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Research involving Lowell Observatory staff 2026
(All publications)

This is a work ever in progress.

(Pulled from ADS* by sel on 2026-03-09)

*We are grateful for all the effort that went into making The SAO/NASA Astrophysics Data System (ADS) possible. The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A and can be found at: https://ui.adsabs.harvard.edu/

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    2026

  1. Brasseur, C., Jardine, M., Daley-Yates, S., et al., 2026, MNRAS, 546, stag042, Electron cyclotron maser emission from ejected stellar prominences on V374 Peg
    We investigate a possible origin for bursty radio emission observed on the active M dwarf V374 Peg, combining data-driven magnetic field modelling with archival radio light curves. We examine whether stellar prominence ejection can plausibly account for the observed radio bursts that have been attributed to electron cyclotron maser (ECM) emission. Our analysis shows that ejected prominences can produce the required energy range to drive the emission, and that modelled ECM visibility exhibits a rotational phase dependence consistent with the limited observational data (four observed bursts). The results support prominence ejection as a viable mechanism for ECM generation on V374 Peg and motivate further observational campaigns to constrain this process.
  2. Hoppe, R., Bergemann, M., Eitner, P., et al., (including Ellwarth, M.), 2026, MNRAS, 546, staf2085, Solar carbon abundance from 3D non-LTE modelling of the diagnostic lines of the CH molecule
    The spectral lines of the CH molecule are a key carbon (C) abundance diagnostic in FGKM-type stars. These lines are detectable in metal-rich and, in contrast to atomic C lines, also in metal-poor late-type stars. However, only 3D LTE analyses of the CH lines have been performed so far. We test the formation of CH lines in the solar spectrum, using for the first time, 3D Non-LTE (NLTE) models. We also aim to derive the solar photospheric abundance of C, using the diagnostic transitions in the optical (4218$4356 \,\rm{\mathring{\rm A}}$) and infrared (33025$37944 \,\rm{\mathring{\rm A}}$). We use the updated NLTE model molecule from S. A. Popa et al. (2023) and different solar 3D radiation-hydrodynamics model atmospheres. The models are contrasted against new spatially resolved optical solar spectra, and the centre-to-limb variation (CLV) of CH lines is studied. We find generally small ($\sim$0.01 dex) NLTE effects in the optical and IR diagnostic CH AX lines in the solar atmosphere. Both 3D NLTE and 3D LTE spectral modelling yield an excellent fit to the solar intensity observations at all viewing angles. The 1D LTE and 1D NLTE models fail to describe the line CLV, and lead to underestimated solar C abundances. The 3D NLTE modelling of diagnostic lines in the optical and IR yields a carbon abundance of A(C) = $8.52\pm 0.07$ dex. The estimate is in agreement with recent results based on neutrino fluxes measured by Borexino. 3D NLTE modelling and tests on spatially resolved solar data are essential to derive robust solar abundances. The analysis presented here focuses on CH, but we expect that similar effects will be present for other molecules of astrophysical interest.
  3. Johns-Krull, C., Flagg, L., Isella, A., et al., (including Tang, S., Prato, L.), 2026, AAS, 58, 112.05, Resolving Accretion onto the Giant Exoplanet DH Tau b
    As giant planets form, it is expected they become surrounded by circumplanetary disks. These young planets are expected to gain additional mass and angular momentum by accreting material from these circumplanetary disks. However, key questions remain such as: What is the geometry of the accretion flows onto forming giant planets? How rapidly do they accrete material from their disks? For example, accretion could occur through an equatorial boundary layer or through a magnetically controlled funnel flow similar to how young stars accrete material from their circumstellar disks. High resolution spectrosccopy of emission line profiles can constrain the geometry of the accretion flow and the line flux can be used to estimate the accretion rate. DH Tau b is an 11 MJup giant planet undergoing active accretion; we use HIRES on Keck I to both spatially and spectrally resolve its H line profile from for the first time. Preliminary results show the measured line profile is single peaked and its shape is generally consistent with expectations from magnetically controlled accretion models. We present these results and discuss their implications.
  4. van Belle, G., 2026, AAS, 58, 148.04, MoonLITE: a CLPS lunar optical interferometer for sensitive, milliarcsecond observing
    MoonLITE (Lunar InTerferometry Explorer) is a proposed mission to design, build, launch, and operate the first separated-aperture optical interferometer in space, capable of achieving sub-milliarcsecond angular resolution. Leveraging NASA's Commercial Lunar Payload Services (CLPS), MoonLITE will deliver a compact optical interferometer to the lunar surfacecombining the exceptional spatial resolution of optical interferometry with the unparalleled stability and sensitivity provided by the lunar environment.

    A CLPS-provided rover will deploy the pre-loaded MoonLITE outboard telescope approximately 100 meters from the lander's inboard telescope, creating a two-element interferometric observatory with a single, automated deployment. MoonLITE will reach sensitivities down to 17th magnitude in the visible, exceeding ground-based interferometric limits by several magnitudes and surpassing the angular resolution of existing space-based optical systems by a factor of 50.

    This breakthrough capability will open an entirely new discovery space, enabling:

    Direct size measurements of the smallest, coolest stars and substellar brown dwarfs;

    Searches for close stellar companions to exoplanet-hosting stars that could affect the inferred occurrence of Earth-like planets;

    Direct imaging of young stellar objects and the terrestrial planet-forming regions around them;

    Characterization of the inner regions and binary nature of active galactic nuclei; and

    Experimental tests of spacetime structure at quantum scales.

    A portion of MoonLITE's observing time will be made available to the broader astronomical community through a Guest Observer Program. By exploiting the CLPS infrastructure, MoonLITE delivers an unprecedented combination of sensitivity, resolution, and cost efficiency, marking a transformative step in optical interferometry and lunar-based astronomy.

  5. Clark, C., Rustamkulov, Z., Everett, M., et al., (including van Belle, G., von Braun, K.), 2026, AAS, 58, 231.02, The POKEMON Distance Limited Catalog (POKEMON-DLC)
    The Solar Neighborhood is dominated by stars smaller, colder, and fainter than the Sun: the M dwarfs. The nearest planets all orbit M dwarfs; if we are to understand the architectures, occurrence rates, and properties of nearby planets, then we must investigate the stellar companion rates and characteristics of our low-mass neighbors. We have therefore carried out the Pervasive Overview of Kompanions of Every M Dwarf in Our Neighborhood (POKEMON) speckle survey of nearby M dwarfs. We created the survey with the goal of observing a volume-limited sample of M dwarfs through M9 out to 15 pc at diffraction-limited resolution. Pre-Gaia parallax measurements yielded a sample of 454 nearby M dwarfs. However, the precise astrometry from Gaia provided an additional 66 low-mass sources within 15 pc. Here we present the POKEMON-Distance Limited Catalog (POKEMON-DLC), which consists of speckle measurements for these 66 additional M dwarfs, including one newly detected stellar companion. These observations increase the number of ultracool (later than M6.5) dwarfs in the 15-pc POKEMON sample by a factor of 1.6. These results emphasize the utility of Gaia for identifying low-mass, nearby sources, and we expect that missions such as SPHEREx will continue to clarify the nature of the Solar Neighborhood.
  6. Zhang, Q., Ye, Q., Knight, M., et al., 2026, AAS, 58, 234.01, Distant Activation of Kreutz Sungrazing Fragment C/2024 S1 (ATLAS)
    The Kreutz sungrazers form a complex of cometary fragments with orbits extending to within one solar radius of the Sun's surface. These objects include several of the brightest comets in history, but also thousands of smaller fragments seen to disintegrate on their final approach toward the Sun in solar coronagraphic and heliospheric imagery. C/2024 S1 (ATLAS) was an unusual member of this complex that was sufficiently bright to have been discovered at night while it was still beyond Earth's orbit, yet disintegrated before even entering the fields-of-view of solar coronagraphs, before most other minor Kreutz fragments become visible at all. We took advantage of this comet's unusually distant activity to characterize its optical gas emission through narrowband imaging and spectroscopy with the Lowell Discovery Telescope. This data enables a quantitative comparison between the compositions of Kreutz sungrazers and the other, non-sungrazing comets visible at night, for which such data is routinely collected, thus hinting at the effects (and lack thereof) of intense heating at sungrazing distances on cometary nuclei. We also analyzed the brightness and morphology of its remnant in SOHO/LASCO, STEREO-A/COR2, and GOES-19/CCOR-1 coronagraphic imagery to evaluate its size and behavior relative to other Kreutz fragments seen with these instruments.
  7. Prato, L., Rector, T., Kerr, R., 2026, AAS, 58, 260.08, Linking Star Formation History and Newly Formed Stars through Herbig-Haro Objects in Ophiuchus
    The presence of Herbig-Haro objects brackets a narrow stage in the early evolution of a star, signaling the presence of active accretion from circumstellar material and collimated outflows that interact with the surrounding molecular cloud and interstellar medium on scales as large as parsecs. These shocked-gas flags of ongoing star formation characterize a regions' age at ~1 Myr or less. In tandem with dynamical data and models of large scale star formation, the location and distribution of Herbig-Haro objects in a young region can delineate the "active face" of star formation and the propagation of feedback across a molecular cloud. Here we present new 4-meter Blanco + DECam data from our sensitive survey of Herbig-Haro objects in the dense and highly obscured Ophiuchus region, and preliminary results from an analysis of the star formation history across the Ophiuchus clouds. We have found over 100 Herbig-Haro objects in the region, confirming most previous identifications while discovering dozens of new objects with the help of a Zooniverse hosted search. This research was supported in part by award AST-2206703 from the National Science Foundation.
  8. Hunter, D., Elmegreen, B., 2026, AAS, 58, 279.02, Ultra-deep imaging of nearby dwarf irregular galaxies: stellar haloes
    We have examined the stellar structure of the far outer disks of 10 nearby dwarf irregular (dIrr) galaxies by fitting ellipses as far out as a V surface brightness of 29 mag/arcsec2. We looked for evidence of the presence of a stellar halo and found suggestions of such in three galaxies at 2.7, 4.1, and 4.7 disk scale lengths. Two of these galaxies have excess emission in the far outer stellar disk that is not consistent with the morphology interior to that. In the third galaxy we see a large change in position angle between the optical morphology at 25 mag/arcsec2 and that at 29 mag/arcsec2. We traced the disks of the galaxies without evidence for a stellar halo to 2.4-7.4 disk scale lengths. Given the simulations of low-mass galaxy evolution that find considerable dynamical evolution from star-formation feedback, it is perhaps surprising that we did not find evidence of halos in more systems.
  9. Polanski, A., 2026, AAS, 58, 327.07, An Aligned Sub-Neptune revealed with MAROON-X and a Tendency Towards Alignment for Small Planets
    The angle between a planet's orbit and its star's spin axis is a key clue to its formation history. While obliquity measurements have been crucial for our understanding of close-in giants, the alignment of smaller planets (8 Earth radii) remains largely uncharted territory. This is now changing with the advent of ultra-precise spectrographs. In this talk, I will present MAROON-X data from Gemini North revealing a 1.5 m/s Rossiter-McLaughlin signal for the sub-Neptune TOI-1759A b. With an obliquity of just 4 degrees, TOI-1759A b is well-alignedthe longest-period, single sub-Neptune with a measured obliquity. I will discuss TOI-1759A b in the context of the merging picture of small planet obliquities and present evidence that planets in compact systems, especially those less than 4 Earth radii, tend to be well-aligned with their star's rotation axis reinforcing the idea of a dynamically cool formation history. In contrast, isolated planets take on a range of obliquities with an apparent pile-up near polar orbits.
  10. Ramiaramanantsoa, T., Shkolnik, E., Bowman, J., et al., (including Llama, J.), 2026, AAS, 58, 332.07, The SPARCS Experimental Design: Capturing Stellar Activity in Action
    SPARCS (Star-Planet Activity Research CubeSat ) is a stellar astrophysics CubeSat observatory ready to be inserted into low-Earth orbit in early 2026 to perform unprecedented photometric monitoring of the flaring and chromospheric activity of low-mass stars in the near-ultraviolet (NUV) and the far-ultraviolet (FUV). SPARCS observations are expected to considerably improve low-mass star UV flare frequency distributions, which are key inputs to the evaluation of the habitability of planets orbiting around them. We will present the SPARCS mission, its science goals, and how we plan SPARCS science observations at the SPARCS Science Operations Center.

    Acknowledgements: Funding for SPARCS is provided by NASA's Astrophysics Research and Analysis (APRA) program.

  11. Xu, S., Meisner, A., Brooks, H., et al., 2026, AAS, 58, 346.08, Exoasteroids: Searching for asteroids around dead stars
    The Solar System has over a million asteroids - leftover building blocks from planet formation that preserve key clues about how planets form and evolve. Can we find exoasteroids - asteroids orbiting other stars? That is the goal of our newly launched Zooniverse citizen-science project, Exoasteroid. The project searches for infrared-variable white dwarfs using data from NASA's Wide-field Infrared Survey Explorer (WISE). Such variability may signal the presence of disintegrating asteroids around these stellar remnants. We have identified several promising candidates and are conducting follow-up observations to uncover the nature of their infrared variability.
  12. Ellwarth, M., Llama, J., 2026, AAS, 58, 352.07, Line-by-Line Diagnostics of Solar Activity
    Stellar activity remains one of the main limitations in the detection of low-mass exoplanets, as it introduces radial velocity (RV) signals that can obscure or imitate planetary signatures. Using the EXtreme PREcision Spectrometer (EXPRES, R 137,500) at the 4.3 m Lowell Discovery Telescope, we monitor the integrated solar spectrum from the 2020 solar minimum to the current maximum to study line-by-line responses to magnetic variability. We analyze hundreds of Fe I absorption lines to characterize their sensitivity to solar activity and identify spectral properties governing this response. In parallel, we investigate the chromospheric He I D3 line as a potential magnetic activity proxy, finding strong correlations between its intensity variations, the Sun's unsigned magnetic flux (from SDO/HMI), and solar RV shifts. Together, these results offer a detailed view of wavelength-dependent activity signatures and highlight He I D3 as a promising diagnostic for disentangling stellar variability from planetary signals in high-precision RV studies.
  13. Cocke, B., Massey, P., Morrell, N., et al., 2026, AAS, 58, 358.04, An Orbit for a Massive Wolf-Rayet Binary in the LMC: Evidence of Binary Evolution
    Wolf-Rayet stars are helium-burning, evolved massive stars in the brief stage before they undergo core collapse. Most Wolf-Rayet stars have lost all of their hydrogen-rich outer layers. Here we report on our work studying a massive Wolf-Rayet binary in the LMC, which finds evidence of evolution via binary stripping. LMC173-1, a WN3 + O7 V binary, was observed over 19 nights from 2013-2025 using the 6.5 meter Magellan Telescopes and international Gemini Observatory. Our spectroscopy revealed LMC173-1 to have a period of 3.52 days with large velocity amplitudes. The mass ratio between the stars shows that the WN3 has only 43% of the mass of the O7 V, a result that cannot be due to stellar winds alone at the relatively low metallicity of the LMC. In this talk, I will discuss the interesting physical properties and evolutionary history of LMC173-1. This work has been supported in part by the National Science Foundation through award AST-2307594 and through the NASA Space Grant program administered through Northern Arizona University.
  14. Meisner, A., Xu, S., Brooks, H., et al., 2026, AAS, 58, 368.03, The Exoasteroids Citizen Science Project
    We present the "Exoasteroids" citizen science project. Exoasteroids searches for infrared variable white dwarfs within NASA's all-sky Wide-field Infrared Survey Explorer (WISE) data set. White dwarf infrared variability can arise from multiple physical mechanisms, including outbursts from disrupting planetesimals orbiting the star, a scenario which represents an opportunity to investigate the composition of extrasolar planets and the ultimate fate of planetary systems. Exoasteroids launched via the Zooniverse online crowdsourcing platform on 2024 September 17 and has thus far received more than 1 million classifications performed by over 5,000 registered volunteers. Through Exoasteroids, we have identified several dozen promising new infrared-variable white dwarf candidates, and have obtained follow-up spectroscopy for many of these with Gemini Observatory. This work has been supported by NASA Citizen Science Seed Funding Program (CSSFP) grant 80NSSC23K1528.
  15. Ayala, C., Dong, D., Kao, M., et al., 2026, AAS, 58, 417.05, Stellar Radio Transients in the 3 GHz VLA Sky Survey
    We present results from a systematic, untargeted search for radio-emitting stars covering three epochs of the 33,885 2 Very Large Array Sky Survey (VLASS) to a depth of ~0.9 mJy. In a new approach, we select Galactic transients: 3 GHz point sources identified as 7 detections in any VLASS epoch but not identified (3) in at least one other, and spatially associated with objects of parallax > 5 in Gaia Data Release 3. The demographics of the 341 highly variable sources in our sample notably differ from samples selected via other methods. In particular, just 11.1% (n=38) are associated with M dwarfs. In contrast, close binaries make up 45.2% (n=154), and young stars 13.5% (n=46). The remaining 30.2% of transients are associated with 99 unclassified stars, 3 magnetic chemically peculiar stars, and 1 colliding-wind binary. Using TESS lightcurves and archival ROSAT observations, we estimate that 67.7% of the radio-emitting stars, regardless of classification, are rapidly rotating and X-ray luminous. This suggests that at ~3 GHz, ~mJy stellar radio transients largely trace magnetic activity from strong fields amplified by rapid rotation. From our sample, we infer a luminosity function and duty cycle for each of the 3 classes. We find that variability will be an efficient means of discovering large samples of radio stars in future epochs of wide-field radio surveys.
  16. Sikora, J., Llama, J., Roettenbacher, R., et al., (including Polanski, A.), 2026, AAS, 58, 443.12, Neutral Fe Detected on MASCARA-5 b's Dayside Using EXPRES
    MASCARA-5 b is a recently discovered ultra-hot Jupiter (UHJ) orbiting a bright Am star. Recent time-series observations obtained with PEPSI@LBT during the planet's post-eclipse phase have revealed neutral Fe emission lines on the planet's dayside that are indicative of a thermally inverted atmosphere (Petz et al. 2025). Here we present pre-eclipse time-series observations obtained with the high-resolution optical spectrograph EXPRES installed on the 4.3m Lowell Discovery Telescope. Our preliminary analysis confirms the presence of neutral Fe on MASCARA-5 b's dayside and demonstrates EXPRES@LDT's suitability for future emission spectroscopy observations of similar UHJs orbiting bright host stars.
  17. Kutra, T., Tofflemire, B., Prato, L., et al., 2026, AAS, 58, 446.02, Contextualizing Circumstellar Disks in Close Young Binaries
    Multiplicity plays a key role in shaping the formation and evolution of circumstellar disks, and thus the initial conditions for planet formation. In this talk, I will share our analysis of four young multiple star systems with circumstellar disks between 4-5 AU: DP Tau, T Tau, ZZ Tau, and SR20. Comparing disk-disk and disk-orbit obliquities, we find that disks in close binaries (separations <40 AU) are preferentially aligned, whereas wider systems from the literature exhibit larger mutual obliquities. This trend supports viscous damping theory, in which disk alignment is rapid in tightly bound systems but increasingly inefficient at larger separations. Our results provide some of the highest-resolution measurements to date of disk geometry in young multiple systems and strengthen the link between stellar multiplicity, disk alignment, and the initial conditions of planet formation.
  18. Moreland, J., van Belle, G., 2026, AAS, 58, 450.06, MoonLITE: Lunar based optical interferometer
    The requirement to maintain precisely known distances between telescopes within an interferometer makes space based optical interferometry a costly and complicated endeavor. Despite this, the benefits of an interferometer unimpeded by the turbulent and obstructive terrestrial atmosphere cannot be understated. In an attempt to design a device that both possesses a stable foundation from which to operate as well as a path of viewing free of a prominent atmosphere, we are proposing the MoonLITE optical lunar based interferometer. Here, we discuss the physical structure of the interferometer as it would deploy on the lunar surface, alongside the engineering behind the constructed testbed beam combiner currently in testing. The science cases behind such an instrument will be presented, along with the practical implications of establishing and operating this instrument on the lunar surface. Additionally, we discuss the costs and limitations associated with such a project. MoonLITE would physically consist of two 5 cm aperture telescopes deployed 100 meters apart on the lunar surface via a rover. The lack of lunar atmosphere would enable long exposures not possible on Earth that would allow the two 5 cm aperture telescopes to observe down to 17th magnitude, far surpassing the brightness limitations of terrestrial interferometers, while also collecting angular size measurements down to 100 as This instrument enables significant new science cases, including observations of the terrestrial planet forming regions around YSOs, as well as close in stellar companions around exoplanet hosts, allowing us to better characterize the exoplanets in the context of their host systems.
  19. Richey-Yowell, T., Godoy-Rivera, D., Santos, A., et al., 2026, AAS, 58, 462.05, The Spin-Down Stalling Signature Persists in Chromospheric Magnetic Activity
    For low-mass stars (M < 1.4 M), the connection between stellar rotation and magnetic activity governs stellar spin-down, shapes the environments and habitability of their exoplanets, and provides an age-diagnostic via magneto-gyro-chronology. Recently, an unexpected phenomenon known as the 'rotational stalling' was discovered, where stars rotate more rapidly than predicted, likely due to internal angular momentum redistribution. This rotational feature has been shown to cause enhanced magnetic activity on the photosphere, as measured by the photometric index from stellar light curves (Sph). However, the influence of the rotational stalling on other magnetic activity proxies has not been explored in depth. In this work, we study the impact of the rotational stalling on chromospheric magnetic activity proxies, namely the CaII-infrared triplet (IRT) index and the near-ultraviolet (NUV) excess. We target the stars observed by the Kepler mission, as this is the largest and most reliable sample with rotation period measurements. We calculate the CaII-IRT and NUV indices for the Kepler stars using data from the Gaia and GALEX missions, respectively. We study the rotation-activity relation as a function of Hertzsprung-Russell (HR) diagram location and spectral type, finding that K-dwarfs are more active than G-dwarfs. Importantly, we find that for main-sequence stars, chromospheric magnetic activity is also enhanced by the rotational stalling, mirroring its effect on the photospheric index Sph. Our work reveals that the rotational stalling marks a genuine transition in stellar magnetic behavior. This highlights the need to account for its multi-wavelength signatures across activity proxies, its impact on exoplanet habitability, and its consequences for age-rotation-activity relations.
  20. Quitral-Pierart, A., Leigh, N., Mathieu, R., et al., (including Horch, E.), 2026, A&A, 706, A177, Mass-luminosity anomalies: Plausible evidence of recent stellar interaction in the extraordinary blue straggler S1082
    Context. We present an observational and theoretical study of the complex stellar system S1082 in the open cluster M67. This system consists of at least four stars: a blue straggler in a 1.07-day eclipsing binary with a main sequence star (binary A) and another blue straggler in a 1185-day orbit with an unknown companion (binary B). Aims. We analyzed observational data to obtain the orbital and stellar parameters of the components of the eclipsing system. We then explored mass transfer and dynamical encounter scenarios that could explain the derived properties of all of the components of S1082. Methods. We combined high-precision photometry from K2 and TESS with archival light curves, new radial-velocity measurements, and speckle imaging to refine the orbital and physical parameters of the system. To explore the formation pathways, we conducted binary evolution simulations with MESA and dynamical scattering experiments with FEWBODY, followed by a tidal evolution modeling procedure. Results. Our revised radial-velocity solutions yield significantly changed dynamical masses for binary A, reducing the tension with the cluster turnoff mass compared to previous studies. Speckle imaging shows two resolved components separated by 390 AU in projection and, in combination with the two spectroscopic orbits, this is suggestive of a hierarchical quadruple configuration. Our results suggest that the two blue stragglers formed separately, with later dynamical encounters assembling the present configuration. This work underscores the importance of stellar dynamics in shaping the evolution of complex stellar systems within cluster environments such as M67.
  21. Zhao, L., Fischer, D., Szymkowiak, A., et al., (including Llama, J.), 2026, ApJS, 282, 71, Uncovering Hidden Systematics in Extreme-precision Radial Velocity Measurements
    We identify and correct for small but coherent instrumental drifts in 7 yr of radial velocity (RV) data from the EXtreme PREcision Spectrograph (EXPRES). The systematics are most notable for the six months before and after 2022 January, when EXPRES experienced larger temperature variations, and we see a systematic trough-to-peak amplitude of 2.8 m s1 in the radial velocities. This is large enough to mimic or obscure planetary signatures. To isolate and correct these effects, we develop a suite of diagnostics that track two-dimensional echellogram shifts, scalings, and rotation, as well as line bisector spans derived from laser frequency comb lines. By combining these empirical tracers with instrument telemetry in a multidimensional regression, we reduce the EXPRES instrument trend traced with solar RVs from an rms of 1.320.43 m s1, a 67% improvement, and the aggregate of 12 chromospherically quiet stars shows a 26% reduction in velocity scatter. Our injection/recovery simulations further demonstrate a doubling in sensitivity to low-amplitude planetary signals after correction. When applied to the stellar time series of Coronae Borealis (CrB), the correction removes a spurious planet d signal, restoring the integrity of the data. These results highlight the need for long-term monitoring and multidimensional calibration diagnostics on the path toward true centimeter-per-second precision in next-generation extreme precision RV instruments.
  22. Zhang, Q., Ye, Q., Battams, K., et al., 2026, PSJ, 7, 31, Covertly Active Comet (139359) 2001 ME1
    On 2018 November 18, coronagraphs onboard the Solar and Heliospheric Observatory (SOHO) captured an unrecognized comet crossing its fields of view. We identified this comet to be the minor planet (139359) 2001 ME1, whose previously unnoticed dust activity near perihelion became optically amplified by efficient forward scattering of sunlight as the comet crossed between the Sun and SOHO/Earth at up to 175.6 phase angle. Simultaneous backscattering observations by the Solar Terrestrial Relations Observatory (STEREO) precisely constrain the comet's 7 mag forward scattering brightening, enabling a direct comparison with the 3 mag brightening of the more active but optically dust-poor comet 2P/Encke seen by SOHO and STEREO under similar geometry in 2017. Earlier STEREO observations from 2014 additionally show the newly recognized activity to be recurrentconsistent with a reanalysis of the comet's associated meteor activityand has likely only been previously overlooked due to the comet's faintness and proximity to the Sun while active. Orbital integrations show the comet has likely followed a near-Earth orbit for at least the past 10 kyr, suggesting that the weakness of its observed activity evolved through its continued depletion of accessible volatiles.
  23. Sandford, N., Li, T., Koposov, S., et al., (including Kuehn, K.), 2026, ApJ, 998, 47, Chemodynamics of Bootes I with S5: Revised Velocity Gradient, Dark Matter Density, and Galactic Chemical Evolution Constraints
    We combine new spectroscopic observations of the ultrafaint dwarf (UFD) galaxy Bootes I (Boo I) from the Southern Stellar Stream Spectroscopic Survey (S5) with 15 yr of archival spectroscopic data to create the largest sample of stellar kinematics and metallicities to date for any Milky Way UFD. Our combined sample includes 148 members extending out to 7 half-light radii (rh), including 24 newly confirmed members, 18 binary candidates, 15 RR Lyrae stars, and 92 [Fe/H] measurements. Using this larger and more spatially extended sample, we provide updated constraints on Boo I's systemic properties, including its radial population gradients. Properly accounting for perspective rotation effects in a UFD for the first time, we detect a 4 line-of-sight velocity gradient of 1.2 0.3 km s1 rh1 aligned along Boo I's orbit and discuss its potential tidal origins. We also infer a metallicity gradient of 0.10 0.02 dex rh1 in agreement with previous studies. Using an axisymmetric Jeans model, we provide updated constraints on Boo I's dark matter density profile, which weakly favors a cusped ( =1.00.6+0.5 ) dark matter profile. Lastly, we reanalyze Boo I's metallicity distribution function with a one-zone galactic chemical evolution model and place new constraints on its rapid, inefficient star formation and strong galactic outflows.
  24. Webber, K., Hansen, T., Marshall, J., et al., (including Kuehn, K.), 2026, ApJ, 998, 114, Detailed Chemical Abundance Analysis of the Brightest Stars in the Turranburra and Willka Yaku Stellar Streams
    We present a detailed chemical abundance analysis of the three brightest known stars from each of the Turranburra and Willka Yaku stellar streams using high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra. Abundances for 27 elements, ranging from carbon to dysprosium, were derived. Our results support the original classification that Turranburra, with a low average metallicity of [Fe/H] = 2.45 0.07, likely originates from a dwarf galaxy progenitor. Willka Yaku has a low average metallicity of [Fe/H] = 2.35 0.03 with a small scatter in the abundances, consistent with a globular cluster progenitor as suggested by previous studies. Both streams exhibit mild enhancements in neutron-capture elements, with averages of [Eu II/Fe] = 0.47 0.09 for Turranburra and 0.44 0.05 for Willka Yaku, consistent with enrichment from an r-process event. A similar enrichment is observed in other stellar streams, and we further discuss this signature as it relates to the potential enrichment histories of these two streams. *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
  25. Bechtol, K., Sevilla-Noarbe, I., Drlica-Wagner, A., et al., (including Kuehn, K.), 2026, ApJS, 282, 62, Dark Energy Survey Year 6 Results: Photometric Dataset for Cosmology
    We describe the photometric dataset assembled from the full 6 yr of observations by the Dark Energy Survey (DES) in support of static-sky cosmology analyses. DES Y6 Gold is a curated dataset derived from DES Data Release 2 (DR2) that incorporates improved measurement, photometric calibration, object classification and value-added information. Y6 Gold comprises nearly 5000 deg2 of grizY imaging in the south Galactic cap and includes 669 million objects with a depth of iAB 23.4 mag at a signal-to-noise ratio 10 for extended objects and a top-of-the-atmosphere photometric uniformity <2 mmag. Y6 Gold augments DES DR2 with simultaneous fits to multiepoch photometry for more robust galaxy shapes, colors, and photometric redshift estimates. Y6 Gold features improved morphological stargalaxy classification with an efficiency of 98.6% and a contamination of 0.8% for galaxies with 17.5 < iAB < 22.5. Additionally, it includes per-object quality information, and accompanying maps of the footprint coverage, masked regions, imaging depth, survey conditions, and astrophysical foregrounds that are used for cosmology analyses. After quality selections, benchmark samples contain 448 million galaxies and 120 million stars. This publication is complemented by data access and documentation.
  26. Hang, Q., Jeffrey, N., Whiteway, L., et al., (including Kuehn, K.), 2026, MNRAS, 546, stag006, Biasing from galaxy trough and peak profiles with the DES Y3 redMaGiC galaxies and the weak lensing mass map
    We measure the correspondence between the distribution of galaxies and matter around troughs and peaks in the projected galaxy density, by comparing redMaGiC galaxies ($0.15< z<0.65$) to weak lensing mass maps from the Dark Energy Survey (DES) Y3 data release. We obtain stacked profiles, as a function of angle $\theta$, of the galaxy density contrast $\delta _{\rm g}$ and the weak lensing convergence $\kappa$, in the vicinity of these identified troughs and peaks, referred to as 'void' and 'cluster' superstructures. The ratio of the profiles depend mildly on $\theta$, indicating good consistency between the profile shapes. We model the amplitude of this ratio using a function $F(\boldsymbol{\eta }, \theta)$ that depends on cosmological parameters $\boldsymbol{\eta }$, scaled by the galaxy bias. We construct templates of $F(\boldsymbol{\eta }, \theta)$ using a suite of N-body (Gower Street) simulations forward-modelled with DES Y3-like noise and systematics. We discuss and quantify the caveats of using a linear bias model to create galaxy maps from the simulation dark matter shells. We measure the galaxy bias in three lens tomographic bins (near to far): $2.32^{+0.86}_{-0.27}, 2.18^{+0.86}_{-0.23}, 1.86^{+0.82}_{-0.23}$ for voids, and $2.46^{+0.73}_{-0.27}, 3.55^{+0.96}_{-0.55}, 4.27^{+0.36}_{-1.14}$ for clusters, assuming the best-fitting Planck cosmology. Similar values with $\sim 0.1\sigma$ shifts are obtained assuming the mean DES Y3 cosmology. The biases from troughs and peaks are broadly consistent, although a larger bias is derived for peaks, which is also larger than those measured from the DES Y3 $3\times 2$-point analysis. This method shows an interesting avenue for measuring field-level bias that can be applied to future lensing surveys.
  27. Elmegreen, B., Hunter, D., Corbelli, E., 2026, ApJ, 997, 235, Pressure and Star Formation in LITTLE THINGS Dwarf Irregular Galaxies
    The surface densities of star formation, SFR, in 24 dwarf irregular (dIrr) galaxies from the LITTLE THINGS survey are combined with gas surface densities and midplane pressures to examine the correlations found previously for spiral galaxies. The pressure is the weight of the disk inside the gas layer, including gas, stars, and dark matter, which usually dominates disk gravity in dIrrs. We compare the results to the outer part of M33, which has similar local properties but a slightly higher metallicity, enabling the detection of CO. All the data are convolved to the H I beam, but to study the effects of resolution, the galaxies are examined first with average radial profiles, and then with maps having 1 . 5 pixels and 244 pc pixels. The correlations are found to be independent of resolution from 24 to 424 pc. The average ratio of molecular to atomic surface density is estimated to be 0.23 0.1, from the H2 surface density in M33 compared to the H I surface density at the same SFR in the dIrrs. With this ratio, the average star formation rate per molecule is about the same for all the dIrrs, and a factor of 2 less than the rate in M33. The pressure in dIrrs is so low that CO is essentially a dense gas tracer, with the same surface density threshold at the low metallicities of dIrrs as HCN has in spiral galaxies. As a result, CO regions in dIrrs should be strongly self-gravitating.
  28. Farrah, D., Ejercito, K., Efstathiou, A., et al., (including van Belle, G.), 2026, ApJ, 997, 150, How Accurately Can Obscured Galaxy Luminosities Be Measured Using Spectral Energy Distribution Fitting of Near- through Far-infrared Observations?
    Infrared-luminous galaxies are important sites of stellar and black hole mass assembly at most redshifts. Their luminosities are often estimated by fitting spectral energy distribution (SED) models to near- to far-infrared data, but the dependence of these estimates on the data used is not well understood. Here, using observations simulated from a well-studied local sample, we compare the effects of wavelength coverage, signal-to-noise ratio, flux calibration, angular resolution, and redshift on the recovery of starburst, active galactic nucleus (AGN), and host luminosities. We show that the most important factors are wavelength coverage that spans the peak in a SED, and dense wavelength sampling. Such observations recover starburst and AGN infrared luminosities with systematic bias below 20%. Starburst luminosities are best recovered with far-infrared observations, while AGN luminosities are best recovered with near- and mid-infrared observations, though the recovery of both are enhanced with near/mid-infrared and far-infrared observations, respectively. Host luminosities are best recovered with near/far-infrared observations, but are usually biased low, by 20%. The recovery of starburst and AGN luminosity is enhanced by observing at high angular resolution. Starburst-dominated systems show more biased recovery of luminosities than do AGN-dominated systems. As redshift increases, far-infrared observations become more capable and mid-infrared observations less capable at recovering luminosities. Our results highlight the transformative power of a far-infrared instrument with dense wavelength coverage, from tens to hundreds of microns, for studying infrared-luminous galaxies. We tabulate estimates of systematic bias and random error for use with JWST and other observatories.
  29. Zhang, Q., Battams, K., 2026, PASP, 138, 014403, Rapid Brightening of 3I/ATLAS Ahead of Perihelion
    Interstellar comet 3I/ATLAS has been approaching its 2025 October 29 perihelion while opposite the Sun from Earth, hindering ground-based optical observations over the preceding month. However, this geometry placed the comet within the fields of view of several space-based solar coronagraphs and heliospheric imagers, enabling its continued observation during its final approach toward perihelion. We report photometry from STEREO-A's SECCHI HI1 and COR2, SOHO's LASCO C3, and GOES-19's CCOR-1 instruments in 2025 SeptemberOctober, which show a rapid rise in the comet's brightness scaling with heliocentric distance r as r7.51.0. CCOR-1 also resolves the comet as an extended source with an apparent coma of 4' in diameter. Furthermore, LASCO/CCOR-1 color photometry shows the comet to be distinctly bluer than the Sun, consistent with gas emission contributing a substantial fraction of the visible brightness near perihelion.
  30. Micheli, M., Devogele, M., Denneau, L., et al., (including Moskovitz, N.), 2026, JAnSc, 73, 8, Astrometric Follow-up of Near-Earth Asteroid 2024 YR4 During a Torino Scale Level 3 Alert
    The discovery of 2024 YR4 presented the planetary defense community with the most significant impact threat in almost two decades, reaching level 3 on the Torino scale. The community, now mature and well-organized, responded with a global observational effort. Astrometric measurements, forming the basis for orbital refinement and impact prediction, were a central component of this response. In this paper, we present the astrometric data collected by the international community, from the time of discovery until the object became too faint for all existing observational assets, including JWST. We also discuss the coordination role played by the International Asteroid Warning Network, and the importance of publicly available image archives to enable precovery searches.
  31. Hsieh, H., Usher, H., Lister, T., et al., (including Thirouin, A.), 2026, RNAAS, 10, 1, Early Observations of New Active Asteroid 2025 VZ8
    We report observations of main-belt asteroid 2025 VZ8 using multiple telescopes from UT 2025 November 24 to UT 2025 December 23 that confirm the presence of visible comet-like activity. These observations were motivated by online reports that an abrupt brightening event may have led to the object's discovery on UT 2025 November 9. In all observations reported here, the object displays a tapered tail approximately 3 long aligned with the antisolar direction. The object has an asteroidal Tisserand parameter value with respect to Jupiter (TJ = 3.371), and is thus considered an active asteroid. We measure an average apparent r' -band magnitude of mr 21.6 mag over the reported observing period. Due to the sudden appearance of activity far from perihelion, we suggest that the activity is more likely due to an impact or rotational destabilization, rather than sublimation.
  32. Prat, J., Gatti, M., Doux, C., et al., (including Kuehn, K.), 2026, MNRAS, 545, staf2152, Dark Energy Survey Year 3 results: wCDM cosmology from simulation-based inference with persistent homology on the sphere
    We present cosmological constraints from Dark Energy Survey Year 3 (DES Y3) weak lensing data using persistent homology, a topological data analysis technique that tracks how features like clusters and voids evolve across density thresholds. For the first time, we apply spherical persistent homology to galaxy survey data through the algorithm TOPOS2, which is optimized for curved-sky analyses and HEALPIX compatibility. Employing a simulation-based inference framework with the Gower Street simulation suite specifically designed to mimic DES Y3 data properties we extract topological summary statistics from convergence maps across multiple smoothing scales and redshift bins. After neural network compression of these statistics, we estimate the likelihood function and validate our analysis against baryonic feedback effects, finding minimal biases (under $0.3\sigma$) in the $\Omega _\mathrm{m}-S_8$ plane. Assuming the wCold Dark Matter model, our combined Betti numbers and second moments analysis yields $S_8 = 0.821 \pm 0.018$ and $\Omega _\mathrm{m} = 0.304\pm 0.037$ constraints 70 per cent tighter than those from cosmic shear two-point statistics in the same parameter plane. Our results demonstrate that topological methods provide a powerful and robust framework for extracting cosmological information, with our spherical methodology readily applicable to upcoming Stage IV wide-field galaxy surveys.

    33. 32 publications and 58 citations in 2026.

32 publications and 58 citations total.

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