197, 9, The Composition of Comets
    This paper is the result of the International Cometary Workshop, held in Toulouse, France in April 2014, where the participants came together to assess our knowledge of comets prior to the ESA Rosetta Mission. In this paper, we look at the composition of the gas and dust from the comae of comets. With the gas, we cover the various taxonomic studies that have broken comets into groups and compare what is seen at all wavelengths. We also discuss what has been learned from mass spectrometers during flybys. A few caveats for our interpretation are discussed. With dust, much of our information comes from flybys. They include in situ analyses as well as samples returned to Earth for laboratory measurements. Remote sensing IR observations and polarimetry are also discussed. For both gas and dust, we discuss what instruments the Rosetta spacecraft and Philae lander will bring to bear to improve our understanding of comet 67P/Churyumov-Gerasimenko as "ground-truth" for our previous comprehensive studies. Finally, we summarize some of the initial Rosetta Mission findings.
  15. Samarasinha, N., Mueller, B., Knight, M., et al., (including Schleicher, D.), 2015, P&SS, 118, 127, Results from the worldwide coma morphology campaign for comet ISON (C/2012 S1)
    We present the results of a global coma morphology campaign for comet C/2012 S1 (ISON), which was organized to involve both professional and amateur observers. In response to the campaign, many hundreds of images, from nearly two dozen groups were collected. Images were taken primarily in the continuum, which help to characterize the behavior of dust in the coma of comet ISON. The campaign received images from January 12 through November 22, 2013 (an interval over which the heliocentric distance decreased from 5.1 AU to 0.35 AU), allowing monitoring of the long-term evolution of coma morphology during comet ISON's pre-perihelion leg. Data were contributed by observers spread around the world, resulting in particularly good temporal coverage during November when comet ISON was brightest but its visibility was limited from any one location due to the small solar elongation. We analyze the northwestern sunward continuum coma feature observed in comet ISON during the first half of 2013, finding that it was likely present from at least February through May and did not show variations on diurnal time scales. From these images we constrain the grain velocities to ~10 m s-1, and we find that the grains spent 2-4 weeks in the sunward side prior to merging with the dust tail. We present a rationale for the lack of continuum coma features from September until mid-November 2013, determining that if the feature from the first half of 2013 was present, it was likely too small to be clearly detected. We also analyze the continuum coma morphology observed subsequent to the November 12 outburst, and constrain the first appearance of new features in the continuum to later than November 13.99 UT.
  16. Zubko, E., Videen, G., Hines, D., et al., (including Knight, M.), 2015, P&SS, 118, 138, Comet C/2012 S1 (ISON) coma composition at ~4 au from HST observations
    We analyze the first color and polarization images of Comet ISON (C/2012 S1) taken during two measurement campaigns of the Hubble Space Telescope (HST) on UTC 2013 April 10 and May 8, when the phase angles of Comet ISON were 13.7 and 12.2, respectively. We model the particles in the coma using highly irregular agglomerated debris particles. Even though the observations were made over a small range of phase angle, the data still place significant constraints on the material properties of the cometary coma. The different photo-polarimetric responses are indicative of spatial chemical heterogeneity of coma in Comet ISON. For instance, at small projected distances to the nucleus (<500 km), our modeling suggests the cometary particles are composed predominantly of small, highly absorbing particles, such as amorphous carbon and/or organics material heavily irradiated with UV radiation; whereas, at longer projected distances (>1000 km), the refractive index of the particles is consistent with organic matter slightly processed with UV radiation, tholins, Mg-Fe silicates, and/or Mg-rich silicates contaminated with ~10% (by volume) amorphous carbon. The modeling suggests low relative abundances of particles with low material absorption in the visible, i.e., Im(m)0.02. Such particles were detected unambiguously in other comets in the vicinity of nucleus through very strong negative polarization near backscattering (P-6%) and very low positive polarization (P3-5%) at side scattering. These materials were previously attributed to Mg-rich silicates forming a refractory surface layer on the surface of cometary nuclei (Zubko et al., 2012). The absence of such particles in Comet ISON could imply an absence of such a layer on its nucleus.
  17. Llama, J., Shkolnik, E., 2015, ESS, 47, 108.05, The impact of stellar activity on X-ray and UV transits
    X-ray and UV observations of transiting exoplanets have revealed the presence of extended atmospheres around a number of systems. At high energies, stellar radiation is absorbed high up in the planetary atmosphere, making X-ray and UV observations a potential tool for investigating the upper atmospheres of exoplanets. However, at these high energies, stellar activity can dramatically impact the observations. At short wavelengths the star appears limb-brightened, and active regions appear as bright features on the stellar disk. These will impact both the transit depth and shape, affecting our ability to measure the true planet-to-star radius ratio.I will show results of simulate exoplanet transit light curves using Solar data obtained in the soft X-ray and UV by NASAs Solar Dynamics Observatory to investigate the impact of stellar activity at these wavelengths. By using a limb-brightened transit model coupled with disk resolved Solar images in the X-ray, extreme- and far-UV I will show how both occulted and unocculted active regions can mimic an inflated planetary atmosphere by changing the depth and shape of the transit profile. I will also show how the disk integrated Lyman-alpha Solar irradiance varies on both short and long timescales and how this variability can impact our ability to recover the true radius ratio of a transiting exoplanet.Finally, I will present techniques on how to overcome these effects to determine the true planet-to-star radius in X-ray and UV observations.
  18. Pugh, T., Gray, D., Griffin, R., 2015, MNRAS, 454, 2344, The orbit and variations of Sagittae
    Radial-velocity observations spanning more than a century are used to produce a reliable orbit of the Sagittae system. We find an orbital period of 3703.7 1.5 d and a semi-amplitude of 7.73 0.05 km s-1. In addition, we find quasi-periodic variations with time-scales in the range of 550-750 d and a typical amplitude of 1 km s-1. The phase and amplitude are both irregular, sometimes changing very abruptly. We consider pulsation, rotational modulation and convection as possible causes of the variations, finally favouring convection.
  19. Polishook, D., Benecchi, S., Jacobson, S., et al., (including Moskovitz, N.), 2015, hst, 14133, Establishing an evolutionary sequence for disintegrated minor planets
    The exciting HST discovery of the asteroid P/2013 R3 disintegrating into multiple ~100 meter-size bodies (Jewitt et al. 2014) gave us a first "live" glimpse of the formation of a multiple system. The R3 event is explained by the rotational-disruption mechanism while other causes have been rejected. It is clear that rotational-disruption events contribute to the overall size-frequency distribution of asteroids and are related to the diversity of observed binary and multi-component systems, although different models of disruption have been suggested. We aim to determine if R3-like events are rare by using HST's WFC3/UVIS to observe 6 asteroids known to have recently split (~10^5-10^6 yr) into at least two objects by the rotational-disruption mechanism. With HST we will search for additional bodies orbiting the larger member of these disrupted asteroid pairs. Finding satellites around known disrupted asteroids will suggest that multi-body disintegration processes are frequent and relevant to binary formation. A null-result will suggest that disintegration events like that of R3 are rare. In addition, both positive or null results will constrain the size distribution of the remnants of rotational-disruption events and will provide a direct probe of asteroids' internal structure and strength.
  20. Orton, G., Fletcher, L., Encrenaz, T., et al., (including Roe, H.), 2015, Icar, 260, 94, Thermal imaging of Uranus: Upper-tropospheric temperatures one season after Voyager
    We report on 18-25 m thermal imaging of Uranus that took place between 2003 and 2011, a time span roughly one season after the thermal maps made by the Voyager-2 IRIS experiment in 1986. We re-derived meridional variations of temperature and para-H2 fraction from the Voyager experiment and compared these with the thermal images, which are sensitive to temperatures in the upper troposphere of Uranus around the 70-400 mbar atmospheric pressure range. The thermal images display a maximum of 3 K of equivalent temperature changes across the disk, and they are consistent with the temperature distribution measured by the Voyager IRIS experiment. This implies that there has been no detectable change of the meridional distribution of upper-tropospheric/lower-stratospheric temperatures over a season. This is inconsistent with seasonally dependent radiative-convective-dynamical models and full global climate models that predict some variability with season if the effective temperature is meridionally constant. We posit that the effective temperature of Uranus could be meridionally variable, with the additional possibility that even the small temperature variations predicted by the GCMs are overestimated.
  21. Bemporad, A., Giordano, S., Raymond, J., et al., (including Knight, M.), 2015, AdSpR, 56, 2288, Study of sungrazing comets with space-based coronagraphs: New possibilities offered by METIS on board Solar Orbiter
    Thanks to the launch of SOHO in the end of 1995 and to the continuous monitoring of the white light (WL) corona offered by the LASCO coronagraphs, it was discovered that sungrazing comets are much more common than previously thought. More than 2800 comets have been discovered so far over nearly 20 years, hence slightly less than a comet every 2 days is observed by coronagraphs. The WL emission seen by SOHO/LASCO and more recently also by the STEREO/SECCHI instruments provides information not only on the comet orbits (hence on their origin), but also on the dust-tail formation, dust-tail disconnection, occurrence of nucleus fragmentation and nucleus disintegration processes. Very interestingly, a few sungrazing comets have also been observed spectroscopically in the UV by the SOHO UV Coronagraph Spectrometer (UVCS), and the strong emission observed in the HI Lyman- 1216 A line provides direct information also on the water outgassing rate, tail chemical composition, nucleus size, and occurrence of nucleus fragmentation. Moreover, the UV cometary emission provides a new method to estimate physical parameters of the coronal plasma met by the comet (like electron density, proton temperature and solar wind velocity), so that these comets can be considered as "local probes" for the solar corona. Unique observations of comets will be provided in the near future by the METIS coronagraph on board the Solar Orbiter mission: METIS will simultaneously observe the corona in WL and in UV (HI Lyman- ), hence it will be a unique instrument capable of studying at the same time the transiting comets and the solar corona. Previous results and new possibilities offered by METIS on these topics are summarized and discussed here.
  22. Teske, J., Everett, M., Hirsch, L., et al., (including Horch, E.), 2015, AJ, 150, 144, A Comparison of Spectroscopic versus Imaging Techniques for Detecting Close Companions to Kepler Objects of Interest
    Kepler planet candidates require both spectroscopic and imaging follow-up observations to rule out false positives and detect blended stars. Traditionally, spectroscopy and high-resolution imaging have probed different host star companion parameter spaces, the former detecting tight binaries and the latter detecting wider bound companions as well as chance background stars. In this paper, we examine a sample of 11 Kepler host stars with companions detected by two techniquesnear-infrared adaptive optics and/or optical speckle interferometry imaging, and a new spectroscopic deblending method. We compare the companion effective temperatures (Teff) and flux ratios (FB/FA, where A is the primary and B is the companion) derived from each technique and find no cases where both companion parameters agree within 1 errors. In 3/11 cases the companion Teff values agree within 1 errors, and in 2/11 cases the companion FB/FA values agree within 1 errors. Examining each Kepler system individually considering multiple avenues (isochrone mapping, contrast curves, probability of being bound), we suggest two cases for which the techniques most likely agree in their companion detections (detect the same companion star). Overall, our results support the advantage that the spectroscopic deblending technique has for finding very close-in companions ( 0.02-0.05) that are not easily detectable with imaging. However, we also specifically show how high-contrast AO and speckle imaging observations detect companions at larger separations ( 0.02-0.05) that are missed by the spectroscopic technique, provide additional information for characterizing the companion and its potential contamination (e.g., position angle, separation, magnitude differences), and cover a wider range of primary star effective temperatures. The investigation presented here illustrates the utility of combining the two techniques to reveal higher-order multiples in known planet-hosting systems.
  23. Evans, K., Massey, P., 2015, AJ, 150, 149, A Runaway Red Supergiant in M31
    A significant percentage of OB stars are runaways, so we can expect a similar percentage of their evolved descendants to also be runaways. However, recognizing such stars presents its own set of challenges, as these older, more evolved stars will have drifted farther from their birthplace, and thus their velocities might not be obviously peculiar. Several Galactic red supergiants (RSGs) have been described as likely runaways based on the existence of bow shocks, including Betelgeuse. Here we announce the discovery of a runaway RSG in M31 based on a 300 km s-1 discrepancy with M31's kinematics. The star is found about 21 (4.6 kpc) from the plane of the disk, but this separation is consistent with its velocity and likely age (10 Myr). The star, J004330.06+405258.4, is an M2 I, with MV = -5.7, {log}L/{L} = 4.76, an effective temperature of 3700 K, and an inferred mass of 12-15M. The star may be a high-mass analog of the hypervelocity stars, given that its peculiar space velocity is probably 400-450 km s-1, comparable to the escape speed from M31's disk.

    Observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. This paper uses data products produced by the OIR Telescope Data Center, supported by the Smithsonian Astrophysical Observatory.

  24. Horch, E., van Belle, G., Davidson, J., et al., 2015, AJ, 150, 151, Observations of Binary Stars with the Differential Speckle Survey Instrument. VI. Measures during 2014 at the Discovery Channel Telescope
    We present the results of 938 speckle measures of double stars and suspected double stars drawn mainly from the Hipparcos Catalog, as well as 208 observations where no companion was noted. One hundred fourteen pairs have been resolved for the first time. The data were obtained during four observing runs in 2014 using the Differential Speckle Survey Instrument at Lowell Observatory's Discovery Channel Telescope. The measurement precision obtained when comparing to ephemeris positions of binaries with very well-known orbits is generally less than 2 mas in separation and 0.5 in position angle. Differential photometry is found to have internal precision of approximately 0.1 mag and to be in very good agreement with Hipparcos measures in cases where the comparison is most relevant. We also estimate the detection limit in the cases where no companion was found. Visual orbital elements are derived for six systems.
  25. Hui, M., Ye, Q., Knight, M., et al., 2015, ApJ, 813, 73, Gone in a Blaze of Glory: The Demise of Comet C/2015 D1 (SOHO)
    We present studies of C/2015 D1 (SOHO), the first sunskirting comet ever seen from ground stations over the past half century. The Solar and Heliospheric Observatory (SOHO) witnessed its peculiar light curve with a huge dip followed by a flare-up around perihelion: the dip was likely caused by sublimation of olivines, directly evidenced by a coincident temporary disappearance of the tail. The flare-up likely reflects a disintegration event, which we suggest was triggered by intense thermal stress established within the nucleus interior. Photometric data reveal an increasingly dusty coma, indicative of volatile depletion. A catastrophic mass-loss rate of 105 kg s-1 around perihelion was seen. Ground-based Xingming Observatory spotted the post-perihelion debris cloud. Our morphological simulations of post-perihelion images find newly released dust grains of size a 10 m in radius however, a temporal increase in amin was also witnessed, possibly owing to swift dispersions of smaller grains swept away by radiation forces without replenishment. Together with the fading profile of the light curve, a power-law dust size distribution with index = 3.2 0.1 is derived. We detected no active remaining cometary nuclei over 0.1 km in radius in post-perihelion images acquired at Lowell Observatory. Applying a radial nongravitational parameter, {{A}}1=ft(1.209+/- 0.118\right) {10}-6 AU day-2, from an isothermal water-ice sublimation model to the SOHO astrometry significantly reduces residuals and sinusoidal trends in the orbit determination. The nucleus mass 108-109 kg and the radius 50-150 m (bulk density d = 0.4 g cm-3 assumed) before the disintegration are deduced from the photometric data; consistent results were determined from the nongravitational effects.
  26. Montet, B., Bowler, B., Shkolnik, E., et al., 2015, ApJL, 813, L11, Dynamical Masses of Young M Dwarfs: Masses and Orbital Parameters of GJ 3305 AB, the Wide Binary Companion to the Imaged Exoplanet Host 51 Eri
    We combine new high resolution imaging and spectroscopy from Keck/NIRC2, Discovery Channel Telescope/DSSI, and Keck/HIRES with published astrometry and radial velocities to measure individual masses and orbital elements of the GJ 3305 AB system, a young (20 Myr) M+M binary (unresolved spectral type M0) member of the Pictoris moving group comoving with the imaged exoplanet host 51 Eri. We measure a total system mass of 1.11 0.04 {M} , a period of 29.03 0.50 year, a semimajor axis of 9.78 0.14 AU, and an eccentricity of 0.19 0.02. The primary component has a dynamical mass of 0.67 0.05 {M} and the secondary has a mass of 0.44 0.05 {M} . The recently updated BHAC15 models are consistent with the masses of both stars to within 1.5 . Given the observed masses the models predict an age of the GJ 3305 AB system of 37 9 Myr. Based on the observed system architecture and our dynamical mass measurement, it is unlikely that the orbit of 51 Eri b has been significantly altered by the Kozai-Lidov mechanism.

    Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  27. Stern, S., Weaver, H., Young, L., et al., (including Grundy, W.), 2015, DPS, 47, 100.01, The Pluto System: Initial Results from the Exploration by New Horizons
    The Pluto system was recently explored by NASAs New Horizons spacecraft, which made closest approach on 14 July 2015. Plutos surface is found to be remarkably diverse in landforms, terrain ages, and albedo, color, and composition gradients. Strong evidence is found for a water-ice crust, geologically young surface units, ice convection, wind streaks, and glacial flow. Plutos atmosphere is found to be very extended, and contains newly discovered trace hydrocarbons, has an extensive global haze layer, and a surprisingly low surface pressure of ~10 microbars. Plutos wide range of surface expressions and long term activity raises fundamental questions about how small planets can have active processes billions of years after their formation. The geology of Plutos large moon Charons is also surprisingly diverse, displaying tectonics and evidence for a heterogeneous crustal composition; the north pole displays puzzling dark terrain. No evidence for a Charon atmosphere is found. Plutos small satellites Hydra and Nix are small, elongated objects with higher albedos than expected. Surprisingly, despite much improved diameter limits, no new satellites are found. We will present an overview of the New Horizons flyby, payload, and results. This work was supported by the NASA New Horizons project.
  28. Weaver, H., Stern, S., Young, L., et al., (including Grundy, W.), 2015, DPS, 47, 100.02, New Horizons Investigations of Charon and Pluto's Small Moons
    During the flyby of the Pluto system in July 2014, the instruments on the New Horizons spacecraft (Weaver et al. 2008, Space Sci. Rev. 140, 75) acquired spatially resolved measurements of Charon and Pluto's small moons (Styx, Nix, Kerberos, and Hydra). The sunlit hemisphere of Charon was mapped in panchromatic light with resolutions as high as 0.15 km/pix using LORRI, and in four different color bands (400-550 nm, 540-700 nm, 780-975 nm, 860-910 nm; the latter is centered on a weak CH4 band) with resolutions as high as 1.4 km/pix using MVIC. Composition maps of Charon were obtained with the LEISA infrared spectral imager in the wavelength range 1.25-2.50 microns, with a spectral resolving power of ~250 and with spatial resolutions up to 4.9 km/pix. Solar occultation observations with the Alice ultraviolet spectrograph, and radio occultation measurements with REX, were used to search for an atmosphere around Charon. Nix was observed by LORRI in panchromatic light at 0.30 km/pix, by MVIC in color at 2.0 km/pix, and by LEISA at 3.6 km/pix (the latter to be downlinked later). Hydra was observed by LORRI in panchromatic light at 1.1 km/pix, in color at 4.6 km/pix, and by LEISA at 14.9 km/pix (the latter to be downlinked later). Limited resolved measurements of Kerberos (2.0 km/pix panchromatic; 8.0 km/pix color) and Styx (3.2 km/pix panchromatic; 8.0 km/pix color) were also obtained but have not yet been downlinked. An extensive series of unresolved, photometric measurements of Pluto's small moons were obtained with LORRI during several months preceeding closest approach in mid-July, which place tight constraints on their shapes and rotational states.The New Horizons data have revealed that Charon has surprisingly diverse terrain, with evidence of tectonics and a heterogeneous crustal composition. Nix and Hydra are highly elongated bodies with high average albedos (suggesting water-ice dominated surfaces) and significant albedo and color variations over their surfaces. We will present estimates for the densities, spin periods, and physical properties of all the small satellites. This work was supported by NASA's New Horizons project.
  29. Grundy, W., Binzel, R., Cook, J., et al., 2015, DPS, 47, 100.04, Pluto System Surface Composition Results
    This talk will present an overview of surface composition discoveries from New Horizons' exploration of the Pluto system. The emphasis will be on results that could only have been obtained thanks to the uniquely high spatial resolution provided by a spacecraft visit. The Ralph instrument is New Horizons' primary tool for investigating surface compositions in the Pluto system. Ralph consists of a near-infrared spectral imager sharing a 75 mm aperture telescope assembly with a color CCD camera system. The Linear Etalon Imaging Spectral Array (LEISA) component of Ralph provides spectral coverage from 1.25 - 2.5 m, at a resolving power (/) of 240. Ices such as CH4, N2, CO, CO2, C2H6, NH3, and H2O have uniquely diagnostic absorption bands in this wavelength region. The Multi-spectral Visible Imaging Camera (MVIC) has 7 CCD arrays of which 4 have interference filters affixed directly on the focal plane. The filters pass wavelengths ranging from 400 through 975 nm, sensitive to coloration by tholin-type materials as well as a weak CH4 ice absorption band at 890 nm. Both Ralph components are usually operated in a scanning mode, rotating the spacecraft about its Z axis to sweep Ralph's field of view across the scene such that each point in the scene is eventually imaged at each wavelength. The width of the scanned region is 0.9 degrees divided into 256 spatial pixels for LEISA and 5.7 degrees spanned by 5000 pixels for MVIC. Over the course of the summer 2015 flyby, numerous Ralph observations targeted the various bodies in the Pluto system. As of late 2015, transmission of the data to Earth continues, but already a number of spectacular data sets are available for analysis, including LEISA scans of Pluto at 6 to 7 km/pixel and of Charon at 3 km/pixel, as well as MVIC scans of Pluto at 700 m/pixel and of Charon at 5 km/pixel. This work was supported by the NASA New Horizons Project.
  30. Olkin, C., Reuter, D., Stern, S., et al., (including Grundy, W.), 2015, DPS, 47, 101.01, Color Variations on Pluto, Charon & Among Plutos Small Satellites
    This summers flyby of NASAs New Horizons spacecraft past Pluto provided the first high spatial resolution imaging of the system. Using the Ralph instrument (Reuter et al. 2008, Space Sci. Rev. 140, 129), color images were obtained in 3 broadband filters and one narrow band filter: blue (400 - 550 nm), red (540-700 nm), NIR (780 - 975 nm) and methane (860 - 910 nm). These data revealed details about Plutos variegated surface including distinct color boundaries in two halves of the region informally named, Tombaugh Regio, and intriguing color variations in Plutos north pole. This talk will discuss the color variations on Pluto, Charon, Nix and Hydra. Color observations of Kerberos and Styx were taken, but will not be downlinked in time for inclusion in this talk. This work was supported by NASAs New Horizons project.
  31. Cruikshank, D., Grundy, W., Stern, S., et al., 2015, DPS, 47, 101.02, Pluto: Distribution of ices and coloring agents from New Horizons LEISA observations
    Pluto was observed at high spatial resolution (maximum ~3 km/px) by the New Horizons LEISA imaging spectrometer. LEISA is a component of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Sci. Rev. 140, 129) and affords a spectral resolving power of 240 in the wavelength range 1.25-2.5 m, and 560 in the range 2.1-2.25 m. Spatially resolved spectra with LEISA are used to map the distributions of the known ices on Pluto (N2, CH4, CO) and to search for other surface components. The spatial distribution of volatile ices is compared with the distribution of the coloring agent(s) on Pluto's surface. The correlation of ice abundance and the degree of color (ranging from yellow to orange to dark red) is consistent with the presence of tholins, which are refractory organic solids of complex structure and high molecular weight, with colors consistent with those observed on Pluto. Tholins are readily synthesized in the laboratory by energetic processing of mixtures of the ices (N2, CH4, CO) known on Pluto's surface. We present results returned from the spacecraft to date obtained from the analysis of the high spatial resolution dataset obtained near the time of closest approach to the planet. Supported by NASAs New Horizons project.
  32. Young, L., Grundy, W., Binzel, R., et al., 2015, DPS, 47, 101.04, Volatile Transport Implications from the New Horizons Flyby of Pluto
    The New Horizons flyby of Pluto has revealed a striking range of terrains, from the very bright region informally named Sputnik Planum, to very dark regions such as the informally named Cthulhu Regio. Such a variety was beyond the scope of recent models of Pluto's seasonal volatile cycle (Young 2013, ApJL 766, L22; Hansen, Paige and Young 2015, Icarus 246, 183), which assumed globally uniform substrate albedos. The "Exchange with Pressure Plateau (EPP)" class of models in Young (2013) and the favored runs from Hansen et al (2015) had long periods of exchange of volatiles between northern and southern hemispheres. In these models, the equators were largely devoid of volatiles; even though the equatorial latitudes received less insolation than the poles over a Pluto year, they were never the coldest place on the icy world. New models that include a variety of substrate albedos can investigate questions such as whether Sputnik Planum has an albedo that is high enough to act as a local cold trap for much of Pluto's year. We will present the implications of this and other assumption-busting revelations from the New Horizons flyby. This work was supported by NASAs New Horizons project.
  33. Singer, K., Schenk, P., Robbins, S., et al., (including Grundy, W.), 2015, DPS, 47, 102.02, Craters on Pluto and Charon: Characteristics and Impactor Population
    Although both Pluto and Charon have a surprising number of young-looking surfaces, there are still plenty of craters for impact-phenomenon enthusiasts. We will present size, morphology, ejecta, and albedo pattern statistics, in addition to correlations with color/composition where possible. We use images and topography from the Long Range Reconnaissance Imager (LORRI; Cheng et al., 2008, SSR 140, 189-215) and data from the Ralph (Reuter et al., 2008, SSR 140, 129-154) color/composition instruments.Impactor sizes will be estimated from relevant scaling laws for cold water ice (see details in Singer and Stern, 2015, ApJL 808, L50). For Pluto, an image strip at 125 m px-1 includes some cratered terrains, and much of the encounter hemisphere (the anti-Charon hemisphere) will be covered at ~400 m px-1. The ~smallest craters observable at these pixel scales (using a 5 pixel limit) would be ~0.63 km, and ~2 km in diameter, respectively, with impactor diameters estimated at ~50 m, and ~200 m. However, it is likely that degradation processes may obscure small craters, thus this lower observation limit will depend on terrain type. Additionally, lighting and observation geometries vary across the disk, which may make crater detection difficult in some areas. All of the illuminated portions of Pluto (during its 6.4 day rotation period) were imaged at ~20 km px-1 or better during the encounter. The highest resolution images of Pluto (at ~80 m px-1) occur in a narrow strip and are not scheduled for downlink before the DPS.The highest resolution Charon coverage (a strip at ~160 m px-1), a broader swath at 400 m px-1, and the entire encounter hemisphere (the sub-Pluto hemisphere) at ~890 m px-1 may yield craters as small as 0.8, 2, and 4.5 km in diameter, respectively. The inferred impactor sizes for these craters would be ~50 m, 160 m, and 440 m.Although the dataset is limited, we will discuss what constraints can be put on the impactor population. This work was supported by the NASA New Horizons project.
  34. Howett, C., Olkin, C., Grundy, W., et al., 2015, DPS, 47, 102.05, Charons Color: A view from New Horizon Ralph/Multispectral Visible Imaging Camer
    The Multispectral Visible Imaging Camera (MVIC; Reuter et al., 2008) is part of Ralph, an instrument on NASAs New Horizons spacecraft. MVIC is the color eyes of New Horizons, observing objects using four bands from blue to infrared wavelengths. MVICs images of Charon show it to be an intriguing place, a far cry from the grey heavily cratered world once postulated. Rather Charon is observed to have large surface areas free of craters, and a northern polar region that is much redder than its surroundings. This talk will describe these initial results in more detail, for example is Charons redder pole caused by molecules that have escaped Plutos atmosphere only to be captured and frozen onto the surface of Charons cold polar region, where they have undergone photolysis? Charons global geological color variations will also be discussed, to put these results into their wider context. This work was supported by NASAs New Horizons project.
  35. Bosh, A., Person, M., Zuluaga, C., et al., (including Levine, S., Dunham, E., Bida, T., Bright, L., Collins, P.), 2015, DPS, 47, 105.03, Haze in Pluto's atmosphere: Results from SOFIA and ground-based observations of the 2015 June 29 Pluto occultation
    We observed the 29 June 2015 occultation by Pluto from SOFIA and several ground-based sites in New Zealand. Pre-event astrometry (described in Zuluaga et al., this conference) allowed us to navigate SOFIA into Pluto's central flash (Person et al., this conference). Fortuitously, the central flash also fell over the Mt. John University Observatory (Pasachoff et al., this conference). We combine all of our airborne and ground-based data to produce a geometric solution for the occultation and to investigate the state of Pluto's atmosphere just two weeks before the New Horizons spacecraft's close encounter with Pluto. We find that the atmosphere parameters at half-light are unchanged from our observations in 2011 (Person et al. 2013) and 2013 (Bosh et al. 2015). By combining our light-curve inversion with recent radius measurements from New Horizons, we find strong evidence for an extended haze layer in Pluto's atmosphere. See also Sickafoose et al. (this conference) for an evaluation of the particle sizes and properties.SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. Support for this work was provided by NASA SSO grants NNX15AJ82G (Lowell Observatory), NNX10AB27G (MIT), and NNX12AJ29G (Williams College), and by the National Research Foundation of South Africa.
  36. Sickafoose, A., Bosh, A., Person, M., et al., (including Levine, S., Dunham, E., Bida, T., Bright, L., Collins, P.), 2015, DPS, 47, 105.04, Investigation of particle sizes in Pluto's atmosphere from the 29 June 2015 occultation
    The 29 June 2015 observations of a stellar occultation by Pluto, from SOFIA and ground-based sites in New Zealand, indicate that haze was present in the lower atmosphere (Bosh et al., this conference). Previously, slope changes in the occultation light curve profile of Plutos lower atmosphere have been attributed to haze, a steep thermal gradient, and/or a combination of the two. The most useful diagnostic for differentiating between these effects has been observing occultations over a range of wavelengths: haze scattering and absorption are functions of particle size and are wavelength dependent, whereas effects due to a temperature gradient should be largely independent of observational wavelength. The SOFIA and Mt. John data from this event exhibit obvious central flashes, from multiple telescopes observing over a range of wavelengths at each site (Person et al. and Pasachoff et al., this conference). SOFIA data include Red and Blue observations from the High-speed Imaging Photometer for Occultations (HIPO, at ~ 500 and 850 nm), First Light Infrared Test Camera (FLITECAM, at ~1800 nm), and the Focal Plan Imager (FPI+, at ~ 600 nm). Mt. John data include open filter, g', r', i', and near infrared. Here, we analyze the flux at the bottom of the light curves versus observed wavelength. We find that there is a distinct trend in flux versus wavelength, and we discuss applicable Mie scattering models for different particle size distributions and compositions (as were used to characterize haze in Pluto's lower atmosphere in Gulbis et al. 2015).SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. Support for this work was provided by the National Research Foundation of South Africa, NASA SSO grants NNX15AJ82G (Lowell Observatory), PA NNX10AB27G (MIT), and PA NNX12AJ29G (Williams College), and the NASA SOFIA Cycle 3 grant NAS2-97001 issued by USRA.
  37. Person, M., Bosh, A., Sickafoose, A., et al., (including Dunham, E., Bida, T., Bright, L., Collins, P.), 2015, DPS, 47, 105.05, Central Flash Analysis of the 29 June 2015 Occultation
    After an extensive prediction effort, the 29 June 2015 occultation by Pluto was observed from both airborne (Stratospheric Observatory for Infrared Astronomy - SOFIA) and numerous ground-based telescopes (Bosh et al. - this meeting). Real-time prediction updates allowed placement of the SOFIA telescope with its four detectors deep within the central-flash region of the atmospheric occultation. Fortuitously, the Mount John University Observatory (Lake Tekapo, New Zealand) was also within the central-flash region (Pasachoff et al. - this meeting). This happenstance resulted in multiple central-flash detections in several colors from each facility allowing direct comparison of different areas of the central-flash evolute.Here we examine and discuss the central-flash signatures from the highest signal-to-noise light curves from each facility. The relative orientations and asymmetries in the central flashes allow us to use them to tightly constrain the lower atmospheric ellipticity and orientation of likely winds with respect to Plutos figure. The ratio of the two separate central flashes is also a strong constraint on the geometric solution for the full occultation data set, and the absolute height of the central flashes with respect to those expected for a clear isothermal atmosphere places constraints on haze densities and thermal gradients in Plutos lower atmosphere. We can also compare the central-flash signatures in several colors (similar to Sickafoose et. al - this meeting) to establish bounds on haze-particle sizes in the lower atmosphere.SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. Support for this work was provided, in part, by NASA grants SSO NNX15AJ82G (Lowell Observatory), PA NNX10AB27G (MIT), and PA NNX12AJ29G (Williams College), as well as the National Research Foundation of South Africa, and the NASA SOFIA Cycle 3 grant NAS2-97001 issued by USRA.
  38. Leith, T., Moskovitz, N., Mayne, R., et al., 2015, DPS, 47, 106.03, Early Evolution of the Main Belt Informed by the Compositional Diversity of Basaltic Asteroids
    We present near-infrared (0.78-2.45 micron) reflectance spectra for eight outer main belt (a > 2.5 AU) asteroids that have been taxonomically classified as V-types based on visible wavelength data. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo spectral catalogue, and thus could represent either spectral end members of the V-type taxonomic class or a small population of a new spectral type. The remainder of the sample are classified as V- or R-type. All of these asteroids are dynamically distinct from the Vestoid family, implying that they originated from differentiated planetesimals which have since been destroyed or ejected from the solar system. The 1- and 2-m band centers of all objects, determined using Modified Gaussian Model fits, were compared to those of 47 Vestoids and fifteen HED meteorites of known composition. Formulas relating Band 1 and Band 2 centers to the pyroxene mineralogies of these asteroids were derived from the sample of HED meteorites and used to determine the Fs numbers of all asteroids. The Fs numbers of the five outer belt V- and R-type asteroids are, on average, between five and ten molar percent lower than those of the Vestoids, implying that these objects formed in a more reducing environment than Vesta. Given the complex evolution of oxygen fugacity in the solar nebula, these compositional results suggest that these outer belt basaltic asteroids formed either interior to Vesta and were later scattered to the outer belt or formed at a later epoch than Vesta.
  39. Grundy, W., Binzel, R., Cook, J., et al., 2015, DPS, 47, 200.01, Configuration of Pluto's Volatile Ices
    We report on near-infrared remote sensing by New Horizons' Ralph instrument (Reuter et al. 2008, Space Sci. Rev. 140, 129-154) of Pluto's N2, CO, and CH4 ices. These especially volatile ices are mobile even at Pluto's cryogenic surface temperatures. Sunlight reflected from these ices becomes imprinted with their characteristic spectral absorption bands. The detailed appearance of these absorption features depends on many aspects of local composition, thermodynamic state, and texture. Multiple-scattering radiative transfer models are used to retrieve quantitative information about these properties and to map how they vary across Pluto's surface. Using parameter maps derived from New Horizons observations, we investigate the striking regional differences in the abundances and scattering properties of Pluto's volatile ices. Comparing these spatial patterns with the underlying geology provides valuable constraints on processes actively modifying the planet's surface, over a variety of spatial scales ranging from global latitudinal patterns to more regional and local processes within and around the feature informally known as Sputnik Planum. This work was supported by the NASA New Horizons Project.
  40. Cook, J., Cruikshank, D., Dalle Ore, C., et al., (including Grundy, W.), 2015, DPS, 47, 200.02, The Search for Pluto Water
    On July 14, 2015, the New Horizons spacecraft made its closest approach to Pluto at about ~12,000 km from Pluto's surface. The LEISA (Linear Etalon Imaging Spectral Array) component of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Sci. Rev. 140, 129) obtained spatially resolved near infrared spectra at scales as small as 3 km/pix. LEISA covers the wavelength range 1.25 to 2.5 m at a spectral resolution (/) of 240, and the 2.1 to 2.25 m range at a resolution of 560. The observations from this instrument are being used to map the distribution of Pluto's known ices such as N2, CH4, CO and C2H6 as well as search for H2O-ice. To date, H2O-ice has evaded detection from Earth bound observatories. Observations based on LORRI, the LOng Range Reconnaissance Imager, suggest H2O-ice is a major component of several mountain ranges around the western perimeter of the landmass informally named Tombaugh Regio. If true, H2O-ice may be found in small isolated regions around Pluto. We will present our analysis of all LESIA data of Pluto in hand to search for and understand the distribution of H2O-ice. If found, we will also discuss limits on crystalline vs. amorphous H2O-ice and temperature measurements based on the 1.65 m crystalline H2O-ice feature. This work was supported by NASA's New Horizons project.
  41. Buie, M., Stern, S., Young, L., et al., (including Grundy, W.), 2015, DPS, 47, 200.03, New Horizons data in the context of prior observations
    The New Horizons encounter data have revealed a diverse and complicated surface and atmosphere for Pluto showing strong correlations between geologic features and the albedo and compositional units known from ground- and HST-based observations over the decades prior. This presentation make detailed comparisons between the long time base and low spatial resolution data and the new high resolution stanpshot of Pluto from the flyby. Special emphasis will be placed on the albedo evolution over time with some attention paid to near-infrared spectral signatures. We will compare the albedo maps from mutual event data and two epochs of HST observations against the New Horizons images, after correcting for viewing geometry. Also included will be a discussion of the evolutionary trends in the hemispherically averaged spectral properties from Lowell Observatory and IRTF data against the resolved compositional and spectral maps from New Horizons. The combination of these data sets now permits an unprecedented ability to constrain time-variability on the surface from apparent changes due to viewing geometry and surface inhomogeneities. This work requires a reconcilliation of surface scattering properties that are enabled by the firm determination of the size of Pluto and this will be discussed as well. This work was supported by the NASA New Horizons project.
  42. Earle, A., Binzel, R., Stern, S., et al., (including Grundy, W.), 2015, DPS, 47, 200.05, Correlating Pluto's Albedo Distribution to Long Term Insolation Patterns
    NASA's New Horizons' reconnaissance of the Pluto system has revealed striking albedo contrasts from polar to equatorial latitudes on Pluto, as well as sharp boundaries for longitudinal variations. These contrasts suggest Pluto undergoes dynamic evolution that drives the redistribution of volatiles. Using the New Horizons results as a template, in this talk we will explore the volatile migration process driven seasonally on Pluto considering multiple timescales. These timescales include the current orbit (248 years) as well as the timescales for obliquity precession (amplitude of 23 degrees over 3 Myrs) and regression of the orbital longitude of perihelion (3.7 Myrs). We will build upon the long-term insolation history model described by Earle and Binzel (2015, Icarus 250, 405-412) with the goal of identifying the most critical timescales that drive the features observed in Plutos current post-perihelion epoch. This work was supported by the NASA New Horizons Project.
  43. Ennico, K., Howett, C., Olkin, C., et al., (including Grundy, W.), 2015, DPS, 47, 200.08, Pluto and Charon Color Light Curves from New Horizons on Approach
    On approach to the Pluto system, New Horizons Ralph Instruments Multicolor Visible Imaging Camera (MVIC) observed Pluto and Charon, spatially separated, between April 9 and June 23, 2015. In this period, Pluto and Charon were observed to transition from unresolved objects to resolved and their integrated disk intensities were measured in four MVIC filters: blue (400-550 nm), red (540-700 nm), near-infrared (780-975 nm), and methane (860-910 nm). The measurement suite sampled the bodies over all longitudes. We will present the color rotational light curves for Pluto and Charon and compare them to previous (Buie, M. et al. 2010 AJ 139, 1117; Buratti, B.J. et al 2015 ApJ 804, L6) and concurrent ground-based BVR monitoring. We will also compare these data to color images of the encounter hemisphere taken during New Horizons July 14, 2015 Pluto and Charon flyby, as this data set provides a unique bridge between Pluto & Charon as viewed as astronomical targets versus the complex worlds that early data from New Horizons has revealed them to be. This work was supported by NASAs New Horizons project.
  44. Dias-Oliveira, A., Sicardy, B., Lellouch, E., et al., (including Thirouin, A., Reichart, D.), 2015, DPS, 47, 200.09, Pluto's atmosphere from stellar occultations in 2012 and 2013
    We present results from two Pluto stellar occultations observed on 18 July 2012 and 04 May 2013, and monitored respectively from five and six sites in South America. Both campaigns involved large telescopes (including the 8.2-m VLT at ESO/Paranal). The high SNR ratios and multi-chord coverage provide amoung the best Pluto atmospheric profiles ever obtained from the ground.We show that a spherically symmetric, clear (no-haze) and pure N2 atmosphere with a unique temperature profile satisfactorily fits the twelve lightcurves provided by the two events. We find, however, a small but significant increase of pressure of 6% (6-sigma level) between the two dates, with values of 2.16 0.2 and 2.30 0.01 bar at the reference radius 1275 km, respectively.We provide atmospheric constrains between 1190 km and 1450 km from Pluto's center, and we determine the temperature profile with accuracy of a few km in vertical scale. Our model shows a stratosphere with strong positive gradient between 1190 km (at 36 K, 11 bar) and r =1215 km (6.0 bar), where a temperature maximum of 110 K is reached. Above it is a mesosphere with negative thermal gradient of -0.2 K/km up to 1,390 km (0.25 bar), at which point, the mesosphere connects itself to a more isothermal upper branch at 81 K. This profile provides (assuming no troposphere) a Pluto surface radius of 1190 5 km, consistent with preliminary values obtained by New Horizons. Currently measured CO abundances are too low to explain the negative mesospheric thermal gradient. We explore the possibility of an HCN (recently detected by ALMA) cooling. This model, however, requires largely supersaturated HCN. Zonal winds and vertical compositional variations of the atmosphere are also unable to explain the observed mesospheric trend.These events are the last useful ground-based occultations recorded before the 29 June 2015 occultation observed from Australia and New Zealand, and before the NASA's New Horizons flyby of July 2015. This work can serve as a benchmark in the New Horizons context, enabling comparisons between ground-based and space results concerning Pluto's atmospheric structure and temporal evolution.
  45. Thirouin, A., Sheppard, S., Noll, K., et al., (including Moskovitz, N.), 2015, DPS, 47, 203.01, Rotational properties of the Haumea family members and candidates: Short-term variability
    Haumea is one of the largest known Trans-Neptunian Objects (TNOs) with several anomalous characteristics. It is a fast rotator with a double-peak period of 3.92 h. Its spectrum is dominated by water ice features and the high albedo suggests nearly pure water ice on the surface. It has two known satellites and a family of at least ten TNOs with very similar proper orbital parameters and spectral properties. The formation of this peculiar family (Haumea, its two moons and, dynamically related bodies) is not well understood despite various models that have been proposed during the past few years.In order to improve our understanding of the formation of this family, we have examined the rotational properties of the family members and candidates (i.e. objects with similar proper orbital elements to the family members but without water ice on their surface or without observations to detect surface water). We report new short-term variability for 5 family members and 7 candidates from data collected over the past five years using multiple ground-based facilities. Thanks to our study, all the Haumea family members have a short-term variability study.From rotational data, assuming fluid-like rubble-pile structure, we constrain ellipsoidal axis ratios for individual objects and set a lower limit to densities. We also compared lightcurve amplitude and rotational frequency distributions for the family members, candidates, and unrelated TNOs to search for additional clues to the progenitor and the formation of this family.
  46. Verbiscer, A., Buie, M., Binzel, R., et al., (including Grundy, W.), 2015, DPS, 47, 210.03, New Horizons and Hubble Space Telescope Photometry of Nix and Hydra
    New Horizons has provided the first spatially-resolved images of Plutos small satellites, enabling the characterization of albedo and scattering properties across their surface. Application of photometric models to yield the physical properties of airless planetary surfaces requires observations spanning the broadest possible range of viewing and illumination geometries, from full disk to thin crescent. While New Horizons observed the Pluto system at phase angles no smaller than 15, full-disk Hubble Space Telescope images (HST Program 13367, M. Buie, PI) at phase angles between 0.06 and 1.7 constrain the phase function near opposition. Together with New Horizons disk-resolved images, we use the near-opposition phase function to test whether ejecta exchange (Stern 2009, Icarus 199, 571) affects photometric properties. With direct measurements of small satellite sizes from New Horizons, we can determine the disk-integrated geometric albedo by extrapolating the HST observations to zero phase. New Horizons observations at larger phase angles reveal surface roughness and directional scattering properties. Finally we place the photometric properties of Plutos small satellites in context with those of similar size in other planetary systems. This work was supported in part by the NASA New Horizons Project.
  47. Lorenzi, V., Pinilla-Alonso, N., Emery, J., et al., (including Grundy, W.), 2015, DPS, 47, 210.08, The visible spectrum of Pluto: secular and longitudinal variation
    Continuous near-infrared spectroscopic observations during the last 30 years enabled the characterization of the Pluto's surface and the study of its variability. Nevertheless, only few data are available in the visible range, where the nature of the complex-organics can be studied.For this reason, we started an observational campaign to obtain the Pluto's relative reflectance in the visible range, with the aim of characterizing the different components of its surface, and providing ground based observations in support of the New Horizons mission. We observed Pluto on six nights in 2014, with the imager/spectrograph ACAM@WHT (La Palma, Spain). We obtained six spectra in the 0.40 - 0.93 m range, that covered a whole Pluto's rotational period (6.4 days).To study longitudinal variations, we computed for all the spectra the spectral slope, and the position and the depth of the methane ice absorption bands. Also, to search for secular or seasonal variations we compared our data with previously published results.All the spectra present a red slope, indicating the presence of complex organics on Pluto's surface, and show the methane ice absorption bands between 0.73 and 0.90 m. We also report the detection of the CH4 absorption band at 0.62 m, already detected in the spectra of Makemake and Eris. The measurement of the band depth at 0.62 m in the new spectra of Pluto, and in the spectra of Makemake and Eris, permits us to estimate the Lambert coefficient, not measured yet at this wavelength, at a temperature of 30 K and 40 K.We find that all the CH4 bands present a blue shift. This shift is minimum at the Charon-facing hemisphere, where the CH4 is also more abundant, indicating a higher degree of saturation of CH4 in the CH4:N2 dilution at this hemisphere.Comparing with data in the literature, we found that the longitudinal and secular variations of the parameters measured in our spectra are in accordance with previous results and with the distribution of the dark and bright material as showed by the Pluto's albedo maps from New Horizons.In 2015, new observations were run quasi-simultaneously with the New Horizons flyby at 10 different Pluto longitudes (July 3 to 14) . The data are currently being reduced.
  48. Throop, H., Grundy, W., Olkin, C., et al., 2015, DPS, 47, 210.09, New rotationally resolved spectra of Pluto-Charon from 350 - 900 nm
    We are using the 11-meter Southern African Large Telescope (SALT) to acquire high-resolution rotationally resolved visible spectra of Pluto-Charon. We use the Robert Stobie Spectrograph (RSS) to observe Pluto-Charon from 350 nm to 900 nm. At 500 nm, resolution is 0.05 nm (R ~ 10,0000) and SNR per spectral resolution element is ~ 500.We planned observations for 13 dates during June-September 2014, and 13 more dates during June-September 2015. The observations for each season were spaced so as to equally sample Pluto's 6.5-day rotational period. As of the abstract submission, we have data from 11 nights (2014) and 9 nights (2015) in hand. Most of the observations were taken with observations of solar-type star HD 146233 to determine the surface reflectivity.Our results will provide constraint on the composition and spatial distribution of material on Pluto's surface, enabling comparison to previous epochs and near-infrared results, and giving a ground-truth for New Horizons' July 2015 flyby. In addition, our data will allow us to search for new spectral features in the range 350 nm to 600 nm, at a sensitivity substantially higher than previously published searches.
  49. Young, E., Young, L., Roe, H., et al., 2015, DPS, 47, 210.10, Spectroscopy of Pluto's Surface from 2.8 - 3.6 m during the New Horizons Flyby
    Spectroscopy of Pluto in the 1 - 2.5 m range has produced key results over the past two decades: identification of nitrogen, CO, methane and ethane ices, longitudinal variability in the concentrations of these ices, evidence of dissolved vs. pure methane and nitrogen ices, and the surface temperature and crystalline state of nitrogen ice (e.g., Doute et al., 1999; Holler et al., 2014). Only a few spectra have been published at wavelengths from 2.5 - 5 m (e.g., Protopapa et al., 2008; Olkin et al. , 2007), but these few L- and M-band spectra changed our interpretation of Pluto's surface: the depth of the 3.3 m methane band precludes significant regions of pure of nitrogen ice, the slope of the methane band at 3.1-3.2 m is sensitive to the fraction of pure methane vs. methane that is diluted in nitrogen frost, and an absorption feature at 4.67 m needs an identified source (but could be due to CO, CH3D or other constituent). The LEISA instrument on New Horizons obtained spectra of Pluto's surface at wavelengths between 1.25 - 2.5 m. To complement the spacecraft instrumentation, we observed Pluto's disk-integrated spectra from 2.8 - 3.6 m on two half-nights (12-JUL-2015 and 14-JUL-2015 (UT)) using the NIRSPEC spectrograph at the W.M. Keck Observatory. Conditions were excellent throughout most of the observing run, with seeing under 0.5" at K. We will compare our results to observations obtained in 2001 with the same instrument and report on evidence for surface constituents that have been found at shorter wavelengths.ReferencesDoute et al., "Evidence for methane segregation at the surface of Pluto." Icarus 142, 421-444 (1999)Holler, B.J. et al., "Evidence for longitudinal variability of ethane ice on the surface of Pluto." Icarus 243, 104-110 (2014)
  50. Umurhan, O., Moore, J., McKinnon, W., et al., (including Grundy, W.), 2015, DPS, 47, 210.11, Glacial Flow on and onto Sputnik Planum
    Sputnik Planum (SP)[1,2] is the high albedo apparently crater-free western portion of Tombaugh Regio imaged in July by the New Horizons LORRI instrument. The relatively high resolution (400 m/pix) LORRI mosaics of the northern portions of the planum bordered by the Cousteau Rupes (CR) scarp reveal surface patterns highly suggestive of viscous flow dynamics. Spectroscopic measurements of SP taken by the New Horizons LEISA instrument also indicate that SP is a region containing a significant amount of CO[2]. It has also been long known that CO and N2 are associated with one another on SP[3-4]. Taken together these observations suggest the possibility that the high albedo material on SP is a volatile ice mix possibly flowing atop a bedrock-like substrate. The apparent notable lack of craters on SP strongly suggests that the flow processes act on relatively fast geologic timescales. Using the known properties of various volatile ice mixtures in the temperature range of interest, we formulate and implement a numerical landform evolution model in order to examine a number of hypothetical evolutionary scenarios for SP and its environs. This work was supported by NASA's New Horizons project.[1] All place names on Pluto and Charon are informally known as such as of the writing of this abstract. [2] Stern, S. A. et al. 2015 Science. [3] Grundy & Buie 2001 Icarus 153, 248. [4] Grundy et al. 2013 Icarus 223, 710.
  51. Pasachoff, J., Babcock, B., Durst, R., et al., (including Levine, S.), 2015, DPS, 47, 210.12, A Central Flash at an Occultation of a Bright Star by Pluto Soon Before New Horizons' Flyby
    From the Mt. John Observatory, New Zealand, we were so close to the center of the occultation path on 29 June 2015 UTC that we observed a modest central flash from the focusing of starlight from a 12th-magnitude star. The star was one of the brightest ever in our years of continual monitoring that started in 2002. At the time of Pluto's perihelion in 1989, it was feared from models that Pluto's atmosphere might collapse by now, a motivation for the timely launch of New Horizons; some models now allow Pluto to retain its atmosphere throughout its orbit.We used our frame-transfer CCD at 10 Hz with GPS timing on the 1-m McLellan telescope of Canterbury U. We also observed with a Lowell Obs. infrared camera on the "AAVSO" 0.6-m Optical Craftsman telescope; and obtained 3-color photometry at a slower cadence on a second 0.6-m telescope. We coordinated with the overflight of SOFIA and its 2.5-m telescope, which benefited from last-minute astrometry, and the Auckland Observatory's and other ground-based telescopes.Our light curves show a modest central flash; our tentative geometrical solution shows that we were only about 50 km from the occultation path's centerline. The flash is from rays lower than otherwise accessible in Pluto's atmosphere. Our light curves, at such high cadence that we see spikes caused by atmospheric effects that we had not seen so well since our 2002 Mauna Kea occultation observations, show that Pluto's atmosphere had not changed drastically since our previous year's observations. Our data provide a long-term context for New Horizon's highly-detailed observations of Pluto's atmosphere in addition to providing a chord for the geometrical solution that includes SOFIA's observations.Our observations were supported by NASA Planetary Astronomy grants NNX12AJ29G to Williams College, NNX15AJ82G to Lowell Observatory, and NNX10AB27G to MIT, and by the National Research Foundation of South Africa. We are grateful to Alan Gilmore, Pam Kilmartin, Robert Lucas, and Carolle Varughese for assistance at Mt. John. We thank the AAVSO for use of the AAVSOnet 0.6-m telescope and Arne Henden for assistance.
  52. Zuluaga, C., Bosh, A., Person, M., et al., (including Levine, S., Bright, L.), 2015, DPS, 47, 210.13, Placing SOFIA in the central flash for the 29 June 2015 Pluto Occultation
    We report on the astrometry prediction process carried out for the 29 June 2015 occultation of an 11.9 magnitude star by Pluto. The occultation star, UCAC2 139-209445 was first identified in 2013 as a good candidate for an occultation to be observed with Stratospheric Observatory for Infrared Astronomy (SOFIA) due to the circumstances of the event. In addition, the event's proximity to the New Horizons encounter with Pluto made the event even more timely. We were awarded time on SOFIA for the Pluto occultation in 2014. From mid-2014 up through the night of the occultation, we tracked Pluto's position. We collected astrometric data from four telescopes: the SARA-CT telescope located in Cerro Tololo International Observatory, Chile; the Lowell Observatory 42-inch Hall telescope; the Lowell Observatory 4.3-m Discover Channel Telescope, both in Flagstaff, AZ; and the USNO 1.55-m Kaj Strand telescope in Flagstaff, AZ. The objective of the astrometric observations was to improve the prediction enough to place the aircraft within the central flash zone (approximately 75 km, 5mas, from the center line of the Pluto shadow).The prediction uncertainties included those of the star position and proper motion, Pluto ephemeris offset, potential zone-dependent offsets in the reference catalog, unknown stellar duplicity, and center-of-mass to center-of-light offsets. Over the two years since we identified this event as promising, we worked to steadily decrease each of the sources of uncertainty.We communicated prediction updates to the SOFIA flight planning team. We provided a pre-take-off update, which was then followed by a later in-flight update that necessitated a change in the flight plan of 320 km. The crew were able to implement this change and SOFIA was able to capture the central flash of this event (Bosh et al., and Person et al., this conference).
  53. Hartig, K., Barry, T., Carriazo, C., et al., (including Wasserman, L.), 2015, DPS, 47, 210.14, Constraints on Pluto's Hazes from 2-Color Occultation Lightcurves
    The controversial question of aerosols in Pluto's atmosphere first arose in 1988, when features in a Pluto occultation lightcurve were alternately attributed to haze opacity (Elliot et al. 1989) or a thermal inversion (Eshleman 1989). A stellar occultation by Pluto in 2002 was observed from several telescopes on Mauna Kea in wavelengths ranging from R- to K-bands (Elliot et al. 2003). This event provided compelling evidence for haze on Pluto, since the mid-event baseline levels were systematically higher at longer wavelengths (as expected if there were an opacity source that scattered more effectively at shorter wavelengths). However, subsequent occultations in 2007 and 2011 showed no significant differences between visible and IR lightcurves (Young et al. 2011).The question of haze on Pluto was definitively answered by direct imaging of forward-scattering aerosols by the New Horizons spacecraft on 14-JUL-2015. We report on results of a bright stellar occultation which we observed on 29-JUN-2015 in B- and H-bands from both grazing and central sites. As in 2007 and 2011, we see no evidence for wavelength-dependent extinction. We will present an analysis of haze parameters (particle sizes, number density profiles, and fractal aggregations), constraining models of haze distribution to those consistent with and to those ruled out by the occultation lightcurves and the New Horizons imaging.References:Elliot, J.L., et al., "Pluto's Atmosphere." Icarus 77, 148-170 (1989)Eshleman, V.R., "Pluto's Atmosphere: Models based on refraction, inversion, and vapor pressure equilibrium." Icarus 80 439-443 (1989)Elliot, J.L., et al., "The recent expansion of Pluto's atmosphere." Nature 424 165-168 (2003)Young, E.F., et al., "Search for Pluto's aerosols: simultaneous IR and visible stellar occultation observations." EPSC-DPS Joint Meeting 2011, held 2-7 October 2011 in Nantes, France (2011)
  54. Resnick, A., Barry, T., Buie, M., et al., 2015, DPS, 47, 210.15, The State of Pluto's Bulk Atmosphere at the Time of the New Horizons Encounter
    On 29-JUL-2015, our team - plus many critical amateur astronomers - observed a stellar occultation by Pluto from sites in Australia and New Zealand. This event was remarkable for two reasons: it preceded the New Horizons flyby of Pluto by just two weeks, and the occulted star was about 10x brighter than Pluto itself, by far the brightest Pluto occultation event observed to date. The separation of ground sites spanned nearly 900 km with respect to the central chord, allowing a good geometric solution for the shadow path. The lightcurves show some inflection points and broad "fangs" that are characteristic of perturbations in the temperature profile. Preliminary fits show that the temperature profile derived from a 2006 occultation (Young et al. 2008) reproduces the 29-JUN-2015 lightcurves well. Assuming a surface radius of 1187 km for Pluto, we find that the surface pressure is 18 +/- 3 bar. This pressure indicates that Pluto's surface has not yet started to cool down, despite a decrease in absorbed solar flux of more than 17% since perihelion in 1988. A surface pressure of 18 bar would correspond to a nitrogen ice surface temperature of 38.0 K.References:Young, E.F., et al. "Vertical Structure in Pluto's Atmosphere from the 2006 June 12 Stellar Occultation," AJ 136 1757-1769 (2008)
  55. Roe, H., Cook, J., Mace, G., et al., 2015, DPS, 47, 210.18, Pluto's atmosphere in 2015 from high-resolution spectroscopy
    Pluto's thin N2/CH4 atmosphere is in vapor-pressure equilibrium with ices on its surface. The atmosphere evolves seasonally with the varying insolation pattern on Pluto's heterogenous surface, perhaps even largely freezing out to the surface during the coldest portion of Pluto's year. We use high-resolution (R25,000-50,000) near-infrared spectroscopy to resolve atmospheric methane absorption lines from Pluto's continuum spectra, as well as separate Pluto's atmospheric lines from the telluric spectrum. In addition to measuring the abundance and temperature of Pluto's atmospheric CH4, with broad wavelength coverage we are able to search for the inevitable products of N2/CH4 photochemistry. In 2015 we are undertaking an intensive campaign using NIRSPEC at Keck Observatory and IGRINS (Immersion Grating INfrared Spectrometer) at McDonald Observatory to coincide with the New Horizons Pluto encounter. We will report initial results from this 2015 campaign and compare the state of Pluto's atmosphere at the time of the New Horizons encounter with earlier years.
  56. Philippe, S., Schmitt, B., Grundy, W., et al., 2015, DPS, 47, 210.19, 12 years of Pluto surface's evolution investigated with radiative transfer modeling
    The evolution of Plutos surface through time, due to surface - atmosphere interactions, remains unknown. New Horizons will provide very high spatial resolution data of its surface state but only as a snapshot. Furthermore, this evolution during the last decades is supposed to be fast due to the recent passage of Pluto through its perihelion (1989). Ground based survey data over a long period of time are thus crucial to understand the long-term evolution of the dwarf planet surface.IRTF/SpeX reflectance spectra of Pluto have been acquired during 13 years (2001-2013) between 0.8-2.4 m (Grundy et al., 2013; Grundy et al., 2014). This set of data present the opportunity to monitor possible changes of the surface in terms of geographical distribution and segregation between different chemical species that are known to be present at the surface in an icy state (N2, CH4 and CO, Owen et al., 1993, Doute et al., 1999). These variations are recorded through changes in the infrared absorption bands of the different ices. A study based on band criteria variation (Grundy et al., 2013) showed that CH4 absorption bands are increasing through time, whereas N2 and CO absorptions bands are decreasing (Grundy et al. 2014). However, quantitative interpretation of these data needs further investigation and detailed radiative transfer modeling.We used the bidirectional reflectance model of Doute & Schmitt (1998) to fit the IRTF/SpeX spectral data. This model takes into account a possible stratification of chemical species, a phenomenon that is likely to occur on Pluto where CH4 is supposed to accumulate on a sublimating molecular mixture of N2-CH4-CO (Doute et al., 1999). Different modelings take into account pure CH4 ice, a molecular mixture of N2-CH4-CO, tholins and water ice. We modeled the grand average spectra and then allowed the parameters to vary around the average values to model individual spectra and get quantitative variations of the different species.Preliminary results of these modelings will be presented in terms of longitudinal and temporal variations. This study could provide a useful precursor for the analysis of the spatially resolved New Horizon hyper spectral data acquired by the RALPH/Leisa instrument.
  57. Dalle Ore, C., Cruikshank, D., Grundy, W., et al., 2015, DPS, 47, 210.27, Crystalline and amorphous H2O on Charon
    Charon, the largest satellite of Pluto, is a gray-colored icy world covered mostly in H2O ice, with spectral evidence for NH3, as previously reported (Cook et al. 2007, Astrophys. J. 663, 1406-1419 Merlin, et al. 2010, Icarus, 210, 930; Cook, et al. 2014, AAS/Division for Planetary Sciences Meeting Abstracts, 46, #401.04). Images from the New Horizons spacecraft reveal a surface with terrains of widely different ages and a moderate degree of localized coloration. The presence of H2O ice in its crystalline form (Brown & Calvin 2000 Science 287, 107-109; Buie & Grundy 2000 Icarus 148, 324-339; Merlin et al, 2010) along with NH3 is consistent with a fresh surface.The phase of H2O ice is a key tracer of variations in temperature and physical conditions on the surface of outer Solar System objects. At Charons surface temperature H2O is expected to be amorphous, but ground-based observations (e.g., Merlin et al. 2010) show a clearly crystalline signature. From laboratory experiments it is known that amorphous H2O ice becomes crystalline at temperatures of ~130 K. Other mechanisms that can change the phase of the ice from amorphous to crystalline include micro-meteoritic bombardment (Porter et al. 2010, Icarus, 208, 492) or resurfacing processes such as cryovolcanism.New Horizons observed Charon with the LEISA imaging spectrometer, part of the Ralph instrument (Reuter, D.C., Stern, S.A., Scherrer, J., et al. 2008, Space Science Reviews, 140, 129). Making use of high spatial resolution (better than 10 km/px) and spectral resolving power of 240 in the wavelength range 1.25-2.5 m, and 560 in the range 2.1-2.25 m, we report on an analysis of the phase of H2O ice on parts of Charons surface with a view to investigate the recent history and evolution of this small but intriguing object.This work was supported by NASAs New Horizons project.
  58. Bosh, A., Dunham, E., Young, L., et al., (including Millis, R., Wasserman, L., Nye, R.), 2015, DPS, 47, 210.31, Revisiting the 1988 Pluto Occultation
    In 1988, Pluto's atmosphere was surmised to exist because of the surface ices that had been detected through spectroscopy, but it had not yet been directly detected in a definitive manner. The key to making such a detection was the stellar occultation method, used so successfully for the discovery of the Uranian rings in 1977 (Elliot et al. 1989; Millis et al. 1993) and before that for studies of the atmospheres of other planets.On 9 June 1988, Pluto occulted a star, with its shadow falling over the South Pacific Ocean region. One team of observers recorded this event from the Kuiper Airborne Observatory, while other teams captured the event from various locations in Australia and New Zealand. Preceding this event, extensive astrometric observations of Pluto and the star were collected in order to refine the prediction.We will recount the investigations that led up to this important Pluto occultation, discuss the unexpected atmospheric results, and compare the 1988 event to the recent 2015 event whose shadow followed a similar track through New Zealand and Australia.
  59. Noll, K., Grundy, W., Ryan, E., et al., 2015, DPS, 47, 211.01, Search for Binary Trojans
    We have reexamined 41 Trojan asteroids observed with the Hubble Space Telescope (HST) to search for unresolved binaries. We have identified one candidate binary with a separation of 53 milliarcsec, about the width of the diffraction limited point-spread function (PSF). Sub-resolution-element detection of binaries is possible with HST because of the high signal-to-noise ratio of the observations and the stability of the PSF. Identification and confirmation of binary Trojans is important because a Trojan Tour is one of five possible New Frontiers missions. A binary could constitute a potentially high value target because of the opportunity to study two objects and to test models of the primordial nature of binaries. The potential to derive mass-based physical information from the binary orbit could yield more clues to the origin of Trojans.
  60. Penteado, P., Trilling, D., Grundy, W., 2015, DPS, 47, 211.06, Constraints to the Cold Classical KBO population from HST observations of faint objects
    The size distribution of the known Kuiper Belt Objects has been described by a double power law, with a break at R magnitude 25. There are two leading interpretations to this break: 1) It is the result of the collisional evolution among these KBOs, with the objects smaller than the break being the population most affected by collisional erosion. 2) The size distribution break is primordial, set during the Kuiper Belt formation.The low inclination Kuiper Belt Objects, the Cold Classical population, is thought to have been dynamically isolated since the formation of the Solar System, and thus only collisions between Cold Classicals would have affected their size distribution. If the size distribution is collisional, it probes parameters of the Kuiper Belt history: strengths of the bodies, impact energies and frequency, and the the number of objects. If the distribution is primordial, it reveals parameters of the Kuiper Belt accretion, as well as limits on its subsequent collisional history.In this work, we obtained new HST observations of 5 faint Cold Classicals, which we combine with previous HST observations, to examine the distribution of two properties of the smallest KBOs: colors and binary fraction. These two properties can differentiate between a primordial and a collisional origin of the size distribution break. If the smaller bodies have been through extensive collisional evolution, they will have exposed materials from their interiors, which has not been exposed to weathering, and thus should be bluer than the old surfaces of the larger bodies. An independent constraint can be derived from the fraction of binary objects: the angular momentum of the observed binaries is typically too high to result from collisions, thus a collisionally-evolved population would have a lower binary fraction, due to the easier separation of binaries, compared to the disruption of similar-sized bodies, and the easier disruption of the binary components, due to the smaller size.We will present the constraints to the color and binary fraction distributions we are measuring from these observations, which probe the smallest KBOs currently observable.
  61. Killen, R., Bida, T., 2015, DPS, 47, 215.01, Observations of the minor species Al, Fe and Ca+ in Mercurys exosphere
    We report here on the first observational evidence of Al and Fe in the exosphere of Mercury, based on measurements of 4-5- resolved emission lines of these metals with Keck-1/HIRES. AlI emission was observed on two separate runs, in 2008 and 2013, with tangent column densities of 2.4 and 3 x 107 Al atoms cm-2 at altitudes of 1300 and 1850 km (1.1 and 1.5 RM), respectively. FeI emission has been observed once, yielding a tangent column of 6.2 x 108 cm-2 at an altitude of 950 km (1.4 RM) in 2009. We also present observations of 3.5- Ca+ emission features near Mercurys equatorial anti-solar limb in 2011, from which a stringent tangent column abundance of 4.0 x 106 cm-2 is derived for the Ca ion.A simple model for zenith column abundances of the neutral species yields 2.0 x 107 Al cm-2, and 8.2 x 108 Fe cm-2. The observations appear to be consistent with production of these species by impact vaporization, with a large fraction of the Al ejecta in molecular form, and that for Fe in mixed atomic and molecular forms. The scale height of the Al gas is consistent with a kinetic temperature of 4800-8200 K while that of Fe is 5000-13000 K. The apparent high temperature and low density of the Al gas would suggest that it may be produced by dissociation of molecules. A large fraction of both Al and Fe appear to condense in a vapor cloud at low altitudes.
  62. Binzel, R., DeMeo, F., Burt, B., et al., (including Moskovitz, N.), 2015, DPS, 47, 301.03, Main-Belt Source Regions for Potentially Hazardous Near-Earth Asteroids and Sample Return Targets
    Spectroscopic and taxonomic information is now available for more than 1000 near-Earth objects (NEOs), thanks in large measure to the NASA IRTF long-term NEO spectral reconnaissance program we call the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) [1]. This sample comprises about 10% of the total NEO population, including Potentially Hazardous Asteroids (PHAs), and finds that all defined main-belt asteroid classes are also present within the near-Earth population. Using this largest available NEO dataset and dynamic source region models (such as [2]) we will present new results on the provenance of PHAs, source regions for each of the asteroid taxonomic classes, and pinpoint sources for major meteorite classes such as H, L, and LL ordinary chondrites. In finding these correlations, we find that source region signatures for B-, C-, and Cg-type NEOs include Jupiter family comets, further adding interest to the sampling of these classes by impending missions [3, 4]. This work is supported by the National Science Foundation Grant 0907766 and NASA Grant NNX10AG27G.[1] Tokunaga, A. et al. (2006) BAAS 38, 59.07. [2] Bottke, W.F. et al. (2002), Icarus 156, 399. [3] Lauretta, D. S. et al. (2015), MAPS 50, 834. [4] Abe, M. et al. (2012) 39th COSPAR, Abstract H0.2-7-12.
  63. Hinkle, M., Moskovitz, N., Trilling, D., et al., 2015, DPS, 47, 301.04, The Bias-Corrected Taxonomic Distribution of Mission-Accessible Small Near-Earth Objects
    Although they are thought to compose the majority of the Near-Earth object (NEO) population, the small (d < 1 km) near-Earth asteroids (NEAs) have not yet been studied as thoroughly as their larger cousins. Sub-kilometer objects are amongst the most abundant newly discovered NEOs and are often targets of opportunity, observable for only a few days to weeks after their discovery. Even at their brightest (V ~ 18), these asteroids are faint enough that they must be observed with large ground-based telescopes.The Mission Accessible Near-Earth Object Survey (MANOS) began in August 2013 as a multi-year physical characterization survey that was awarded survey status by NOAO. MANOS will target several hundred mission-accessible NEOs across visible and near-infrared wavelengths, ultimately providing a comprehensive catalog of physical properties (astrometry, light curves, spectra).Fifty-seven small, mission-accessible NEAs were observed between mid 2013 and mid 2015 using GMOS at Gemini North & South observatories as well as the DeVeny spectrograph at Lowell Observatory's Discovery Channel Telescope. Archival data of 43 objects from the MIT-UH-IRTF Joint Campaign for NEO Spectral Reconnaissance (PI R. Binzel) were also used. Taxonomic classifications were obtained by fitting our spectra to the mean reflectance spectra of the Bus asteroid taxonomy (Bus & Binzel 2002). Small NEAs are the likely progenitors of meteorites; an improved understanding of the abundance of meteorite parent body types in the NEO population improves understanding of how the two populations are related as well as the biases Earth's atmosphere imposes upon the meteorite collection.We present classifications for these objects as well as results for the debiased distribution of taxa(as a proxy for composition) as a function of object size and compare to the observed fractions of ordinary chondritemeteorites and asteroids with d > 1 km. Amongst the smallest NEOs we find an unexpected distribution of taxonomic types that differs from both large NEOs and meteorites.We acknowledge funding support from NASA NEOO grant number NNX14AN82G.
  64. DeMeo, F., Polishook, D., Carry, B., et al., (including Moskovitz, N.), 2015, DPS, 47, 301.08, Olivine-rich asteroids in the main asteroid belt
    Olivine-dominated asteroids, classified as A-types with near-infrared spectral measurements are largely thought to be the mantle remnants of disrupted differentiated small bodies. These A-type asteroids hold clues to asteroid differentiation and to the collisional history of those differentiated bodies. Preliminary studies of the abundance and distribution of A-type asteroids were performed by Carvano et al. (2010) and DeMeo & Carry (2013, 2014) using the Sloan Digital Sky Survey (SDSS). To confidently identify these olivine-dominated A-type asteroids, however, near-infrared spectral measurements are needed to identify the distinct broad and deep 1-micron olivine absorption feature. Using the Sloan Digital Sky Survey Moving Object Catalog to select A-type asteroid candidates, we have performed a near-infrared spectral survey of over 70 asteroids with SpeX on the IRTF. We present the abundance and distribution of A-type asteroids throughout the main asteroid belt and compare these results with similar surveys for basalt-rich V-type asteroids (e.g. Moskovitz et al. 2008). This work is supported by NASA under grant number NNX12AL26G issued through the Planetary Astronomy Program.
  65. Tuttle Keane, J., Siu, H., Moskovitz, N., et al., 2015, DPS, 47, 307.09, Surprise! The oft-ignored Moon might actually be important for changing the spins of asteroids during Earth flybys
    Analysis near-Earth asteroid archival data has revealed that asteroids with Earth MOIDs (minimum orbit intersection distance; a proxy for flyby distance) smaller than 1.0-1.5 lunar distances have a systematically larger dispersion in spin rate than more distant flybys (Siu, et al. 2015, DPS). While tidal torques during close encounters are expected to alter the spin states of asteroids (e.g. Scheeres et al. 2000, Icarus), there is no intrinsic reason to expect the observed sharp transition in spin rate distribution at 1.0-1.5 lunar distances, as tidal forces drop off smoothly with distance.While the Moon itself is too diminutive to directly alter the spin-states of asteroids, we show that its presence is enough to significantly affect asteroid encounter trajectories. Asteroids entering the Earth-Moon system are subject to three-body dynamics (due to the combined gravitational effects of the Earth and Moon). Depending on the flyby geometry, the Moon can act as a temporary sink for the asteroid's geocentric orbital energy. This allows some fraction of asteroids to have closer approaches with the Earth than expected when considering the Earth-Moon barycenter alone. In rare cases (~0.1%) this process enables the capture of temporary moons around the Earth (Granvik et al. 2012, Icarus). Asteroids that undergo these "enhanced" flybys can have both closer-than-expected encounter distances (resulting in more significant tidal perturbations), and repeated encounters with the Earth and Moon before leaving the system (resulting in the accumulation of multiple tidal interactions). By numerically solving the circular restricted three-body problem, we show that this process naturally produces a sharp transition in the asteroid population: asteroids with MOIDs less than 1.5 lunar distances can undergo these enhanced close approaches, possibly explaining the sharp transition in the dispersion of asteroid spin rates at this distance. Future work will investigate the efficiency of this process, and the relationship between the physical response of the asteroid to tidal perturbations and the statistical distribution of asteroid spin rates.
  66. Cibulkova, H., Durech, J., Kaasalainen, M., et al., (including Bowell, E.), 2015, DPS, 47, 307.10, Distributions of spin axes and shapes of asteroids
    We developed a new simplified model for the determination of shapes and spin states of asteroids to fully exploit photometric data sparse in time (few measurements per night) which are produced by all-sky surveys and were re-calibrated into the Lowell photometric database by Bowell et al. (2014). We model asteroids as geometrically scattering triaxial ellipsoids. The model compares observed values of mean brightness and the dispersion of brightness with computed values obtained from the parameters of the model - ecliptical longitude and latitude of the pole and the ratio a/b of axes of the ellipsoid. These parameters are optimized to get the best agreement with the observation. We revealed that the distribution of for the main-belt asteroids is anisotropic (in agreement with findings of Bowell et al. (2014)) and dependent on the inclination of orbit (for sin i < 0.04 there is an excess of ~ 70 +/- 180). We are looking for a physical or observational mechanism that would explain this distribution. From the analysis of the distribution of a/b we found that larger asteroids (D > 25 km) are more often spherical (a/b ~ 1) than the smaller.
  67. Mommert, M., Harris, A., Mueller, M., et al., (including Knight, M.), 2015, DPS, 47, 308.04, Dormant Comets in the Near-Earth Asteroid Population
    The population of near-Earth objects comprises active comets and asteroids, covering a wide range of dynamical parameters and physical properties. Dormant (or extinct) comets, masquerading as asteroids, have long been suspected of supplementing the near-Earth asteroid (NEA) population. We present a search for asteroidal objects of cometary origin based on dynamical and physical considerations. Our study is based on albedos derived within the ExploreNEOs program and is extended by adding data from NEOWISE and the Akari asteroid catalog. We use a statistical approach to identify asteroids on orbits that resemble those of short-period near-Earth comets using the Tisserand parameter with respect to Jupiter, the aphelion distance, and the minimum orbital intersection distance with respect to Jupiter. We identify a total of 23 near-Earth asteroids from our sample that are likely to be dormant short-period near-Earth comets and, based on a de-biasing procedure applied to the cryogenic NEOWISE survey, estimate both magnitude-limited and size-limited fractions of the NEA population that are dormant short-period comets. We find that 0.3-3.3% of the NEA population with H <= 21, and 9(+2/-5)% of the population with diameters d >= 1 km, are dormant short-period near-Earth comets. We also present an observation program that utilizes the 1.8m Vatican Advanced Technology Telescope (VATT) on Mt. Graham, AZ, to identify dormant comet candidates and search for activity in these objects. Our targets are NEAs on comet-like orbits, based on the dynamical criteria derived in the above study, that are accessible with the VATT (V <= 22). We identify dormant comets based on their optical spectral slope, represented by V-R color measurements, as albedo measurements for most of these objects are not available. For each target we measure and monitor its V magnitude in order to reveal activity outbreaks. We also search for extended emission around our targets using deep imaging and a point-spread-function subtraction technique that allows us to obtain an upper limit on the dust production rate in each target. We present preliminary results from this program. This work is supported in part by funding from the Spitzer Science Center.
  68. Moskovitz, N., Avner, L., Binzel, R., et al., (including Burt, B., Schottland, R., Thirouin, A., Wasserman, L.), 2015, DPS, 47, 308.10, The Mission Accessible Near-Earth Object Survey (MANOS) First Results
    The Mission Accessible Near-Earth Object Survey (MANOS) began in August 2013 as a multi-year physical characterization survey that was awarded survey status by NOAO and has since expanded operations to include facilities at Lowell Observatory and the University of Hawaii. MANOS will target several hundred mission-accessible NEOs across visible and near-infrared wavelengths, providing a comprehensive catalog of physical properties (astrometry, light curves, spectra). Particular focus is paid to sub-km NEOs, where little data currently exists. These small bodies are essential to understanding the link between meteorites and asteroids, pose the most immediate impact hazard to the Earth, and are highly relevant to a variety of planetary mission scenarios. Observing these targets is enabled through a combination of classical, queue, and target-of-opportunity observations carried out at 1- to 8-meter class facilities in both the northern and southern hemispheres. The MANOS observing strategy enables the characterization of roughly 10% of newly discovered NEOs before they fade beyond observational limits.To date MANOS has obtained data on over 200 sub-km NEOs and will ultimately provide major advances in our understanding of the NEO population as a whole and for specific objects of interest. Here we present first results from the survey including: (1) the de-biased taxonomic distribution of spectral types for NEOs smaller than ~100 meters, (2) the distribution of rotational properties for small objects with high Earth-encounter probabilities, (3) progress in developing a new set of online tools at asteroid.lowell.edu that will help to facilitate observational planning for the small body observer community, and (4) physical properties derived from rotational light curves.MANOS is supported through telescope allocations from NOAO, Lowell Observatory and the University of Hawaii. We acknowledge funding support from NASA NEOO grant number NNX14AN82G and an NSF Astronomy and Astrophysics Postdoctoral Fellowship to N. Moskovitz.
  69. Thomas, C., Lim, L., Moskovitz, N., et al., 2015, DPS, 47, 308.13, Searching for a Differentiated Asteroid Family: A Spectral Survey of the Massalia, Merxia, and Agnia Families
    Asteroid families were formed by catastrophic collisions or large cratering events that caused fragmentation of the parent body and ejection of asteroidal fragments with velocities sufficient to prevent re-accretion. Due to these formation processes, asteroid families should provide us with the opportunity to probe the interiors of the former parent bodies. Differentiation of a large initially chondritic parent body is expected to result in an "onion shell" object with an iron-nickel core, a thick olivine-dominated mantle, and a thin plagioclase/pyroxene crust. However, most asteroid families tend to show similar spectra (and therefore composition) among the members. Spectroscopic studies have observed a paucity of metal-like materials and olivine-dominated assemblages within the Main Belt asteroid families.The deficit of olivine-rich mantle material in the meteorite record and in asteroid observations is known as the "Missing Mantle" problem. For years the best explanation has been the "battered to bits" hypothesis: that all differentiated parent bodies (aside from Vesta) were disrupted very early in the Solar System and the resulting olivine-rich material was collisionally broken down over time until the object diameters fell below our observational limits. In a competing hypothesis, Elkins-Tanton et al. (2013) have suggested that previous work has overestimated the amount of olivine produced by the differentiation of a chondritic parent body.We are conducting a visible and near-infrared wavelength spectral survey of asteroids in the Massalia, Merxia, and Agnia S-type Main Belt asteroid families. These families were carefully chosen for the proposed spectroscopic survey because they have compositions most closely associated with a history of thermal metamorphism and because they represent a range of collisional formation scenarios. In addition, the relatively young ages (under 400 Myr) of these families permit testing of the battering to bits'' timescale. We will present initial results from our ongoing spectral survey of these three Main Belt families and discuss evidence for differentiation among the family members.We acknowledge funding support from the NASA Planetary Astronomy program.
  70. Hora, J., Trilling, D., Mommert, M., et al., (including Moskovitz, N.), 2015, DPS, 47, 312.21, The (new) Mid-Infrared Spectrometer and Imager (MIRSI) for the NASA Infrared Telescope Facility
    The Mid-Infrared Spectrometer and Imager (MIRSI) was developed at Boston University and has been in use since 2002 on the Infrared Telescope Facility (IRTF), making observations of asteroids, planets, and comets in the 2 - 25 m wavelength range. Recently the instrument has been unavailable due to electronics issues and the high cost of supplying liquid helium on Maunakea. We have begun a project to upgrade MIRSI to a cryocooler-based system with new array readout electronics and a dichroic and optical camera to simultaneously image the science field for image acquisition and optical photometry. The mechanical cryocooler will enable MIRSI to be continuously mounted on the IRTF multiple instrument mount (MIM) along with the other facility instruments, making it available to the entire community for multi-wavelength imaging and spectral observations. We will propose to use the refurbished MIRSI to measure the 10 m flux from Near Earth Objects (NEOs) and determine their diameters and albedos through the use of a thermal model. We plan to observe up to 750 NEOs over the course of a three year survey, most of whose diameters will be under 300 meters. Here we present an overview of the MIRSI upgrade and give the current status of the project.This work is funded by the NASA Solar System Observations/NEOO program.
  71. Polishook, D., Moskovitz, N., Binzel, R., et al., (including Thirouin, A.), 2015, DPS, 47, 402.02, Challenging the wall of fast rotating asteroids - constraining internal cohesive strength for MBAs and NEAs
    We report an observation of a 2 km size main belt asteroid (MBA), (60716) 2000 GD65, with a lightcurve indicating a rotation period of 1.95290.0002 hours, i.e. challenging the rubble pile spin barrier. This adds to a handful of MBAs, recently observed by the Palomar Transient Factory (PTF) survey (Chang et al. 2014, 2015), with diameters between 0.5-1.5 km and lightcurves indicating rotation periods of 1.2-1.9 hours. These asteroids are relatively large compared to the population of small near-Earth asteroids (NEAs; D<300 m) that can reach rotation periods as fast as 15.797 seconds as is the case of NEA 2014 RC (Moskovitz and MANOS team).We apply the Holsapple (2007) model to these two distinct populations in order to constrain the cohesion within these objects and to search for monolithic asteroids. We use the lightcurves amplitude as indication of the triaxial shape ratio a/b, and assume b/c=1 (i.e. a>b=c). While the density is a free parameter, the given cohesion is the average of values for density ranges between 1.5 to 2.5 gr cm^-3, which are measured density values for asteroids (Carry 2012).We find that the fast rotating MBAs must have internal cohesive strength of at least ~25 to ~250 Pa in order to prevent disruption against centrifugal acceleration. Similar cohesion values have been found within lunar soils (100-1000 Pa; Mitchell et al. 1974). However, since only a few MBAs rotate so quickly, such internal cohesive strength might be rare within the population of km-size MBAs. Among NEAs, about 25% have minimal constrained cohesion values similar to those found for the fast rotating MBAs. Approximately 65% have no need for substantial cohesion values >25 Pa. Only ~10% of NEAs must have substantial internal cohesion of over 1000 Pa to prevent disruption, however none of them are rotating fast enough to require a fully monolithic body, i.e. cohesion >10 kPa.
  72. Chit Siu, H., Keane, J., Moskovitz, N., et al., 2015, DPS, 47, 402.03, Effects of Earth Encounters on the Rotational Properties of Near-Earth Objects
    The effects of Earth encounters on the physical properties of near-Earth objects (NEOs) have been shown to be significant factors in their evolution. Previous studies have examined the effects of these encounters on reflectance spectra, and effects such as spin state and shape changes have been studied for specific asteroids and through simulation. In this study, archive data from previous NEO surveys were used to investigate rotational frequencies as a function of minimum orbit intersection distance (MOID), which we use as a proxy for Earth encounter likelihood.When comparing objects of similar sizes, we find a highly significant difference in the dispersion of rotational frequency (p < 0.01; significant at a >99% confidence level) between NEO populations that were likely to have had an Earth encounter and those that are less likely to have had such an encounter. The encounter/non-encounter distinction is found at a dividing MOID value of 1 lunar distance (LD). These results were robust to changes in the size of the moving average window, as well as to removal of the smallest objects from the encounter population and the largest objects from the non-encounter population, which would be most strongly affected by a known size/spin period bias where smaller objects tend to have shorter periods. There was no statistically significant difference in the mean rotation rates of encounter and non-encounter objects, however, indicating that encounters cause greater dispersion, but do not preferentially spin objects up or down at a detectable level. Recent modeling work also lends credibility to the idea that NEO interactions with the Earth-Moon system as a whole may be leading to the dispersion difference boundary at 1 LD (Keane et al. 2015, DPS).
  73. Steffl, A., Feldman, P., A'Hearn, M., et al., (including Knight, M.), 2015, DPS, 47, 413.08, Dust Outbursts From Comet 67P/Churyumov-Gerasimenko Observed by Rosetta-Alice
    The comet 67P/Churyumov-Gerasimenko, passed through perihelion on 13 August 2015. In the weeks surrounding the perihelion passage, several dramatic outbursts of dust have been observed by instruments aboard ESAs Rosetta spacecraft. These outbursts are typically intense and short-lived, with timescales on the order of several tens of minutes to a few hours. We report on the two largest of these dusty outbursts observed by the Alice far-ultraviolet (700-2050A) spectrograph, which occurred on 10 July 2015 and 22 August 2015. On 10 July 2015 02:06 UTC, Alice spectra of the sunward limb, nucleus and anti-sunward limb show typical levels of dust-scattered sunlight, with the sunward limb 3-4x brighter than the anti-sunward limb. Beginning around 02:10 UTC, the dust on the anti-sunward side of the nucleus brightened rapidly, increasing by a factor of 21 over pre-outburst levels, when integrated over a 10-minute exposure. A 40s exposure beginning at 02:20 showed an additional factor of two increase in brightness. During the outburst, the dust became significantly brighter than the sunlit nucleus. Concurrent NAVCAM images show a large dust cloud expanding out from the night side of the nucleus. Despite this forty-fold increase in dust brightness, the Alice data show no evidence of enhancements of H2O, CO, CO2, O2, O, or H in the post-outburst spectra. By 04:24 UTC, after a 2-hour data gap, the comet had returned to pre-event levels. Although complicated by the scanning motion of the spacecraft, the start of Alice observations on 22 August 2015 revealed a major dust outburst in progress, this time confined to the sunward side of the nucleus. Between 07:03 and 07:54, the brightness of dust on the sunward side faded by a factor of 7. NAVCAM images from this period also show a dramatic fan-shaped cloud of dust. Unlike the 10 July event, the 22 August event shows some evidence of increased gas emissions.
  74. Hines, D., Levasseur-Regourd, A., Hadamcik, E., et al., (including Knight, M.), 2015, DPS, 47, 413.13, Hubble Space Telescope Imaging Polarimetry of Comet 67P/Churyumov-Gerasimenko Obtained During the Rosetta Mission
    We present pre- and post-perihelion, high-spatial resolution (0.05 arcsec/pixel) 0.6 micron imaging polarimetry of Comet 67P/Churyumov-Gerasimenko taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope (HST). The pre-perihelion observations were obtained at two epochs chosen to bracket the times when the closest orbits of Rosetta were flown (down to 10 km for extended periods: 2014-Aug-19: rh = 3.52 au, = 2.76 au, 12.0) and the Philae landing took place (2014-Nov-17: rh = 2.96 au, = 3.43 au, 15.7). Our preliminary analyses of both pre-perihelion epochs shows that the polarization position angle lies in the scattering plane, thus is negative, with a degree of polarization p% -2%. The two post-perihelion epochs were matched to the first time after perihelion that the comet was observable with HST (2015-Oct-10: rh = 1.43 au, = 1.80 au, 33.5), and when the comet was again viewed at small phase angle (2016-Feb-19: rh = 2.40 au, = 1.49 au, 12.0). We discuss our polarimetry results in context with in situ measurements of dust particles obtained with the Rosetta spacecraft.
  75. Samarasinha, N., Lejoly, C., Barrera, J., et al., (including Schleicher, D.), 2015, DPS, 47, 415.05, Comparing CN Features in Two Comets: 1P/Halley and 103P/Hartley 2
    Comets 1P/Halley and 103P/Hartley 2 show distinct CN features in their respecive comae. Both comets are non-principal-axis rotators. 1P/Halley is the proto-type for Halley-type comets with the Oort Cloud as its possible source region, whereas 103P/Hartley 2 is a Jupiter-Family comet that possibly originated from the Kuiper Belt. Both comets were spacecraft targets and studied widely from both space and from the ground.We will discuss the properties of CN features, and in particular the behavior of the derived outflow velocities based on the CN features present in the groundbased coma images of these two comets. The corresponding heliocentric distances for CN images of comet 1P/Halley range from approximately 0.8 AU to 2.0 AU (during its post-perihelion leg of the 1986 apparition). For CN images of comet 103P/Hartley 2, the corresponding heliocentric distances range from 1.31 AU through the perihelion (at 1.06 AU) to 1.25 AU (during its 2010 apparition).Ultimately, these results will be used to understand the rotational states and the activity behaviors of these two comets.
  76. Hui, M., Ye, Q., Manning Knight, M., et al., 2015, DPS, 47, 415.18, Gone in a Blaze of Glory: the Demise of Comet C/2015 D1 (SOHO)
    We present studies of C/2015 D1 (SOHO), the first sunskirting comet ever seen from ground stations over the past half century. The Solar and Heliospheric Observatory (SOHO) witnessed its peculiar light curve with a huge dip followed by a flareup around perihelion: the dip was likely caused by sublimation of olivines, directly evidenced by a coincident temporary disappearance of the tail. The flareup likely reflects a disintegration event, which we suggest was triggered by intense thermal stress established within the nucleus interior. Photometric data reveal an increasingly dusty coma, indicative of volatile depletion. A catastrophic mass loss rate of ~105 kg s-1 around perihelion was seen. Ground-based Xingming Observatory spotted the post-perihelion debris cloud. Our morphological simulations of post-perihelion images find newly released dust grains of size a >~ 15 m in radius, however, a temporal increase in amin was also witnessed, possibly due to swift dispersions of smaller grains swept away by radiation forces without replenishment. Together with the fading profile of the light curve, a power law dust size distribution with index = 3.2 0.1 is derived. We detected no active remaining cometary nuclei over ~0.1 km in radius in post-perihelion images acquired at Lowell Observatory. Applying radial non-gravitational parameter, A1 = (1.209 0.118) 10-6 AU day-2, from an isothermal water-ice sublimation model to the SOHO astrometry significantly reduces residuals and sinusoidal trends in the orbit determination. The nucleus mass ~108--109 kg, and the radius ~50--150 m (bulk density d = 0.4 g cm-3 assumed) before the disintegration are deduced from the photometric data; consistent results were determined from the non-gravitational effects.
  77. Feaga, L., Feldman, P., A'Hearn, M., et al., (including Knight, M.), 2015, DPS, 47, 503.06, Comet 67P/Churyumov-Gerasimenkos Increasing Atomic Sulfur Abundance Observed by Rosetta Alice
    Alice, NASAs lightweight and low-power far-ultraviolet (FUV) imaging spectrograph onboard ESAs comet orbiting spacecraft Rosetta (Stern et al. 2007), is continuing its characterization of the nucleus and coma of the Jupiter family comet 67P/Churyumov-Gerasimenko (C-G) as it approaches and recedes from perihelion. With a spectral range from 700-2050 A, Alice has the ability to detect the atomic sulfur multiplets at 1429 A, 1479 A and 1814 A. Sulfur in C-Gs coma is most likely a dissociation product of CS2 and OCS, but could also be produced after a secondary dissociation from H2S and SO2, all molecular species measured in C-Gs coma by ROSINA, the Rosetta orbiters mass spectrometer.Due to low abundances, Alice did not detect sulfur atoms at C-G until May 2015 when the comet was at ~1.7 AU and still 3 months from perihelion. Now, sulfur is ubiquitous in Alice observations above the limb of the nucleus. There is evidence that there is not a strong dependence of the abundance of sulfur on the distance from the nucleus in the pre-perihelion radial profiles of the gas, which may be indicative of the parent molecule and its distribution. This will be investigated further. The evolution of the presence of the three sulfur multiplets, their relative abundances and excitation processes, and behavior pre- and post-perihelion will be presented.
  78. Knight, M., Fitzsimmons, A., Kelley, M., et al., 2015, DPS, 47, 506.11, 322P/SOHO 1: Sunskirting Comet or Asteroid?
    Comet 322P/SOHO 1 (P/1999 R1) is a unique object: a short period comet (P = 3.99 yr) on a sunskirting orbit (q = 0.053 AU, or ~11 solar radii) with no dynamical linkage to any other known comets. 322P was discovered in SOHO images in 1999, and has been seen by SOHO on every subsequent orbit: 2003, 2007, and 2011 (it is expected to be observed by SOHO again during its next perihelion passage in 2015 September). During this time it has not displayed an obvious coma or tail in SOHO images, but has exhibited a non-asteroidal lightcurve that strongly suggests the presence of an unresolved coma. Equilibrium temperatures during these observations exceed 1000 K, so it is unclear if 322P is active due to sublimation of volatile ices like a typical comet or if it is an otherwise inactive object that is losing material through more exotic processes such as sublimation of refractory materials or thermal fracturing. Due to the very large uncertainty in orbits derived from SOHO observations and 322Ps assumed small size, 2015 was the first reasonable opportunity to recover it at large heliocentric distance and attempt to determine its heritage: traditional comet or asteroid. We recovered 322P on 2015 May 22 with the VLT and observed it again on five epochs in June and July with Spitzer, the VLT, and the Discovery Channel Telescope. These are the first successful observations of any SOHO-discovered short period comet at traditional cometary distances. 322P appeared pointlike in all images (heliocentric distances from 2.1 to 1.2 AU), implying an inactive object having a diameter of a few hundred meters. We will report on these observations, focusing on constraining properties of 322P such as activity level, color, and albedo that may help us deduce whether or not it is of a cometary or asteroidal origin.
  79. Holler, B., Young, L., Grundy, W., et al., 2015, DPS, 47, 508.09, Composition and evolution of Triton's icy surface between 2002-2014 from SpeX/IRTF
    We observed Triton in the near-infrared (0.7-2.5 m) over 63 nights using the SpeX instrument at NASA's Infrared Telescope Facility (IRTF) between 2002 and 2014. Tritons spectrum has absorption features due to N2, CO, CH4, CO2, and H2O in this wavelength range. We calculated the equivalent width (or fractional band depth for H2O) of select absorption bands in each of the 63 night-averaged spectra. Longitudinal distributions for the volatile ices (N2, CO, CH4) show large rotational amplitude, while the non-volatile ices (CO2, H2O) show little amplitude over one Triton rotation. Absorption from N2 and CH4 increased over the period of the observations, whereas absorption from the non-volatile ices remained constant. The sub-solar latitude on Triton is currently at -42 degrees south, so some areas of Triton are visible for a full rotation. Combined with our findings, this suggests that the southern latitudes are dominated by non-volatile ices, with larger concentrations of volatile ices found in the observable region north of the equator. Changing viewing geometry over the period of the observations explains the increase in volatile absorption: As the sub-solar point moves northwards, more of the volatile-rich northern regions are coming directly into view. Geological evidence from Voyager 2 pointed to a southern hemisphere dominated by volatile ices; significant changes have occurred over the intervening quarter century.
  80. Pal, A., Kiss, C., Horner, J., et al., (including Thirouin, A.), 2015, A&A, 583, A93, Physical properties of the extreme Centaur and super-comet candidate 2013 AZ60
    We present estimates of the basic physical properties including size and albedo of the extreme Centaur 2013 AZ60. These properties have been derived from optical and thermal infrared measurements. Our optical measurements revealed a probable full period of 9.4 h with a shallow amplitude of 4.5%. By combining optical brightness information and thermal emission data, we are able to derive a diameter of 62.3 5.3 km and a geometric albedo of 2.9%, which corresponds to an extremely dark surface. Additionally, our finding of 50 Jm-2 K-1 s- 1/2 for the thermal inertia is also remarkable for objects in such a distance. The results of dynamical simulations yield an unstable orbit, with a 50% probability that the target will be ejected from the solar system within 700 000 yr. The current orbit of this object and its instability could imply a pristine cometary surface. This possibility agrees with the observed low geometric albedo and red photometric colour indices for the object, which match the surface of a dormant comet well, as would be expected for a long-period cometary body approaching perihelion. Although it was approaching ever closer to the Sun, however, the object exhibited star-like profiles in each of our observations, lacking any sign of cometary activity. According to the albedo, 2013 AZ60 is a candidate for the darkest body among the known trans-Neptunian objects.
  81. Schindler, K., 2015, enas, 1406, Lowell, Percival
    No abstract found.
  82. Egeland, R., Metcalfe, T., Hall, J., et al., 2015, ApJ, 812, 12, Sun-like Magnetic Cycles in the Rapidly-rotating Young Solar Analog HD 30495
    A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial (2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, a 1 Gyr old G1.5 V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at 1.7 years and a long cycle of 12 years. We measure three individual long-period cycles and find durations ranging from 9.6 to 15.5 years. We find the short-term variability to be intermittent, but present throughout the majority of the time series, though its occurrence and amplitude are uncorrelated with the longer cycle. These essentially solar-like variations occur in a Sun-like star with more rapid rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence.
  83. Kokotanekova, R., Lacerda, P., Snodgrass, C., et al., (including Thirouin, A.), 2015, EPSC, EPSC2015-433, A Magnitude Limited Survey of the Rotational Properties of Kuiper Belt Objects
    We will present the first results from a magnitudelimited survey of over 60 Kuiper belt objects (KBOs) observed within a Large Program at the 3.6-m ESO New Technology Telescope (NTT). The multi-band observations are used to obtain lightcurves for targets from all KBO dynamical classes. We are aiming to derive the individual targets' physical and rotational characteristics as well as to use the bulk properties of the different KBO populations as sources of information for their formation mechanisms and collisional history.
  84. Duffard, R., Alvarez-candal, A., Pinilla-Alonso, N., et al., (including Thirouin, A.), 2015, EPSC, EPSC2015-717, Absolute magnitudes of trans-neptunian objects
    Accurate measurements of diameters of trans- Neptunian objects are extremely complicated to obtain. Radiomatric techniques applied to thermal measurements can provide good results, but precise absolute magnitudes are needed to constrain diameters and albedos. Our objective is to measure accurate absolute magnitudes for a sample of trans- Neptunian objects, many of which have been observed, and modelled, by the "TNOs are cool" team, one of Herschel Space Observatory key projects grantes with ~ 400 hours of observing time. We observed 56 objects in filters V and R, if possible. These data, along with data available in the literature, was used to obtain phase curves and to measure absolute magnitudes by assuming a linear trend of the phase curves and considering magnitude variability due to rotational light-curve. In total we obtained 234 new magnitudes for the 56 objects, 6 of them with no reported previous measurements. Including the data from the literature we report a total of 109 absolute magnitudes.
  85. Buie, M., Keller, J., Wasserman, L., 2015, EPSC, EPSC2015-845, RECON - A new system for probing the outer solar system with stellar occultations
    The Research and Education Collaborative Occultation Network (RECON) is a new system for coordinated occultation observations of outer solar system objects. Occultations by objects in the outer solar system are more difficult to predict due to their large distance and limited duration of the astrometric data used to determine their orbits and positions. This project brings together the research and educational community into a unique citizen-science partnership to overcome the difficulties of observing these distant objects. The goal of the project is to get sizes and shapes for TNOs with diameters larger than 100 km. As a result of the system design it will also serve as a probe for binary systems with spatial separations too small to be resolved directly. Our system takes the new approach of setting up a large number of fixed observing stations and letting the shadows come to the network. The nominal spacing of the stations is 50 km. The spread of the network is roughly 2000 km along a roughly north-south line in the western United States. The network contains 56 stations that are committed to the project and we get additional ad hoc support from the International Occultation Timing Association. At our minimum size, two stations will record an event while the other stations will be probing for secondary events. Larger objects will get more chords and will allow determination of shape profiles. The stations are almost exclusively sited and associated with schools, usually at the 9-12 grade level. We have successfully completed our first TNO observation which is presented in the compainion paper by G. Rossi et al (this conference).
  86. Young, E., Skrutskie, M., Wasserman, L., et al., 2015, EPSC, EPSC2015-899, Pluto's Atmosphere at the Time of the New Horizons Flyby from the 29-JUN-2015 Occultation
    Pluto is expected to occult a star on 29-JUN-2015, only two weeks before the scheduled New Horizons flyby on Pluto on 14-JUL-2015. This occultation should be remarkable for several reasons in addition to its synergy with the spacecraft observations. First, the occulted star is by far the brightest ever to be observed in a Pluto occultation: its V-mag is 12.10 0.03, about ten times brighter than Pluto itself. We are deploying a wide array of telescopes to obtain quality lightcurves at 10 Hz, sufficient to resolve vertical atmospheric structure (e.g., gravity waves) at the 2.5-km scale over a range of radii from about 1195 to 1300 km. Second, we plan to obtain lighcurves in infrared wavelengths near 1.7 m, where the star's H-mag (about 11) is bright enough to provide useful signal-to-noise ratios, albeit at slower cadences near 1 Hz (about two points per scale height). The combination of simultaneous IR and visible wavelength lightcurves should address the decades-old question: is there haze in Pluto's atmosphere, and if so, what is its opacity? New Horizons should image haze layers in reflected light as the occultation quantifies haze extinction in transmitted light: the combination could potentially let us solve for haze phase functions. Third, the current predicted shadow path is centered over much of New Zealand. We plan to deploy three portable telescopes in New Zealand to locations that are candidates for observing central flashes. If successful, these lightcurves can tell us (a) the oblateness of Pluto's atmosphere and (b) the detailed density gradient profile at radii near 1215 km, which (in turn) is a function of trace abundances of CO and CH4 a few tens of km above Pluto's surface. We will report on lightcurves obtained on 29-JUN- 2015, the column abundance of Pluto's atmosphere just two weeks before the New Horizons flyby, the detection (or not) of haze, and - if central flashes are obtained - the oblateness of Pluto's atmosphere.
  87. Stern, S., Bagenal, F., Ennico, K., et al., (including Grundy, W.), 2015, Sci, 350, aad1815, The Pluto system: Initial results from its exploration by New Horizons
    The Pluto system was recently explored by NASAs New Horizons spacecraft, making closest approach on 14 July 2015. Plutos surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Plutos atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Plutos diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Plutos large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.
  88. Gouliermis, D., Thilker, D., Elmegreen, B., et al., (including Hunter, D.), 2015, MNRAS, 452, 3508, Hierarchical star formation across the ring galaxy NGC 6503
    We present a detailed clustering analysis of the young stellar population across the star-forming ring galaxy NGC 6503, based on the deep Hubble Space Telescope photometry obtained with the Legacy ExtraGalactic UV Survey. We apply a contour-based map analysis technique and identify in the stellar surface density map 244 distinct star-forming structures at various levels of significance. These stellar complexes are found to be organized in a hierarchical fashion with 95 per cent being members of three dominant super-structures located along the star-forming ring. The size distribution of the identified structures and the correlation between their radii and numbers of stellar members show power-law behaviours, as expected from scale-free processes. The self-similar distribution of young stars is further quantified from their autocorrelation function, with a fractal dimension of 1.7 for length-scales between 20 pc and 2.5 kpc. The young stellar radial distribution sets the extent of the star-forming ring at radial distances between 1 and 2.5 kpc. About 60 per cent of the young stars belong to the detected stellar structures, while the remaining stars are distributed among the complexes, still inside the ring of the galaxy. The analysis of the time-dependent clustering of young populations shows a significant change from a more clustered to a more distributed behaviour in a time-scale of 60 Myr. The observed hierarchy in stellar clustering is consistent with star formation being regulated by turbulence across the ring. The rotational velocity difference between the edges of the ring suggests shear as the driving mechanism for this process. Our findings reveal the interesting case of an inner ring forming stars in a hierarchical fashion.
  89. Zellem, R., Griffith, C., Pearson, K., et al., (including Biddle, L.), 2015, ApJ, 810, 11, XO-2b: A Hot Jupiter with a Variable Host Star That Potentially Affects Its Measured Transit Depth
    The transiting hot Jupiter XO-2b is an ideal target for multi-object photometry and spectroscopy as it has a relatively bright (V-mag = 11.25) K0V host star (XO-2N) and a large planet-to-star contrast ratio (Rp/Rs 0.015). It also has a nearby (31.21) binary stellar companion (XO-2S) of nearly the same brightness (V-mag = 11.20) and spectral type (G9V), allowing for the characterization and removal of shared systematic errors (e.g., airmass brightness variations). We have therefore conducted a multiyear (2012-2015) study of XO-2b with the University of Arizonas 61 (1.55 m) Kuiper Telescope and Mont4k CCD in the Bessel U and Harris B photometric passbands to measure its Rayleigh scattering slope to place upper limits on the pressure-dependent radius at, e.g., 10 bar. Such measurements are needed to constrain its derived molecular abundances from primary transit observations. We have also been monitoring XO-2N since the 2013-2014 winter season with Tennessee State Universitys Celestron-14 (0.36 m) automated imaging telescope to investigate stellar variability, which could affect XO-2bs transit depth. Our observations indicate that XO-2N is variable, potentially due to cool star spots, with a peak-to-peak amplitude of 0.0049 0.0007 R-mag and a period of 29.89 0.16 days for the 2013-2014 observing season and a peak-to-peak amplitude of 0.0035 0.0007 R-mag and 27.34 0.21 day period for the 2014-2015 observing season. Because of the likely influence of XO-2Ns variability on the derivation of XO-2bs transit depth, we cannot bin multiple nights of data to decrease our uncertainties, preventing us from constraining its gas abundances. This study demonstrates that long-term monitoring programs of exoplanet host stars are crucial for understanding host star variability.
  90. Dias-Oliveira, A., Sicardy, B., Lellouch, E., et al., (including Thirouin, A.), 2015, ApJ, 811, 53, Plutos Atmosphere from Stellar Occultations in 2012 and 2013
    We analyze two multi-chord stellar occultations by Pluto that were observed on 2012 July 18th and 2013 May 4th, and respectively monitored from five and six sites. They provide a total of fifteen light curves, 12 of which were used for a simultaneous fit that uses a unique temperature profile, assuming a clear (no haze) and pure N2 atmosphere, but allowing for a possible pressure variation between the two dates. We find a solution that satisfactorily fits (i.e., within the noise level) all of the 12 light curves, providing atmospheric constraints between 1190 km (pressure 11 bar) and 1450 km (pressure 0.1 bar) from Plutos center. Our main results are: (1) the best-fitting temperature profile shows a stratosphere with a strong positive gradient between 1190 km (at 36 K, 11 bar) and r = 1215 km (6.0 bar), where a temperature maximum of 110 K is reached; above it is a mesosphere with a negative thermal gradient of -0.2 K km-1 up to 1390 km (0.25 bar), where the mesosphere connects itself to a more isothermal upper branch around 81 K; (2) the pressure shows a small (6%) but significant increase (6 level) between the two dates; (3) without a troposphere, Plutos radius is found to be {R}{{P}}=1190\+/- 5 km. Allowing for a troposphere, RP is constrained to lie between 1168 and 1195 km; and (4) the currently measured CO abundance is too small to explain the mesospheric negative thermal gradient. Cooling by HCN is possible, but only if this species is largely saturated. Alternative explanations like zonal winds or vertical compositional variations of the atmosphere are unable to explain the observed mesospheric negative thermal gradient.

    Partly based on observations made with the ESO camera NACO at the Very Large Telescope (Paranal), under program IDs 089.C-0314(C) and 291.C-5016. The prediction uses observations made with the WFI camera at the 2.2 m Telescope, under program ID 079.A-9202(A).

  91. Rubio, M., Elmegreen, B., Hunter, D., et al., 2015, Natur, 525, 218, Dense cloud cores revealed by CO in the low metallicity dwarf galaxy WLM
    Understanding stellar birth requires observations of the clouds in which they form. These clouds are dense and self-gravitating, and in all existing observations they are molecular, with H2 the dominant species and carbon monoxide (CO) the best available tracer. When the abundances of carbon and oxygen are low compared with that of hydrogen, and the opacity from dust is also low, as in primeval galaxies and local dwarf irregular galaxies, CO forms slowly and is easily destroyed, so it is difficult for it to accumulate inside dense clouds. Here we report interferometric observations of CO clouds in the local group dwarf irregular galaxy Wolf-Lundmark-Melotte (WLM), which has a metallicity that is 13 per cent of the solar value and 50 per cent lower than the previous CO detection threshold. The clouds are tiny compared to the surrounding atomic and H2 envelopes, but they have typical densities and column densities for CO clouds in the Milky Way. The normal CO density explains why star clusters forming in dwarf irregulars have similar densities to star clusters in giant spiral galaxies. The low cloud masses suggest that these clusters will also be low mass, unless some galaxy-scale compression occurs, such as an impact from a cosmic cloud or other galaxy. If the massive metal-poor globular clusters in the halo of the Milky Way formed in dwarf galaxies, as is commonly believed, then they were probably triggered by such an impact.
  92. Schleicher, D., Bair, A., Sackey, S., et al., (including Alciatore Stinnett, L., Williams, R., Smith-Konter, B.), 2015, AJ, 150, 79, The Evolving Photometric Lightcurve of Comet 1P/Halleys Coma during the 1985/86 Apparition
    We present new analyses of the photometric lightcurve of Comet 1P/Halley during its 1985/86 apparition. As part of a worldwide campaign coordinated by the International Halley Watch (IHW), narrowband photometry using standardized filters was obtained with telescopes at 18 observatories. Following submissions to and basic reductions by the Photometry and Polarimetry Network of the IHW, we further reduced the resulting fluxes to production rates and, following temporal binning, created composite lightcurves for each species. These were used to measure how the apparent rotational period (7.35 days), along with its shape, evolved with time during the apparition. The lightcurve shape systematically varied from double-peaked to triple-peaked and back again every 8-9 weeks, due to Halley's non-principal axis (complex) rotation and the associated component periods. Unexpectedly, we found that a phase shift of one-half cycle also took place during this interval, and therefore the actual beat frequency between the component periods is twice this interval or 16-18 weeks. Preliminary modeling suggests that a single source might produce the entire post-perihelion lightcurve variability and associated evolution, and an additional source is probably also required to explain additional features before perihelion. The detailed evolution of the apparent period varied in a nonsmooth manner between 7.2 and 7.6 days, likely due to a combination of synodic effects and the interaction of solar illumination with isolated source regions on a body in complex rotation. The need to simultaneously reproduce each of these characteristics will provide very strong additional constraints on Halley's component periods associated with its complex rotation. To assist in these and future analyses, we created a synthetic lightcurve based directly on the measured data and how the lightcurve shape evolved week to week. This synthetic lightcurve was successfully compared to other data sets of Halley and provides a valuable estimate of Halley's activity even when no narrowband photometry measurements were obtained. We unexpectedly discovered a strong correlation of start times of ion tail disconnection events with minima in the comet's gas production, implying that a decrease in outgassing is another cause of these events.
  93. Grundy, W., Porter, S., Benecchi, S., et al., (including Roe, H., Thirouin, A.), 2015, Icar, 257, 130, The mutual orbit, mass, and density of the large transneptunian binary system Varda and Ilmare
    From observations by the Hubble Space Telescope, Keck II Telescope, and Gemini North Telescope, we have determined the mutual orbit of the large transneptunian object (174567) Varda and its satellite Ilmare. These two objects orbit one another in a highly inclined, circular or near-circular orbit with a period of 5.75 days and a semimajor axis of 4810 km. This orbit reveals the system mass to be (2.664 0.064) 1020 kg, slightly greater than the mass of the second most massive main-belt asteroid (4) Vesta. The dynamical mass can in turn be combined with estimates of the surface area of the system from Herschel Space Telescope thermal observations to estimate a bulk density of 1.24-0.35+0.50g cm - 3 . Varda and Ilmare both have colors similar to the combined colors of the system, B-V = 0.886 0.025 and V-I = 1.156 0.029.
  94. Ciardi, D., van Eyken, J., Barnes, J., et al., (including . Mclane, J., Prato, L., van Belle, G., von Braun, K.), 2015, ApJ, 809, 42, Follow-up Observations of PTFO 8-8695: A 3 Myr Old T-Tauri Star Hosting a Jupiter-mass Planetary Candidate
    We present Spitzer 4.5 m light curve observations, Keck NIRSPEC radial velocity observations, and LCOGT optical light curve observations of PTFO 8-8695, which may host a Jupiter-sized planet in a very short orbital period (0.45 days). Previous work by van Eyken et al. and Barnes et al. predicts that the stellar rotation axis and the planetary orbital plane should precess with a period of 300-600 days. As a consequence, the observed transits should change shape and depth, disappear, and reappear with the precession. Our observations indicate the long-term presence of the transit events (\gt 3 years), and that the transits indeed do change depth, disappear and reappear. The Spitzer observations and the NIRSPEC radial velocity observations (with contemporaneous LCOGT optical light curve data) are consistent with the predicted transit times and depths for the {M}\star =0.34 {M} precession model and demonstrate the disappearance of the transits. An LCOGT optical light curve shows that the transits do reappear approximately 1 year later. The observed transits occur at the times predicted by a straight-forward propagation of the transit ephemeris. The precession model correctly predicts the depth and time of the Spitzer transit and the lack of a transit at the time of the NIRSPEC radial velocity observations. However, the precession model predicts the return of the transits approximately 1 month later than observed by LCOGT. Overall, the data are suggestive that the planetary interpretation of the observed transit events may indeed be correct, but the precession model and data are currently insufficient to confirm firmly the planetary status of PTFO 8-8695b.
  95. Benedict, G., Henry, T., McArthur, B., et al., (including Franz, O., Wasserman, L.), 2015, IAUGA, 29, 2244346, V and K-band Mass-Luminosity Relations for M Dwarf Stars
    Applying Hubble Space Telescope Fine Guidance Sensor astrometric techniques developed to establish relative orbits for binary stars (Franz et al. 1998, AJ, 116, 1432), determine masses of binary components (Benedict et al. 2001, AJ, 121, 1607), and measure companion masses of exoplanet host stars (McArthur et al. 2010, ApJ, 715, 1203), we derive masses with an average 2% error for 28 components of 14 M dwarf binary star systems. With these and other published masses we update the lower Main Sequence V-band Mass-Luminosity Relation first shown in Henry et al. 1999, ApJ, 512, 864. We demonstrate that a Mass-Luminosity Relation in the K-band has far less scatter. These relations can be used to estimate the masses of the ubiquitous red dwarfs (75% of all stars) to an accuracy of better than 5%.
  96. Thirouin, A., Moskovitz, N., Binzel, R., et al., 2015, IAUGA, 29, 2245003, The Mission Accessible Near-Earth Object Survey (MANOS): first photometric results.
    The Mission Accessible Near-Earth Object Survey (MANOS) is a physical characterization survey of Near Earth Objects (NEOs) that was originally awarded multi-year survey status by NOAO and recently has employed additional facilities available to Lowell Observatory and the University of Hawaii. Our main goal is to provide physical data, such as rotational properties and composition, for several hundred mission accessible NEOs across visible and near-infrared wavelengths.As of February 2015, 12,287 NEOs have been discovered. Despite this impressive number, physical information for the majority of these objects remains limited. Typical NEOs fade in a matter of days or weeks after their discovery, thus their characterization requires a challenging set of rapid response observations.Using a variety of 1-m to 4-m class telescopes, we aim to observe 5 to 10 newly discovered sub-km NEOs per month in order to derive their rotational properties. Such rotational data can provide useful information about physical properties, like shape, surface heterogeneity/homogeneity, density, internal structure, and internal cohesion. Here, we present early results of the MANOS photometric survey for more than 50 NEOs. One of the goals of this survey is to increase the number of sub-km NEOs whose short-term variability has been studied and to compile a high quality homogeneous database which may be used to perform statistical analyses.We report light curves from our first two years of observing and show objects with rotational periods from a couple of hours down to few seconds. We consider the spin rate distributions of several sub-samples according to their size and other physical parameters. Our results were merged with rotational parameters of other asteroids in the literature to build a larger sample. This allows us to identify correlations of rotational properties with orbital parameters. In particular, we want to study MOID vs. rotation period/morphology/elongation/amplitude, rotation properties vs spectral type/composition, etc. We are also planning to observe some objects at different epochs to potentially constrain shape and/or phase curves.
  97. Sokal, K., Johnson, K., Massey, P., et al., 2015, IAUGA, 29, 2247500, Wolf-Rayet Ionization and Feedback as the Tipping Point in Super Star Cluster Emergence
    The feedback from massive stars is extremely important to super star cluster (SSC) evolution, especially the timescales on which it occurs. SSCs form embedded in thick material, and eventually, the cluster is cleared out and revealed at optical wavelengths. However, this transition is not well understood, particularly which physical processes are essential and how they couple to the surrounding material. If radiation pressure were solely responsible, we would expect clusters to be cleared in less than ~2 Myr. Yet, some SSCs are observed to remain embedded until ~4 Myr. Although previously thought to appear after the cluster has fully removed natal material, embedded SSCs can host large populations of Wolf-Rayet (WR) stars that provide ionization and mechanical feedback. We hypothesize that WR feedback may be the tipping point in the combined feedback processes that drive some SSCs to emerge - the process of which could impact their ability to remain bound. We are investigating this critical SSC evolutionary transition with a multi-wavelength observational campaign that was spurred by an in-depth pilot study of the massive cluster S26 in NGC 4449. Utilizing optical spectra obtained with the 4m Mayall Telescope at Kitt Peak National Observatory and the 6.5m MMT combined with archival data from Hubble, Spitzer, and Herschel Space Telescopes, we have compiled a sample of (partially) embedded SSCs that are likely undergoing this short-lived evolutionary phase and in which we confirm the presence of Wolf-Rayet stars. In each source, we determine the massive star populations and study the physical environments such as metallicity and age; we then compare the sample to predictions as well as observations of SSCs in other evolutionary phases. The ionizing radiation is clearly extreme throughout the sample -- observed optical ionized line ratios of H-alpha, H-beta, [NII], and [OIII] show that these sources border the theoretical and empirical limits produced by star formation alone.
  98. Elmegreen, B., Hunter, D., Ashley, T., et al., 2015, IAUGA, 29, 2251098, Gas accretion from halos to disks: observations, curiosities, and problems
    Accretion of gas from the cosmic web to galaxy halos and ultimately their disks is a prediction of modern cosmological models but is rarely observed directly or at the full rate expected from star formation. Here we illustrate possible large-scale cosmic HI accretion onto the nearby dwarf starburst galaxy IC10, observed with the VLA and GBT. We also suggest that cosmic accretion is the origin of sharp metallicity drops in the starburst regions of other dwarf galaxies, as observed with the 10-m GCT. Finally, we question the importance of cosmic accretion in normal dwarf irregulars, for which a recent study of their far-outer regions sees no need for, or evidence of, continuing gas buildup.
  99. Polishook, D., Moskovitz, N., 2015, IAUGA, 29, 2252589, Searching for color variation on fast rotating asteroids with simultaneous V-J observations
    Motivation: Boulders, rocks and regolith on fast rotating asteroids (~2.5 hours) might slide towards the equator due to a strong centrifugal force and a low cohesion force, as described by models (Walsh et al. 2008, Sanchez & Scheeres 2014). As a result, a fresh material might be exposed, if the surface consists of weathered ordinary chondrite (S-complex). Detecting color variation, due to the exposure of fresh material, will allow us to model the mass shedding process, its extent and age, and thus support or reject hypotheses of rotational-fission.Method: Detecting color variation on small and fast rotating asteroids is difficult with spectroscopy since color differences are mild while the exposure time must be short to measure a narrow rotational phase. Broadband photometry is also problematic since it introduces large systematic errors when images in different filters are calibrated with standard stars. We describe a novel technique in which the asteroid is simultaneously observed in the visible and near-IR wavelength ranges. This technique is possible if a dichroic split the light into two beams that hit two detectors. In this technique atmospheric interference are self-calibrated between the visible and the near-IR image. We use a V and a J filters since the distinction between fresh and weathered surfaces are most prominent in these wavelengths and range between 10-20%.Observations: We observed 3 asteroids with CTIOs 1.3m telescope and ANDICAM detector. The asteroids were observed during 2 rotational cycles to confirm features on the color-curve. There is ~5% variation of the mean color. There are a few measurements with a larger/smaller color in the range of ~10%, but these do not repeat in a second rotation cycle and we cannot confirm them as real. Therefore, we cannot detect fresh colors (as seen on Q-type asteroids) on the surface. This suggests one of the following statements: 1. No landslides occurred within the timescale of space weathering. 2. Landslides occurred but the exposed patches are too small for the measurements uncertainty. 3. Slides occurred but did not expose fresh material.
  100. Mommert, M., Trilling, D., Hora, J., et al., (including Moskovitz, N.), 2015, IAUGA, 29, 2253974, Thermal-Infrared Surveys of Near-Earth Object Diameters and Albedos with Spitzer and IRTF/MIRSI
    More than 12000 Near-Earth Objects (NEOs) have been discovered over the past few decades and current discovery surveys find on average 4 new NEOs every night. In comparison to asteroid discovery, the physical characterization of NEOs lags far behind: measured diameters and albedos exist only for roughly 10% of all known NEOs. We describe a current and a future observing program that provide diameter and albedo measurements of a large number of NEOs.In our Spitzer Space Telescope Exploration Science program 'NEOSurvey', we are performing a fast and efficient flux-limited survey in which we measure the diameters and albedos of ~600 NEOs in a total of 710 hrs of observing time. We measure the thermal emission of our targets at 4.5 micron and combine these measurements with optical data in a thermal model. Our diameters and albedos come with highly realistic uncertainties that account for a wide range of potential asteroid properties. Our primary goal is to create a large and uniform catalog of NEO properties, including diameters, albedos, and flux density data. This catalog is publicly accessible and provides the latest results usually within 2 weeks after the observation.Starting in 2016, we will also make use of the refurbished and recommissioned MIRSI mid-infrared imaging camera on NASA's InfraRed Telescope Facility (IRTF) to derive the diameters and albedos of up to 750 NEOs over a period of 3 yrs. MIRSI will be equipped with an optical camera that will allow for simultaneous optical imaging, which will improve our thermal modeling results. With MIRSI, we will focus on newly discovered NEOs that are close to Earth and hence relatively bright.The results from both programs, together with already exisiting diameter and albedo results from the literature, will form the largest database of NEO physical properties available to date. With this data set, we will be able to refine the size distribution of small NEOs and the corresponding impact frequency, and compare the albedo distribution of NEOs with those of their potential source populations. These projects are supported by NASA and the Spitzer Science Center.
  101. Mommert, M., Trilling, D., Butler, N., et al., (including Moskovitz, N.), 2015, IAUGA, 29, 2254031, Spectrophotometric Rapid-Response Classification of Near-Earth Objects
    Small NEOs are, as a whole, poorly characterized, and we know nothing about the physical properties of the majority of all NEOs. The rate of NEO discoveries is increasing each year, and projects to determine the physical properties of NEOs are lagging behind. NEOs are faint, and generally even fainter by the time that follow-up characterizations can be made days or weeks after their discovery. There is a need for a high-throughput, high-efficiency physical characterization strategy in which hundreds of faint NEOs can be characterized each year. Broadband photometry in the near-infrared is sufficiently diagnostic to assign taxonomic types, and hence constrain both the individual and ensemble properties of NEOs.We present results from our rapid response near-infrared spectrophotometric characterization program of NEOs. We are using UKIRT (on Mauna Kea) and the RATIR instrument on the 1.5m telescope at the San Pedro Martir Observatory (Mexico) to allow us to make observations most nights of the year in robotic/queue mode. We derive taxonomic classifications for our targets using machine-learning techniques that are trained on a large sample of measured asteroid spectra. For each target we assign a probability for it to belong to a number of different taxa. Target selection, observation, data reduction, and analysis are highly automated, requiring only a minimum of user interaction, making this technique powerful and fast. Our targets are NEOs that are generally too faint for other characterization techniques, or would require many hours of large telescope time.
  102. Egeland, R., Metcalfe, T., Hall, J., et al., 2015, IAUGA, 29, 2254437, Sun-like Magnetic Cycles in the Fast-Rotating Young Solar Analog HD 30495
    A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial (~2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it has an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic and photometric cycles in the young solar analog HD 30495, a ~500 Myr-old G1.5V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at ~1.6 years and a long cycle of ~12 years. We measure three individual cycle episodes and find cycle durations ranging from 9.4-14.6 years. These essentially solar-like variations occur in a solar-like star with faster-than-solar rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence.
  103. Moskovitz, N., Thirouin, A., Binzel, R., et al., (including Burt, B.), 2015, IAUGA, 29, 2255616, The Mission Accessible Near-Earth Object Survey (MANOS) -- Science Highlights
    Near-Earth objects (NEOs) are essential to understanding the origin of the Solar System through their compositional links to meteorites. As tracers of other parts of the Solar System they provide insight to more distant populations. Their small sizes and complex dynamical histories make them ideal laboratories for studying ongoing processes of planetary evolution. Knowledge of their physical properties is essential to impact hazard assessment. And the proximity of NEOs to Earth make them favorable targets for a variety of planetary mission scenarios. However, in spite of their importance, only the largest NEOs are well studied and a representative sample of physical properties for sub-km NEOs does not exist.MANOS is a multi-year physical characterization survey, originally awarded survey status by NOAO. MANOS is targeting several hundred mission-accessible, sub-km NEOs across visible and near-infrared wavelengths to provide a comprehensive catalog of physical properties (astrometry, light curves, spectra). Accessing these targets is enabled through classical, queue, and target-of-opportunity observations carried out at 1- to 8-meter class facilities in the northern and southern hemispheres. Our observing strategy is designed to rapidly characterize newly discovered NEOs before they fade beyond observational limits.Early progress from MANOS includes: (1) the de-biased taxonomic distribution of spectral types for NEOs smaller than ~100 meters, (2) the distribution of rotational properties for approximately 100 previously unstudied NEOs, (3) detection of the fastest known rotation period of any minor planet in the Solar System, (4) an investigation of the influence of planetary encounters on the rotational properties of NEOs, (5) dynamical models for the evolution of the overall NEO population over the past 0.5 Myr, and (6) development of a new set of online tools at asteroid.lowell.edu that will enable near realtime public dissemination of our data products while providing a portal to facilitate observation planning and coordination within the small body observer community. We will present highlights of these early MANOS science results.
  104. Georgy, C., Ekstrom, S., Hirschi, R., et al., (including Massey, P.), 2015, IAUGA, 29, 2256831, The luminosity distribution of RSGs to test their mass-loss rate
    The red supergiant phase is an important phase of the evolution of massive star, as it mostly determines its final stages. One of the most important driver of the evolution during this phase is mass loss. However, the mass-loss rates prescription used for red supergiants in current stellar evolution models are still very inaccurate.In this talk, I will discuss how varying the mass-loss rate during the RSG phase modifies the populations of red supergiants. Indeed, varying the mass-loss rate makes the star evolves for some time in yellow/blue regions of the HRD, modifying the number of RSGs in some luminosity ranges. I will show how the luminosity distribution of RSGs is modified for various mass-loss prescriptions, and finally, discuss the possibility to use this distribution to constrain the mass-loss rate of RSGs by comparing with the observed one.
  105. Hall, J., 2015, IAUGA, 29, 2256949, Activity and Brightness Variations of Sun-Like Stars
    Long-term observations of variations in Sun-like stars now span a half century. The Mount Wilson Observatory (MWO) HK Project operated from 1966 to 2003, and the Lowell Observatory Solar-Stellar Spectrograph (SSS) project has operated since 1994; together these programs provide a record of chromospheric activity over multiple stellar cycles for more than 100 stars of V < ~7.5. Long-term photometric monitoring of Sun-like stars, including many of the MWO and SSS targets, began in the early 1980s and continues today at the Fairborn Observatory south of Tucson. I will review progress to date in combining and interpreting the spectrosopic and photometric data sets, including some new results from the most recent years of SSS and Fairborn data. I will also review where deficiencies remain in reconciling and combining the major data sets, and will discuss efforts presently underway to remedy this and provide a long-term record for the benefit of the community.
  106. Wooden, D., Lederer, S., Bus, S., et al., (including Moskovitz, N.), 2015, IAUGA, 29, 2257359, NEAs: Phase Angle Dependence of Asteroid Class and Diameter from Observational Studies
    We will discuss the results of a planned observation campaign of Near Earth Asteroids (NEAs), 1999 CU3, 2002 GM2, 2002 FG7, and 3691 Bede with instruments on the United Kingdom Infrared Telescope (UKIRT) from 15-Mar-2015 to 28-April 2015 UT. We will study the phase-angle dependence of the reflectance and thermal emission spectra. Recent publications reveal that the assignment of the asteroid class from visible and near-IR spectroscopy can change with phase angle for NEAs with silicate-bearing minerals on their surfaces (S-class asteroids) (Thomas et al. 2014, Icarus 228, 217; Sanchez et al. 2012 Icarus 220, 36). Only three of the larger NEAs have been measured at a dozen phase angles and the trends are not all the same, so there is not yet enough information to create a phase-angle correction. Also, the phase angle effect is not characterized well for the thermal emission including determination of the albedo and the thermal emission. The few NEAs were selected for our study amongst many possible targets based on being able to observe them through a wide range of phase angles, ranging from less than about 10 degrees to greater than 45 degrees over the constrained date range. The orbits of NEAs often generate short observing windows at phase angles higher than 45 deg (i.e., whizzing by Earth and/or close to dawn or dusk). Ultimately, lowering the uncertainty of the translation of asteroid class to meteorite analog and of albedo and size determinations are amongst our science goals. On a few specific nights, we plan to observe the 0.75-2.5 micron spectra with IRTF+SpeX for comparison with UKIRT data including 5-20 micron with UKIRT+UIST/Michelle to determine as best as possible the albedos. To ensure correct phasing of spectroscopic data, we augment with TRAPPIST-telescope light curves and R-band guider image data. Our observations will contribute to understanding single epoch mid-IR and near-IR measurements to obtain albedo, size and IR beaming parameters (the outcomes of thermal models) and asteroid spectral class.
  107. Jorgensen, A., Mozurkewich, D., Schmitt, H., et al., (including Van Belle, G.), 2015, IAUGA, 29, 2257427, Multi-baseline Bootstrapping and Imaging with the NPOI
    The Navy Precision Optical Interferometer (NPOI) is uniquely configured for baseline bootstrapping. Imaging requires observations on long resolving baselines, and the resulting low visibilities require coherent integration. Tracking fringes on these long baselines requires baseline and/or wavelength bootstrapping and equally-spaced arrays are normally optimal for this task. The New Classic instrument and the stellar surface imaging project are designed to take advantage of the unique NPOI configuration and to develop the necessary methods to carry out routine imaging. This presentation outlines the projects and shows some initial results.
  108. Hinkle, M., Moskovitz, N., Trilling, D., et al., 2015, IAUGA, 29, 2257980, The Bias-Corrected Taxonomic Distribution of Mission-Accessible Small Near-Earth Objects
    As relics of the inner solar system's formation, asteroids trace the origins of solar system material. Near-Earth asteroids (NEAs) are the intermediaries between material that falls to Earth as meteorites and the source regions of those meteorites in the main belt. A better understanding of the physical parameters of NEAs, in particular their compositions, provides a more complete picture of the processes that shaped the inner solar system and that deliver material from the main belt to near-Earth space.Across the entire NEA population, the smallest (d < 1 km) objects have not been well-studied. These very small objects are often targets of opportunity, observable for only a few days to weeks after their discovery. Even at their brightest (V ~ 18), these asteroids are faint enough that they must be observed with large ground-based telescopes.The Mission Accessible Near-Earth Object Survey (MANOS) began in August 2013 as a multi-year physical characterization survey that was awarded survey status by NOAO. MANOS will target several hundred mission-accessible NEOs across visible and near-infrared wavelengths, ultimately providing a comprehensive catalog of physical properties (astrometry, light curves, spectra). Seventy small, mission-accessible NEAs were observed between mid 2013 and mid 2015 using the Gemini Multi-Object Spectrograph at Gemini North & South observatories. Taxonomic classifications were obtained by fitting our spectra to the mean reflectance spectra of the Bus asteroid taxonomy (Bus & Binzel 2002). The smallest near-Earth asteroids are the likely progenitors of meteorites; we expect the observed fraction of ordinary chondrite meteorites to match that of their parent bodies, S-type asteroids. The distribution of the population of small NEAs should also resemble that of their parent bodies, the larger asteroids (d > 1 km). We present classifications for these objects as well as preliminary results for the debiased distribution of taxa (as a proxy for composition) as a function of object size and compare to the observed fractions of ordinary chondrite meteorites and asteroids with d > 1 km.
  109. Green, R., Diaz Castro, J., Allen, L., et al., (including Hall, J.), 2015, IAUGA, 29, 2258199, A Tale of Two Regions: Site Protection Experience and Updated Regulations in Arizona and the Canary Islands
    Some of the world's largest telescopes and largest concentrations of telescopes are on sites in Arizona and the Canary Islands. Active site protection efforts are underway in both regions; the common challenge is getting out ahead of the LED revolution in outdoor lighting. We review the work with local, regional, and national government bodies, with many successful updates of outdoor lighting codes. A successful statewide conference was held in Arizona to raise awareness of public officials about issues of light pollution for astronomy, safety, wildlife, and public health. We also highlight interactions with key entities near critical sites, including mines and prisons, leading to upgrades of their lighting to more astronomy-friendly form. We describe ongoing and planned sky monitoring efforts, noting their importance in quantifying the "impact on astronomy" increasingly requested by regulators.
  110. Krick, J., Ingalls, J., Carey, S., et al., (including von Braun, K.), 2015, IAUGA, 29, 2258223, Spitzer IRAC Sparsely Sampled Phase Curve of WASP-14b
    We present a new technique of sparsely sampling phase curves of hot jupiters with Spitzer IRAC. Snapshot phase curves are enabled by technical advances of precision pointing as well as careful characterization of a portion of the central pixel on the array. This method allows for observations which are a factor of ~2 more efficient than full phase curve observations, and are easy to schedule. We present the first results from this program using the exoplanet WASP-14b. As our pilot study, this planet has data taken both as a sparsely sampled phase curve as well as a staring mode phase curve as proof of technique. We successfully recover physical parameters for the transit and eclipse depths as well as phase curve shape of this slightly eccentric hot jupiter.
  111. Keane, J., Milam, S., Coulson, I., et al., (including Knight, M.), 2015, IAUGA, 29, 2258485, Catastrophic Disruption of comet ISON: Determination of Size and Drift Velocity of ISON Fragments
    We report submillimeter dust continuum observations for comet C/2012 S1(ISON) obtained during the time period immediately before perihelion on 2013 November 28 (r = 0.0125AU). Prior to perihelion passage on 28 November 2013, the observed right ascension (RA) and declination (Dec) coordinates of comet C/2012 S1 (ISON) significantly lagged the predicted JPL (# 53) ephemeris. We show that this braking effect is due to a dynamic pressure exerted by sublimating gases on the sunward side of the nucleus. When comet ISON was first detected at 850 m, the 1-mm-sized dust particles were tightly bound to the comet nucleus until at least November 23. Three days later, the dust was less tightly bound, elongated and diffuse, spread out over as much as 120 arc seconds (80,000 km) in the anti-solar direction, suggesting a fragmentation event. We calculate the average braking velocity of the nucleus of comet ISON by comparing the central RA position with the predicted JPL ephemeris. The difference in the observed nucleus distance from the predicted ephemeris in the elapsed time between two observations yields an average drift velocity for the comet. We apply a sublimation mass-loss model to determine the size and fragmentation of the comet ISON's nucleus over time.
  112. Prato, L., Mace, G., Rice, E., et al., 2015, ApJ, 808, 12, Radial Velocity Variability of Field Brown Dwarfs
    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R 20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity (RV) precision of 2 km s-1, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1 upper limit for very low mass binary frequency is 18%. Our targets included seven known, wide brown dwarf binary systems. No significant RV variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant fraction of the orbital period. Specialized techniques are required to reach the high precisions sensitive to motion in orbits of very low-mass systems. For eight objects, including six T dwarfs, we present the first published high-resolution spectra, many with high signal to noise, that will provide valuable comparison data for models of brown dwarf atmospheres.
  113. Cottaar, M., Covey, K., Foster, J., et al., 2015, ApJ, 807, 27, IN-SYNC. III. The Dynamical State of IC 348 - A Super-virial Velocity Dispersion and a Puzzling Sign of Convergence
    Most field stars will have encountered the highest stellar density and hence the largest number of interactions in their birth environment. Yet the stellar dynamics during this crucial phase are poorly understood. Here we analyze the radial velocities measured for 152 out of 380 observed stars in the 2-6 Myr old star cluster IC 348 as part of the SDSS-III APOGEE. The radial velocity distribution of these stars is fitted with one or two Gaussians, convolved with the measurement uncertainties including binary orbital motions. Including a second Gaussian improves the fit; the high-velocity outliers that are best fit by this second component may either (1) be contaminants from the nearby Perseus OB2 association, (2) be a halo of ejected or dispersing stars from IC 348, or (3) reflect that IC 348 has not relaxed to a Gaussian velocity distribution. We measure a velocity dispersion for IC 348 of 0.72 0.07 km s-1 (or 0.64 0.08 km s-1 if two Gaussians are fitted), which implies a supervirial state, unless the gas contributes more to the gravitational potential than expected. No evidence is found for a dependence of this velocity dispersion on distance from the cluster center or stellar mass. We also find that stars with lower extinction (in the front of the cloud) tend to be redshifted compared with stars with somewhat higher extinction (toward the back of the cloud). This data suggest that the stars in IC 348 are converging along the line of sight. We show that this correlation between radial velocity and extinction is unlikely to be spuriously caused by the small cluster rotation of 0.024 0.013 km s-1 arcmin-1 or by correlations between the radial velocities of neighboring stars. This signature, if confirmed, will be the first detection of line of sight convergence in a star cluster. Possible scenarios for reconciling this convergence with IC 348's observed supervirial state include: (a) the cluster is fluctuating around a new virial equilibrium after a recent disruption due to gas expulsion or a merger event, or (b) the population we identify as IC 348 results from the chance alignment of two sub-clusters converging along the line of sight. Additional measurements of tangential and radial velocities in IC 348 will be important for clarifying the dynamics of this region and informing models of the formation and evolution of star clusters. The radial velocities analyzed in this paper have been made available online.
  114. Massey, P., Neugent, K., Morrell, N., 2015, ApJ, 807, 81, A Modern Search for Wolf-Rayet Stars in the Magellanic Clouds. II. A Second Year of Discoveries
    The numbers and types of evolved massive stars found in nearby galaxies provide an exacting test of stellar evolution models. Because of their proximity and rich massive star populations, the Magellanic Clouds have long served as the linchpins for such studies. Yet the continued accidental discoveries of Wolf-Rayet (WR) stars in these systems demonstrate that our knowledge is not as complete as usually assumed. Therefore, we undertook a multi-year survey for WRs in the Magellanic Clouds. Our results from our first year (reported previously) confirmed nine new LMC WRs. Of these, six were of a type never before recognized, with WN3-type emission combined with O3-type absorption features. Yet these stars are 2-3 mag too faint to be WN3+O3 V binaries. Here we report on the second year of our survey, including the discovery of four more WRs, two of which are also WN3/O3s, plus two slash WRs. This brings the total of known LMC WRs to 152, 13 (8.2%) of which were found by our survey, which is now 60% complete. We find that the spatial distribution of the WN3/O3s is similar to that of other WRs in the LMC, suggesting that they are descended from the same progenitors. We call attention to the fact that 5 of the 12 known SMC WRs may in fact be similar WN3/O3s rather than the binaries they have often assumed to be. We also discuss our other discoveries: a newly discovered Onfp-type star, and a peculiar emission-line object. Finally, we consider the completeness limits of our survey.

    This paper includes data gathered with the 1 m Swope and 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  115. Angerhausen, D., Mandushev, G., Mandell, A., et al., (including Dunham, E., Collins, P.), 2015, JATIS, 1, 034002, First exoplanet transit observation with the Stratospheric Observatory for Infrared Astronomy: confirmation of Rayleigh scattering in HD 189733 b with the High-Speed Imaging Photometer for Occultations
    Here, we report on the first successful exoplanet transit observation with the Stratospheric Observatory for Infrared Astronomy (SOFIA). We observed a single transit of the hot Jupiter HD 189733 b, obtaining two simultaneous primary transit lightcurves in the B and z bands as a demonstration of SOFIA's capability to perform absolute transit photometry. We present a detailed description of our data reduction, in particular, the correlation of photometric systematics with various in-flight parameters unique to the airborne observing environment. The derived transit depths at B and z wavelengths confirm a previously reported slope in the optical transmission spectrum of HD 189733 b. Our results give new insights to the current discussion about the source of this Rayleigh scattering in the upper atmosphere and the question of fixed limb darkening coefficients in fitting routines.
  116. Navarrete, C., Chaname, J., Ramirez, I., et al., (including Shkolnik, E.), 2015, ApJ, 808, 103, The Kapteyn Moving Group Is Not Tidal Debris From Centauri
    The Kapteyn moving group has been postulated as tidal debris from Centauri. If true, members of the group should show some of the chemical abundance patterns known for stars in the cluster. We present an optical and near-infrared high-resolution, high-signal-to-noise ratio spectroscopic study of 14 stars of the Kapteyn group, plus 10 additional stars (the Cen group) that, while not listed as members of the Kapteyn group as originally defined, have nevertheless been associated dynamically with Centauri. Abundances for Na, O, Mg, Al, Ca, and Ba were derived from the optical spectra, while the strength of the chromospheric He i 10830 A line is studied as a possible helium abundance indicator. The resulting Na-O and Mg-Al patterns for stars of the combined Kapteyn and Cen group samples do not resemble those of Centauri, and are not different from those of field stars of the Galactic halo. The distribution of equivalent widths of the He i 10830 A line is consistent with that found among non-active field stars. Therefore, no evidence is found for second-generation stars within our samples, which most likely rules out a globular-cluster origin. Moreover, no hint of the unique barium overabundance at the metal-rich end, well established for Centauri stars, is seen among stars of the combined samples. Because this specific Ba pattern is present in Centauri irrespective of stellar generation, this would rule out the possibility that our entire sample might be composed of only first-generation stars from the cluster. Finally, for the stars of the Kapteyn group, the possibility of an origin in the hypothetical parent galaxy of Centauri is disfavored by the different run of -elements with metallicity between our targets and stars from present-day dwarf galaxies.

    Based on observations collected at the European Southern Observatory, Chile (ESO Program 090.B-0605) and observations gathered with the 6.5 m Magellan Telescopes at Las Campanas Observatory, Chile.

  117. Alam, S., Albareti, F., Allende Prieto, C., et al., (including Covey, K.), 2015, ApJS, 219, 12, The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
    The third generation of the Sloan Digital Sky Survey (SDSS-III) took data from 2008 to 2014 using the original SDSS wide-field imager, the original and an upgraded multi-object fiber-fed optical spectrograph, a new near-infrared high-resolution spectrograph, and a novel optical interferometer. All of the data from SDSS-III are now made public. In particular, this paper describes Data Release 11 (DR11) including all data acquired through 2013 July, and Data Release 12 (DR12) adding data acquired through 2014 July (including all data included in previous data releases), marking the end of SDSS-III observing. Relative to our previous public release (DR10), DR12 adds one million new spectra of galaxies and quasars from the Baryon Oscillation Spectroscopic Survey (BOSS) over an additional 3000 deg2 of sky, more than triples the number of H-band spectra of stars as part of the Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE), and includes repeated accurate radial velocity measurements of 5500 stars from the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The APOGEE outputs now include the measured abundances of 15 different elements for each star. In total, SDSS-III added 5200 deg2 of ugriz imaging; 155,520 spectra of 138,099 stars as part of the Sloan Exploration of Galactic Understanding and Evolution 2 (SEGUE-2) survey; 2,497,484 BOSS spectra of 1,372,737 galaxies, 294,512 quasars, and 247,216 stars over 9376 deg2; 618,080 APOGEE spectra of 156,593 stars; and 197,040 MARVELS spectra of 5513 stars. Since its first light in 1998, SDSS has imaged over 1/3 of the Celestial sphere in five bands and obtained over five million astronomical spectra.
  118. Knight, M., Mueller, B., Samarasinha, N., et al., (including Schleicher, D.), 2015, AJ, 150, 22, A Further Investigation of Apparent Periodicities and the Rotational State of Comet 103P/Hartley 2 from Combined Coma Morphology and Light Curve Data Sets
    We present an analysis of Kitt Peak National Observatory and Lowell Observatory observations of comet 103P/Hartley 2 obtained from 2010 August through December. The results are then compared with contemporaneous observations made by the EPOXI spacecraft. Each ground-based data set has previously been investigated individually; the combined data set has complementary coverage that reduces the time between observing runs and allows us to determine additional apparent periods at intermediate times. We compare CN coma morphology between ground-based data sets, making nine new measurements of apparent periods. The first five are consistent with the roughly linearly increasing apparent period during the apparition found by previous authors. The final four suggest that the change in apparent period slowed or stopped by late November. We also measure an inner coma light curve in both CN and R-band ground-based images, finding a single-peaked light curve which repeats in phase with the coma morphology. The apparent period from the light curve had significantly larger uncertainties than from the coma morphology, but varied over the apparition in a similar manner. Our ground-based light curve aligns with the published EPOXI light curve, indicating that the light curve represents changing activity rather than viewing geometry of structures in the coma. The EPOXI light curve can best be phased by a triple-peaked period near 54-55 hr that increases from October to November. This phasing reveals that the spacing between maxima is not constant, and that the overall light curve shape evolves from one triple-peaked cycle to the next. These behaviors suggest that much of the scatter in apparent periods derived from ground-based data sets acquired at similar epochs are likely due to limited sampling of the data.
  119. Carnerero, M., Raiteri, C., Villata, M., et al., (including Taylor, B.), 2015, MNRAS, 450, 2677, Multiwavelength behaviour of the blazar OJ 248 from radio to -rays
    We present an analysis of the multiwavelength behaviour of the blazar OJ 248 at z = 0.939 in the period 2006-2013. We use low-energy data (optical, near-infrared, and radio) obtained by 21 observatories participating in the Gamma-Ray Large Area Space Telescope (GLAST)-AGILE Support Program of the Whole Earth Blazar Telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (-rays) satellites, to study flux and spectral variability and correlations among emissions in different bands. We take into account the effect of absorption by the Damped Lyman intervening system at z = 0.525. Two major outbursts were observed in 2006-2007 and in 2012-2013 at optical and near-IR wavelengths, while in the high-frequency radio light curves prominent radio outbursts are visible peaking at the end of 2010 and beginning of 2013, revealing a complex radio-optical correlation. Cross-correlation analysis suggests a delay of the optical variations after the -ray ones of about a month, which is a peculiar behaviour in blazars. We also analyse optical polarimetric and spectroscopic data. The average polarization percentage P is less than 3 per cent, but it reaches 19 per cent during the early stage of the 2012-2013 outburst. A vague correlation of P with brightness is observed. There is no preferred electric vector polarization angle and during the outburst the linear polarization vector shows wide rotations in both directions, suggesting a complex behaviour/structure of the jet and possible turbulence. The analysis of 140 optical spectra acquired at the Steward Observatory reveals a strong Mg II broad emission line with an essentially stable flux of 6.2 10- 15 erg cm- 2 s- 1 and a full width at half-maximum of 2053 km s- 1.
  120. Aigrain, S., Llama, J., Ceillier, T., et al., 2015, MNRAS, 450, 3211, Testing the recovery of stellar rotation signals from Kepler light curves using a blind hare-and-hounds exercise
    We present the results of a blind exercise to test the recoverability of stellar rotation and differential rotation in Kepler light curves. The simulated light curves lasted 1000 d and included activity cycles, Sun-like butterfly patterns, differential rotation and spot evolution. The range of rotation periods, activity levels and spot lifetime were chosen to be representative of the Kepler data of solar-like stars. Of the 1000 simulated light curves, 770 were injected into actual quiescent Kepler light curves to simulate Kepler noise. The test also included five 1000-d segments of the Sun's total irradiance variations at different points in the Sun's activity cycle. Five teams took part in the blind exercise, plus two teams who participated after the content of the light curves had been released. The methods used included Lomb-Scargle periodograms and variants thereof, autocorrelation function and wavelet-based analyses, plus spot modelling to search for differential rotation. The results show that the `overall' period is well recovered for stars exhibiting low and moderate activity levels. Most teams reported values within 10 per cent of the true value in 70 per cent of the cases. There was, however, little correlation between the reported and simulated values of the differential rotation shear, suggesting that differential rotation studies based on full-disc light curves alone need to be treated with caution, at least for solar-type stars. The simulated light curves and associated parameters are available online for the community to test their own methods.
  121. French, L., Stephens, R., Coley, D., et al., (including Wasserman, L.), 2015, Icar, 254, 1, Rotation lightcurves of small jovian Trojan asteroids
    Several lines of evidence support a common origin for, and possible hereditary link between, cometary nuclei and jovian Trojan asteroids. Due to their distance and low albedos, few comet-sized Trojans have been studied. We present new lightcurve information for 19 Trojans 30 km in diameter, more than doubling the number of objects in this size range for which some rotation information is known. The minimum densities for objects with complete lightcurves are estimated and are found to be comparable to those measured for cometary nuclei. A significant fraction (40%) of this observed small Trojan population rotates slowly (P > 24 h), with measured periods as long as 375 h (Warner, B.D., Stephens, R.D. [2011]. Minor Planet Bull. 38, 110-111). The excess of slow rotators may be due to the YORP effect. Results of the Kolmogorov-Smirnov test suggest that the distribution of Trojan rotation rates is dissimilar to those of Main Belt Asteroids of the same size. Concerted observations of a large number of Trojans could establish the spin barrier (Warner, B.D., Harris, A.W., Pravec, P. [2009]. Icarus 202, 134-146), making it possible to estimate densities for objects near the critical period.
  122. Johnson, M., Hunter, D., Wood, S., et al., (including Herrmann, K., Levine, S.), 2015, AJ, 149, 196, The Shape of LITTLE THINGS Dwarf Galaxies DDO 46 and DDO 168: Understanding the Stellar and Gas Kinematics
    Determining the shape of dwarf irregular (dIrr) galaxies is controversial because if one assumes that these objects are disks and if these disks are randomly distributed over the sky, then their projected minor-to-major axis ratios should follow a particular statistical distribution, which is not observed. Thus, different studies have led to different conclusions. Some believe that the observed distributions can be explained by assuming the dIrrs are thick disks while others have concluded that dIrrs are triaxial. Fortunately, the central stellar velocity dispersion, z,0, combined with maximum rotation speed, Vmax, provides a kinematic measure, Vmax/z,0, which gives the three-dimensional shape of a system. In this work, we present the stellar and gas kinematics of DDO 46 and DDO 168 from the Local Irregulars That Trace Luminosity Extremes; The H i Nearby Galaxy Survey (LITTLE THINGS) and determine their respective Vmax/z,0 values. We used the Kitt Peak National Observatory's Mayall 4 m telescope with the Echelle spectrograph as a long-slit spectrograph, which provided a two-dimensional, 3-long slit. We acquired spectra of DDO 168 along four position angles (PAs) by placing the slit over the morphological major and minor axes and two intermediate PAs. However, due to poor weather conditions during our observing run for DDO 46, we were able to extract only one useful data point from the morphological major axis. We determined a central stellar velocity dispersion perpendicular to the disk, z,0, of 13.5 8 km s-1 for DDO 46 and < {{ }z,0}> of 10.7 2.9 km s-1 for DDO 168. We then derived the maximum rotation speed in both galaxies using the LITTLE THINGS H i data. We separated bulk motions from non-circular motions using a double Gaussian decomposition technique and applied a tilted-ring model to the bulk velocity field. We corrected the observed H i rotation speeds for asymmetric drift and found a maximum velocity, Vmax, of 77.4 3.7 and 67.4 4.0 for DDO 46 and DDO 168, respectively. Thus, we derived a kinematic measure, Vmax/z,0, of 5.7 0.6 for DDO 46 and 6.3 0.3 for DDO 168. Comparing these values to ones determined for spiral galaxies, we find that DDO 46 and DDO 168 have Vmax/z,0 values indicative of thin disks, which is in contrast to minor-to-major axis ratio studies.
  123. Kane, S., Boyajian, T., Henry, G., et al., (including von Braun, K.), 2015, ApJ, 806, 60, A Comprehensive Characterization of the 70 Virginis Planetary System
    An on-going effort in the characterization of exoplanetary systems is the accurate determination of host star properties. This effort extends to the relatively bright host stars of planets discovered with the radial velocity method. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is aiding in these efforts as part of its observational campaign for exoplanet host stars. One of the first known systems is that of 70 Virginis, which harbors a jovian planet in an eccentric orbit. Here we present a complete characterization of this system with a compilation of TERMS photometry, spectroscopy, and interferometry. We provide fundamental properties of the host star through direct interferometric measurements of the radius (1.5% uncertainty) and through spectroscopic analysis. We combined 59 new Keck HIRES radial velocity measurements with the 169 previously published from the ELODIE, Hamilton, and HIRES spectrographs, to calculate a refined orbital solution and construct a transit ephemeris for the planet. These newly determined system characteristics are used to describe the Habitable Zone of the system with a discussion of possible additional planets and related stability simulations. Finally, we present 19 years of precision robotic photometry that constrain stellar activity and rule out central planetary transits for a Jupiter-radius planet at the 5 level, with reduced significance down to an impact parameter of b = 0.95.
  124. Elmegreen, B., Hunter, D., 2015, ApJ, 805, 145, A Star Formation Law for Dwarf Irregular Galaxies
    The radial profiles of gas, stars, and far-ultraviolet radiation in 20 dwarf Irregular galaxies are converted to stability parameters and scale heights for a test of the importance of two-dimensional (2D) instabilities in promoting star formation. A detailed model of this instability involving gaseous and stellar fluids with self-consistent thicknesses and energy dissipation on a perturbation crossing time gives the unstable growth rates. We find that all locations are effectively stable to 2D perturbations, mostly because the disks are thick. We then consider the average volume densities in the midplanes, evaluated from the observed H i surface densities and calculated scale heights. The radial profiles of the star-formation rates are equal to about 1% of the H i surface densities divided by the free fall times at the average midplane densities. This 1% resembles the efficiency per unit free fall time commonly found in other cases. There is a further variation of this efficiency with radius in all of our galaxies, following the exponential disk with a scale length equal to about twice the stellar mass scale length. This additional variation is modeled by the molecular fraction in a diffuse medium using radiative transfer solutions for galaxies with the observed dimensions and properties of our sample. We conclude that star formation is activated by a combination of three-dimensional gaseous gravitational processes and molecule formation. Implications for outer disk structure and formation are discussed.
  125. Oh, S., Hunter, D., Brinks, E., et al., 2015, AJ, 149, 180, High-resolution Mass Models of Dwarf Galaxies from LITTLE THINGS
    We present high-resolution rotation curves and mass models of 26 dwarf galaxies from Local Irregulars That Trace Luminosity Extremes, The H i Nearby Galaxy Survey (LITTLE THINGS). LITTLE THINGS is a high-resolution (6 angular; <2.6 km s-1 velocity resolution) Very Large Array H i survey for nearby dwarf galaxies in the local volume within 11 Mpc. The high-resolution H i observations enable us to derive reliable rotation curves of the sample galaxies in a homogeneous and consistent manner. The rotation curves are then combined with Spitzer archival 3.6 m and ancillary optical U, B, and V images to construct mass models of the galaxies. This high quality multi-wavelength data set significantly reduces observational uncertainties and thus allows us to examine the mass distribution in the galaxies in detail. We decompose the rotation curves in terms of the dynamical contributions by baryons and dark matter (DM) halos, and compare the latter with those of dwarf galaxies from THINGS as well as CDM Smoothed Particle Hydrodynamic (SPH) simulations in which the effect of baryonic feedback processes is included. Being generally consistent with THINGS and simulated dwarf galaxies, most of the LITTLE THINGS sample galaxies show a linear increase of the rotation curve in their inner regions, which gives shallower logarithmic inner slopes of their DM density profiles. The mean value of the slopes of the 26 LITTLE THINGS dwarf galaxies is =-0.32+/- 0.24 which is in accordance with the previous results found for low surface brightness galaxies ( =-0.2+/- 0.2) as well as the seven THINGS dwarf galaxies ( =-0.29+/- 0.07). However, this significantly deviates from the cusp-like DM distribution predicted by DM-only CDM simulations. Instead our results are more in line with the shallower slopes found in the CDM SPH simulations of dwarf galaxies in which the effect of baryonic feedback processes is included. In addition, we discuss the central DM distribution of DDO 210 whose stellar mass is relatively low in our sample to examine the scenario of inefficient supernova feedback in low mass dwarf galaxies predicted from recent CDM SPH simulations of dwarf galaxies where central cusps still remain.
  126. Protopapa, S., Grundy, W., Tegler, S., et al., 2015, Icar, 253, 179, Absorption coefficients of the methane-nitrogen binary ice system: Implications for Pluto
    The methane-nitrogen phase diagram of Prokhvatilov and Yantsevich (1983. Sov. J. Low Temp. Phys. 9, 94-98) indicates that at temperatures relevant to the surfaces of icy dwarf planets like Pluto, two phases contribute to the methane absorptions: nitrogen saturated with methane N2 :CH4 and methane saturated with nitrogen CH4 :N2 . No optical constants are available so far for the latter component limiting construction of a proper model, in compliance with thermodynamic equilibrium considerations. New optical constants for solid solutions of methane diluted in nitrogen (N2 :CH4) and nitrogen diluted in methane (CH4 :N2) are presented at temperatures between 40 and 90 K, in the wavelength range 1.1-2.7 m at different mixing ratios. These optical constants are derived from transmission measurements of crystals grown from the liquid phase in closed cells. A systematic study of the changes of methane and nitrogen solid mixtures spectral behavior with mixing ratio and temperature is presented.
  127. Borsa, F., Scandariato, G., Rainer, M., et al., (including Shkolnik, E.), 2015, A&A, 578, A64, The GAPS programme with HARPS-N at TNG. VII. Putting exoplanets in the stellar context: magnetic activity and asteroseismology of Bootis A

    Aims: We observed the Boo system with the HARPS-N spectrograph to test a new observational strategy aimed at jointly studying asteroseismology, the planetary orbit, and star-planet magnetic interaction.
    Methods: We collected high-cadence observations on 11 nearly consecutive nights and for each night averaged the raw FITS files using a dedicated software. In this way we obtained spectra with a high signal-to-noise ratio, used to study the variation of the Ca ii H&K lines and to have radial velocity values free from stellar oscillations, without losing the oscillations information. We developed a dedicated software to build a new custom mask that we used to refine the radial velocity determination with the HARPS-N pipeline and perform the spectroscopic analysis.
    Results: We updated the planetary ephemeris and showed the acceleration caused by the stellar binary companion. Our results on the stellar activity variation suggest the presence of a high-latitude plage during the time span of our observations. The correlation between the chromospheric activity and the planetary orbital phase remains unclear. Solar-like oscillations are detected in the radial velocity time series: we estimated asteroseismic quantities and found that they agree well with theoretical predictions. Our stellar model yields an age of 0.9 0.5 Gyr for Boo and further constrains the value of the stellar mass to 1.38 0.05 M.

    Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF at the Spanish Observatorio Roque de los Muchachos of the IAC in the frame of the program Global Architecture of the Planetary Systems (GAPS).Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr ( or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A64

  128. Bowler, B., Shkolnik, E., Liu, M., et al., (including Flagg, L.), 2015, ApJ, 806, 62, Planets Around Low-mass Stars (PALMS). V. Age-dating Low-mass Companions to Members and Interlopers of Young Moving Groups
    We present optical and near-infrared adaptive optics (AO) imaging and spectroscopy of 13 ultracool (>M6) companions to late-type stars (K7-M4.5), most of which have recently been identified as candidate members of nearby young moving groups (YMGs; 8-120 Myr) in the literature. Three of these are new companions identified in our AO imaging survey, and two others are confirmed to be comoving with their host stars for the first time. The inferred masses of the companions (10-100 MJup) are highly sensitive to the ages of the primary stars; therefore we critically examine the kinematic and spectroscopic properties of each system to distinguish bona fide YMG members from old field interlopers. The new M7 substellar companion 2MASS J02155892-0929121 C (40-60 MJup) shows clear spectroscopic signs of low gravity and, hence, youth. The primary, possibly a member of the 40 Myr Tuc-Hor moving group, is visually resolved into three components, making it a young low-mass quadruple system in a compact (100 AU) configuration. In addition, Li i 6708 absorption in the intermediate-gravity M7.5 companion 2MASS J15594729+4403595 B provides unambiguous evidence that it is young (200 Myr) and resides below the hydrogen-burning limit. Three new close-separation (<1) companions (2MASS J06475229-2523304 B, PYC J11519+0731 B, and GJ 4378 Ab) orbit stars previously reported as candidate YMG members, but instead are likely old (1 Gyr) tidally locked spectroscopic binaries without convincing kinematic associations with any known moving group. The high rate of false positives in the form of old active stars with YMG-like kinematics underscores the importance of radial velocity and parallax measurements to validate candidate young stars identified via proper motion and activity selection alone. Finally, we spectroscopically confirm the cool temperature and substellar nature of HD 23514 B, a recently discovered M8 benchmark brown dwarf orbiting the dustiest-known member of the Pleiades.

    Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile (ESO Program 090.A-9010(A)).

  129. Mann, A., Feiden, G., Gaidos, E., et al., (including von Braun, K.), 2015, ApJ, 804, 64, How to Constrain Your M Dwarf: Measuring Effective Temperature, Bolometric Luminosity, Mass, and Radius
    Precise and accurate parameters for late-type (late K and M) dwarf stars are important for characterization of any orbiting planets, but such determinations have been hampered by these stars complex spectra and dissimilarity to the Sun. We exploit an empirically calibrated method to estimate spectroscopic effective temperature (Teff) and the Stefan-Boltzmann law to determine radii of 183 nearby K7-M7 single stars with a precision of 2%-5%. Our improved stellar parameters enable us to develop model-independent relations between Teff or absolute magnitude and radius, as well as between color and Teff. The derived Teff-radius relation depends strongly on [Fe/H], as predicted by theory. The relation between absolute KS magnitude and radius can predict radii accurate to 3%. We derive bolometric corrections to the V{{R}C}{{I}C}grizJH{{K}S} and Gaia passbands as a function of color, accurate to 1%-3%. We confront the reliability of predictions from Dartmouth stellar evolution models using a Markov chain Monte Carlo to find the values of unobservable model parameters (mass, age) that best reproduce the observed effective temperature and bolometric flux while satisfying constraints on distance and metallicity as Bayesian priors. With the inferred masses we derive a semi-empirical mass-absolute magnitude relation with a scatter of 2% in mass. The best-agreement models overpredict stellar Teff values by an average of 2.2% and underpredict stellar radii by 4.6%, similar to differences with values from low-mass eclipsing binaries. These differences are not correlated with metallicity, mass, or indicators of activity, suggesting issues with the underlying model assumptions, e.g., opacities or convective mixing length.
  130. Reddy, V., Vokrouhlicky, D., Bottke, W., et al., (including Moskovitz, N., Skiff, B.), 2015, Icar, 252, 129, Link between the potentially hazardous Asteroid (86039) 1999 NC43 and the Chelyabinsk meteoroid tenuous
    We explored the statistical and compositional link between Chelyabinsk meteoroid and potentially hazardous Asteroid (86039) 1999 NC43 to investigate their proposed relation proposed by Borovicka et al. (Borovicka, J., et al. [2013]. Nature 503, 235-237). First, using a slightly more detailed computation we confirm that the orbit of the Chelyabinsk impactor is anomalously close to the Asteroid 1999 NC43. We find (1-3) 10-4 likelihood of that to happen by chance. Taking the standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43 by a cratering or rotational fission event, we run a forward probability calculation, which is an independent statistical test. However, we find this scenario is unlikely at the (10-3-10-2) level. Secondly, we note that efforts to conclusively prove separation of the Chelyabinsk meteoroid from (86039) 1999 NC43 in the past needs to meet severe criteria: relative velocity 1-10 m/s or smaller, and 100 km distance (i.e. about the Hill sphere distance from the parent body). We conclude that, unless the separation event was an extremely recent event, these criteria present an insurmountable difficulty due to the combination of strong orbital chaoticity, orbit uncertainty and incompleteness of the dynamical model with respect to thermal accelerations. This situation leaves the link of the two bodies unresolved and calls for additional analyses. With that goal, we revisit the presumed compositional link between (86039) 1999 NC43 and the Chelyabinsk body. Borovicka et al. (Borovicka, J., et al. [2013]. Nature 503, 235-237) noted that given its Q-type taxonomic classification, 1999 NC43 may pass this test. However, here we find that while the Q-type classification of 1999 NC43 is accurate, assuming that all Q-types are LL chondrites is not. Our experiment shows that not all ordinary chondrites fall under Q-taxonomic type and not all LL chondrites are Q-types. Spectral curve matching between laboratory spectra of Chelyabinsk and 1999 NC43 spectrum shows that the spectra do not match. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8) Flora (the largest member of the presumed LL chondrite parent family) shows that their olivine and pyroxene chemistries are similar to LL chondrites. Similar analysis of 1999 NC43 shows that its olivine and pyroxene chemistries are more similar to L chondrites than LL chondrites (like Chelyabinsk). Analysis of the spectrum using Modified Gaussian Model (MGM) suggests 1999 NC43 is similar to LL or L chondrite although we suspect this ambiguity is due to lack of temperature and phase angle corrections in the model. While some asteroid pairs show differences in spectral slope, there is no evidence for L and LL chondrite type objects fissioning out from the same parent body. We also took photometric observations of 1999 NC43 over 54 nights during two apparitions (2000, 2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of tumblers in Short-Axis Mode (SAM) with the mean wobbling angle 20-30. The very slow rotation of 1999 NC43 could be a result of slow-down by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. While, a mechanism of the non-principal axis rotation excitation is unclear, we can rule out the formation of asteroid in disruption of its parent body as a plausible cause, as it is unlikely that the rotation of an asteroid fragment from catastrophic disruption would be nearly completely halted. Considering all these facts, we find the proposed link between the Chelyabinsk meteoroid and the Asteroid 1999 NC43 to be unlikely.
  131. Maldonado, J., Affer, L., Micela, G., et al., (including Shkolnik, E.), 2015, A&A, 577, A132, Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths
    Context. Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. As a consequence, Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are providing huge quantities of optical spectra of M dwarfs. However, determining the stellar parameters of M dwarfs using optical spectra has proven to be challenging.
    Aims: We aim to calibrate empirical relationships to determine accurate stellar parameters for early-M dwarfs (spectral types M0-M4.5) using the same spectra as those that are used for radial velocity determinations, without the necessity of acquiring IR spectra or relying on atmospheric models and/or photometric calibrations.
    Methods: Our methodology consists of using ratios of pseudo-equivalent widths of spectral features as a temperature diagnostic, a technique frequently used in solar-type stars. Stars with effective temperatures obtained from interferometric estimates of their radii are used as calibrators. Empirical calibrations for the spectral type are also provided. Combinations of features and ratios of features are used to derive calibrations for the stellar metallicity. Our methods are then applied to a large sample of M dwarfs that are currently being observed in the framework of the HARPS GTO search for extrasolar planets. The derived temperatures and metallicities are used together with photometric estimates of mass, radius, and surface gravity to calibrate empirical relationships for these parameters.
    Results: A long list of spectral features in the optical spectra of early-M dwarfs was identified. This list shows that the pseudo-equivalent width of roughly 43% of the features is strongly anticorrelated with the effective temperature. The correlation with the stellar metallicity is weaker. A total of 112 temperature sensitive ratios were identified and calibrated over the range 3100-3950 K, providing effective temperatures with typical uncertainties of about 70 K. Eighty-two ratios of pseudo-equivalent widths of features were calibrated to derive spectral types within 0.5 subtypes for stars with spectral types between K7V and M4.5V. We calibrated 696 combinations of the pseudo-equivalent widths of individual features and temperature-sensitive ratios for the stellar metallicity over a metallicity range from -0.54 to +0.24 dex, with estimated uncertainties in the range of 0.07-0.10 dex. We provide our own empirical calibrations for stellar mass, radius, and surface gravity. These parameters depend on the stellar metallicity. For a given effective temperature, lower metallicities predict lower masses and radii as well as higher gravities.

    Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes ID 072.C-0488(E), 082.C-0718(B), 085.C-0019(A), 180.C-0886(A), 183.C-0437(A), and 191.C-0505(A), as well as data from the Italian Telescopio Nazionale Galileo (TNG) Archive (programmes ID CAT-147, and A27CAT_83).Our computational codes including the full version of Tables 2, 4, and 6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr ( or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A132Appendix A is available in electronic form at http://www.aanda.org

  132. Garcia, E., Dupuy, T., Allers, K., et al., 2015, ApJ, 804, 65, On the Binary Frequency of the Lowest Mass Members of the Pleiades with Hubble Space Telescope Wide Field Camera 3
    We present the results of a Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging survey of 11 of the lowest mass brown dwarfs in the Pleiades known (25-40 MJup). These objects represent the predecessors to T dwarfs in the field. Using a semi-empirical binary point-spread function (PSF)-fitting technique, we are able to probe to 0. 03 (0.75 pixel), better than 2x the WFC3/UVIS diffraction limit. We did not find any companions to our targets. From extensive testing of our PSF-fitting method on simulated binaries, we compute detection limits which rule out companions to our targets with mass ratios of 0.7 and separations 4 AU. Thus, our survey is the first to attain the high angular resolution needed to resolve brown dwarf binaries in the Pleiades at separations that are most common in the field population. We constrain the binary frequency over this range of separation and mass ratio of 25-40 MJup Pleiades brown dwarfs to be <11% for 1 (<26% at 2). This binary frequency is consistent with both younger and older brown dwarfs in this mass range.
  133. Ortiz, J., Duffard, R., Pinilla-Alonso, N., et al., (including Thirouin, A.), 2015, A&A, 576, A18, Possible ring material around centaur (2060) Chiron
    We propose that several short-duration events observed in past stellar occultations by Chiron were produced by ring material. Some similarities between these events and the characteristics of Chariklo's rings could indicate common mechanisms around centaurs. From a reanalysis of the stellar occultation data in the literature, we determined two possible orientations of the pole of Chiron's rings, with ecliptic coordinates = (352 10), = (37 10) or = (144 10), = (24 10). The mean radius of the rings is (324 10) km. One can use the rotational lightcurve amplitude of Chiron at different epochs to distinguish between the two solutions for the pole. Both solutions imply a lower lightcurve amplitude in 2013 than in 1988, when the rotational lightcurve was first determined. We derived Chiron's rotational lightcurve in 2013 from observations at the 1.23 m CAHA telescope, and indeed its amplitude was smaller than in 1988. We also present a rotational lightcurve in 2000 from images taken at the CASLEO 2.15 m telescope that is consistent with our predictions. Out of the two poles, the = (144 10), = (24 10) solution provides a better match to a compilation of rotational lightcurve amplitudes from the literature and those presented here. We also show that using this preferred pole orientation, Chiron's long-term brightness variations are compatible with a simple model that incorporates the changing brightness of the rings while the tilt angle with respect to the Earth is changing with time. Also, the variability of the water ice band in Chiron's spectra as seen in the literature can be explained to a large degree by an icy ring system whose tilt angle changes with time and whose composition includes water ice, analogously to the case of Chariklo. We present several possible formation scenarios for the rings from qualitative points of view and speculate on why rings might be common in centaurs. We also speculate on whether the known bimodal color distribution of the centaurs could be due to centaurs with rings and centaurs without rings.

    Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr ( or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A18

  134. Johnson, J., Grundy, W., Lemmon, M., et al., 2015, Icar, 248, 25, Spectrophotometric properties of materials observed by Pancam on the Mars Exploration Rovers: 3. Sols 500-1525
    The Panoramic Camera (Pancam) on the Mars Exploration Rovers Spirit and Opportunity acquired visible/near-infrared (432-1009 nm) multispectral observations of soils and rocks under varying viewing and illumination geometries. Data retrieved from these images were modeled using radiative transfer theory to study the microphysical and surface scattering nature of materials at both sites. Nearly 57,000 individual measurements from 1900 images were collected of rock and soil units identified by their color and morphologic properties over a wide range of phase angles (0-150). Images were acquired between Sols 500 and 1525 in the Columbia Hills and regions around Home Plate in Gusev Crater and in the plains and craters between Erebus and Victoria Craters in Meridiani Planum. Corrections for diffuse skylight incorporated sky models based on observations of atmospheric opacity throughout the mission. Disparity maps created from Pancam stereo images allowed estimates of local facet orientations. For Spirit, soils at lower elevations near Home Plate were modeled with lower single scattering albedo (w) values than those on the summit of Husband Hill, but otherwise soils exhibited similar scattering properties to previous Gusev soils. Dark ripple sands at the El Dorado dunes were among the most forward-scattering materials modeled. Silica-rich soils and nodules near Home Plate were analyzed for the first time, and exhibited increased forward scattering behavior with increasing wavelength, consistent with microporosity inferred from previous high resolution images and thermal infrared spectroscopy. For Opportunity, the opposition effect width parameter for sandstone outcrop rocks was modeled for the first time, and demonstrated average values consistent with surfaces of intermediate porosity and/or grain size distribution between those modeled for spherule-rich soils and darker, clast-poor soils. Soils outside a wind streak emanating from the northern rim of Victoria Crater exhibited w values 16% higher than soils inside the streak. Overall, w values and scattering properties for outcrop rocks, spherule-rich soils, and rover tracks were similar to previous Meridiani Planum analyses, emphasizing the homogeneity of these materials across nearly 12 km of rover odometry.
  135. Llama, J., Shkolnik, E., 2015, ApJ, 802, 41, Transiting the Sun: the Impact of Stellar Activity on X-Ray and Ultraviolet Transits
    Transits of hot Jupiters in X-rays and the ultraviolet have been shown to be both deeper and more variable than the corresponding optical transits. This variability has been attributed to hot Jupiters having extended atmospheres at these wavelengths. Using resolved images of the Sun from NASAs Solar Dynamics Observatory spanning 3.5 yr of Solar Cycle 24 we simulate transit light curves of a hot Jupiter to investigate the impact of Solar-like activity on our ability to reliably recover properties of the planets atmosphere in soft X-rays (94 A), the UV (131-1700 A), and the optical (4500 A). We find that for stars with activity levels similar to those of the Sun, the impact of stellar activity results in underestimating the derived radius of the planet in soft X-ray/EUV by up-to 25% or overestimating it by up to 50% depending on whether the planet occults active regions. We also find that in up to 70% of the X-ray light curves the planet transits over bright starspots. In the far-ultraviolet (1600 A and 1700 A), we find the mean recovered value of {{R}p}/{{R}*} to be over-estimated by up to 20%. For optical transits we are able to consistently recover the correct planetary radius. We also address the implications of our results for transits of WASP-12 b and HD 189733b at short wavelengths.
  136. Sozzetti, A., Bonomo, A., Biazzo, K., et al., (including Shkolnik, E.), 2015, A&A, 575, L15, The GAPS programme with HARPS-N at TNG. VI. The curious case of TrES-4b
    We update the TrES-4 system parameters using high-precision HARPS-N radial-velocity measurements and new photometric light curves. A combined spectroscopic and photometric analysis allows us to determine a spectroscopic orbit with a semi-amplitude K = 51 3 m s-1. The derived mass of TrES-4b is found to be Mp = 0.49 0.04 MJup, significantly lower than previously reported. Combined with the large radius () inferred from our analysis, TrES-4b becomes the transiting hot Jupiter with the second-lowest density known. We discuss several scenarios to explain the puzzling discrepancy in the mass of TrES-4b in the context of the exotic class of highly inflated transiting giant planets.

    Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF at the Spanish Observatorio del Roque de los Muchachos of the IAC in the frame of the program Global Architecture of Planetary Systems (GAPS), and with the Zeiss 1.23-m telescope at the German-Spanish Astronomical Center at Calar Alto, Spain. Tables 1 and 3 are available in electronic form at http://www.aanda.org

  137. Del Castillo, E., Corbally, C., Falco, E., et al., (including Hall, J.), 2015, HiA, 16, 747, Dark Sky Collaborators: Arizona (AZ) Observatories, Communities, and Businesses
    With outdoor lighting ordinances in Arizona first in place around observatories in 1958 and 1972, then throughout the state since 1986, Arizonans have extensive experience working with communities and businesses to preserve our dark skies. Though communities are committed to the astronomy sector in our state, astronomers must collaborate with other stakeholders to implement solutions. Ongoing education and public outreach is necessary to enable ordinance updates as technology changes. Despite significant population increases, sky brightness measurements over the last 20 years show that ordinance updates are worth our efforts as we seek to maintain high quality skies around our observatories. Collaborations are being forged and actions taken to promote astronomy for the longer term in Arizona.
  138. Meynet, G., Chomienne, V., Ekstrom, S., et al., (including Massey, P.), 2015, A&A, 575, A60, Impact of mass-loss on the evolution and pre-supernova properties of red supergiants
    Context. The post-main-sequence evolution of massive stars is very sensitive to many parameters of the stellar models. Key parameters are the mixing processes, the metallicity, the mass-loss rate, and the effect of a close companion.
    Aims: We study the change in the red supergiant (RSG) lifetimes, the tracks in the Hertzsprung-Russel diagram (HRD), the positions in this diagram of the pre-supernova progenitor and the structure of the stars at that time for various mass-loss rates during the RSG phase and for two different initial rotation velocities.
    Methods: Stellar models were computed with the Geneva code for initial masses between 9 and 25 M at solar metallicity (Z = 0.014) with 10 times and 25 times the standard mass-loss rates during the RSG phase, with and without rotation.
    Results: The surface abundances of RSGs are much more sensitive to rotation than to the mass-loss rates during that phase. A change of the RSG mass-loss rate has a strong impact on the RSG lifetimes and in turn on the luminosity function of RSGs. An observed RSG is associated with a model of higher initial mass when models with an enhanced RSG mass-loss rate are used to deduce that mass. At solar metallicity, models with an enhanced mass-loss rate produce significant changes in the populations of blue, yellow, and RSGs. When extended blue loops or blueward excursions are produced by enhanced mass-loss, the models predict that a majority of blue (yellow) supergiants are post-RSG objects. These post-RSG stars are predicted to show much lower surface rotational velocities than similar blue supergiants on their first crossing of the HR gap. Enhanced mass-loss rates during the RSG phase have little impact on the Wolf-Rayet populations. The position in the HRD of the end point of the evolution depends on the mass of the hydrogen envelope. More precisely, whenever at the pre-supernova stage the H-rich envelope contains more than about 5% of the initial mass, the star is a RSG, and whenever the H-rich envelope contains less than 1% of the total mass, the star is a blue supergiant. For intermediate situations, intermediate colors and effective temperatures are obtained. Yellow progenitors for core-collapse supernovae can be explained by models with an enhanced mass-loss rate, while the red progenitors are better fitted by models with the standard mass-loss rate.

    Tracks of the enhanced mass loss rates models are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr ( or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A60

  139. Creevey, O., Thevenin, F., Berio, P., et al., (including von Braun, K.), 2015, A&A, 575, A26, Benchmark stars for Gaia Fundamental properties of the Population II star HD 140283 from interferometric, spectroscopic, and photometric data
    Metal-poor halo stars are important astrophysical laboratories that allow us to unravel details about many aspects of astrophysics, including the chemical conditions at the formation of our Galaxy, understanding the processes of diffusion in stellar interiors, and determining precise effective temperatures and calibration of colour-effective temperature relations. To address any of these issues the fundamental properties of the stars must first be determined. HD 140283 is the closest and brightest metal-poor Population II halo star (distance = 58 pc and V = 7.21), an ideal target that allows us to approach these questions, and one of a list of 34 benchmark stars defined for Gaia astrophysical parameter calibration. In the framework of characterizing these benchmark stars, we determined the fundamental properties of HD 140283 (radius, mass, age, and effective temperature) by obtaining new interferometric and spectroscopic measurements and combining them with photometry from the literature. The interferometric measurements were obtained using the visible interferometer VEGA on the CHARA array and we determined a 1D limb-darkened angular diameter of 1D = 0.353 0.013 milliarcsec. Using photometry from the literature we derived the bolometric flux in two ways: a zero reddening solution (AV = 0.0 mag) of Fbol of 3.890 0.066 10-8 erg s-1 cm-2, and a maximum of AV = 0.1 mag solution of 4.220 0.067 10-8 erg s-1 cm-2. The interferometric Teff is thus between 5534 103 K and 5647 105 K and its radius is R = 2.21 0.08R. Spectroscopic measurements of HD 140283 were obtained using HARPS, NARVAL, and UVES and a 1D LTE analysis of H line wings yielded Teffspec = 5626 75 K. Using fine-tuned stellar models including diffusion of elements we then determined the mass M and age t of HD 140283. Once the metallicity has been fixed, the age of the star depends on M, initial helium abundance Yi, andmixing-length parameter , only two of which are independent. We derive simple equations to estimate one from the other two. We need to adjust to much lower values than the solar one (~2) in order to fit the observations, and if AV = 0.0 mag then 0.5 1. We give an equation to estimate t from M, Yi (), and AV. Establishing a reference = 1.00 and adopting Yi = 0.245 we derive a mass and age of HD 140283: M = 0.780 0.010M and t = 13.7 0.7 Gyr (AV = 0.0 mag), or M = 0.805 0.010M and t = 12.2 0.6 Gyr (AV = 0.1 mag). Our stellar models yield an initial (interior) metal-hydrogen mass fraction of [ Z/X ] i = -1.70 and log g = 3.65 0.03. Theoretical advances allowing us to impose the mixing-length parameter would greatly improve the redundancy between M,Yi, and age, while from an observational point of view, accurate determinations of extinction along with asteroseismic observations would provide critical information allowing us to overcome the current limitations in our results.

    Based on observations with the VEGA/CHARA spectrointerferometer.Based on NARVAL and HARPS data obtained within the Gaia DPAC (Data Processing and Analysis Consortium) and coordinated by the GBOG (Ground-Based Observations for Gaia) working group, and on data retrieved from the ESO-ADP database.Full Table 12 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr ( or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A26

  140. Mann, A., von Braun, K., 2015, PASP, 127, 102, Revised Filter Profiles and Zero Points for Broadband Photometry
    Estimating accurate bolometric fluxes for stars requires reliable photometry to absolutely flux calibrate the spectra. This is a significant problem for studies of very bright stars, which are generally saturated in modern photometric surveys. Instead we must rely on photometry with less precise calibration. We utilize precisely flux-calibrated spectra to derive improved filter bandpasses and zero points for the most common sources of photometry for bright stars. In total we test 40 different filters in the General Catalog of Photometric Data as well as those from Tycho-2 and Hipparcos. We show that utilizing inaccurate filter profiles from the literature can create significant color terms resulting in fluxes that deviate by >10% from actual values. To remedy this we employ an empirical approach; we iteratively adjust the literature filter profile and zero point, convolve it with catalog spectra, and compare to the corresponding flux from the photometry. We adopt the passband values that produces the best agreement between photometry and spectroscopy and is independent of stellar color. We find that while most zero points change by <5%, a few systems change by 10-15%. Our final profiles and zero points are similar to recent estimates from the literature. Based on determinations of systematic errors in our selected spectroscopic libraries, we estimate that most of our improved zero points are accurate to 0.5-1% or better.
  141. Hsieh, H., Hainaut, O., Novakovic, B., et al., (including Moskovitz, N., Wasserman, L.), 2015, ApJL, 800, L16, Sublimation-Driven Activity in Main-Belt Comet 313p/Gibbs
    We present an observational and dynamical study of newly discovered main-belt comet 313P/Gibbs. We find that the object is clearly active both in observations obtained in 2014 and in precovery observations obtained in 2003 by the Sloan Digital Sky Survey, strongly suggesting that its activity is sublimation-driven. This conclusion is supported by a photometric analysis showing an increase in the total brightness of the comet over the 2014 observing period, and dust modeling results showing that the dust emission persists over at least three months during both active periods, where we find start dates for emission no later than 2003 July 24 10 for the 2003 active period and 2014 July 28 10 for the 2014 active period. From serendipitous observations by the Subaru Telescope in 2004 when the object was apparently inactive, we estimate that the nucleus has an absolute R-band magnitude of HR = 17.1 0.3, corresponding to an effective nucleus radius of re 1.00 0.15 km. The objects faintness at that time means we cannot rule out the presence of activity, and so this computed radius should be considered an upper limit. We find that 313Ps orbit is intrinsically chaotic, having a Lyapunov time of Tl = 12,000 yr and being located near two three-body mean-motion resonances with Jupiter and Saturn, 11J-1S-5A and 10J+12S-7A, yet appears stable over >50 Myr in an apparent example of stable chaos. We furthermore find that 313P is the second main-belt comet, after P/2012 T1 (PANSTARRS), to belong to the 155 Myr old Lixiaohua asteroid family.
  142. Tanner, A., Boyajian, T., von Braun, K., et al., (including van Belle, G.), 2015, ApJ, 800, 115, Stellar Parameters for HD 69830, a Nearby Star with Three Neptune Mass Planets and an Asteroid Belt
    We used the CHARA Array to directly measure the angular diameter of HD 69830, home to three Neptune mass planets and an asteroid belt. Our measurement of 0.674 0.014 mas for the limb-darkened angular diameter of this star leads to a physical radius of R * = 0.9058 0.0190 R and luminosity of L * = 0.622 0.014 L when combined with a fit to the spectral energy distribution of the star. Placing these observed values on an Hertzsprung-Russel diagram along with stellar evolution isochrones produces an age of 10.6 4 Gyr and mass of 0.863 0.043 M . We use archival optical echelle spectra of HD 69830 along with an iterative spectral fitting technique to measure the iron abundance ([Fe/H] = -0.04 0.03), effective temperature (5385 44 K), and surface gravity (log g = 4.49 0.06). We use these new values for the temperature and luminosity to calculate a more precise age of 7.5 3 Gyr. Applying the values of stellar luminosity and radius to recent models on the optimistic location of the habitable zone produces a range of 0.61-1.44 AU partially outside the orbit of the furthest known planet (d) around HD 69830. Finally, we estimate the snow line at a distance of 1.95 0.19 AU, which is outside the orbit of all three planets and its asteroid belt.
  143. Foster, J., Cottaar, M., Covey, K., et al., 2015, ApJ, 799, 136, IN-SYNC. II. Virial Stars from Subvirial Coresthe Velocity Dispersion of Embedded Pre-main-sequence Stars in NGC 1333
    The initial velocity dispersion of newborn stars is a major unconstrained aspect of star formation theory. Using near-infrared spectra obtained with the APOGEE spectrograph, we show that the velocity dispersion of young (1-2 Myr) stars in NGC 1333 is 0.92 0.12 km s-1 after correcting for measurement uncertainties and the effect of binaries. This velocity dispersion is consistent with the virial velocity of the region and the diffuse gas velocity dispersion, but significantly larger than the velocity dispersion of the dense, star-forming cores, which have a subvirial velocity dispersion of 0.5 km s-1. Since the NGC 1333 cluster is dynamically young and deeply embedded, this measurement provides a strong constraint on the initial velocity dispersion of newly formed stars. We propose that the difference in velocity dispersion between stars and dense cores may be due to the influence of a 70 G magnetic field acting on the dense cores or be the signature of a cluster with initial substructure undergoing global collapse.
  144. Calzetti, D., Lee, J., Sabbi, E., et al., (including Hunter, D.), 2015, AJ, 149, 51, Legacy Extragalactic UV Survey (LEGUS) With the Hubble Space Telescope. I. Survey Description
    The Legacy ExtraGalactic UV Survey (LEGUS) is a Cycle 21 Treasury program on the Hubble Space Telescope aimed at the investigation of star formation and its relation with galactic environment in nearby galaxies, from the scales of individual stars to those of kiloparsec-size clustered structures. Five-band imaging from the near-ultraviolet to the I band with the Wide-Field Camera 3 (WFC3), plus parallel optical imaging with the Advanced Camera for Surveys (ACS), is being collected for selected pointings of 50 galaxies within the local 12 Mpc. The filters used for the observations with the WFC3 are F275W(2704 A), F336W(3355 A), F438W(4325 A), F555W(5308 A), and F814W(8024 A) the parallel observations with the ACS use the filters F435W(4328 A), F606W(5921 A), and F814W(8057 A). The multiband images are yielding accurate recent (50 Myr) star formation histories from resolved massive stars and the extinction-corrected ages and masses of star clusters and associations. The extensive inventories of massive stars and clustered systems will be used to investigate the spatial and temporal evolution of star formation within galaxies. This will, in turn, inform theories of galaxy evolution and improve the understanding of the physical underpinning of the gas-star formation relation and the nature of star formation at high redshift. This paper describes the survey, its goals and observational strategy, and the initial scientific results. Because LEGUS will provide a reference survey and a foundation for future observations with the James Webb Space Telescope and with ALMA, a large number of data products are planned for delivery to the community.

    Based on observations obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA Contract NAS 5-26555.

  145. Boyajian, T., von Braun, K., Feiden, G., et al., (including van Belle, G.), 2015, MNRAS, 447, 846, Stellar diameters and temperatures - VI. High angular resolution measurements of the transiting exoplanet host stars HD 189733 and HD 209458 and implications for models of cool dwarfs
    We present direct radii measurements of the well-known transiting exoplanet host stars HD 189733 and HD 209458 using the CHARA Array interferometer. We find the limb-darkened angular diameters to be LD = 0.3848 0.0055 and 0.2254 0.0072 mas for HD 189733 and HD 209458, respectively. HD 189733 and HD 209458 are currently the only two transiting exoplanet systems where detection of the respective planetary companion's orbital motion from high-resolution spectroscopy has revealed absolute masses for both star and planet. We use our new measurements together with the orbital information from radial velocity and photometric time series data, Hipparcos distances, and newly measured bolometric fluxes to determine the stellar effective temperatures (Teff = 4875 43, 6092 103 K), stellar linear radii (R* = 0.805 0.016, 1.203 0.061 R), mean stellar densities (* = 1.62 0.11, 0.58 0.14 ), planetary radii (Rp = 1.216 0.024, 1.451 0.074 RJup), and mean planetary densities (p = 0.605 0.029, 0.196 0.033 Jup) for HD 189733b and HD 209458b, respectively. The stellar parameters for HD 209458, an F9 dwarf, are consistent with indirect estimates derived from spectroscopic and evolutionary modelling. However, we find that models are unable to reproduce the observational results for the K2 dwarf, HD 189733. We show that, for stellar evolutionary models to match the observed stellar properties of HD 189733, adjustments lowering the solar-calibrated mixing-length parameter to MLT =1.34 need to be employed.
  146. Heesen, V., Brinks, E., Krause, M., et al., (including Hunter, D.), 2015, MNRAS, 447, L1, The non-thermal superbubble in IC 10: the generation of cosmic ray electrons caught in the act.
    Superbubbles are crucial for stellar feedback, with supposedly high (of the order of 10 per cent) thermalization rates. We combined multiband radio continuum observations from the Very Large Array (VLA) with Effelsberg data to study the non-thermal superbubble (NSB) in IC 10, a starburst dwarf irregular galaxy in the Local Group. Thermal emission was subtracted using a combination of Balmer H and VLA 32 GHz continuum maps. The bubble's non-thermal spectrum between 1.5 and 8.8 GHz displays curvature and can be well fitted with a standard model of an ageing cosmic ray electron population. With a derived equipartition magnetic field strength of 44 8 G, and measuring the radiation energy density from Spitzer MIPS maps as 5 1 10-11 erg cm-3, we determine, based on the spectral curvature, a spectral age of the bubble of 1.0 0.3 Myr. Analysis of the LITTLE THINGS H I data cube shows an expanding H I hole with 100 pc diameter and a dynamical age 3.8 0.3 Myr, centred to within 16 pc on IC 10 X-1, a massive stellar mass black hole (M > 23 M). The results are consistent with the expected evolution for a superbubble with a few massive stars, where a very energetic event like a Type Ic supernova/hypernova has taken place about 1 Myr ago. We discuss alternatives to this interpretation.
  147. Moore, J., Howard, A., Schenk, P., et al., (including Grundy, W.), 2015, Icar, 246, 65, Geology before Pluto: Pre-encounter considerations
    The cameras of New Horizons will provide robust data sets that should be imminently amenable to geological analysis of the Pluto system's landscapes. In this paper, we begin with a brief discussion of the planned observations by the New Horizons cameras that will bear most directly on geological interpretability. Then we broadly review the major geological processes that could potentially operate on the surfaces of Pluto and its major moon Charon. We first survey exogenic processes (i.e. those for which energy for surface modification is supplied externally to the planetary surface): impact cratering, sedimentary processes (including volatile migration), and the work of wind. We conclude with an assessment of the prospects for endogenic activity in the form of tectonics and cryovolcanism.
  148. Cruikshank, D., Grundy, W., DeMeo, F., et al., 2015, Icar, 246, 82, The surface compositions of Pluto and Charon
    The surface of Pluto as it is understood on the eve of the encounter of the New Horizons spacecraft (mid-2015) consists of a spatially heterogeneous mix of solid N2, CH4, CO, C2H6, and an additional component that imparts color, and may not be an ice. The known molecular ices are detected by near-infrared spectroscopy. The N2 ice occurs in the hexagonal crystalline -phase, stable at T > 35.6 K. Spectroscopic evidence for wavelength shifts in the CH4 bands attests to the complex mixing of CH4 and N2 in the solid state, in accordance with the phase diagram for N2 + CH4. Spectra obtained at several aspects of Pluto's surface as the planet rotates over its 6.4-day period show variability in the distribution of CH4 and N2 ices, with stronger CH4 absorption bands associated with regions of higher albedo, in correlation with the visible rotational light curve. CO and N2 ice absorptions are also strongly modulated by the rotation period; the bands are strongest on the anti-Charon hemisphere of Pluto. Longer term changes in the strengths of Pluto's absorption bands occur as the viewing geometry changes on seasonal time-scales, although a complete cycle has not been observed. The non-ice component of Pluto's surface may be a relatively refractory material produced by the UV and cosmic-ray irradiation of the surface ices and gases in the atmosphere, although UV does not generally penetrate the atmospheric CH4 to interact with the surface. Laboratory simulations indicate that a rich chemistry ensues by the irradiation of mixtures of the ices known to occur on Pluto, but specific compounds have not yet been identified in spectra of the planet. Charon's surface is characterized by spectral bands of crystalline H2O ice, and a band attributed to one or more hydrates of NH3. Amorphous H2O ice may also be present; the balance between the amorphization and crystallization processes on Charon remains to be clarified. The albedo of Charon and its generally spatially uniform neutral color indicate that a component, not yet identified, is mixed in some way with the H2O and NH3nH2O ices. Among the many known small bodies in the transneptunian region, several share characteristics with Pluto and Charon, including the presence of CH4, N2, C2H6, H2O ices, as well as components that yield a wide variety of surface albedo and color. The New Horizons investigation of the Pluto-Charon system will generate new insight into the physical properties of the broader transneptunian population, and eventually to the corresponding bodies expected in the numerous planetary systems currently being discovered elsewhere in the Galaxy.
  149. Olkin, C., Young, L., Borncamp, D., et al., (including Wasserman, L.), 2015, Icar, 246, 220, Evidence that Pluto's atmosphere does not collapse from occultations including the 2013 May 04 event
    Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013, and models of energy balance between Pluto's surface and atmosphere, we find the preferred models are consistent with Pluto retaining a collisional atmosphere throughout its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N2 ice cap at Pluto's north rotational pole.
  150. Bosh, A., Person, M., Levine, S., et al., (including Dunham, E.), 2015, Icar, 246, 237, The state of Pluto's atmosphere in 2012-2013
    We observed two stellar occultations on UT 4 May 2013 and UT 9 September 2012, with the aim of measuring Pluto's atmospheric parameters. Both of these events were observed by world-wide collaborations of many observers, and both occurred within 1 month of Pluto's stationary points. The PC20120909 event was observed at the McDonald Observatory (MONET 1.2-m), and Olin Observatory (the Ortega 0.8-m); the P20130504 event was observed at the Las Campanas Observatory (du Pont 2.5-m), the Cerro Tololo Inter-American Observatory (SMARTS 1-m), and the Cerro Calan National Astronomical Observatory (Goto 0.45-m). Analysis of the data indicates an atmospheric state similar to that in June 2011. The shadow radius for the event is unchanged from recent events, indicating an atmosphere that is holding stable and not in the midst of global collapse. We discuss the advantages and disadvantages of comparing various atmospheric parameters across events (the shadow radius vs. the pressure at a particular radius). These analyses suggest that Pluto will still have an atmosphere when the New Horizons spacecraft arrives in July 2015.
  151. Porter, S., Grundy, W., 2015, Icar, 246, 360, Ejecta transfer in the Pluto system
    The small satellites of the Pluto system (Styx, Nix, Kerberos, and Hydra) have very low surface escape velocities, and impacts should therefore eject a large amount of material from their surfaces. We show that most of this material then escapes from the Pluto system, though a significant fraction collects on the surfaces of Pluto and Charon. The velocity at which the dust is ejected from the surfaces of the small satellites strongly determines which object it is likely to hit, and where on the surfaces of Pluto and Charon it is most likely to impact. We also show that the presence of an atmosphere around Pluto eliminates most particle size effects and increases the number of dust impacts on Pluto. In total, Pluto and Charon may have accumulated several centimeters of small-satellite dust on their surfaces, which could be observed by the New Horizons spacecraft.
  152. Ricker, G., Winn, J., Vanderspek, R., et al., (including Dunham, E.), 2015, JATIS, 1, 014003, Transiting Exoplanet Survey Satellite (TESS)
    The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its 2-year mission, TESS will employ four wide-field optical charge-coupled device cameras to monitor at least 200,000 main-sequence dwarf stars with IC4-13 for temporary drops in brightness caused by planetary transits. Each star will be observed for an interval ranging from 1 month to 1 year, depending mainly on the star's ecliptic latitude. The longest observing intervals will be for stars near the ecliptic poles, which are the optimal locations for follow-up observations with the James Webb Space Telescope. Brightness measurements of preselected target stars will be recorded every 2 min, and full frame images will be recorded every 30 min. TESS stars will be 10 to 100 times brighter than those surveyed by the pioneering Kepler mission. This will make TESS planets easier to characterize with follow-up observations. TESS is expected to find more than a thousand planets smaller than Neptune, including dozens that are comparable in size to the Earth. Public data releases will occur every 4 months, inviting immediate community-wide efforts to study the new planets. The TESS legacy will be a catalog of the nearest and brightest stars hosting transiting planets, which will endure as highly favorable targets for detailed investigations.
  153. Gunther, H., Poppenhaeger, K., Testa, P., et al., (including Shkolnik, E.), 2015, csss, 18, 25, Upgrading the Solar-Stellar Connection: News about activity in Cool Stars
    In this splinter session, ten speakers presented results on solar and stellar activity and how the two fields are connected. This was followed by a lively discussion and supplemented by short, one-minute highlight talks. The talks presented new theoretical and observational results on mass accretion on the Sun, the activity rate of flare stars, the evolution of the stellar magnetic field on time scales of a single cycle and over the lifetime of a star, and two different approaches to model the radial-velocity jitter in cool stars that is due to the granulation on the surface. Talks and discussion showed how much the interpretation of stellar activity data relies on the sun and how the large number of objects available in stellar studies can extend the parameter range of activity models.
  154. von Braun, K., Boyajian, T., van Belle, G., et al., 2015, csss, 18, 839, Characterizing the Parents: Exoplanets Around Cool Stars
    The large majority of stars in the Milky Way are late-type dwarfs, and the frequency of especially low-mass exoplanets in orbits around these late-type dwarfs appears to be high. In order to characterize the radiation environments and habitable zones of the cool exoplanet host stars, stellar radius and effective temperature, and thus luminosity, are required. It is in the stellar low-mass regime, however, where the predictive power of stellar models is often limited by sparse data quantity with which to calibrate the methods. We show results from our CHARA survey that provides directly determined stellar parameters based on interferometric diameter measurements, trigonometric parallax, and spectral energy distribution fitting.
  155. Levesque, E., Massey, P., Zytkow, A., et al., 2015, IAUS, 307, 57, Discovery of a Thorne-Zytkow object candidate in the Small Magellanic Cloud
    Thorne-Zytkow objects (TZOs) are a theoretical class of star in which a compact neutron star is surrounded by a large, diffuse envelope. Supergiant TZOs are predicted to be almost identical in appearance to red supergiants (RSGs), with their very red colors and cool temperatures placing them at the Hayashi limit on the H-R diagram. The only features that can be used at present to distinguish TZOs from the general RSG population are the unusually strong heavy-element and lithium lines present in their spectra. These elements are the unique products of the stars fully convective envelope linking the photosphere with the extraordinarily hot burning region in the vicinity of the neutron star core. We have recently discovered a TZO candidate in the Small Magellanic Cloud. It is the first star to display the distinctive chemical profile of anomalous element enhancements thought to be characteristic of TZOs however, up-to-date models and additional observable predictions (including potential asteroseismological signatures) are required to solidify this discovery. The definitive detection of a TZO would provide the first direct evidence for a completely new model of stellar interiors, a theoretically predicted fate for massive binary systems, and never-before-seen nucleosynthesis processes that would offer a new channel for heavy-element and lithium production in our universe.
  156. Massey, P., Neugent, K., Morrell, N., et al., 2015, IAUS, 307, 64, A New Class of Wolf-Rayet Stars: WN3/O3s
    Our new survey for Wolf-Rayet stars in the Magellanic Clouds is only 15% complete but has already found 9 new Wolf-Rayet (WR) stars in the Large Magellanic Cloud (LMC). This suggests that the total WR population in the LMC may be underestimated by 10-40%. Eight of the nine are of the WN subtype, demonstrating that the ``observed'' WC to WN ratio is too large, and is biased towards WC stars. The ninth is another rare WO star, the second we have found in the LMC in the past two years. Five (and possibly six) of the 8 WNs are of a new class of WRs, which pose a significant challenge to our understanding. Naively we would classify these stars as ``WN3+O3V,'' but there are several reasons why such a pairing is unlikely, not the least of which is that the absolute visual magnitudes of these stars are faint, with MV ~ -2.3 to -3.1. We have performed a preliminary analysis with the atmospheric code CMFGEN, and we find that (despite the faint visual magnitudes) the bolometric luminosities of these stars are normal for early-type WNs. Our fitting suggests that these stars are evolved, with significantly enriched N and He. Their effective temperatures are also normal for early-type WNs. What is unusual about these stars is that they have a surprisingly small mass-loss rate compared to other early-type WNs. How these stars got to be the way they are (single star evolution? binary evolution?) remains an open question. For now, we are designating this class as WN3/O3, in analogy to the late-type WN ``slash'' stars.
  157. Neugent, K., Massey, P., 2015, IAUS, 307, 127, The Close Binary Frequency of Wolf-Rayet Stars as a Function of Metallicity in M31 and M33
    Here we investigate whether the inability of the Geneva evolutionary models to predict a large enough WC/WN ratio at high metallicities (while succeeding at lower metallicities) is due to their single star nature. We hypothesize that Roche-lobe overflow in close binary systems may produce a greater number of WC stars at higher metallicities. But, this would suggest that the frequency of close massive binaries is metallicity dependent. We now present our results based on observations of ~100 Wolf-Rayet binaries in the varying metallicity environments of M31 and M33.
  158. van Belle, G., 2015, IAUS, 307, 252, Basics of Optical Interferometry: A Gentle Introduction
    The basic concepts of long-baseline optical interferometery are presented herein.
  159. Pasachoff, J., Person, M., Bosh, A., et al., (including Levine, S.), 2015, AAS, 225, 137.15, Trio of stellar occultations by Pluto One Year Prior to New Horizons' Arrival
    Our campaign in July 2014 yielded three successful stellar occultations (~m=15, 17, and 18) of Pluto (~m=14), observed from telescopes in New Zealand, Australia, and Chile. Telescopes involved included Chile: Magellan's Clay (6.5 m), SOAR (4.1 m), Carnegie's DuPont (2.4 m); Australia: AAT (4 m); and Canterbury's Mt. John McLellan (1-m); as well as various smaller telescopes in Australia and Chile. One of the events was also observed, with negative results, from GROND on La Silla (2.2 m) and SMARTS's ANDICAM at CTIO (1.3 m). Though our observations were coordinated across continents, each successfully observed event was seen from only one site because of bad weather at the other sites. Two of the events were uniquely observed from Mt. John (Pasachoff et al., DPS 2014) and one, with only Chile sites in the predicted path, from the Clay (Person et al., DPS 2014). This last event was expected to be of the brightest star with the largest telescope we have ever observed for a Pluto occultation, but clouds arrived at the 6.5-m Clay 90 s before the predicted time; a 1% occultation was nonetheless seen and eventually, confirmed by Keck AO observations, to be of a 15th magnitude star previously hidden in the brightness of the 12th mag star. Our scientific conclusion is that as of these observations, one year before New Horizons' passage of Pluto, the atmosphere of Pluto remained robust and of the same size. Details on our analysis of the three events will be presented.Acknowledgments: This work was supported in part by NASA Planetary Astronomy grants to Williams College (NNX12AJ29G) and to MIT (NNX10AB27G), as well as grants from USRA (#8500-98-003) and Ames Research (#NAS2-97-01) to Lowell Observatory. A.R.S. was supported by NSF grant AST-1005024 for the Keck Northeast Astronomy Consortium REU, with partial support from U.S. DoD's ASSURE program. P.R. acknowledges support from FONDECYT through grant 1120299. J.M.P. thanks Andrew Ingersoll and Caltech Planetary Astronomy for hospitality.
  160. Lister, T., Knight, M., Snodgrass, C., et al., 2015, AAS, 225, 137.22, LCOGT Network observations of spacecraft target comets
    Las Cumbres Observatory Global Telescope (LCOGT) network currently has 12 telescopes at 6 locations in the northern and southern hemispheres with expansion plans for more. This network is versatile and can respond rapidly to target of opportunity events and also perform long term monitoring of slowly changing astronomical phenomena.We have been using the LCOGT Network to perform photometric monitoring of comet 67P/Churyumov-Gerasimenko to support the ESA Rosetta comet mission and of C/2013 A1 (Siding Spring) as part of the ground-based observation teams for these important comets. This broadband photometry will allow a vital link between the detailed in-situ measurements made by the spacecraft and the global properties of the coma, at a time when the comet is only visible for short periods from single sites. The science we can extract includes the rotational state of the nucleus, characterization of the nucleus' activity, gas and dust properties in the coma (e.g., outflow velocities), chemical origin of gas species in the coma, and temporal behavior of the coma structure when the comet is close to the sun. Comet Siding Spring is a dynamically new comet on its first approach to the Sun that will pass close to Mars, so we can directly sample the composition of an original unaltered remnant of the protoplanetary disc. We will also be making use of specialized comet filters available at LCOGT's 2-m Faulkes Telescope North (FTN) to obtain a unique data set on comet C/2013 A1 (Siding Spring), as part of a large worldwide campaign. As one of only two robotic telescope equipped with cometary narrowband filters in the Northern hemisphere and having the largest aperture plus a high quality site, FTN can provide critical regular monitoring that cannot be achieved by any other single facility in the campaign.
  161. Benedict, G., Henry, T., McArthur, B., et al., (including Franz, O., Wasserman, L.), 2015, AAS, 225, 138.05, V and K-band Mass-Luminosity Relations for M dwarf Stars
    Applying Hubble Space Telescope Fine Guidance Sensor astrometric techniques developed to establish relative orbits for binary stars (Franz et al. 1998, AJ, 116, 1432), determine masses of binary components (Benedict et al. 2001, AJ, 121, 1607), and measure companion masses of exoplanet host stars (McArthur et al. 2010, ApJ, 715, 1203), we derive masses with an average 2.1% error for 24 components of 12 M dwarf binary star systems. Masses range 0.08 to 0.40 solar masses. With these we update the lower Main Sequence V-band Mass-Luminosity Relation first shown in Henry et al. (1999, ApJ, 512, 864). We demonstrate that a Mass-Luminosity Relation in the K-band has far less scatter than in the V-band. For the eight binary components for which we have component magnitude differences in the K-band the RMS residual drops from 0.5 magnitude in the V-band to 0.05 magnitude in the K-band. These relations can be used to estimate the masses of the ubiquitous red dwarfs that account for 75% of all stars, to an accuracy of 5%, which is much better than ever before.
  162. Douglas, S., Agueros, M., Covey, K., et al., 2015, AAS, 225, 138.19, Rotation and Activity in Praesepe and the Hyades
    Open clusters are single-age stellar populations that can be used to investigate the connection between angular-momentum evolution and magnetic activity for stars of different masses over their lifetimes. The Palomar Transient Factory (PTF) Open Cluster Survey (POCS) is an effort to measure rotation periods (Prot) and tracers of magnetic activity for stars in clusters ranging from 80 Myr and 3 Gyr. We present the results of a comparative study of the rotation-activity relationship in two benchmark 600 Myr-old open clusters: Praesepe and the Hyades. As they have similar ages and approximately solar metallicity, these clusters serve as an ideal laboratory for testing the agreement between theoretical and empirical rotation-activity relations at this age. We have compiled a sample of spectra -- more than half of which are new observations -- for 516 high-confidence members of Praesepe, along with new observations of 130 high-confidence Hyads. We have also collected Prot for 135 Praesepe members (including 40 Prot from POCS) and 87 Hyads. Unlike previous authors, we find no difference between the two clusters in their H-alpha equivalent width distributions, and therefore take the merged H-alpha and Prot data to be representative of 600-Myr-old stars. Our analysis shows that H-alpha activity in these stars is saturated for Rossby numbers Ro<0.11. Above that value activity declines as a power-law with a slope of -0.73, which is much shallower than has been observed for activity-rotation relations in the literature. These data provide a useful anchor for calibrating the age-activity-rotation relation beyond 600 Myr.
  163. Peacock, S., Barman, T., Shkolnik, E., 2015, AAS, 225, 138.26, HAZMAT II: Modeling the Evolution of Extreme-UV Radiation from M Stars
    M dwarf stars make up nearly 75% of the Milky Way's stellar population. Due to their low luminosities, the habitable zones around these stars are very close in (~0.1-0.4 AU), increasing the probability of finding terrestrial planets located in these regions. While there is evidence that stars emit their highest levels of far and near ultraviolet (FUV; NUV) radiation in the earliest stages of their evolution while planets are simultaneously forming and accumulating their atmospheres, we are currently unable to directly measure the extreme UV radiation (EUV). High levels of EUV radiation can alter the abundance of important molecules such as H2O, changing the chemistry in extrasolar planet atmospheres. Most previous stellar atmosphere models under-predict FUV and EUV emission from M dwarfs; here we present new models for M stars that include prescriptions for the hot, lowest density, atmospheric layers (chromosphere, transition region and corona), from which this radiation is emitted. By comparing our model spectra to GALEX near and far ultraviolet fluxes, we are able to predict the evolution of EUV radiation for M dwarfs from 10 Myr - 1 Gyr. This research is the next major step in the HAZMAT (HAbitable Zones and M dwarf Activity across Time) project to analyze how the habitable zone evolves with the evolving properties of stellar and planetary atmospheres.
  164. Blaha, C., Baildon, T., Mehta, S., et al., (including Massey, P.), 2015, AAS, 225, 141.07, Local Group Galaxy Emission-line Survey
    We present the results of the Local Group Galaxy Emission-line Survey of H emission regions in M31, M33 and seven dwarf galaxies in (NGC6822, IC10, WLM, Sextans A and B, Phoenix and Pegasus). Using data from the Local Group Galaxy Survey (LGGS - see Massey et al, 2006), we used continuum-subtracted Ha emission line images to define emission regions with a faint flux limit of 10 -17 ergs-sec-1-cm-2above the background. We have obtained photometric measurements for roughly 7450 H emission regions in M31, M33 and five of the seven dwarf galaxies (no regions for Phoenix or Pegasus). Using these regions, with boundaries defined by H-emission flux limits, we also measured fluxes for the continuum-subtracted [OIII] and [SII] images and constructed a catalog of H fluxes, region sizes and [OIII]/ H and [SII]/ H line ratios. The HII region luminosity functions and size distributions for the spiral galaxies M31 and M33 are compared with those of the dwarf galaxies NGC 6822 and IC10. For M31 and M33, the average [SII]/ H and [OIII]/ H line ratios, plotted as a function of galactocentric radius, display a linear trend with shallow slopes consistent with other studies of metallicity gradients in these galaxies. The galaxy-wide averages of [SII]/ H line ratios correlate with the masses of the dwarf galaxies following the previously established dwarf galaxy mass-metallicity relationship. The slope of the luminosity functions for the dwarf galaxies varies with galaxy mass. The Carleton Catalog of this Local Group Emission-line Survey will be made available on-line.
  165. Elmegreen, B., Struck, C., Hunter, D., 2015, AAS, 225, 143.09, Shrinking Galaxy Disks with Fountain-Driven Accretion from the Halo
    Star formation in most galaxies requires cosmic gas accretion because the gas consumption time is short compared to the Hubble time. This accretion presumably comes from a combination of infalling satellite debris, cold flows, and condensation of hot halo gas at the cool disk interface, perhaps aided by a galactic fountain. In general, the accretion will have a different specific angular momentum than the part of the disk that receives it, even if the gas comes from the nearby halo. Then the gas disk expands or shrinks over time. Here we show that condensation of halo gas at a rate proportional to the star formation rate in the fountain model will preserve an initial shape, such as an exponential, with a shrinking scale length, leaving behind a stellar disk with a slightly steeper profile of younger stars near the center. This process is slow for most galaxies, producing imperceptible radial speeds, and it may be dominated by other torques, but it could be important for Blue Compact Dwarfs, which tend to have large, irregular gas reservoirs and steep blue profiles in their inner stellar disks.
  166. Bowler, B., Liu, M., Shkolnik, E., et al., 2015, AAS, 225, 207.05, The Outer Architecture of M Dwarf Planetary Systems
    High-contrast imaging probes the outer architecture of planetary systems and enables direct studies of extrasolar giant planet atmospheres. M dwarfs have largely been neglected from previous surveys despite having more favorable planet-star contrasts and representing about 75% of all stars. As a result, little is known about the population of gas-giant planets at moderate separations (10-100 AU) in this stellar mass regime. I will describe results from the Planets Around Low-Mass Stars (PALMS) high-contrast adaptive optics imaging program targeting nearby (<35 pc) young (<300 Myr) M dwarfs with Keck/NIRC2 and Subaru/HiCIAO. With a sample size of over 120 stars, PALMS is the largest direct imaging planet search in this stellar mass regime. I will present the survey discoveries, statistical results, and implications for the formation of gas-giant planets around the most common stars in our galaxy.
  167. Cigan, P., Young, L., Cormier, D., et al., (including Hunter, D.), 2015, AAS, 225, 212.08, Herschel's View of LITTLE THINGS Metal-Poor Dwarf Galaxies
    Dwarf galaxies present interesting challenges for the studies of various galaxy properties, due in part to their faintness and their typically low metal content. Low metallicity can lead to quite different physical conditions in the ISM of these systems, which can affect star formation and other processes. To determine the structure of star-forming molecular clouds at low metallicity and moderate star formation rates, far infrared (FIR) fine-structure lines were mapped with Herschel in selected regions of five dwarf irregular galaxies with metal abundances ranging from 13% down to 5% of solar. Abundances of [C II] 158, [O I] 63, [N II] 122, and [O III] 88 microns - the major FIR cooling lines - help to probe the conditions in the gas, and allow us to put these dwarfs in context with spirals and other galaxy types. We report our integrated fluxes and line ratios, and discuss the results: [C II] is the dominant FIR coolant in these systems, and it mostly originates in PDRs instead of the more diffuse phase. Funding for this project was provided by NASA JPL RSA grant 1433776.
  168. Shkolnik, E., Rolph, K., Peacock, S., et al., 2015, AAS, 225, 229.01, Predicting Lyman-alpha and Mg II Fluxes from Low-Mass Stars
    A star's UV emission can greatly affect the atmospheric chemistry and physical properties of closely orbiting planets with the potential for severe mass loss. In particular, the Lyman-alpha emission line at 1216 A, which dominates the far-ultraviolet (FUV) spectrum, is a major source of photodissociation of important atmospheric molecules such as water and methane. The intrinsic flux of Lyman-alpha, however, cannot be directly measured due to the absorption of neutral hydrogen in the interstellar medium and contamination by geocoronal emission. To date, reconstruction of the intrinsic Lyman-alpha line based on Hubble Space Telescope spectra has been accomplished for a few dozen nearby stars, 28 of which have also been observed by the Galaxy Evolution Explorer (GALEX). Our investigation provides a correlation between published intrinsic Lyman-alpha and GALEX FUV and near-ultraviolet (NUV) chromospheric fluxes for K and M stars. The negative correlations between the ratio of the Lyman-alpha to the GALEX fluxes reveal how the relative strength of Lyman-alpha compared to the broadband fluxes weakens as the FUV and NUV excess flux increase. We also correlate GALEX fluxes with the strong near-ultraviolet Mg II h+k spectral emission lines formed at lower chromospheric temperatures than Lyman-alpha. The reported correlations provide estimates of intrinsic Lyman-alpha and Mg II fluxes for the thousands of K and M stars in the GALEX all-sky surveys. These will constrain new stellar upper-atmosphere models for cool stars and provide realistic inputs to models describing exoplanetary photochemistry and atmospheric evolution in the absence of ultraviolet spectroscopy.
  169. Prato, L., 2015, AAS, 225, 240.10, The Lowell Observatory Predoctoral Scholar Program
    Lowell Observatory is pleased to solicit applications for our Predoctoral Scholar Fellowship Program. Now beginning its seventh year, this program is designed to provide unique research opportunities to graduate students in good standing, currently enrolled at Ph.D. granting institutions. Lowell staff research spans a wide range of topics, from astronomical instrumentation, to icy bodies in our solar system, exoplanet science, stellar populations, star formation, and dwarf galaxies. The Observatory's new 4.2 meter Discovery Channel Telescope has successfully begun science operations and we anticipate the commissioning of several new instruments in 2015, making this a particularly exciting time in our history. Student research is expected to lead to a thesis dissertation appropriate for graduation at the doctoral level at the student's home institution. The Observatory provides competitive compensation and full benefits to student scholars. For more information, see http://www2.lowell.edu/rsch/predoc.php and links therein. Applications for Fall 2015 are due by May 1, 2015.
  170. Kitchener, B., Brinks, E., Heesen, V., et al., (including Hunter, D., Zhang, H.), 2015, AAS, 225, 248.16, A Radio Continuum Study of Dwarf Galaxies: 6 cm imaging of LITTLE THINGS
    To bypass uncertainties introduced by extinction caused by dust at optical wavelengths, we examine to what extent the radio continuum can probe star formation (SF) in dwarf galaxies. We provide VLA 6-cm C-array (4 to 8 GHz) radio continuum images with integrated flux densities for 40 dwarf galaxies taken from LITTLE THINGS. We find 27 harbor significant emission coincident with SF tracers; 17 are new detections. We infer the average thermal fraction to be 39 +- 25%. The LITTLE THINGS galaxies follow the Condon radio continuum - star formation rate (SFR) relation down to an SFR of 0.1 Msol/yr. At lower rates they follow a power-law characterized by a slope of 1.2 +- 0.1 with a scatter of 0.2 dex . We interpret this as an underproduction of the non-thermal radio continuum component. When considering the non-thermal radio continuum to star formation rate slope on its own, we find the slope to be 1.2. The magnetic field strength we find is typically 9.4 +- 3.8 muG in and around star forming regions which is similar to that in spiral galaxies. In a few dwarfs, the magnetic field strength can reach as high as 30 muG in localized 100 pc star forming regions. The underproduction of non-thermal radio continuum is likely due to the escape of Cosmic Ray electrons from the galaxy. The LITTLE THINGS galaxies are consistent with the radio continuum - far infrared luminosity relation. We observe a power-law slope of 1.06 +- 0.08 with a scatter of 0.24 dex which suggests that the 'conspiracy' of the radio continuum - far infrared relation continues to hold even for dwarf galaxies.
  171. Hunter, D., Rubio, M., Cigan, P., et al., 2015, AAS, 225, 248.17, CO at Low-metallicity: Molecular Clouds in the dwarf galaxy WLM
    Metallicity is not a passive result of galaxy evolution, but a crucial driver. Dwarf galaxies are low in heavy elements, which has important consequences for the ability to form cold, dense clouds that form stars. Molecular cores shrink and atomic envelopes grow in star-forming clouds as the metallicity drops. We are testing this picture of changing structure with metallicity with Herschel [CII]158 micron images of the photo-dissociation regions and ALMA maps of CO in star-forming regions in 4 dwarf irregular galaxies. These galaxies cover a range in metallicity from 13% solar to 5% solar. Here we report on the structure of the molecular clouds in WLM, a dwarf galaxy at 13% solar abundance where we for the first time detected CO emission at such a low heavy element abundance.The Herschel part of this work was supported by grant RSA #1433776 from JPL.
  172. Bruhns, S., Prato, L., 2015, AAS, 225, 256.04, An Investigation of Three Methods for Determining Young Star Spectral Types
    We present an investigation of several spectral typing techniques applied to 6 young, low-mass binary systems in the Taurus star-forming region (2 Myr). Spectra of resolution ~2000 were taken in the K band at Keck II using NIRC2 in grism spectroscopy mode where adaptive optics allowed us to resolve subarcsecond separations. We tested three different methods to determine spectral type to compare and contrast the strengths and weaknesses of each method. First, we used fits to standard star spectra to determine spectral types, extinctions, and K-band excesses. This method resulted in anomalously high extinctions not supported in the literature. It was also often difficult to distinguish between best fits. Second, we used the equivalent width ratios of IRTF SpeX standards to determine linear relationships onto which we plotted the equivalent width ratios of our sample stars. This method was complicated by low signal to noise in weak lines and the presence of significant circumstellar material around some of our sample of young stars, which may have inconsistently veiled and skewed our results. Third, we used K-band spectral indices and solar metallicity models to infer effective temperatures for our sample. This promising approach, applicable for the M-type stars in our sample, yields effective temperatures of several hundred degrees Kelvin lower than the other methods. Our main goal in this work is to highlight the uncertainties inherent in the typical procedures used for determining young star spectral types and encourage a concerted effort to define a more accurate and precise approach to the measurement of pre-main sequence effective temperature. Temperature is a fundamental stellar property without which our calibration of young star evolution, and by inference planet formation, is highly uncertain, even in the face of precisely measured stellar masses.
  173. Prato, L., Schaefer, G., 2015, AAS, 225, 256.11, Low-Mass Visual Companions to Young Spectroscopic Binaries
    Astronomers' knowledge of higher order multiplicity in young spectroscopic binaries is mostly anecdotal. However, surveys have found that most short-period, main sequence spectroscopic binaries are associated with companions. We present incremental results from our diffraction-limited adaptive optics imaging program to survey all pre-main sequence, spectroscopic binaries for tertiary companions down to delta(mag)=5 at separations >1" and delta(mag)=2 at >0.04'. We will explore the timescale for angular momentum evolution by comparing our results to the results from surveys of main sequence binaries in the literature.
  174. von Braun, K., Boyajian, T., Feiden, G., et al., (including van Belle, G.), 2015, AAS, 225, 257.02, Fundamental Parameters of the Two Hall-of-Famers HD 189733 and HD 209458
    HD 189733 and HD 209458 are two of the most thoroughly studied exoplanet systems. They also represent the only transiting systems for which spectroscopy studies have produced radial velocity signatures of both the planets and the parent stars, yielding direct mass measurements. We present the results of our interferometric radius measurements and spectrophotometric observations of these two hall-of-fame exoplanet hosts. Our results, combined with trigonometric parallaxes and literature broad-band photometry, yield empirical values for stellar and planetary radii and stellar effective temperatures and luminosities. Using the directly determined component masses from previous studies, we calculate surface gravities and bulk densities for the parent stars and their exoplanets, creating a nearly model-independent set of fundamental astrophysical parameters for two of exoplanet science's most important stepping stones.
  175. Boyajian, T., von Braun, K., Feiden, G., et al., 2015, AAS, 225, 257.03, Empirically determined properties of the K-dwarf HD 189733 and implications for evolutionary models of low-mass stars
    We present direct measurements of the stellar radii and effective temperatures for HD189733 and HD209458 (see poster by von Braun et al.). We use the stellar radius and temperature along with the mass from the Keplerian orbital solution to explore deviations with model predictions. The stellar properties for HD209458, a F9 dwarf, are consistent with indirect estimates derived from spectroscopic and evolutionary modeling. However, we find that models are unable to reproduce the observational results for the K2 dwarf, HD 189733. We show that, for stellar evolutionary models to match the observed stellar properties of HD 189733, adjustments lowering the solar-calibrated mixing length parameter need to be employed.
  176. Plavchan, P., Gao, P., Gagne, J., et al., (including Prato, L.), 2015, AAS, 225, 258.21, Precise Near-Infrared Radial Velocities
    We present precise radial velocity time-series from a 2.3 micron near-infrared survey to detect exoplanets around ~30 red, low mass, and young stars. We use the CSHELL spectrograph (R~46,000) at the NASA InfraRed Telescope Facility, combined with an isotopic methane absorption gas cell for common optical path relative wavelength calibration. We have developed a sophisticated RV forward modeling code that accounts for fringing and other instrumental artifacts present in the spectra (see poster by Gao et al. at this meeting). We are able to reach long-term radial velocity dispersions of ~15-30 m/s on our survey targets. With a spectral grasp of only 5 nm, this performance is near the expected photon and detector noise limit. We highlight future applications of our instrumentation and RV forward modeling code to iSHELL at IRTF (R~75,000), and an upgraded NIRSPEC on the Keck II telescope (R~50,000). With the increased spectral grasp of both spectrometers, we should be able to obtain a precision of less than 5 m/s in the near-infrared.
  177. Gao, P., Plavchan, P., Gagne, J., et al., (including Prato, L.), 2015, AAS, 225, 258.22, Retrieval of Precise Radial Velocities from High Resolution Near-Infrared Spectra of M Dwarfs
    We present a data analysis pipeline focused on obtaining precision radial velocities (RV) of M Dwarfs from spectra taken between 2.309 and 2.316 microns by the CSHELL spectrograph (R~46,000) at NASA's Infrared Telescope Facility with the aid of a methane isotopologue gas cell (see poster by Plavchan et al. at this meeting). The pipeline compares the observed spectra with a forward model defined by parameters that are optimized using a simplex amoeba algorithm. The stellar template is optimized simultaneously with the fit parameters in an iterative process. The pipeline accounts for temporal variations in the spectral wavelength solution, line spread function, and interference fringes due to instrumental effects. We apply our pipeline to the M Dwarfs GJ 15 A and GJ 876 and the M Giant SV Peg. For GJ 15 A, we are able to obtain 30 m/s RV precision. For the planet host GJ 876, the two most massive planets are easily retrievable from our RV curve. For SV Peg, the single night RV precision can be as low as 15 m/s, with < 5 m/s obtainable through data stacking.
  178. Llama, J., 2015, AAS, 225, 306.01, Detecting Exoplanetary Magnetic Fields
    Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System.Near-UV observations of the WASP-12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. A number of possible explanations have been suggested for this variation, including the presence of a magnetospheric bow shock arising from the interaction of the planet's magnetic field with the stellar wind from it's host star. Such observations provide the first method for directly detecting the presence of a magnetic field on exoplanets.The shape and size of such asymmetries is highly dependent on the structure of the host stars magnetic field at the time of observation. This implies we may observe highly varying near-UV transit light curves for the same system. These variations can then be used to learn about the geometry of the host star's magnetic field.In this presentation I will show modelling a bow shock around an exoplanet can help us to not only detect, but also also place constraints on the magnetic field strength of hot Jupiters. For some systems, such as HD 189733, we have maps of the surface magnetic field of the star at various epochs. I will also show how incorporating these maps into a stellar wind model, I can model the formation of a bow shock around the planet and hence demonstrate the variability of the near-UV transits.
  179. Henden, A., Levine, S., Terrell, D., et al., 2015, AAS, 225, 336.16, APASS - The Latest Data Release
    The AAVSO Photometric All-Sky Survey has just finished a new data release. This survey calibrates the entire sky, from 10.5mag to 16.5mag at V, and with 2.5arcsec resolution. Johnson B,V and Sloan g',r',i' filters are included. Each field is observed a minimum of 4 times on separate nights, with nightly calibrations using Landolt and SDSS standard stars. The current accuracy is 0.02mag photometry and 200mas astrometry. We have nearly completed the data acquisition for the main survey, and are starting a bright extension, measuring stars as bright as 7th magnitude and with additional u',z' and Y bandpasses. Copies of the current release can be obtained from our website or at the poster.
  180. van Belle, G., Ciardi, D., von Braun, K., et al., 2015, AAS, 225, 342.05, The PTI Giant Star Angular Size Survey: Effective Temperatures & Linear Radii
    We report new interferometric angular diameter observations of over 200 giant stars observed with the Palomar Testbed Interferometer (PTI). These angular diameters are combined with bolometric fluxes derived from detailed spectral energy distribution (SED) fits, to produce robust estimates of effective temperature (T_EFF). These SED fits include reddening estimates and are based upon fits of empirical spectral templates to literature photometry, and narrow-band photometry obtained at the Lowell 31" telescope. Over the range from G5III to M8III, T_EFF estimates are precise to 50K per spectral type. Radius estimates are limited by the improved Hipparcos estimates of van Leeuwen (2007) and are typically ~10% per star.
  181. Barandi, B., Massey, P., Levesque, E., 2015, AAS, 225, 342.23, Identification of Red Supergiants in the Magellanic Clouds.
    The number and characteristics of red supergiants (RSGs) in the low metallicity environment of the Large and Small Magellanic Clouds (LMC, SMC) provide tests of stellar evolutionary tracks for massive stars. One complication is identifying Magellanic members due to the contamination of foreground stars in the Milky Way. We used the colors and magnitudes from the 2MASS survey to identify RSG candidates in the LMC and SMC, and used the Anglo Australian Telescope coupled with the AAOmega spectrograph to take spectra of 325 LMC and 423 SMC RSG candidates. Using the Ca II triplet, we measured the radial velocity of each candidate by cross correlation and assigned membership. Methods along with physical properties of each star will be presented. We gratefully acknowledge support by the National Science Foundation through the REU program at Lowell Observatory and Northern Arizona University (AST-1004107) and through PM's grant AST-1008020.
  182. Encalada, F., Rosero, V., Prato, L., et al., 2015, AAS, 225, 345.10, Stellar Masses in the Mysterious Young Triple Star System AS 205
    The lack of accurate absolute mass measurements for young, low-mass pre-main sequence stars is problematic for the calibration of stellar evolutionary track models. An on-going program to increase the sample of young star masses begins with mass ratio measurements in spectroscopic binaries. By the end of its 5-year duration, the GAIA all-sky mission will provide new astrometric measurements for young spectroscopic binaries down to separations of tens of microarcseconds, yielding absolute masses for double-lined systems. We obtain mass ratios by taking high-resolution spectra of young double-lined spectroscopic binaries over a few epochs to construct a radial velocity versus phase diagram. For the young spectroscopic binary AS 205B, using eight of our own spectra supplied by the CSHELL instrument on the IRTF at Mauna Kea, plus one from the literature, we estimate a period of approximately 140 days, an eccentricity of 0.7, and a mass-ratio of 0.5. This spectroscopic system comprises the secondary in a 1.4'' visual binary in which both the A and B components are surrounded by optically thick, actively accreting disks, making AS 205B a member of that rare class of young spectroscopic binaries with a primordial circumbinary disk.
  183. Hollyday, G., Hunter, D., Little Things Team, 2015, AAS, 225, 435.01, Turbulence and Star Formation in Dwarf Galaxies
    We are interested in understanding the nature and role of turbulence in the interstellar medium of dwarf irregular galaxies. Turbulence, resulting from a variety of processes, is a potential source for cloud formation, and thus star formation. We have undertaken an indirect analysis of turbulence via the third (skewness) and fourth (kurtosis) moments of the distribution of atomic hydrogen gas densities using the LITTLE THINGS data for a 40-count sample of nearby (<10.3 Mpc) dwarf galaxies. We followed the formulism used by Burkhart et al. (2010) in a study of the SMC. We found that there is evidence of turbulence in dwarf galaxies at a level comparable to that found in the SMC, but we have found no correlation between integrated star formation rates and integrated kurtosis values nor a clear correlation between kurtosis as a function of radius with gas surface density and star formation profiles. We are grateful for a summer internship provided by the Research Experiences for Undergraduates program at Northern Arizona University, run by Dr. Kathy Eastwood and Dr. David Trilling and funded by the National Science Foundation through grant AST-1004107.
  184. Bowler, B., Liu, M., Shkolnik, E., et al., 2015, ApJS, 216, 7, Planets around Low-mass Stars (PALMS). IV. The Outer Architecture of M Dwarf Planetary Systems
    We present results from a high-contrast adaptive optics imaging search for giant planets and brown dwarfs (gsim1 M Jup) around 122 newly identified nearby (lsim40 pc) young M dwarfs. Half of our targets are younger than 135 Myr and 90% are younger than the Hyades (620 Myr). After removing 44 close stellar binaries (implying a stellar companion fraction of >35.4% 4.3% within 100 AU), 27 of which are new or spatially resolved for the first time, our remaining sample of 78 single M dwarfs makes this the largest imaging search for planets around young low-mass stars (0.1-0.6 M ) to date. Our H- and K-band coronagraphic observations with Keck/NIRC2 and Subaru/HiCIAO achieve typical contrasts of 12-14 mag and 9-13 mag at 1'', respectively, which correspond to limiting planet masses of 0.5-10 M Jup at 5-33 AU for 85% of our sample. We discovered four young brown dwarf companions: 1RXS J235133.3+312720 B (32 6 M Jup; L0+2-1; 120 20 AU), GJ 3629 B (64+30-23 M Jup; M7.5 0.5; 6.5 0.5 AU), 1RXS J034231.8+121622 B (35 8 M Jup; L0 1; 19.8 0.9 AU), and 2MASS J15594729+4403595 B (43 9 M Jup; M8.0 0.5; 190 20 AU). Over 150 candidate planets were identified; we obtained follow-up imaging for 56% of these but all are consistent with background stars. Our null detection of planets enables strong statistical constraints on the occurrence rate of long-period giant planets around single M dwarfs. We infer an upper limit (at the 95% confidence level) of 10.3% and 16.0% for 1-13 M Jup planets between 10-100 AU for hot-start and cold-start (Fortney) evolutionary models, respectively. Fewer than 6.0% (9.9%) of M dwarfs harbor massive gas giants in the 5-13 M Jup range like those orbiting HR 8799 and Pictoris between 10-100 AU for a hot-start (cold-start) formation scenario. The frequency of brown dwarf (13-75 M Jup) companions to single M dwarfs between 10-100 AU is 2.8+2.4-1.5%. Altogether we find that giant planets, especially massive ones, are rare in the outskirts of M dwarf planetary systems. Although the first directly imaged planets were found around massive stars, there is currently no statistical evidence for a trend of giant planet frequency with stellar host mass at large separations as predicted by the disk instability model of giant planet formation.

    Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This work was also based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  185. Liu, Y., Herczeg, G., Gong, M., et al., (including Shkolnik, E.), 2015, A&A, 573, A63, Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hydrae association
    We conducted Herschel/PACS observations of five very low-mass stars or brown dwarfs located in the TW Hya association with the goal of characterizing the properties of disks in the low stellar mass regime. We detected all five targets at 70 m and 100 m and three targets at 160 m. Our observations, combined with previous photometry from 2MASS, WISE, and SCUBA-2, enabled us to construct spectral energy distributions (SEDs) with extended wavelength coverage. Using sophisticated radiative transfer models, we analyzed the observed SEDs of the five detected objects with a hybrid fitting strategy that combines the model grids and the simulated annealing algorithm and evaluated the constraints on the disk properties via the Bayesian inference method. The modeling suggests that disks around low-mass stars and brown dwarfs are generally flatter than their higher mass counterparts, but the range of disk mass extends to well below the value found in T Tauri stars, and the disk scale heights are comparable in both groups. The inferred disk properties (i.e., disk mass, flaring, and scale height) in the low stellar mass regime are consistent with previous findings from large samples of brown dwarfs and very low-mass stars. We discuss the dependence of disk properties on their host stellar parameters and find a significant correlation between the Herschel far-IR fluxes and the stellar effective temperatures, probably indicating that the scaling between the stellar and disk masses (i.e., Mdisk M) observed mainly in low-mass stars may extend down to the brown dwarf regime.

    Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendix A is available in electronic form at http://www.aanda.org

  186. Knight, M., Schleicher, D., 2015, AJ, 149, 19, Observations of Comet ISON (C/2012 S1) from Lowell Observatory
    We observed the dynamically new sungrazing comet ISON (C/2012 S1) extensively at Lowell Observatory throughout 2013 in order to characterize its behavior prior to perihelion. ISON had typical abundances for an Oort Cloud comet. Its dust production, as measured by Af , remained nearly constant during the apparition but its CN gas production increased by 50 . The minimum active area necessary to support observed water production rates exceeded the likely surface area of the nucleus and suggests a population of icy grains in the coma. Together with the flattening of the dust radial profile over time, this is consistant with ejection of a large quantity of slow moving dust and icy grains in the coma at large heliocentric distance. The dust morphology was dominated by the tail, but a faint sunward dust fan was detected in March, April, May, and September. We imaged multiple gas species in September, October, and November. All gas species were more extended than the dust coma, although only CN had sufficient signal-to-noise for detailed morphological study. Excess CN signal was observed in the sunward hemisphere in September and early October. In November the excess CN signal was in the tailward hemisphere and two faint CN features appeared approximately orthogonal to the tail with position angles varying by about 20 from night to night. Using numerical modeling, we best reproduced the orientation and shape of these features as well as the bulk brightness with a pole oriented approximately toward the Sun and a single source located within 35 of the equator. Variations in position angle and relative brightness of the CN features from night to night suggest a rotation period shorter than 24 hr. The production rates and coma morphology suggest a nucleus that was active over nearly its entire sunward facing hemisphere in September and October but which underwent a significant mass loss event, potentially including fragmentation, shortly before November 1. Significant subsequent mass loss likely continued at the same site over subsequent days/weeks and may have catastrophically weakened the nucleus prior to perihelion.
  187. Hunter, D., 2015, llg, 243, Dwarf Irregular Galaxies of the Local Group: A Conference in honour of David Block and Bruce Elmegreen
    Local Group dwarf irregulars (dIrrs) cover an enormous range in star formation properties. Here I discuss these tiny galaxies as probes of star formation at the extremes of low gas densities and low metallicities. We have learned that (1) Star formation is inefficient in dIrrs and yet at very low _HI <0.5 M_{\odot}^{-2}) the star formation rate is higher than expected from a linear extrapolation from star formation at higher _HI. (2) Star formation correlates with existing stars and stellar feedback could be important. (3) Stellar disks go on for a long ways, often with very regular surface brightness profiles and reaching very low _HI. (4) Breaks in surface brightness profiles occur at about the same magnitude in both spirals and dwarfs, so something fundamental is taking place there. (5) Dwarf disks appear to grow from the "outside-in", contrary to spirals. (6) At low metallicity, star formation takes place in giant molecular clouds, but the photodissociation region is large.
  188. Vidotto, A., Bisikalo, D., Fossati, L., et al., (including Llama, J.), 2015, ASSL, 411, 153, Interpretations of WASP-12b Near-UV Observations
    The near-UV<IndexTerm> observations of the hot-Jupiter WASP-12b<IndexTerm> obtained by Fossati et al. have revealed the presence of an asymmetric transit lightcurve that is both more pronounced in the near-UV and starts at an earlier time than the optical lightcurve<IndexTerm> . These features of the near-UV transit of WASP-12b<IndexTerm> have intrigued several modellers. In this Chapter, we review the different interpretations of the near-UV observations of the system.
  189. Kloppenborg, B., van Belle, G., 2015, ASSL, 408, 157, Optical Interferometry of Giants and Supergiants
    Over the last several decades optical interferometers have made substantial gains in ability, evolving from simple two-telescope arrays with 10-m baselines that primarily measured the angular diameters of stars, to four- to six-telescope arrays with 300-m baselines that are capable of imaging objects at high spatial resolution (0.3 milli-arcseconds) and high spectral resolution (R 30, 000). This chapter highlights how optical interferometers have been used during the last three decades to study single and binary systems containing giant and supergiant stars. It reviews diameter measurements and astrometry for single and binary stars, discusses the asymmetric mass-loss processes seen in asymptotic giant-branch stars, shows how resolving stellar disks is helping to solve long-standing problems related to carbon stars, and summarizes some of the state-of-the-art techniques that are now being used to image spots and convective cells on supergiants.
  190. 189 publications and 8671 citations in 2015.

189 publications and 8671 citations total.