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Research involving Lowell Observatory staff 2015
(Articles and chapters)

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Years: 2015 Bottom

    2015

  1. Rebull, L., Stauffer, J., Cody, A., Gunther, H., Hillenbrand, L., Poppenhaeger, K., Wolk, S., Hora, J., Hernandez, J., Bayo, A., Covey, K., Forbrich, J., Gutermuth, R., Morales-Calderon, M., Plavchan, P., Song, I., Bouy, H., Terebey, S., Cuillandre, J., Allen, L., 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. Cochran, A., Levasseur-Regourd, A., Cordiner, M., Hadamcik, E., Lasue, J., Gicquel, A., Schleicher, D., Charnley, S., Mumma, M., Paganini, L., Bockelee-Morvan, D., Biver, N., Kuan, Y., 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.
  3. Samarasinha, N., Mueller, B., Knight, M., Farnham, T., Briol, J., Brosch, N., Caruso, J., Gao, X., Gomez, E., Lister, T., Hergenrother, C., Hoban, S., Prouty, R., Holloway, M., Howes, N., Guido, E., Hui, M., Jones, J., Penland, T., Thomas, S., Wyrosdick, J., Kiselev, N., Ivanova, A., Kaye, T., Eluo, J., Lau, B., Lin, Z., Martin, J., Moskvitin, A., Nicolini, M., Ottum, B., Pruzenski, C., Vogel, D., Kellett, L., Rapson, V., Schmid, J., Doyle, B., Dimino, F., Carlino, S., Safonova, M., Murthy, J., Sutaria, F., Schleicher, D., Snodgrass, C., Tezcan, C., Yorukoglu, O., Trowbridge, D., Whitmer, D., Ye, Q., 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.
  4. Zubko, E., Videen, G., Hines, D., Shkuratov, Y., Kaydash, V., Muinonen, K., Knight, M., Sitko, M., Lisse, C., Mutchler, M., Wooden, D., Li, J., Kobayashi, H., 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.
  5. 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.
  6. Orton, G., Fletcher, L., Encrenaz, T., Leyrat, C., Roe, H., Fujiyoshi, T., Pantin, E., 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.
  7. Bemporad, A., Giordano, S., Raymond, J., 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.
  8. Teske, J., Everett, M., Hirsch, L., Furlan, E., Horch, E., Howell, S., Ciardi, D., Gonzales, E., Crepp, J., 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.
  9. 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.

  10. Horch, E., van Belle, G., Davidson, J., Ciastko, L., Everett, M., Bjorkman, K., 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.
  11. Hui, M., Ye, Q., Knight, M., Battams, K., Clark, D., 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.
  12. Montet, B., Bowler, B., Shkolnik, E., Deck, K., Wang, J., Horch, E., Liu, M., Hillenbrand, L., Kraus, A., Charbonneau, D., 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.

  13. Pal, A., Kiss, C., Horner, J., Szakats, R., Vilenius, E., Muller, T., Acosta-Pulido, J., Licandro, J., Cabrera-Lavers, A., Sarneczky, K., Szabo, G., Thirouin, A., Sipocz, B., Dozsa, A., Duffard, R., 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.
  14. Schindler, K., 2015, enas, 1406, Lowell, Percival
    No abstract found.
  15. Egeland, R., Metcalfe, T., Hall, J., Henry, G., 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.
  16. Stern, S., Bagenal, F., Ennico, K., Gladstone, G., Grundy, W., McKinnon, W., Moore, J., Olkin, C., Spencer, J., Weaver, H., Young, L., Andert, T., Andrews, J., Banks, M., Bauer, B., Bauman, J., Barnouin, O., Bedini, P., Beisser, K., Beyer, R., Bhaskaran, S., Binzel, R., Birath, E., Bird, M., Bogan, D., Bowman, A., Bray, V., Brozovic, M., Bryan, C., Buckley, M., Buie, M., Buratti, B., Bushman, S., Calloway, A., Carcich, B., Cheng, A., Conard, S., Conrad, C., Cook, J., Cruikshank, D., Custodio, O., Dalle Ore, C., Deboy, C., Dischner, Z., Dumont, P., Earle, A., Elliott, H., Ercol, J., Ernst, C., Finley, T., Flanigan, S., Fountain, G., Freeze, M., Greathouse, T., Green, J., Guo, Y., Hahn, M., Hamilton, D., Hamilton, S., Hanley, J., Harch, A., Hart, H., Hersman, C., Hill, A., Hill, M., Hinson, D., Holdridge, M., Horanyi, M., Howard, A., Howett, C., Jackman, C., Jacobson, R., Jennings, D., Kammer, J., Kang, H., Kaufmann, D., Kollmann, P., Krimigis, S., Kusnierkiewicz, D., Lauer, T., Lee, J., Lindstrom, K., Linscott, I., Lisse, C., Lunsford, A., Mallder, V., Martin, N., McComas, D., McNutt, R., Mehoke, D., Mehoke, T., Melin, E., Mutchler, M., Nelson, D., Nimmo, F., Nunez, J., Ocampo, A., Owen, W., Paetzold, M., Page, B., Parker, A., Parker, J., Pelletier, F., Peterson, J., Pinkine, N., Piquette, M., Porter, S., Protopapa, S., Redfern, J., Reitsema, H., Reuter, D., Roberts, J., Robbins, S., Rogers, G., Rose, D., Runyon, K., Retherford, K., Ryschkewitsch, M., Schenk, P., Schindhelm, R., Sepan, B., Showalter, M., Singer, K., Soluri, M., Stanbridge, D., Steffl, A., Strobel, D., Stryk, T., Summers, M., Szalay, J., Tapley, M., Taylor, A., Taylor, H., Throop, H., Tsang, C., Tyler, G., Umurhan, O., Verbiscer, A., Versteeg, M., Vincent, M., Webbert, R., Weidner, S., Weigle, G., White, O., Whittenburg, K., Williams, B., Williams, K., Williams, S., Woods, W., Zangari, A., Zirnstein, E., 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.
  17. Gouliermis, D., Thilker, D., Elmegreen, B., Elmegreen, D., Calzetti, D., Lee, J., Adamo, A., Aloisi, A., Cignoni, M., Cook, D., Dale, D., Gallagher, J., Grasha, K., Grebel, E., Davo, A., Hunter, D., Johnson, K., Kim, H., Nair, P., Nota, A., Pellerin, A., Ryon, J., Sabbi, E., Sacchi, E., Smith, L., Tosi, M., Ubeda, L., Whitmore, B., 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.
  18. Zellem, R., Griffith, C., Pearson, K., Turner, J., Henry, G., Williamson, M., Ryleigh Fitzpatrick, M., Teske, J., 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.
  19. Dias-Oliveira, A., Sicardy, B., Lellouch, E., Vieira-Martins, R., Assafin, M., Camargo, J., Braga-Ribas, F., Gomes-Junior, A., Benedetti-Rossi, G., Colas, F., Decock, A., Doressoundiram, A., Dumas, C., Emilio, M., Fabrega Polleri, J., Gil-Hutton, R., Gillon, M., Girard, J., Hau, G., Ivanov, V., Jehin, E., Lecacheux, J., Leiva, R., Lopez-Sisterna, C., Mancini, L., Manfroid, J., Maury, A., Meza, E., Morales, N., Nagy, L., Opitom, C., Ortiz, J., Pollock, J., Roques, F., Snodgrass, C., Soulier, J., Thirouin, A., Vanzi, L., Widemann, T., Reichart, D., LaCluyze, A., Haislip, J., Ivarsen, K., Dominik, M., Jrgensen, U., Skottfelt, J., 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).

  20. Rubio, M., Elmegreen, B., Hunter, D., Brinks, E., Cortes, J., Cigan, P., 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.
  21. Schleicher, D., Bair, A., Sackey, S., 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.
  22. Grundy, W., Porter, S., Benecchi, S., Roe, H., Noll, K., Trujillo, C., Thirouin, A., Stansberry, J., Barker, E., Levison, H., 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.
  23. Ciardi, D., van Eyken, J., Barnes, J., Beichman, C., Carey, S., Crockett, C., Eastman, J., Johns-Krull, C., Howell, S., Kane, S., . Mclane, J., Plavchan, P., Prato, L., Stauffer, J., 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.
  24. Prato, L., Mace, G., Rice, E., McLean, I., Kirkpatrick, J., Burgasser, A., Kim, S., 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.
  25. Cottaar, M., Covey, K., Foster, J., Meyer, M., Tan, J., Nidever, D., Chojnowski, S., da Rio, N., Flaherty, K., Frinchaboy, P., Majewski, S., Skrutskie, M., Wilson, J., Zasowski, G., 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.
  26. 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.

  27. Angerhausen, D., Mandushev, G., Mandell, A., Dunham, E., Becklin, E., Collins, P., Hamilton, R., Logsdon, S., McElwain, M., McLean, I., Pfuller, E., Savage, M., Shenoy, S., Vacca, W., van Cleve, J., Wolf, J., 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.
  28. Navarrete, C., Chaname, J., Ramirez, I., Meza, A., Anglada-Escude, G., 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.

  29. Alam, S., Albareti, F., Allende Prieto, C., Anders, F., Anderson, S., Anderton, T., Andrews, B., Armengaud, E., Aubourg, E., Bailey, S., Basu, S., Bautista, J., Beaton, R., Beers, T., Bender, C., Berlind, A., Beutler, F., Bhardwaj, V., Bird, J., Bizyaev, D., Blake, C., Blanton, M., Blomqvist, M., Bochanski, J., Bolton, A., Bovy, J., Shelden Bradley, A., Brandt, W., Brauer, D., Brinkmann, J., Brown, P., Brownstein, J., Burden, A., Burtin, E., Busca, N., Cai, Z., Capozzi, D., Carnero Rosell, A., Carr, M., Carrera, R., Chambers, K., Chaplin, W., Chen, Y., Chiappini, C., Chojnowski, S., Chuang, C., Clerc, N., Comparat, J., Covey, K., Croft, R., Cuesta, A., Cunha, K., da Costa, L., Da Rio, N., Davenport, J., Dawson, K., De Lee, N., Delubac, T., Deshpande, R., Dhital, S., Dutra-Ferreira, L., Dwelly, T., Ealet, A., Ebelke, G., Edmondson, E., Eisenstein, D., Ellsworth, T., Elsworth, Y., Epstein, C., Eracleous, M., Escoffier, S., Esposito, M., Evans, M., Fan, X., Fernandez-Alvar, E., Feuillet, D., Filiz Ak, N., Finley, H., Finoguenov, A., Flaherty, K., Fleming, S., Font-Ribera, A., Foster, J., Frinchaboy, P., Galbraith-Frew, J., Garcia, R., Garcia-Hernandez, D., Garcia Perez, A., Gaulme, P., Ge, J., Genova-Santos, R., Georgakakis, A., Ghezzi, L., Gillespie, B., Girardi, L., Goddard, D., Gontcho, S., Gonzalez Hernandez, J., Grebel, E., Green, P., Grieb, J., Grieves, N., Gunn, J., Guo, H., Harding, P., Hasselquist, S., Hawley, S., Hayden, M., Hearty, F., Hekker, S., Ho, S., Hogg, D., Holley-Bockelmann, K., Holtzman, J., Honscheid, K., Huber, D., Huehnerhoff, J., Ivans, I., Jiang, L., Johnson, J., Kinemuchi, K., Kirkby, D., Kitaura, F., Klaene, M., Knapp, G., Kneib, J., Koenig, X., Lam, C., Lan, T., Lang, D., Laurent, P., Le Goff, J., Leauthaud, A., Lee, K., Lee, Y., Licquia, T., Liu, J., Long, D., Lopez-Corredoira, M., Lorenzo-Oliveira, D., Lucatello, S., Lundgren, B., Lupton, R., Mack, C., Mahadevan, S., Maia, M., Majewski, S., Malanushenko, E., Malanushenko, V., Manchado, A., Manera, M., Mao, Q., Maraston, C., Marchwinski, R., Margala, D., Martell, S., Martig, M., Masters, K., Mathur, S., McBride, C., McGehee, P., McGreer, I., McMahon, R., Menard, B., Menzel, M., Merloni, A., Meszaros, S., Miller, A., Miralda-Escude, J., Miyatake, H., Montero-Dorta, A., More, S., Morganson, E., Morice-Atkinson, X., Morrison, H., Mosser, B., Muna, D., Myers, A., Nandra, K., Newman, J., Neyrinck, M., Nguyen, D., Nichol, R., Nidever, D., Noterdaeme, P., Nuza, S., O'Connell, J., O'Connell, R., O'Connell, R., Ogando, R., Olmstead, M., Oravetz, A., Oravetz, D., Osumi, K., Owen, R., Padgett, D., Padmanabhan, N., Paegert, M., Palanque-Delabrouille, N., Pan, K., Parejko, J., Paris, I., Park, C., Pattarakijwanich, P., Pellejero-Ibanez, M., Pepper, J., Percival, W., Perez-Fournon, I., Perez-Rafols, I., Petitjean, P., Pieri, M., Pinsonneault, M., Porto de Mello, G., Prada, F., Prakash, A., Price-Whelan, A., Protopapas, P., Raddick, M., Rahman, M., Reid, B., Rich, J., Rix, H., Robin, A., Rockosi, C., Rodrigues, T., Rodriguez-Torres, S., Roe, N., Ross, A., Ross, N., Rossi, G., Ruan, J., Rubino-Martin, J., Rykoff, E., Salazar-Albornoz, S., Salvato, M., Samushia, L., Sanchez, A., Santiago, B., Sayres, C., Schiavon, R., Schlegel, D., Schmidt, S., Schneider, D., Schultheis, M., Schwope, A., Scoccola, C., Scott, C., Sellgren, K., Seo, H., Serenelli, A., Shane, N., Shen, Y., Shetrone, M., Shu, Y., Silva Aguirre, V., Sivarani, T., Skrutskie, M., Slosar, A., Smith, V., Sobreira, F., Souto, D., Stassun, K., Steinmetz, M., Stello, D., Strauss, M., Streblyanska, A., Suzuki, N., Swanson, M., Tan, J., Tayar, J., Terrien, R., Thakar, A., Thomas, D., Thomas, N., Thompson, B., Tinker, J., Tojeiro, R., Troup, N., Vargas-Magana, M., Vazquez, J., Verde, L., Viel, M., Vogt, N., Wake, D., Wang, J., Weaver, B., Weinberg, D., Weiner, B., White, M., Wilson, J., Wisniewski, J., Wood-Vasey, W., Ye`che, C., York, D., Zakamska, N., Zamora, O., Zasowski, G., Zehavi, I., Zhao, G., Zheng, Z., Zhou, X., Zhou, Z., Zou, H., Zhu, G., 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.
  30. Knight, M., Mueller, B., Samarasinha, N., 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.
  31. Carnerero, M., Raiteri, C., Villata, M., Acosta-Pulido, J., D'Ammando, F., Smith, P., Larionov, V., Agudo, I., Arevalo, M., Arkharov, A., Bach, U., Bachev, R., Benitez, E., Blinov, D., Bozhilov, V., Buemi, C., Bueno Bueno, A., Carosati, D., Casadio, C., Chen, W., Damljanovic, G., di Paola, A., Efimova, N., Ehgamberdiev, S., Giroletti, M., Gomez, J., Gonzalez-Morales, P., Grinon-Marin, A., Grishina, T., Gurwell, M., Hiriart, D., Hsiao, H., Ibryamov, S., Jorstad, S., Joshi, M., Kopatskaya, E., Kurtanidze, O., Kurtanidze, S., Lahteenmaki, A., Larionova, E., Larionova, L., Lazaro, C., Leto, P., Lin, C., Lin, H., Manilla-Robles, A., Marscher, A., McHardy, I., Metodieva, Y., Mirzaqulov, D., Mokrushina, A., Molina, S., Morozova, D., Nikolashvili, M., Orienti, M., Ovcharov, E., Panwar, N., Pastor Yabar, A., Puerto Gimenez, I., Ramakrishnan, V., Richter, G., Rossini, M., Sigua, L., Strigachev, A., Taylor, B., Tornikoski, M., Trigilio, C., Troitskaya, Y., Troitsky, I., Umana, G., Valcheva, A., Velasco, S., Vince, O., Wehrle, A., Wiesemeyer, H., 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.
  32. Aigrain, S., Llama, J., Ceillier, T., Chagas, M., Davenport, J., Garcia, R., Hay, K., Lanza, A., McQuillan, A., Mazeh, T., de Medeiros, J., Nielsen, M., Reinhold, T., 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.
  33. French, L., Stephens, R., Coley, D., Wasserman, L., Sieben, J., 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.
  34. Johnson, M., Hunter, D., Wood, S., Oh, S., Zhang, H., 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.
  35. Kane, S., Boyajian, T., Henry, G., Feng, Y., Hinkel, N., Fischer, D., von Braun, K., Howard, A., Wright, J., 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.
  36. 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.
  37. Oh, S., Hunter, D., Brinks, E., Elmegreen, B., Schruba, A., Walter, F., Rupen, M., Young, L., Simpson, C., Johnson, M., Herrmann, K., Ficut-Vicas, D., Cigan, P., Heesen, V., Ashley, T., Zhang, H., 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.
  38. Protopapa, S., Grundy, W., Tegler, S., Bergonio, J., 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.
  39. Borsa, F., Scandariato, G., Rainer, M., Bignamini, A., Maggio, A., Poretti, E., Lanza, A., Di Mauro, M., Benatti, S., Biazzo, K., Bonomo, A., Damasso, M., Esposito, M., Gratton, R., Affer, L., Barbieri, M., Boccato, C., Claudi, R., Cosentino, R., Covino, E., Desidera, S., Fiorenzano, A., Gandolfi, D., Harutyunyan, A., Maldonado, J., Micela, G., Molaro, P., Molinari, E., Pagano, I., Pillitteri, I., Piotto, G., Shkolnik, E., Silvotti, R., Smareglia, R., Southworth, J., Sozzetti, A., Stelzer, B., 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 (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A64

  40. Bowler, B., Shkolnik, E., Liu, M., Schlieder, J., Mann, A., Dupuy, T., Hinkley, S., Crepp, J., Johnson, J., Howard, A., Flagg, L., Weinberger, A., Aller, K., Allers, K., Best, W., Kotson, M., Montet, B., Herczeg, G., Baranec, C., Riddle, R., Law, N., Nielsen, E., Wahhaj, Z., Biller, B., Hayward, T., 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)).

  41. Mann, A., Feiden, G., Gaidos, E., Boyajian, T., 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.
  42. Reddy, V., Vokrouhlicky, D., Bottke, W., Pravec, P., Sanchez, J., Gary, B., Klima, R., Cloutis, E., Galad, A., Guan, T., Hornoch, K., Izawa, M., Kusnirak, P., Le Corre, L., Mann, P., Moskovitz, N., Skiff, B., Vrastil, J., 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.
  43. Maldonado, J., Affer, L., Micela, G., Scandariato, G., Damasso, M., Stelzer, B., Barbieri, M., Bedin, L., Biazzo, K., Bignamini, A., Borsa, F., Claudi, R., Covino, E., Desidera, S., Esposito, M., Gratton, R., Gonzalez Hernandez, J., Lanza, A., Maggio, A., Molinari, E., Pagano, I., Perger, M., Pillitteri, I., Piotto, G., Poretti, E., Prisinzano, L., Rebolo, R., Ribas, I., Shkolnik, E., Southworth, J., Sozzetti, A., Suarez Mascareno, A., 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 (ftp://130.79.128.5) 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

  44. Garcia, E., Dupuy, T., Allers, K., Liu, M., Deacon, N., 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.
  45. Ortiz, J., Duffard, R., Pinilla-Alonso, N., Alvarez-Candal, A., Santos-Sanz, P., Morales, N., Fernandez-Valenzuela, E., Licandro, J., Campo Bagatin, A., 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 (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/576/A18

  46. Johnson, J., Grundy, W., Lemmon, M., Bell, J., Deen, R., 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.
  47. 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.
  48. Sozzetti, A., Bonomo, A., Biazzo, K., Mancini, L., Damasso, M., Desidera, S., Gratton, R., Lanza, A., Poretti, E., Rainer, M., Malavolta, L., Affer, L., Barbieri, M., Bedin, L., Boccato, C., Bonavita, M., Borsa, F., Ciceri, S., Claudi, R., Gandolfi, D., Giacobbe, P., Henning, T., Knapic, C., Latham, D., Lodato, G., Maggio, A., Maldonado, J., Marzari, F., Martinez Fiorenzano, A., Micela, G., Molinari, E., Mordasini, C., Nascimbeni, V., Pagano, I., Pedani, M., Pepe, F., Piotto, G., Santos, N., Scandariato, G., Shkolnik, E., Southworth, J., 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

  49. Del Castillo, E., Corbally, C., Falco, E., Green, R., Hall, J., Williams, G., 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.
  50. Meynet, G., Chomienne, V., Ekstrom, S., Georgy, C., Granada, A., Groh, J., Maeder, A., Eggenberger, P., Levesque, E., 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 (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A60

  51. Creevey, O., Thevenin, F., Berio, P., Heiter, U., von Braun, K., Mourard, D., Bigot, L., Boyajian, T., Kervella, P., Morel, P., Pichon, B., Chiavassa, A., Nardetto, N., Perraut, K., Meilland, A., Mc Alister, H., ten Brummelaar, T., Farrington, C., Sturmann, J., Sturmann, L., Turner, N., 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 (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A26

  52. 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.
  53. Hsieh, H., Hainaut, O., Novakovic, B., Bolin, B., Denneau, L., Fitzsimmons, A., Haghighipour, N., Kleyna, J., Kokotanekova, R., Lacerda, P., Meech, K., Micheli, M., Moskovitz, N., Schunova, E., Snodgrass, C., Wainscoat, R., Wasserman, L., Waszczak, A., 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.
  54. Tanner, A., Boyajian, T., von Braun, K., Kane, S., Brewer, J., Farrington, C., van Belle, G., Beichman, C., Fischer, D., ten Brummelaar, T., McAlister, H., Schaefer, 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.
  55. Foster, J., Cottaar, M., Covey, K., Arce, H., Meyer, M., Nidever, D., Stassun, K., Tan, J., Chojnowski, S., da Rio, N., Flaherty, K., Rebull, L., Frinchaboy, P., Majewski, S., Skrutskie, M., Wilson, J., Zasowski, G., 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.
  56. Calzetti, D., Lee, J., Sabbi, E., Adamo, A., Smith, L., Andrews, J., Ubeda, L., Bright, S., Thilker, D., Aloisi, A., Brown, T., Chandar, R., Christian, C., Cignoni, M., Clayton, G., da Silva, R., de Mink, S., Dobbs, C., Elmegreen, B., Elmegreen, D., Evans, A., Fumagalli, M., Gallagher, J., Gouliermis, D., Grebel, E., Herrero, A., Hunter, D., Johnson, K., Kennicutt, R., Kim, H., Krumholz, M., Lennon, D., Levay, K., Martin, C., Nair, P., Nota, A., Ostlin, G., Pellerin, A., Prieto, J., Regan, M., Ryon, J., Schaerer, D., Schiminovich, D., Tosi, M., Van Dyk, S., Walterbos, R., Whitmore, B., Wofford, A., 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.

  57. Boyajian, T., von Braun, K., Feiden, G., Huber, D., Basu, S., Demarque, P., Fischer, D., Schaefer, G., Mann, A., White, T., Maestro, V., Brewer, J., Lamell, C., Spada, F., Lopez-Morales, M., Ireland, M., Farrington, C., van Belle, G., Kane, S., Jones, J., ten Brummelaar, T., Ciardi, D., McAlister, H., Ridgway, S., Goldfinger, P., Turner, N., Sturmann, L., 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.
  58. Heesen, V., Brinks, E., Krause, M., Harwood, J., Rau, U., Rupen, M., Hunter, D., Chyzy, K., Kitchener, G., 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.
  59. Moore, J., Howard, A., Schenk, P., McKinnon, W., Pappalardo, R., Ewing, R., Bierhaus, E., Bray, V., Spencer, J., Binzel, R., Buratti, B., Grundy, W., Olkin, C., Reitsema, H., Reuter, D., Stern, S., Weaver, H., Young, L., Beyer, R., 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.
  60. Cruikshank, D., Grundy, W., DeMeo, F., Buie, M., Binzel, R., Jennings, D., Olkin, C., Parker, J., Reuter, D., Spencer, J., Stern, S., Young, L., Weaver, H., 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.
  61. Olkin, C., Young, L., Borncamp, D., Pickles, A., Sicardy, B., Assafin, M., Bianco, F., Buie, M., de Oliveira, A., Gillon, M., French, R., Ramos Gomes, A., Jehin, E., Morales, N., Opitom, C., Ortiz, J., Maury, A., Norbury, M., Braga-Ribas, F., Smith, R., Wasserman, L., Young, E., Zacharias, M., Zacharias, N., 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.
  62. Bosh, A., Person, M., Levine, S., Zuluaga, C., Zangari, A., Gulbis, A., Schaefer, G., Dunham, E., Babcock, B., Davis, A., Pasachoff, J., Rojo, P., Servajean, E., Forster, F., Oswalt, T., Batcheldor, D., Bell, D., Bird, P., Fey, D., Fulwider, T., Geisert, E., Hastings, D., Keuhler, C., Mizusawa, T., Solenski, P., Watson, B., 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.
  63. 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.
  64. Ricker, G., Winn, J., Vanderspek, R., Latham, D., Bakos, G., Bean, J., Berta-Thompson, Z., Brown, T., Buchhave, L., Butler, N., Butler, R., Chaplin, W., Charbonneau, D., Christensen-Dalsgaard, J., Clampin, M., Deming, D., Doty, J., De Lee, N., Dressing, C., Dunham, E., Endl, M., Fressin, F., Ge, J., Henning, T., Holman, M., Howard, A., Ida, S., Jenkins, J., Jernigan, G., Johnson, J., Kaltenegger, L., Kawai, N., Kjeldsen, H., Laughlin, G., Levine, A., Lin, D., Lissauer, J., MacQueen, P., Marcy, G., McCullough, P., Morton, T., Narita, N., Paegert, M., Palle, E., Pepe, F., Pepper, J., Quirrenbach, A., Rinehart, S., Sasselov, D., Sato, B., Seager, S., Sozzetti, A., Stassun, K., Sullivan, P., Szentgyorgyi, A., Torres, G., Udry, S., Villasenor, J., 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.
  65. Gunther, H., Poppenhaeger, K., Testa, P., Borgniet, S., Brun, A., Cegla, H., Garraffo, C., Kowalski, A., Shapiro, A., Shkolnik, E., Spada, F., Vidotto, A., 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.
  66. von Braun, K., Boyajian, T., van Belle, G., Mann, A., Kane, S., 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.
  67. Levesque, E., Massey, P., Zytkow, A., Morrell, N., 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.
  68. Massey, P., Neugent, K., Morrell, N., Hillier, D., 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.
  69. 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.
  70. 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.
  71. Bowler, B., Liu, M., Shkolnik, E., Tamura, M., 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.

  72. Liu, Y., Herczeg, G., Gong, M., Allers, K., Brown, J., Kraus, A., Liu, M., Shkolnik, E., van Dishoeck, 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

  73. 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.
  74. 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.
  75. Vidotto, A., Bisikalo, D., Fossati, L., 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.
  76. 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.
  77. 76 publications and 8669 citations in 2015.

76 publications and 8669 citations total.

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