Showing 1–50 of 371 results for author: Vanderburg, A

Atmospheric Signatures of Common Envelope Evolution in White Dwarf Planets

Authors: Sydney Jenkins, Andrew Vanderburg, James Mang, Juliette Becker, Caroline V. Morley, Melinda Soares-Furtado, Ricardo Yarza

Abstract: The majority of confirmed exoplanets orbit within 1 au of a main-sequence (MS) star. When their stellar hosts evolve off the MS, many of these planets will be engulfed and destroyed, creating empty "forbidden" zones around the stars as they evolve to their final state as a white dwarf (WD). However, several confirmed and candidate WD planets have been found within this forbidden zone. Two formatio… ▽ More The majority of confirmed exoplanets orbit within 1 au of a main-sequence (MS) star. When their stellar hosts evolve off the MS, many of these planets will be engulfed and destroyed, creating empty "forbidden" zones around the stars as they evolve to their final state as a white dwarf (WD). However, several confirmed and candidate WD planets have been found within this forbidden zone. Two formation scenarios have been proposed to explain the existence of these close-in planets: high-eccentricity migration and common envelope evolution (CEE). There are currently few observational tests to distinguish between these pathways. In this study, we investigate whether CEE could leave a detectable atmospheric signature. Using Modules for Experiments in Stellar Astrophysics (MESA) models, we simulate an engulfed planet inspiraling into an AGB star, and allow the planet to accrete mass via Bondi-Hoyle-Lyttleton accretion. Assuming a range of planet masses (1$-$13 M$_{\mathrm{Jup}}$) and accretion efficiencies (0.01$-$1.0), we find that the planet can accrete up to 48% of its initial mass in the most extreme Eddington-limited scenario. Because this accreted material is enriched in hydrogen and helium, we expect it to decrease the planet's bulk metallicity. Using simulated emission spectra, we find that CEE can increase thermal emission by up to 9.0% for a cool planet such as WD 1856 b. For lower accretion efficiencies (0.01$-$0.5), thermal emission increases between 0.1$-$3.6%. This signature may be observable in the most favorable cases, providing a potential new probe for investigating the dynamical history of close-in planets around WDs. △ Less

Submitted 30 July, 2026; originally announced July 2026.

Comments: 16 pages, 5 figures, 3 tables

Journal ref: ApJ 1006, 241 (2026)

Refined parameters, formation, and dynamical stability of the wild exoplanet system K2-312=HD 80653

Authors: L. Naponiello, E. Poretti, K. Rice, A. S. Bonomo, L. Malavolta, M. Stalport, A. Vanderburg, C. Ziegler, L. Affer, M. Cecconi, A. Collier Cameron, R. Cosentino, M. Damasso, X. Dumusque, Y. N. E. Eschen, A. Ghedina, D. W. Latham, M. López-Morales, T. Lu, A. Massa, A. Mortier, B. A. Nicholson, L. Palethorpe, F. A. Pepe, A. Sozzetti , et al. (2 additional authors not shown)

Abstract: The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. We present an extended radial velocity (RV) monitoring of the bright star K2-312=HD80653, known to… ▽ More The architecture of planetary systems hosting ultra-short-period (USP) planets is a key diagnostic for understanding formation and migration scenarios. The presence of outer giant companions in these systems is of particular interest to test theories regarding dynamical effects and pebble accretion. We present an extended radial velocity (RV) monitoring of the bright star K2-312=HD80653, known to host a rocky USP super-Earth ($P_b=0.720$d). Previous studies identified a long-term trend and subsequently a Keplerian signal due to an outer highly eccentric giant planet, K2-312c. We aim to refine the orbital parameters of K2-312c by precisely monitoring its periastron passage and to model the formation and dynamical evolution of the system. We analyzed a set of 237 HARPS-N high-resolution spectra, extending the observation baseline of previous literature by almost 4 years. We performed a joint analysis of the RVs together with K2 and TESS photometry to refine the ephemerides and properties of the two planets. To account for stellar activity, we coupled the Keplerian models with a Gaussian processes regression. K2-312c is a cold Jupiter on a wide orbit (orbital period refined to $P_c=871.32$d), with a minimum mass of Msin(i)$\sim5 M_{Jup}$ and a refined eccentricity of $e_c \sim 0.85$. It is among the most eccentric cold Jupiters known in multi-planet systems, and the only one that is highly eccentric and has a USP planet companion. Our simulations suggest that planet-planet scattering between two giant planets could have driven K2-312c to its current high eccentricity, ejected the other giant, and still allowed for the survival of K2-312b. The extended observation baseline further allowed us to identify the stellar rotation period and a long activity cycle, while a new K2 reduction improved the significance of the secondary eclipse detection for K2-312b. △ Less

Submitted 21 July, 2026; originally announced July 2026.

Comments: Received by A&A on June 3rd, 2026; Accepted on July 16th, 2026

Understanding eccentric temperate giants: an in-depth study of the architecture and stellar obliquity of the TOI-2134 system

Authors: Federica Rescigno, Manu Stalport, Ancy Anna John, Tiger Lu, Daisy A. Turner, Lorena Acuña-Aguirre, Anand Bhongade, Anjali A. A. Piette, Vedad Kunovac, Michael Cretignier, Andrew Vanderburg, Ken Rice, Annelies Mortier, Rishikesh Sharma, Guillaume Hébrard, Abhijit Chakraborty, Alessandro Sozzetti, Andrew Collier Cameron, Pía Cortés-Zuleta, Rosario Cosentino, Florian Destriez, Mercedes López-Morales, Luca Malavolta, Jesús Maldonado, Giacomo Mantovan , et al. (6 additional authors not shown)

Abstract: We revisit the TOI-2134 planetary system with three new high-cadence TESS sectors and 98 more spectra. This new analysis confirms the two orbiting planets by simultaneously modelling a total of eight sectors of corrected TESS photometry and 280 HARPS-N and SOPHIE radial velocities: an inner mini-Neptune in a near-circular $9.229198\pm0.000003$ days orbit, and an outer temperate sub-Saturn orbiting… ▽ More We revisit the TOI-2134 planetary system with three new high-cadence TESS sectors and 98 more spectra. This new analysis confirms the two orbiting planets by simultaneously modelling a total of eight sectors of corrected TESS photometry and 280 HARPS-N and SOPHIE radial velocities: an inner mini-Neptune in a near-circular $9.229198\pm0.000003$ days orbit, and an outer temperate sub-Saturn orbiting with a $95.852840\pm0.000042$ days period and eccentricity of $0.31\pm0.01$. The masses and radii of the planets were computed to be $9.37\pm0.54$ Me and $2.735\pm0.068$ Re for planet b, and $58.3\pm1.9$ Me and $7.35\pm0.18$ Re for planet c. The new data not only improves the detection significance and precisions on the planetary orbits, but also breaks the original multimodality in the eccentricity solution for the outer planet. We also detect a long-term trend in the radial velocity data, which we attribute to a stellar magnetic cycle. We investigate the spin-orbit alignment of the system via observations of the Rossiter-McLaughlin effect for TOI-2134~b with EXPRES and TOI-2134~c with PARAS-2. No RM effect was detected for planet b, but we find a 4.7$σ$ detection of a $59\pm31^{\circ}$ obliquity for planet c. Finally, we examine the architecture of the system, assess its completeness, investigate the planetary interior, and their suitability for follow-up atmospheric analysis. △ Less

Submitted 9 July, 2026; v1 submitted 1 July, 2026; originally announced July 2026.

Comments: 26 pages, accepted at MNRAS

Kepler Image-Subtracted Light Curves and Variable Star Catalog of NGC 6819

Authors: Melinda Soares-Furtado, Rianna Kuenzi, Rachel Lee McClure, Nicholas T. Marston, Evan Linck, Robert D. Mathieu, Andrew Vanderburg, Joel D. Hartman, Kyle Cudworth, Robert Gagliano, Thomas Jacobs, Martti H. Kristiansen, Mark Omohundro, Hans Martin Schwengeler

Abstract: Variable stars in open clusters are valuable probes of stellar evolution. They provide precise measurements of stellar properties, constrain cluster ages and distances, and trace the angular momentum evolution of stellar populations. To advance these studies, we applied image subtraction and systematic reduction techniques to the NGC 6819 Kepler superstamp time-series data (Quarters 1-16), using t… ▽ More Variable stars in open clusters are valuable probes of stellar evolution. They provide precise measurements of stellar properties, constrain cluster ages and distances, and trace the angular momentum evolution of stellar populations. To advance these studies, we applied image subtraction and systematic reduction techniques to the NGC 6819 Kepler superstamp time-series data (Quarters 1-16), using the Gaia DR3 catalog to identify the positions of individual sources. We produce 81,498 high-precision light curves for 11,055 sources in the crowded field harboring the 2.5 Gyr open cluster NGC 6819. Our detrended light curves achieve a best root-mean-square precision of 33 ppm (6.5-hour bins) for stars with Kepler magnitudes 12 - 12.5 mag, falling to 79 ppm at 14 - 14.5 mag. Using Gaia DR3 proper motions, and parallaxes, we distinguished likely cluster members from field stars. We identified and classified 87 periodic variables that are potential members of NGC 6819, including 26 newly-discovered variables. We make our light curves and variable classifications publicly available to enable further studies of stellar variability and angular momentum evolution in this intermediate-aged open cluster. △ Less

Submitted 29 June, 2026; v1 submitted 23 June, 2026; originally announced June 2026.

Comments: 19 pages, 6 figures, 1 table. Accepted for publication in The Astronomical Journal

Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE) II: a 135 Myr planet on an aligned orbit with transit timing variations

Authors: Madyson G. Barber, Andrew W. Mann, Sydney Vach, Leah J. Boff, Andrew W. Boyle, Andrew Vanderburg, Adam L. Kraus, Benjamin M. Tofflemire, Marshall C. Johnson, Allyson Bieryla, David W. Latham, Karen A. Collins, Steve B. Howell, Richard P. Schwarz, Gregorg Srdoc, Francis P. Wilkin, Felipe Murgas, Enric Palle, Chris Stockdale

Abstract: Young planets (<1 Gyr) provide opportunities to directly probe planet formation and evolution processes in action. However, due to heightened stellar activity, there is a lack of known transiting planets in adolescence (~100-500 Myr). Here we present the validation of TIC 150070085 b, a 3.6 R_E planet on a 10.47 day orbit, and report the candidate TIC 150070085 c, a 3.0 R_E planet on a 15.90 day o… ▽ More Young planets (<1 Gyr) provide opportunities to directly probe planet formation and evolution processes in action. However, due to heightened stellar activity, there is a lack of known transiting planets in adolescence (~100-500 Myr). Here we present the validation of TIC 150070085 b, a 3.6 R_E planet on a 10.47 day orbit, and report the candidate TIC 150070085 c, a 3.0 R_E planet on a 15.90 day orbit. While we are unable to validate the second signal, the proximity to mean motion resonance (3:2) and transit timing variations observed in the transits of TIC 150070085 b strongly suggest the signal is planetary. We confirm the host star as a member of Alessi 84 and combine the group's CMD, rotation, and variability properties to update the age to 135 +/- 10 Myr. We additionally use MAROON-X to observe the Rossiter-McLaughlin signal of TIC 150070085 b and measure the sky projected obliquity angle ($λ$). We find TIC 150070085 b is consistent with a near-aligned orbit with its host star (|$λ$| = 18 +/- 12$^\circ$), in line with similarly aged transiting planets with measured $λ$ values. Continued discovery and characterization of planets in this age regime are vital to link planetary infancy (<50 Myr) and maturity (>1 Gyr). △ Less

Submitted 8 June, 2026; originally announced June 2026.

Comments: Accepted for publication in the Journals of the AAS

Upper limits on exosatellites around $β$ Pictoris b

Authors: M. A. Kenworthy, R. Landman, A. Vanderburg, J. E. Rodriguez, J. L. Birkby, I. Macias, D. González Picos, S. A. Jenkins, E. Kleisioti, T. Stolker, I. Koutalios

Abstract: $β$ Pictoris b is one of the closest known directly-imaged gas giant exoplanets with an orbit that is almost edge-on to our line of sight, making it an ideal target for radial velocity monitoring to search for massive exomoons. We measure the radial velocity of $β… ▽ More $β$ Pictoris b is one of the closest known directly-imaged gas giant exoplanets with an orbit that is almost edge-on to our line of sight, making it an ideal target for radial velocity monitoring to search for massive exomoons. We measure the radial velocity of $β$ Pictoris b over several epochs between October 2024 and March 2025 by using the cross-correlation of a template spectrum with absorption lines in the planet's atmosphere, giving a mean precision of 160 m s$^{-1}$. The resultant set of radial velocities is analysed with a periodogram to search for candidate RV signals indicating a massive exomoon. Although we do not detect an exomoon signal in our data, our detection limits for a single moon are 80 Earth masses at P=1 day and 1 Jupiter at P=200 days, comparable to RV exomoon searches around other substellar companions. The RV limit is comparable with the astrometric exomoon limit at a period of 7 days and a mass of 150 Earth masses, where for longer periods the astrometric searches have lower mass limits. With an additional observing season, CRIRES+ can detect a planet/moon mass ratio of $10^{-3}$ (4 Earth masses) with a period of up to one day, and can detect a Neptune-mass moon at hundreds of Jupiter radii. △ Less

Submitted 3 June, 2026; originally announced June 2026.

Comments: 6 pages, 7 figures, 1 table, accepted for publication in MNRAS. This paper is in a reproducible workflow repository at https://github.com/mkenworthy/BetaPicbExomoons

Lithium Enrichment in a Subgiant Star with a Brown Dwarf Companion: A Planetary Engulfment Candidate

Authors: Brooke Kotten, Melinda Soares-Furtado, Ricardo Yarza, Andrew C. Nine, Seth A. Jacobson, Noah Vowell, Olivia Maynard, Allyson Bieryla, Andrew Vanderburg, Jack Schulte, Claudia Aguilera-Gomez, Enrico Ramirez-Ruiz, Joseph E. Rodriguez, David W. Latham

Abstract: Theoretical models predict that subgiants within a narrow mass regime can retain detectable lithium enrichment signatures from planetary engulfment. We test this prediction using TOI-5882, selected because it occupies this favorable subgiant parameter space and hosts a massive brown dwarf ($22 \, M_{ \rm J}$, $P=7.1 \,{\rm d}$) companion capable of dynamically perturbing inner planets. We investig… ▽ More Theoretical models predict that subgiants within a narrow mass regime can retain detectable lithium enrichment signatures from planetary engulfment. We test this prediction using TOI-5882, selected because it occupies this favorable subgiant parameter space and hosts a massive brown dwarf ($22 \, M_{ \rm J}$, $P=7.1 \,{\rm d}$) companion capable of dynamically perturbing inner planets. We investigate whether: (1) TOI-5882 exhibits lithium enhancement among similar subgiants, (2) planetary material would be deposited in the convective zone, and (3) the required engulfed mass lies within a plausible range for planetary engulfment. Using spectra from the Tillinghast Reflector Echelle Spectrograph, we measured a Li I equivalent width of $75.39 \pm 3.58$ mA and an abundance of A(Li) $=2.49 \pm 0.12$ dex. Comparing these values to a control sample of 61 subgiants from the GALactic Archaeology with HERMES (GALAH) DR4 survey, we find that TOI-5882 ranks in the 98.4th percentile in both metrics, confirming significant lithium enrichment. We evaluate the engulfment scenario by modeling convective zone deposition and estimating the mass required to reproduce the observed enhancement relative to the control sample. We perform an estimate of the engulfed planetary mass incorporating CI chondritic Li abundances, as planets formed via core accretion are enriched in heavy elements and lithium partitions with these metals. This yields a required engulfed mass of $9$-$95\,M_\oplus$--an order of magnitude lower than the $5.6 \, M_{\rm J}$ implied by proto-solar assumptions. TOI-5882's lithium excess can plausibly result from the ingestion of a super-Earth to Neptune-mass planet, motivating further studies to test this scenario. △ Less

Submitted 20 May, 2026; originally announced May 2026.

Comments: 21 pages, 6 figures, 2 tables. Accepted to The Astrophysical Journal

JWST unveils a high mean molecular weight atmosphere for mini-Neptune TOI-1130b: Evidence for formation beyond the water ice line

Authors: Saugata Barat, Tyler Fairnington, Shelby Courreges, Chelsea Huang, Andrew Vanderburg, Caroline V. Morley, Judith Korth, Hannu Parviainen, Alexis Brandeker, George Zhou, Thomas M. Evans-Soma, Lizhou Sha, Douglas N. C. Lin, Duncan Wright, Ava Morrissey, Emma Nabbie, Karen A. Collins Phil Evans, Tristan Guillot, Keith Horne, Don J. Radford, Richard P. Schwarz, Avi Shporer, Gregorg Srdoc, Olga Suarez

Abstract: We present the combined JWST/NIRSpec G395H and NIRISS SOSS transmission spectrum of a warm mini-Neptune, TOI-1130b (3.66 R$_{\oplus}$, 19.8 M$_{\oplus}$, $T_{eq}\sim825$ K). It is part of a rare and unique multi-planet system TOI-1130, which hosts an inner mini-Neptune and an outer hot Jupiter locked in a 2:1 mean motion resonance. From the transmission spectrum of TOI-1130b we detect multiple mol… ▽ More We present the combined JWST/NIRSpec G395H and NIRISS SOSS transmission spectrum of a warm mini-Neptune, TOI-1130b (3.66 R$_{\oplus}$, 19.8 M$_{\oplus}$, $T_{eq}\sim825$ K). It is part of a rare and unique multi-planet system TOI-1130, which hosts an inner mini-Neptune and an outer hot Jupiter locked in a 2:1 mean motion resonance. From the transmission spectrum of TOI-1130b we detect multiple molecules -- H$_2$O (7.5$σ$), CO$_2$ (3.3$σ$), and SO$_2$ (3.6$σ$), as well as a tentative detection of CH$_4$ ($\sim$2$σ$). We find a strong optical slope in the NIRISS/SOSS spectrum, which is consistent with TESS and CHEOPS transit depth measurements. From equilibrium chemistry retrievals we measure the atmospheric metallicity ($\log{Z/Z_{\odot}}=1.8^{+0.4}_{-0.3}$) and C/O ratio ($<$0.75 at 3$σ$ level confidence) and constrain the atmospheric mean molecular weight, $μ$ = 5.5$^{+1.3}_{-0.8}$ amu. These constraints are consistent with self-consistent forward model grids. We detect no significant He I 1.083$μ$m absorption signal and put a mass-loss rate upper limit of $10^{11}$g\s$^{-1}$. The volatile-rich high mean molecular weight atmosphere of TOI-1130b along with the `pebble-filtering' effect of the outer hot Jupiter supports the ex-situ formation scenario beyond the water ice line and subsequent migration, coherent with its present orbital architecture. A volatile-rich formation scenario could also potentially explain the location of TOI-1130b at the edge of the `radius cliff'. This result hints that the mini-Neptune population may not a homogeneous formation history; rather, volatile-rich ex-situ formation also contributes to its population. △ Less

Submitted 3 May, 2026; originally announced May 2026.

Comments: Accepted ApJ Letters

Direct Imaging Constraints on Binary Planets and Exomoons around Epsilon Indi A b

Authors: Matson Garza, Mary Anne Limbach, Rachel Bowens-Rubin, Matthew De Furio, Elisabeth C. Matthews, Kyle Franson, Sarah C. Millholland, Logan A. Pearce, Andrew Vanderburg

Abstract: Epsilon Indi A b is a directly imaged $\sim6 M_{\rm Jup}$ exoplanet orbiting a nearby (3.6 pc) K-dwarf at $\sim 30$ AU. We analyze archival JWST/MIRI 15 $μ$m coronagraphic imaging of this planet to search for directly imaged satellites orbiting Eps Ind A b. Within the planet's Hill sphere (radius $R_H \approx 2.3$ AU or $1.3 λ/D$), we compare single- and double-PSF models using Bayesian evidence.… ▽ More Epsilon Indi A b is a directly imaged $\sim6 M_{\rm Jup}$ exoplanet orbiting a nearby (3.6 pc) K-dwarf at $\sim 30$ AU. We analyze archival JWST/MIRI 15 $μ$m coronagraphic imaging of this planet to search for directly imaged satellites orbiting Eps Ind A b. Within the planet's Hill sphere (radius $R_H \approx 2.3$ AU or $1.3 λ/D$), we compare single- and double-PSF models using Bayesian evidence. We find that a double-PSF (binary planet) fit is preferred. This apparent preference can most plausibly be explained by systematics, although follow-up observations would be required to fully rule out a binary planet interpretation. We construct a contrast curve of the exoplanet after removing this feature, demonstrating sensitivity to companions as faint as $0.03\times$ the F1550C flux of Eps Ind A b (equivalent to $T = 130$ K, $1.3 M_{\rm Jup}$) at large separations (>2 AU). We also demonstrate sensitivity to brighter companions $0.2\times$ the F1550C flux of Eps Ind A b (equivalent to $T = 180$ K, $2.5 M_{\rm Jup}$) down to separations of 0.52 AU (1.3 pixels; $0.29 λ/D$; 144 mas). This study demonstrates that JWST/MIRI can directly detect exomoons or binary planets inside the Hill sphere of directly imaged exoplanets orbiting neighboring stars. △ Less

Submitted 25 April, 2026; originally announced April 2026.

Comments: Accepted to AJ, 14 pages with 5 figures

A Search for Wide-orbit Planets Around M-dwarfs using Deep MIRI 15-micron Images

Authors: Yihan Li, Yifan Zhou, Rachel Bowens-Rubin, Mary Anne Limbach, Hannah Diamond-Lowe, Cassidy E. Walker, Kevin B. Stevenson, Andrew Vanderburg, Giovanni Strampelli, Gregory J. Herczeg

Abstract: Wide-orbit ($>$10 AU) gas giant planets shape the architecture of planetary systems, yet their occurrence rate remains poorly constrained. JWST has obtained the deepest mid-infrared images of nearby stars to date through substantial MIRI time-series observations of transiting planets, providing sensitive probes for wide-orbit companions. Here we leverage 15 micron observations from four programs t… ▽ More Wide-orbit ($>$10 AU) gas giant planets shape the architecture of planetary systems, yet their occurrence rate remains poorly constrained. JWST has obtained the deepest mid-infrared images of nearby stars to date through substantial MIRI time-series observations of transiting planets, providing sensitive probes for wide-orbit companions. Here we leverage 15 micron observations from four programs targeting ten M-dwarf systems to search for such planets. By applying reference differential imaging for precise PSF subtraction, we achieve a 5$σ$ contrast of $8.9 \times 10^{-4} - 6.2 \times 10^{-3}$ (sensitivity in apparent magnitude of 14.8-15.8 mag) at a separation of 1" and $1.2 -9.1 \times 10^{-4}$ (16.5-17.9 mag) at separations $\gtrsim$3". The sensitivity is converted to planet detection probability for each system as a function of planet mass versus semimajor axis. Assuming solar metallicity and a clear atmosphere, we are sensitive to Jupiter-sized planets with an effective temperature of ${\sim}$233 K at separations beyond 20 AU in systems at 12.5 pc. Additionally, we catalog the nearby sources and estimate their possible impact on future observations assuming they are background sources. Our results demonstrate that archival MIRI time-series imaging data is a powerful window into the population of wide-orbit gas giants around M-dwarfs. △ Less

Submitted 2 June, 2026; v1 submitted 8 April, 2026; originally announced April 2026.

Comments: 20 pages, 13 figures, 3 tables; accepted for publication in AJ; corrected an error in the contrast curve calculation and updated the corresponding figures and results

The JWST Search for Earth-Luna Analogs: Upper Limits on Exomoons and Refined Ephemerides for TOI 700 d and e

Authors: Emily K. Pass, David Charbonneau, Andrew Vanderburg, Jacob L. Bean

Abstract: While no conclusive detections of exomoons have been reported to date, planet formation theories predict that Luna-analog satellites should be a common outcome of the collisional dynamics in early extrasolar systems. Such satellites have the potential to unlock new avenues to learn about exoplanet systems, speaking to topics of habitability, tidal heating, planet formation, late-stage growth, plan… ▽ More While no conclusive detections of exomoons have been reported to date, planet formation theories predict that Luna-analog satellites should be a common outcome of the collisional dynamics in early extrasolar systems. Such satellites have the potential to unlock new avenues to learn about exoplanet systems, speaking to topics of habitability, tidal heating, planet formation, late-stage growth, planetary compositions, and more. Here we describe the results of our JWST program to search for Luna-analog exomoons around the rocky, habitable-zone M-dwarf planets TOI 700 d and e. We refine the ephemerides of both worlds, providing an order-of-magnitude improvement in period precision and a factor of 2-3 improvement in planetary radii. We identify a strong correlated noise signal with a timescale of $16\pm4$ minutes and an amplitude of $46\pm4$ ppm; similar signals have been observed in previous JWST analyses of other stars and have been ascribed to stellar granulation. This noise source inflates our error by a factor of 4 relative to photon-noise expectations in 10-minute bins and limits our sensitivity to moons: we determine that our observations are sensitive mainly to moons larger than Ganymede on periods longer than 2 days (i.e., moons larger than our solar system's natural satellites). If this noise could be corrected, we would be sensitive to Luna-analog moons. Future work to address this noise source will thus be critical for detecting exomoons in stellar transits, as well as for all other science cases that hope to take advantage of JWST white-light curves in the photon-noise limit. △ Less

Submitted 29 July, 2026; v1 submitted 6 April, 2026; originally announced April 2026.

Comments: Accepted for publication in AJ; 17 pages, 11 figures, 2 tables

A Planetary Illusion's Funeral: Non-detection of a Gaia DR3 Exoplanet Candidate, and the Role of Intermediate-precision Radial Velocities in Gaia Exoplanet Follow-up

Authors: Alexander Venner, Chelsea X. Huang, David W. Latham, Samuel N. Quinn, Allyson Bieryla, Andrew Vanderburg, Robert A. Wittenmyer

Abstract: The detection of exoplanets using astrometry has long been an area of interest, but is fraught with challenges. The Gaia mission is fundamentally reshaping this field thanks to its unprecedentedly precise all-sky astrometric observations. The 2022 release of Gaia DR3 brought the first exoplanets discovered from the Gaia astrometry, including a new candidate around the bright ($V=6.6$) solar-type s… ▽ More The detection of exoplanets using astrometry has long been an area of interest, but is fraught with challenges. The Gaia mission is fundamentally reshaping this field thanks to its unprecedentedly precise all-sky astrometric observations. The 2022 release of Gaia DR3 brought the first exoplanets discovered from the Gaia astrometry, including a new candidate around the bright ($V=6.6$) solar-type star HD 12800. However, two years after announcement, the Gaia exoplanet candidate was retracted. In this work we report radial velocity observations of HD 12800 acquired with the TRES spectrograph, which we began immediately after the release of Gaia DR3. Our observations failed to detect the planet candidate; nonetheless, we emphasise that the originally proposed companion would have been easily detected in our radial velocity observations. We conclude with a discussion on the role of intermediate-precision ($\approx$10 m s$^{-1}$) RV spectrographs in the follow-up of Gaia astrometric exoplanet candidates, relevant to the forthcoming release of Gaia DR4. We argue that such observations may play an important role in planet confirmation for stars between approximately $8<G<12$, likely to represent a significant fraction of Gaia exoplanet discoveries. △ Less

Submitted 19 March, 2026; originally announced March 2026.

Comments: 8 pages, 2 tables, 1 figure. Accepted to AJ

Stars stably accreting from substellar objects

Authors: Aaron Householder, Kaitlyn Shin, Kevin B. Burdge, Thomas R. Marsh, Saul A. Rappaport, Kareem El-Badry, Joheen Chakraborty, Emma Chickles, Fei Dai, Matthew J. Graham, S. R. Kulkarni, Pablo Rodríguez-Gil, Andrew Vanderburg, Samuel Whitebook

Abstract: Substellar objects such as brown dwarfs and planets are generally expected to remain detached from their main-sequence host stars unless orbital decay or stellar expansion brings them into contact, leading to rapid engulfment and destruction. Such a fate is predicted for the Earth and other rocky planets in our solar system; however, in certain cases, theory also allows for stable long-lived mass… ▽ More Substellar objects such as brown dwarfs and planets are generally expected to remain detached from their main-sequence host stars unless orbital decay or stellar expansion brings them into contact, leading to rapid engulfment and destruction. Such a fate is predicted for the Earth and other rocky planets in our solar system; however, in certain cases, theory also allows for stable long-lived mass transfer from a substellar object onto its main-sequence host, though such accretion has never been directly observed. Here we report the first direct observations of stable mass transfer from a substellar object onto a main-sequence star. In particular, we identify two binaries, ZTF J0440+2325 and ZTF J1444+4820, with orbital periods of just 87 and 67 minutes, respectively, in which a brown dwarf stably transfers mass onto an M dwarf companion. These systems demonstrate that the fate of some substellar objects is not rapid engulfment and destruction, but instead gradual consumption for potentially billions of years. △ Less

Submitted 17 March, 2026; originally announced March 2026.

Comments: 29 pages, 10 figures (3 main + 7 extended data), 1 table. Submitted to Nature Astronomy

Constraining Small Planet Compositions for Future Missions

Authors: Larissa Palethorpe, Annelies Mortier, Jo Ann Egger, Ken Rice, Thomas G. Wilson, Andrew Vanderburg, Aldo S. Bonomo, Walter Boschin, Andrew Collier Cameron, Yoshi Nike Emilia Eschen, Avet Harutyunyan, Luca Malavolta, Aldo F. Martínez Fiorenzano, Alessandro Sozzetti, Manu Stalport, Vincent Van Eylen, Christopher Allan Watson

Abstract: Accurate mass and radius measurements of small transiting exoplanets are essential for probing their compositions, formation histories, and potential habitability. We present a uniform analysis of six planetary systems (each hosting at least one small transiting planet): K2-79, K2-106, K2-111, K2-222, K2-263, and TOI-1634. Our study combines new CHEOPS transit observations with archival photometry… ▽ More Accurate mass and radius measurements of small transiting exoplanets are essential for probing their compositions, formation histories, and potential habitability. We present a uniform analysis of six planetary systems (each hosting at least one small transiting planet): K2-79, K2-106, K2-111, K2-222, K2-263, and TOI-1634. Our study combines new CHEOPS transit observations with archival photometry from K2, TESS, and ground-based facilities, alongside new and archival radial velocity data from HARPS-N, HIRES, ESPRESSO, and others. For each system, we perform joint transit and RV modelling, achieving typical precisions better than 15% and 5% for mass and radius, respectively, and thus enabling precise bulk density determinations. These reveal a range of compositions, including rocky planets near the radius valley (e.g. K2-106 b, TOI-1634 b), intermediate-density planets requiring steam-rich or mixed volatile envelopes (e.g. K2-111 b, K2-263 b), and low-density regimes, consistent with gas dwarfs or water-worlds (e.g. K2-79 b, K2-222 b). Several systems show evidence of additional companions detectable via RVs but not seen in transit. The results highlight the value of coordinated CHEOPS and HARPS-N observations in delivering some of the most precise bulk densities for small planets to date and support the preparation for future atmospheric characterisation missions. △ Less

Submitted 15 March, 2026; originally announced March 2026.

Comments: 30 pages, 16 figures, 6 tables, accepted for publication in MNRAS

To What Extent Are Star Cluster Ages Encoded in Their Environments? Exploring the Spatial Distribution of Age-Related Information with PHANGS-HST Imaging and Convolutional Neural Networks

Authors: Javier Viaña, Janice C. Lee, Andrew Vanderburg, John F. Wu, M. Jimena Rodríguez, Remy Indebetouw, Médéric Boquien, Ralf S. Klessen, Sophia Rivera, Erik Rosolowsky, Oleg Y. Gnedin, Daniel A. Dale, Kirsten L. Larson, David A. Thilker, Gagandeep Anand

Abstract: The environments around star clusters evolve as stellar feedback reshapes the interstellar medium and dynamical processes reorganize the structure of the surrounding stellar field. As approximately single-age populations, star clusters can serve as clocks to trace these environmental changes. In this exploratory study, we test whether convolutional neural networks (CNNs) can identify age-dependent… ▽ More The environments around star clusters evolve as stellar feedback reshapes the interstellar medium and dynamical processes reorganize the structure of the surrounding stellar field. As approximately single-age populations, star clusters can serve as clocks to trace these environmental changes. In this exploratory study, we test whether convolutional neural networks (CNNs) can identify age-dependent changes in cluster environments. We take cluster ages as given from basic SED fitting of five-band UV-optical aperture photometry from the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) HST survey. We first show that CNNs can be trained on image cutouts centered on clusters to recover ages directly from imaging. This demonstration provides the foundation for this study, which examines whether the information used by CNNs to predict age is coherent and physically meaningful. We perform controlled image occlusion experiments as an explainable AI method. These show that the CNNs extract age-predictive environmental cues in the absence of cluster light and when information on SED shape is removed by combining the five filters into one image. We find that reliance on environmental information increases at the youngest (<10 Myr) and oldest (>1 Gyr) ages, where clusters can exhibit similarly red colors. Our results are consistent with the long-recognized picture that cluster environments evolve systematically with age. We demonstrate that this information is encoded at a level detectable by machine-learning and recoverable from broadband imaging. This establishes a path for using new techniques to connect image-based age inference to the physical evolution of cluster environments. △ Less

Submitted 7 March, 2026; originally announced March 2026.

Comments: 22 pages, 8 figures, 2 tables. Submitted to The Astrophysical Journal (ApJ)

TESS Hunt for Young and Maturing Exoplanets (THYME) XIV: A Comoving-Based Age Constraint for KELT-20

Authors: Adam Distler, Melinda Soares-Furtado, Andrew W. Mann, Adam L. Kraus, Jonathan Gagné, Juliette Becker, Ritvik Sai Narayan, Max Clark, Andrew Vanderburg, Joseph E. Rodriguez, Laura K. Rogers, Ronan Kerr

Abstract: Young stellar moving groups offer unique opportunities to investigate the early evolution of stellar and planetary systems. In continuation of an ongoing effort to age-date compelling planetary systems, we provide an in-depth age analysis of KELT-20, a young A-type star that hosts a well-aligned ultra-hot Jupiter. This system poses a useful case study to investigate migration mechanisms at early s… ▽ More Young stellar moving groups offer unique opportunities to investigate the early evolution of stellar and planetary systems. In continuation of an ongoing effort to age-date compelling planetary systems, we provide an in-depth age analysis of KELT-20, a young A-type star that hosts a well-aligned ultra-hot Jupiter. This system poses a useful case study to investigate migration mechanisms at early stages of evolution. Using Gaia DR3 data, we identify 77 stars with proper motions consistent with KELT-20, including 19 with measured radial velocities that enable full 3D kinematic confirmation. Using isochronal analyses, gyrochronology, photometric variability, and stellar activity indicators, we converge on an age of $58 \pm 5\,$Myr. This constraint provides critical insights into the dynamical processes shaping hot Jupiter formation. △ Less

Submitted 1 March, 2026; originally announced March 2026.

Comments: Accepted in AJ

Identifying Exoplanets with Deep Learning VI. Enhancing neural network mitigation of stellar activity RV signals with additional metrics

Authors: Naomi McWilliam, Zoë L. de Beurs, Andrew Vanderburg, Javier Viaña, Annelies Mortier, Lars A. Buchhave, Andrew Collier Cameron, Rosario Cosentino, Xavier Dumusque, Adriano Ghedina, Ben Lakeland, Marcello Lodi, Mercedes López-Morales, Dimitar Sasselov, Alessandro Sozzetti

Abstract: The measurement of exoplanet masses using the radial velocity (RV) technique is currently limited by stellar activity, which introduces quasiperiodic variability signals that must be modeled and removed to enhance the sensitivity of the RV measurements to exoplanet signals. Neural networks have previously been demonstrated effective in modeling stellar activity signals in HARPS-N solar data using… ▽ More The measurement of exoplanet masses using the radial velocity (RV) technique is currently limited by stellar activity, which introduces quasiperiodic variability signals that must be modeled and removed to enhance the sensitivity of the RV measurements to exoplanet signals. Neural networks have previously been demonstrated effective in modeling stellar activity signals in HARPS-N solar data using white light cross correlation functions (CCFs). Building on this work, we train a neural network on six years of HARPS-N solar data with additional parameters commonly associated to stellar activity, including chromatic CCFs, line shape metrics, spectral activity indicators, total solar irradiance (TSI) light curves from SORCE and TSIS-1, and TSI time derivatives. Our results show that parameters such as the bisector inverse slope and Na D equivalent widths do not significantly improve the neural network's ability to predict activity-induced RV variations compared to using the white light CCFs alone. However, parameters such as unsigned magnetic flux, the TSI and its time derivative, S-index, H-alpha equivalent width, chromatic CCFs, contrast, and full width at half maximum do improve the neural network's ability to predict RV scatter. Our new model reduces the RV scatter in a held-out test set from 147.1 cm/s to 93.3 cm/s, consistent with supergranulation noise levels reported in previous studies. These results suggest that finding effective tracers for (super)granulation will be critical to train models capable of further mitigating RV jitter, and necessary for characterizing Earth analogues. △ Less

Submitted 19 February, 2026; originally announced February 2026.

Comments: 31 pages, 16 figures, 5 tables. Accepted for publication in AJ

Gas-depleted planet formation occurred in the four-planet system around the red dwarf LHS 1903

Authors: Thomas G. Wilson, Anna M. Simpson, Andrew Collier Cameron, Ryan Cloutier, Vardan Adibekyan, Ancy Anna John, Yann Alibert, Manu Stalport, Jo Ann Egger, Andrea Bonfanti, Nicolas Billot, Pascal Guterman, Pierre F. L. Maxted, Attila E. Simon, Sergio G. Sousa, Malcolm Fridlund, Mathias Beck, Anja Bekkelien, Sebastien Salmon, Valerie Van Grootel, Luca Fossati, Alexander James Mustill, Hugh P. Osborn, Tiziano Zingales, Matthew J. Hooton , et al. (151 additional authors not shown)

Abstract: Small exoplanet radii show two populations, referred to as super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This may be produced by the removal of atmospheres due to stellar or internal heating, or lack of an initial envelope. We us transit photometry and radial velocity measurements to detect and characterize four planets orbiting LHS 1903, a red dwarf (M-dwarf) star… ▽ More Small exoplanet radii show two populations, referred to as super-Earths and sub-Neptunes, separated by a gap known as the radius valley. This may be produced by the removal of atmospheres due to stellar or internal heating, or lack of an initial envelope. We us transit photometry and radial velocity measurements to detect and characterize four planets orbiting LHS 1903, a red dwarf (M-dwarf) star in the Milky Way's thick disk. The planets have orbital periods between 2.2 and 29.3 days, and span the radius valley within a single planetary system. The derived densities indicate that LHS 1903 b is rocky, while LHS 1903 c and LHS 1903 d have extended atmospheres. Although the most distant planet from the host star, LHS 1903 e, has no gaseous envelope, indicating it formed from gas-depleted material. △ Less

Submitted 11 February, 2026; originally announced February 2026.

Comments: Accepted for publication in Science

Exomoons and Exorings with the Habitable Worlds Observatory II: Finding Endor with Lunar Eclipses

Authors: Mary Anne Limbach, Beck Dacus, Brooke Kotten, Elizabeth Lane, Jacob Lustig-Yaeger, Ryan MacDonald, Tyler D. Robinson, Jean-Baptiste Ruffio, Andrew Vanderburg

Abstract: Giant planets in the habitable zone may host exomoons with conditions conducive to life. In this paper we describe a method by which the Habitable Worlds Observatory (HWO) could detect such moons: broadband reflected-light lunar eclipses (e.g., the moon passing into the shadow of the planet). We find that an Earth-like moon orbiting a Jovian-size planet at 1au can outshine its host planet near 1 m… ▽ More Giant planets in the habitable zone may host exomoons with conditions conducive to life. In this paper we describe a method by which the Habitable Worlds Observatory (HWO) could detect such moons: broadband reflected-light lunar eclipses (e.g., the moon passing into the shadow of the planet). We find that an Earth-like moon orbiting a Jovian-size planet at 1au can outshine its host planet near 1 micron, producing frequent (days time-scale) lunar eclipses with depths of order 50%. We determine that single eclipse events out to $\sim$12pc may be detectable for Earth-like moons around giant planets, down to $0.9R_\oplus$. Detection of smaller moons, $\sim$0.5$R_\oplus$ (corresponding to about the size of Mars or Ganymede), may be possible, but would generally require multiple events for most systems. These several-hour events provide a clear pathway to detecting habitable moons with HWO, given sufficient stare-time on each system to detect lunar eclipses. The occurrence rate of habitable exomoons remains unconstrained, however, making the ultimate yield uncertain. HWO will be capable of placing the first meaningful constraints on the frequency of habitable exomoons around giant planets; if it is non-negligible, HWO could also search for life on these worlds, possibly with lunar eclipse spectroscopy. △ Less

Submitted 27 January, 2026; originally announced January 2026.

Comments: Accepted to AJ

A Cool Earth-sized Planet Candidate Transiting a Tenth Magnitude K-dwarf From K2

Authors: Alexander Venner, Andrew Vanderburg, Chelsea X. Huang, Shishir Dholakia, Hans Martin Schwengeler, Steve B. Howell, Robert A. Wittenmyer, Martti H. Kristiansen, Mark Omohundro, Ivan A. Terentev

Abstract: The transit method is currently one of our best means for the detection of potentially habitable "Earth-like" exoplanets. In principle, given sufficiently high photometric precision, cool Earth-sized exoplanets orbiting Sun-like stars could be discovered via single transit detections; however, this has not previously been achieved. In this work, we report a 10-hour long single transit event which… ▽ More The transit method is currently one of our best means for the detection of potentially habitable "Earth-like" exoplanets. In principle, given sufficiently high photometric precision, cool Earth-sized exoplanets orbiting Sun-like stars could be discovered via single transit detections; however, this has not previously been achieved. In this work, we report a 10-hour long single transit event which occurred on the $V=10.1$ K-dwarf HD 137010 during K2 Campaign 15 in 2017. The transit is comparatively shallow ($225\pm10$ ppm), but is detected at high signal-to-noise thanks to the exceptionally high photometric precision achieved for the target. Our analysis of the K2 photometry, historical and new imaging observations, and archival radial velocities and astrometry strongly indicate that the event was astrophysical, occurred on-target, and can be best explained by a transiting planet candidate, which we designate HD 137010 b. The single observed transit implies a radius of $1.06^{+0.06}_{-0.05}$ $R_\oplus$, and assuming negligible orbital eccentricity we estimate an orbital period of $355^{+200}_{-59}$ days ($a=0.88^{+0.32}_{-0.10}$ AU), properties comparable to Earth. We project an incident flux of $0.29^{+0.11}_{-0.13}$ $I_\oplus$, which would place HD 137010 b near the outer edge of the habitable zone. This is the first planet candidate with Earth-like radius and orbital properties that transits a Sun-like star bright enough for substantial follow-up observations. △ Less

Submitted 27 January, 2026; originally announced January 2026.

Comments: 22 pages, 7 figures, 6 tables. Published in ApJL

Discovery and characterisation of two exoplanets orbiting the metal-poor, solar-type star TOI-5788 with TESS, CHEOPS, and HARPS-N

Authors: Ben S. Lakeland, A. Mortier, R. D. Haywood, S. Ulmer-Moll, Z. Garai, A. Vanderburg, J A. Egger, D. A. Turner, D. Kubyshkina, A. C. M. Correia, H. P. Osborn, L. A. Buchhave, L. Malavolta, A. Bonfanti, W. Boschin, A. Cameron, A. Castro-González, R. Cosentino, M. Damasso, X. Dumusque, D. Ehrenreich, Z. Essack, S. Filomeno, L. Fossati, D. Gandolfi , et al. (26 additional authors not shown)

Abstract: We present the discovery and characterisation of two transiting exoplanets orbiting the metal-poor, solar-type star TOI-5788. From our analysis of six \textit{TESS} sectors and a dedicated \textit{CHEOPS} programme, we identify an inner planet (TOI-5788~b; $P = 6.340758\pm0.000030\,\si{\day}$) with radius $1.528\pm0.075\,\mathrm{R_\oplus}$ and an outer planet (TOI-5788~c;… ▽ More We present the discovery and characterisation of two transiting exoplanets orbiting the metal-poor, solar-type star TOI-5788. From our analysis of six \textit{TESS} sectors and a dedicated \textit{CHEOPS} programme, we identify an inner planet (TOI-5788~b; $P = 6.340758\pm0.000030\,\si{\day}$) with radius $1.528\pm0.075\,\mathrm{R_\oplus}$ and an outer planet (TOI-5788~c; $P = 16.213362\pm0.000026\,\si{\day}$) with radius $2.272\pm0.039\,\mathrm{R_\oplus}$. We obtained 125 radial-velocity spectra from HARPS-N and constrain the masses of TOI-5788~b and~c as $3.72\pm0.94\,\mathrm{M_\oplus}$ and $6.4\pm1.2\,\mathrm{M_\oplus}$, respectively. Although dynamical analyses indicate that a third planet could exist in a stable orbit between 8 and 14 days, we find no evidence of additional planets. Since the TOI-5788 system is one of the few systems with planets straddling the radius gap, and noting that there are even fewer such systems around metal poor stars, it is a promising system to constrain planet formation theories. We therefore model the interior structures of both planets. We find that TOI-5788~b is consistent with being a rocky planet with almost no envelope, or having an atmosphere of a high mean molecular weight. We find that TOI-5788~c is consistent with both gas-dwarf and water-world hypotheses of mini-Neptune formation. We model the atmospheric evolution history of both planets. Whilst both scenarios are consistent with the atmospheric evolution of TOI-5788~c, the gas-dwarf model is marginally preferred. The results of the atmospheric evolution analysis are not strongly dependent on stellar evolution. This makes the system a promising target to test internal structure and atmospheric evolution models. △ Less

Submitted 20 January, 2026; originally announced January 2026.

Comments: 17 pages, 13 figures, 7 tables, accepted for publication in MNRAS

The Occurrence Rate of Nearby Planetary Companions to Hot Jupiters

Authors: Lizhou Sha, Andrew M. Vanderburg, Chelsea X. Huang, Samuel Christian, Kevin Burdge, Nicholas Saunders, Khalid Barkaoui, Alexander Belinski, Serge Bergeron, Zoë L. de Beurs, Allyson Bieryla, Karen A. Collins, Giuseppe Conzo, Gareb Fernández-Rodríguez, Akihiko Fukui, Davide Gandolfi, Tristan Guillot, Joel D. Hartman, Kai Ikuta, David W. Latham, Jerome P. de Leon, Bob Massey, Gabriel Murawski, Felipe Murgas, Norio Narita , et al. (11 additional authors not shown)

Abstract: Of the > 500 confirmed transiting hot jupiters and approximately 2000 additional candidates today, only ten are known to have nearby companion planets. The survival of nearby companions means that these hot jupiters cannot have migrated to their present location via dynamically disruptive high-eccentricity migration but instead have undergone disk migration or formed in situ. The occurrence rate f… ▽ More Of the > 500 confirmed transiting hot jupiters and approximately 2000 additional candidates today, only ten are known to have nearby companion planets. The survival of nearby companions means that these hot jupiters cannot have migrated to their present location via dynamically disruptive high-eccentricity migration but instead have undergone disk migration or formed in situ. The occurrence rate for these nearby companions, therefore, constrains the relative efficiency of different hot jupiter formation pathways. Here, we perform a uniform box least-squares search for nearby transiting companions to hot jupiters in the first five years of TESS data. Accounting for observational completeness and detection efficiency, we arrive at an occurrence rate of $(7.6^{+5.5}_{-3.8})\%$, which is a lower limit on the fraction of hot jupiters that underwent disk migration or in situ formation. Comparing this rate with that derived from transit-timing variation searches suggests that hot jupiters are likely mostly aligned with their nearby companions, but their apparently higher incidence of grazing transits may point to a slight preferential misalignment. We also synthesize evidence that hot jupiters with nearby companions may have cold companions at a rate similar to that of other hot jupiters. Comprehensive transit, radial velocity, and stellar obliquity measurements in hot jupiter systems with nearby companions will be necessary to fully account for the relative prevalence of proposed hot jupiter formation pathways. △ Less

Submitted 15 July, 2026; v1 submitted 19 January, 2026; originally announced January 2026.

Comments: 17 pages, 7 figures, 1 table (machine-readable ECSV file available as an ancillary file). Accepted by AJ

A young progenitor for the most common planetary systems in the Galaxy

Authors: John H. Livingston, Erik A. Petigura, Trevor J. David, Kento Masuda, James Owen, David Nesvorný, Konstantin Batygin, Jerome de Leon, Mayuko Mori, Kai Ikuta, Akihiko Fukui, Noriharu Watanabe, Jaume Orell Miquel, Felipe Murgas, Hannu Parviainen, Judith Korth, Florence Libotte, Néstor Abreu García, Pedro Pablo Meni Gallardo, Norio Narita, Enric Pallé, Motohide Tamura, Atsunori Yonehara, Andrew Ridden-Harper, Allyson Bieryla , et al. (17 additional authors not shown)

Abstract: The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii). The planets form a chain of ne… ▽ More The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii). The planets form a chain of near-resonances that result in transit-timing variations of several hours. Here we present a multi-year campaign to characterize this system with transit-timing variations, a method insensitive to the intense magnetic activity of the star. Through targeted observations, we first resolved the previously unknown orbital period of the outermost planet. The full 9-year baseline from these and archival data then enabled robust determination of the masses and orbital parameters for all four planets. We find the planets have low, sub-Neptune masses and nearly circular orbits, implying a dynamically tranquil history. Their low masses and large radii indicate that the inner planets underwent a period of rapid cooling immediately after dispersal of the protoplanetary disk. Still, they are much less dense than mature planets of comparable size. We predict the planets will contract to 1.5-4.0 Earth radii and join the population of super-Earths and sub-Neptunes that nature produces in abundance. △ Less

Submitted 15 January, 2026; originally announced January 2026.

Comments: 45 pages, 11 figures, 6 tables

Journal ref: Nature 649, 310-314 (2026)

A Characterization of JWST MIRI Detector Persistence and Implications for High-Contrast Imaging

Authors: Alisha Vasan, Mary Anne Limbach, Andrew Vanderburg, Rachel Bowens-Rubin, Kevin B. Stevenson

Abstract: The JWST MIRI detector exhibits a flux deficit persistence, but its timescales and impacts remain largely uncharacterized, particularly at the longest imaging wavelengths. In this study, we analyze full-field MIRI imager observations at 21 $μ$m (F2100W) to quantify detector persistence following a saturation event by a bright (K = 5.65 mag) nearby (8.12 $\pm$ 0.04 pc) mid M-dwarf star, IRAS 21500+… ▽ More The JWST MIRI detector exhibits a flux deficit persistence, but its timescales and impacts remain largely uncharacterized, particularly at the longest imaging wavelengths. In this study, we analyze full-field MIRI imager observations at 21 $μ$m (F2100W) to quantify detector persistence following a saturation event by a bright (K = 5.65 mag) nearby (8.12 $\pm$ 0.04 pc) mid M-dwarf star, IRAS 21500+5903. Unlike typical persistence that appears as excess flux, this effect presents as a flux deficit in pixels previously illuminated by the saturating or near saturating source. We measure persistence at two post-saturation epochs: shortly after saturation (11.6 minutes) and an hour later (1.39 hours). Immediately after the saturation event, we detect a persistence level of $1.69 \pm 0.10$%. By fitting a Bayesian exponential decay model to the two epochs, we estimate that persistence decreases to one-tenth of its initial value after $5.16^{+1.49}_{-0.94}$ hours. We examine the implications of persistence for MIRI high-contrast imaging using the imager (not coronagraphy). Specifically, we discuss how MIRI detector persistence can produce false-positive exoplanet signals in direct imaging surveys, as well as degrade PSF subtraction, particularly at small inner working angles. We also outline mitigation strategies to avoid these impacts in future observations. △ Less

Submitted 17 December, 2025; originally announced December 2025.

Comments: Accepted to ApJS

Searching for Transit Timing Variations in young transiting systems

Authors: Ana Isabel Lopez Murillo, Andrew W. Mann, Madyson G. Barber, Andrew Vanderburg, Pa Chia Thao, Andrew W. Boyle

Abstract: The discovery of young (<800 Myr) transiting planets has provided a new avenue to explore how planets form and evolve over their lifetimes. Mass measurements for these planets would be invaluable, but radial velocity surveys of young systems are often overwhelmed by stellar activity. Transit timing variations (TTVs) offer an alternative route to measure masses that are less impacted by signals fro… ▽ More The discovery of young (<800 Myr) transiting planets has provided a new avenue to explore how planets form and evolve over their lifetimes. Mass measurements for these planets would be invaluable, but radial velocity surveys of young systems are often overwhelmed by stellar activity. Transit timing variations (TTVs) offer an alternative route to measure masses that are less impacted by signals from the host star. Here we search for candidate TTVs in a sample of 39 young systems hosting 53 transiting planets using data from Kepler, K2, and TESS. We recover previously reported TTVs for 11 planets, including those in V1298 Tau, TOI-2076, Kepler-51, and TOI-1227, and identify new candidate TTVs for four planets (DS Tuc Ab, HD 63433b, K2-101b, and Kepler-1643b). In total, 28.3 +/- 6.2% of young planets in our sample show evidence of TTVs, which is higher than the rate from Kepler on mostly older systems (7.3 +/- 0.6%). Accounting for differences in data coverage and quality between Kepler and TESS only increases this difference (> 4$σ$), although differences in methodology make a totally fair comparison challenging. We show that spots have a weak-to-negligible impact on our results, and similarly cannot explain the higher TTV fraction. Longer-term monitoring will be required to validate these TTVs as planetary in nature and confirm the high TTV rate. While the candidate TTV signals detected here are sparsely sampled, our work provides a clear priority list for additional ground-based observations, and for multi-planet TTVs, attempt to measure the masses and eccentricities of these planets. △ Less

Submitted 4 December, 2025; originally announced December 2025.

Comments: Accepted for publication into AJ

First Astrometric Limits on Binary Planets and Exomoons orbiting $β$ Pictoris b

Authors: Isabella Macias, Sydney Jenkins, Andrew Vanderburg

Abstract: The search for exomoons, or moons in other star systems, has attracted significant interest in recent years, driven both by advancements in detection sensitivity and by the expanding population of known exoplanets. The $β$ Pictoris system is a particularly favorable target, as its proximity and directly imaged planets allow for precise astrometric monitoring. We present astrometric constraints on… ▽ More The search for exomoons, or moons in other star systems, has attracted significant interest in recent years, driven both by advancements in detection sensitivity and by the expanding population of known exoplanets. The $β$ Pictoris system is a particularly favorable target, as its proximity and directly imaged planets allow for precise astrometric monitoring. We present astrometric constraints on the presence of binary planets and exomoons in the $β$ Pictoris system using archival observations from the GRAVITY interferometer and SPHERE instruments. We calculate these limits by modeling the motion of the two orbiting planets and introducing an additional perturbation to the model that simulates the astrometric motion caused by an exomoon orbiting the planet $β$ Pictoris b. We find that for short orbital periods ($\approx50$ days), a lunar companion is only allowed if its mass remains below $\approx 180~M_{\oplus}$ ($0.6~M_{\text{Jup}}$) at $3σ$ confidence. At intermediate periods near 300 days, we exclude moons more massive than $\approx 65~M_{\oplus}$ ($0.2~M_{\text{Jup}}$) at $3σ$ confidence. At longer orbital periods, we place the tightest constraints, ruling out any potential exomoon above $\approx 50~M_{\oplus}$ ($0.15~M_{\text{Jup}}$) at $700$ days and $\approx 30~M_{\oplus}$ ($0.1~M_{\text{Jup}}$) at $1,100$ days (both at $3σ$ confidence). These results place the first astrometric constraints on moons and binary planets in the $β$ Pictoris system and demonstrate the sensitivity of interferometric observations for exomoon studies. △ Less

Submitted 3 February, 2026; v1 submitted 28 November, 2025; originally announced December 2025.

Comments: 16 pages, 4 figures, 4 tables. Submitted to AAS Journals. A machine-readable version of Table 4 is available in LaTeX source

Stellar Obliquities of Young Systems, Atmospheres Undergoing Contraction and Escape (SOYSAUCE): a likely aligned orbit for the 3 Myr planet TIDYE-1 b

Authors: Madyson G. Barber, Andrew W. Mann, Marshall C. Johnson, Mayuko Mori, John Livingston, Daniel M. Krolikowski, Norio Narita, Akihiko Fukui, Teruyuki Hirano, Andrew Vanderburg, Adam L. Kraus, Benjamin M. Tofflemire, Sydney Vach, Sarah Blunt, Lissa Haskell

Abstract: Despite the wide range of planet-star (mis)alignments in the mature population of transiting exoplanets, the small number of known young transiting planets are nearly all aligned with the rotation axes of their host stars, as determined by the sky-projected obliquity angle. The small number of young systems with measured obliquities limits statistical conclusions. Here we determine the sky-project… ▽ More Despite the wide range of planet-star (mis)alignments in the mature population of transiting exoplanets, the small number of known young transiting planets are nearly all aligned with the rotation axes of their host stars, as determined by the sky-projected obliquity angle. The small number of young systems with measured obliquities limits statistical conclusions. Here we determine the sky-projected obliquity ($λ$) of the 3 Myr transiting planet with a misaligned outer protoplanetary disk, TIDYE-1 b (IRAS 04125+2902 b), using the Rossiter-McLaughlin (RM) effect. Our dataset lacks a pre-transit baseline and ingress, complicating a blind RM fit. Instead, we use contemporaneous spectra and photometry from a mass-measurement campaign to model the stellar activity trend across the transit and provide an external prior on the velocity baseline. We determine $|λ|=11.8^{+5.9\,\circ}_{-5.0}$. Combined with the published rotational velocity of the star, we find a true three-dimensional obliquity of $ψ=15.2^{+7.3\,\circ}_{-5.7}$. Our result is consistent with an aligned orbit, suggesting the planet remains aligned to its star even though the outer disk is misaligned, though additional RM observations are needed to exclude the low-probability tail of misaligned ($>30^{\circ}$) scenarios present in our posterior. △ Less

Submitted 18 November, 2025; originally announced November 2025.

Comments: Accepted for publication in ApJ Letters

The KPF SURFS-UP Survey I: Transmission Spectroscopy of WASP-76 b

Authors: Aaron Householder, Fei Dai, Aurora Kesseli, Andrew W. Howard, Samuel Halverson, Benjamin J. Fulton, Yapeng Zhang, Alex S. Polanski, Julie Inglis, Nick Tusay, Aaron Bello-Arufe, Ashley D. Baker, Kevin B. Burdge, Jerry Edelstein, Steven Giacalone, Steven R. Gibson, Gregory J. Gilbert, Luke B. Handley, Howard Isaacson, Russ R. Laher, Erik A. Petigura, Kodi Rider, Arpita Roy, Ryan A. Rubenzahl, Chris Smith , et al. (3 additional authors not shown)

Abstract: We introduce the KPF SURFS-UP (Spectroscopy of the Upper-atmospheres and ReFractory Species in Ultra-hot Planets) Survey, a high-resolution survey to investigate the atmospheric composition and dynamics of a sample of ultra-hot Jupiters with the Keck Planet Finder (KPF). Due to the unique design of KPF, we developed a publicly available pipeline for KPF that performs blaze removal, continuum norma… ▽ More We introduce the KPF SURFS-UP (Spectroscopy of the Upper-atmospheres and ReFractory Species in Ultra-hot Planets) Survey, a high-resolution survey to investigate the atmospheric composition and dynamics of a sample of ultra-hot Jupiters with the Keck Planet Finder (KPF). Due to the unique design of KPF, we developed a publicly available pipeline for KPF that performs blaze removal, continuum normalization, order stitching, science spectra combination, telluric correction, and atmospheric detection via cross-correlation. As a first demonstration, we applied this pipeline to a transit of WASP-76 b and achieved some of the highest signal-to-noise detections of refractory species in WASP-76 b to date (e.g., Fe I is detected at a SNR of 14.5). We confirm previous observations of an asymmetry in Fe I absorption, but find no measurable ingress-egress asymmetry in Na I and Ca II. Together, these results suggest variations within different layers of the atmosphere of WASP-76 b: neutral metals such as Fe I trace deeper regions with stronger asymmetries, while Na I and Ca II probe regions higher in the atmosphere where the ingress-egress asymmetries are weaker. Unlike some other ultra-hot Jupiters, our results are qualitatively consistent with GCM predictions of decreasing velocity asymmetry with altitude and do not require a high-altitude super-rotating jet that has been invoked for other planets (e.g., WASP-121 b). These results suggest that atmospheric circulation patterns in ultra-hot Jupiters may be more diverse than previously thought, highlighting the need for broader surveys to study how atmospheric dynamics depend on planetary and stellar properties. △ Less

Submitted 5 July, 2026; v1 submitted 18 November, 2025; originally announced November 2025.

TESS Investigation -- Demographics of Young Exoplanets (TI-DYE) IV: a Jovian radius planet orbiting a 34 Myr Sun-like star in the Vela association

Authors: Madyson G. Barber, Andrew W. Mann, Andrew Vanderburg, Khalid Barkaoui, Karen A. Collins, Sebastian Carrazco-Gaxiola, Phil Evans, Matthew J. Fields, Michael Gillon, Todd J. Henry, Katharine M. Hesse, Wei-Chun Jao, Emmanuel Jehin, Sydney Jenkins, Tim Johns, David R. Rodriguez, Richard P. Schwarz, William C. Storch, Cristilyn N. Watkins, Francis P. Wilkin

Abstract: The discovery of infant (< 50 Myr), close-in (<30-day period) planets is vital in understanding the formation mechanisms that lead to the distribution of mature transiting planets as discovered by Kepler. Despite several discoveries in this age bin, the sample is still too small for a robust statistical comparison to older planets. Here we report the validation of TOI-6448 b, an 8.8 +/- 0.8 Re pla… ▽ More The discovery of infant (< 50 Myr), close-in (<30-day period) planets is vital in understanding the formation mechanisms that lead to the distribution of mature transiting planets as discovered by Kepler. Despite several discoveries in this age bin, the sample is still too small for a robust statistical comparison to older planets. Here we report the validation of TOI-6448 b, an 8.8 +/- 0.8 Re planet on a 14.8 day orbit. TOI-6448 was previously identified to be a likely member of Vela Population IV. We confirm the star's membership and re-derive the age of the cluster using isochrones, variability, and gyrochronology. We find the star, and thus planet, to be 34 +/- 3 Myr. Like other young planets, TOI-6448 b lands in a region of parameter space with few older planets. While just one data point, this fits with prior findings of an excess of 5-11Re planets around young stars far beyond what can be explained by reduced sensitivity at young ages. Our ongoing search of Vela, Taurus-Auriga, Sco-Cen, and Orion are expected to reveal dozens more < 50 Myr transiting planets. △ Less

Submitted 13 November, 2025; originally announced November 2025.

Comments: Accepted for publication in Journals of the AAS

Searching for Exoplanets Born Outside the Milky Way: VOYAGERS Survey Design

Authors: Robert Aloisi, Andrew Vanderburg, Melinda Soares-Furtado, Phillip Cargile, Ke Zhang, Lina Necib, David W. Latham, Sam Quinn, Emily Pass, Anne Dattilo, Giacomo Mantovan, Francesco Amadori, Mariona Badenas-Agusti, Perry Berlind, Francesco Borsa, Walter Boschin, Lorenzo Cabona, Michael L. Calkins, Hans J. Deeg, Xavier Dumusque, Gilbert A. Esquerdo, Yoshi Nike Emilia Eschen, S. Filomeno, S. Geraldía-González, Natalia Guerrero , et al. (22 additional authors not shown)

Abstract: Observations over the past few decades have found that planets are common around nearby stars in our Galaxy, but little is known about planets that formed outside the Milky Way. We describe the design and early implementation of a survey to test whether planets also exist orbiting the remnant stars of ancient dwarf galaxies that merged with the Milky Way, and if so, how they differ from their Milk… ▽ More Observations over the past few decades have found that planets are common around nearby stars in our Galaxy, but little is known about planets that formed outside the Milky Way. We describe the design and early implementation of a survey to test whether planets also exist orbiting the remnant stars of ancient dwarf galaxies that merged with the Milky Way, and if so, how they differ from their Milky Way counterparts. VOYAGERS (Views Of Yore - Ancient Gaia-enceladus Exoplanet Revealing Survey) is a radial velocity (RV) search using precision spectrographs to discover exoplanets orbiting very low metallicity ($-2.8 < [\mathrm{Fe/H}] \leq -0.8$) stars born in the dwarf galaxy Enceladus, which merged with the Milky Way galaxy about 10 Gyr ago. A sample of 22 candidates have been screened from a catalog of Gaia-Enceladus-Sausage (GES) members using a combination of stellar properties and reconnaissance observations from the TRES spectrograph. Precision RV measurements have been initiated using the NEID, HARPS-N, and CARMENES spectrographs. We plan to focus most upcoming observations on 10 main sequence targets. Data collection is well underway, with 778 observations on 22 candidates (385 of which are 10 focus targets), but far from complete. This survey is designed to be sensitive to sub-Neptune mass planets with periods up to hundreds of days. We note that the RV analysis gives mass multiplied by $\sin (inclination)$ or the minimum mass for exoplanets. The expected survey yield is three planets, assuming that occurrence rates are similar to those in the Milky Way and taking into account the degeneracy with inclination in our yield models. Our survey is designed to detect at least one exoplanet if occurrence rates are similar to known Milky Way exoplanets or, if no exoplanets are discovered, to rule out a Milky Way-like planet population in GES with 95% confidence level. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 19 pages, 3 tables, 10 figures, accepted to PASP

Reassessing the Relationship Between Stellar X-ray Luminosity and Age with eROSITA Data Release 1

Authors: Nadja Aldarondo Quiñones, Sydney Jenkins, Andrew Vanderburg, Melinda Soares-Furtado, Michael A. McDonald

Abstract: Accurate stellar dating provides crucial information about the formation and development of planetary systems. Existing age-dating techniques are limited in terms of both the spectral type and age range they can accurately probe, and many are unreliable for stars older than 1 Gyr. Recent studies have suggested that a star's X-ray luminosity correlates strongly with stellar age and shows a steep fa… ▽ More Accurate stellar dating provides crucial information about the formation and development of planetary systems. Existing age-dating techniques are limited in terms of both the spectral type and age range they can accurately probe, and many are unreliable for stars older than 1 Gyr. Recent studies have suggested that a star's X-ray luminosity correlates strongly with stellar age and shows a steep fall-off at ages older than 1 Gyr. In this work, we present X-ray luminosity relationship values from eROSITA for four previously unassessed stars. Additionally, we reassess the X-ray luminosity/age relationship present in 24 main-sequence stars older than a gigayear. We confirm that a correlation does appear to exist between stellar age and X-ray luminosity at ages older than 1 Gyr. However, we measure a shallower slope with age than previous research for older stars, similar to what was found for younger stars. We also find evidence for significant astrophysical variability in a star's X-ray luminosity, which will likely limit the precision with which X-ray measurements can yield age estimates. We also find weak evidence for mass dependence in the X-ray luminosity/age relationship. These results suggest that although X-ray luminosity correlates with stellar age, it may not serve as a reliable standalone age indicator and is better used as part of a broader suite of age-dating methods. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 11 pages, 3 tables, 2 figures, accepted to PASP

A Decade of Solar High-Fidelity Spectroscopy and Precise Radial Velocities from HARPS-N

Authors: X. Dumusque, K. Al Moulla, M. Cretignier, N. Buchschacher, D. Segransan, D. F. Phillips, L. Affer, S. Aigrain, A. Anna John, A. S. Bonomo, V. Bourrier, L. A. Buchhave, A. Collier Cameron, H. M. Cegla, P. Cortes-Zuleta, R. Cosentino, J. Costes, M. Damasso, Z. L de Beurs, D. Ehrenreich, A. Ghedina, M. Gonzales, R. D. Haywood, B. Klein, B. S. Lakeland , et al. (31 additional authors not shown)

Abstract: We recently released 10 years of HARPS-N solar telescope and the goal of this manuscript is to present the different optimisations made to the data reduction, to describe data curation, and to perform some analyses that demonstrate the extreme RV precision of those data. By analysing all the HARPS-N wavelength solutions over 13 years, we bring to light instrumental systematics at the 1 m/s level… ▽ More We recently released 10 years of HARPS-N solar telescope and the goal of this manuscript is to present the different optimisations made to the data reduction, to describe data curation, and to perform some analyses that demonstrate the extreme RV precision of those data. By analysing all the HARPS-N wavelength solutions over 13 years, we bring to light instrumental systematics at the 1 m/s level. After correction, we demonstrate a peak-to-peak precision on the HARPS-N wavelength solution better than 0.75 m/s over 13 years. We then carefully curate the decade of HARPS-N re-reduced solar observations by rejecting 30% of the data affected either by clouds, bad atmospheric conditions or well-understood instrumental systematics. Finally, we correct the curated data for spurious sub-m/s RV effects caused by erroneous instrumental drift measurements and by changes in the spectral blaze function over time. After curation and correction, a total of 109,466 HARPS-N solar spectra and respective RVs over a decade are available. The median photon-noise precision of the RV data is 0.28 m/s and, on daily timescales, the median RV rms is 0.49 m/s, similar to the level imposed by stellar granulation signals. On 10-year timescales, the large RV rms of 2.95 m/s results from the RV signature of the Sun's magnetic cycle. When modelling this long-term effect using the Magnesium II activity index, we demonstrate a long-term RV precision of 0.41 m/s. We also analysed contemporaneous HARPS-N and NEID solar RVs and found the data from both instruments to be of similar quality and precision, with an overall RV differece rms of 0.79 m/s. This decade of high-cadence HARPS-N solar observations with short- and long-term precision below 1 m/s represents a crucial dataset to further understand stellar activity signals in solar-type stars , and to advance other science cases requiring such an extreme precision. △ Less

Submitted 31 October, 2025; originally announced October 2025.

Comments: 22 pages, 13 figures, version after first reviewing round

Journal ref: A&A 706, A231 (2026)

52 Eclipsing Quadruple Star Candidates Discovered in TESS Full Frame Images

Authors: Veselin B. Kostov, Brian P. Powell, Saul A. Rappaport, Tamas Borkovits, Robert Gagliano, Mark Omohundro, Thomas L. Jacobs, Martti H. Kristiansen, Guillermo Torres, Gerald Handler, Allan R. Schmitt, Hans M. Schwengeler, Tibor Mitnyan, Ivan A. Terentev, Daryll M. LaCourse, Andrew Vanderburg, Svetoslav D. Alexandrov, Cledison Marcos da Silva, Marco Z. Di Fraia, Aline U. Fornear, Marc Huten, Davide Iannone, Julien S. de Lambilly, Sam Lee, Jerome Orosz , et al. (3 additional authors not shown)

Abstract: We present the discovery of 52 eclipsing quadruple star candidates detected in TESS Full Frame Image eleanor data by machine learning and citizen scientists. The uniformly-vetted and -validated targets exhibit two sets of eclipses following two distinct periods, representing quadruple systems with a 2+2 hierarchical configuration. Detailed photocenter measurements confirmed that both sets of eclip… ▽ More We present the discovery of 52 eclipsing quadruple star candidates detected in TESS Full Frame Image eleanor data by machine learning and citizen scientists. The uniformly-vetted and -validated targets exhibit two sets of eclipses following two distinct periods, representing quadruple systems with a 2+2 hierarchical configuration. Detailed photocenter measurements confirmed that both sets of eclipses originate within ~0.1-0.2 pixels (~2-4 arcsec) of the corresponding target, and ruled out resolved nearby field stars. The catalog includes a number of systems producing prominent eclipse timing variations and/or apsidal motion, a quadruple with an outer period of ~1,400 days, and even a 2+2 quadruple in a likely wide quintuple with a resolved co-moving star. Additionally, two systems have complete astrometric solutions for the outer orbits from Gaia. We provide the measured ephemerides, eclipse depths and durations, overall statistical properties, and highlight potentially interesting systems that merit further investigations. △ Less

Submitted 31 October, 2025; originally announced October 2025.

Comments: 33 pages, 24 figures, 18 tables, AJ accepted

A Deep Search for Exomoons Around WISE 0855 With JWST

Authors: Mikayla J. Wilson, Mary Anne Limbach, Andrew J. Skemer, Johanna M. Vos, Brittany E. Miles, Melanie J. Rowland, Andrew Vanderburg, Adam C. Schneider, Caroline Morley, Brooke Kotten, Andrew Householder, Roxana Lupu, James Mang, Richard Freedman

Abstract: JWST is collecting time-series observations of many free-floating planets (FFPs) to study their weather, but these light curves are the ideal datasets to search for exomoons that transit the FFP during observations. In this paper, we present observations of the planetary-mass Y dwarf ($T=250-285K$, $M = 6.5\pm3.5 M_{Jup}$, d = 2.3$\,$pc) WISE J085510.83-071442.5 (WISE 0855), whose proximity and br… ▽ More JWST is collecting time-series observations of many free-floating planets (FFPs) to study their weather, but these light curves are the ideal datasets to search for exomoons that transit the FFP during observations. In this paper, we present observations of the planetary-mass Y dwarf ($T=250-285K$, $M = 6.5\pm3.5 M_{Jup}$, d = 2.3$\,$pc) WISE J085510.83-071442.5 (WISE 0855), whose proximity and brightness make it ideal for a transiting exomoon search. We examine 11 hours of time-series spectra from the JWST Near-Infrared Spectrograph (NIRSpec) whose sensitivity, in combination with Gaussian process (GP) modeling, allows for the disentanglement of exomoon transits from WISE 0855's variability. We do not find statistically significant evidence of an exomoon transit in this dataset. Using injection and recovery tests of artificial transits for depths ranging between 0.1-1% (0.35-1.12 $R_{\oplus}$) we explore the exomoon parameter space where we could successfully detect transits. For transit depths $\geq 0.5\%$ (1.96$\,R_{\text{Titan}}$), our detection rate is 96%, which, for WISE 0855, corresponds to a moon with a companion-to-host mass ratio similar to that of Titan and Saturn. Given our sensitivity, transit probabilities, and our observational duration, we determine a $\sim$91% probability of detecting a Titan mass analog exomoon after 18 such observations if every observed system hosts a Titan mass analog exomoon in a Galilean-like system. This suggests that JWST observations of dozens of FFPs could yield meaningful constraints on the occurrence rate of exomoons. This paper is the first demonstration that JWST is sensitive to Galilean moon mass analogs around FFPs. △ Less

Submitted 28 October, 2025; originally announced October 2025.

Comments: 19 pages, 18 figures, accepted for publication in AJ

Sensitivity to Sub-Io-sized Exosatellite Transits in the MIRI LRS Lightcurve of the Nearest Substellar Worlds

Authors: Andrew Householder, Mary Anne Limbach, Beth Biller, Brooke Kotten, Mikayla J. Wilson, Johanna M. Vos, Andrew Skemer, Andrew Vanderburg, Ben J. Sutlieff, Xueqing Chen, Ian J. M. Crossfield, Nicolas Crouzet, Trent Dupuy, Jacqueline Faherty, Pengyu Liu, Elena Manjavacas, Allison McCarthy, Caroline V. Morley, Philip S. Muirhead, Natalia Oliveros-Gomez, Genaro Suárez, Xianyu Tan, Yifan Zhou

Abstract: JWST's unprecedented sensitivity enables precise spectrophotometric monitoring of substellar worlds, revealing atmospheric variability driven by mechanisms operating across different pressure levels. This same precision now permits exceptionally sensitive searches for transiting exosatellites, small terrestrial companions to these worlds. Using a novel simultaneous dual-band search method to addre… ▽ More JWST's unprecedented sensitivity enables precise spectrophotometric monitoring of substellar worlds, revealing atmospheric variability driven by mechanisms operating across different pressure levels. This same precision now permits exceptionally sensitive searches for transiting exosatellites, small terrestrial companions to these worlds. Using a novel simultaneous dual-band search method to address host variability, we present a search for transiting exosatellites in an 8-hour JWST/MIRI LRS lightcurve of the nearby ($2.0\,pc$) substellar binary WISE J1049-5319AB, composed of two $\sim30 M_{\rm Jup}$ brown dwarfs separated by $3.5\,au$ and viewed near edge-on. Although we detect no statistically significant transits, our injection-recovery tests demonstrate sensitivity to satellites as small as $0.275\,R_{\oplus}$ ($0.96\,R_{\rm Io}$ or $\sim$1 lunar radius), corresponding to 300ppm transit depths, and satellite-to-host mass ratios $>$$10^{-6}$. This approach paves the way for detecting Galilean-moon analogs around directly imaged brown dwarfs, free-floating planets, and wide-orbit exoplanets, dozens of which are already scheduled for JWST lightcurve monitoring. In our Solar System, each giant planet hosts on average 3.5 moons above this threshold, suggesting that JWST now probes a regime where such companions are expected to be abundant. The technique and sensitivities demonstrated here mark a critical step toward detecting exosatellites and ultimately enabling constraints on the occurrence rates of small terrestrial worlds orbiting $1\text{-}70$$M_{\rm Jup}$ hosts. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Comments: Published in ApJ Letters

Twinkle Twinkle Little Star, Roman Sees Where You Are: Predicting Exoplanet Transit Yields in the Rosette Nebula with the Nancy Grace Roman Space Telescope

Authors: Ritvik Sai Narayan, Melinda Soares-Furtado, Mary Anne Limbach, Nishanth Ramanujam, Andrew Vanderburg, Johanna M. Vos

Abstract: Young stars host only a small fraction of the known exoplanet population because their photometric variability, magnetic activity, and frequent placement in dense, poorly-resolved regions hamper exoplanet detections. Yet, measuring planets at these ages is crucial since these phases are when dynamical processes that drive planetary migration are most active. We assess the expected yield of a hypot… ▽ More Young stars host only a small fraction of the known exoplanet population because their photometric variability, magnetic activity, and frequent placement in dense, poorly-resolved regions hamper exoplanet detections. Yet, measuring planets at these ages is crucial since these phases are when dynamical processes that drive planetary migration are most active. We assess the expected yield of a hypothetical Nancy Grace Roman Space Telescope transit survey of the Rosette Nebula, a ${\sim}10$ Myr star-forming region with a dense and diverse stellar population. Using the Roman Exposure Time Calculator to quantify sensitivity to Rosette members, we establish detection thresholds for companions and evaluate yields via Monte Carlo injection-recovery simulations, accounting for nebular extinction and youth-driven stellar variability. We predict the detection of $33 \pm 9$ young transiting exoplanets orbiting stellar hosts in a month-long survey, and $29 \pm 8$ in a two-week survey. The extended baseline primarily improves sensitivity to longer-period planets orbiting FGK stars, while most M dwarf detections are well-sampled within two weeks. Irrespective of the temporal baseline, transit detections are dominated by of 1-2 $R_\oplus$ super-Earths and sub-Neptunes with $P\lesssim8$ days. Such a sample would substantially expand the census of only three detected transiting planets younger than 20 Myr around stars less massive than the Sun, probing an age regime in which planetary radii remain inflated, the stability of close-in orbits is uncertain, and planetary migration may still be ongoing. This survey offers a path to constrain early planetary evolution and establish prime follow-up targets for JWST, Rubin, and the Habitable Worlds Observatory. △ Less

Submitted 17 March, 2026; v1 submitted 27 October, 2025; originally announced October 2025.

Comments: 22 pages, 9 figures, 4 tables, accepted for publication in the Astronomical Journal

Journal ref: AJ (2026), 171, 282

NGTS-11 c: a transiting Neptune-mass planet interior to the warm Saturn NGTS-11 b

Authors: David R. Anderson, Jose I. Vines, Katharine Hesse, Louise Dyregaard Nielsen, Rafael Brahm, Maximiliano Moyano, Peter J. Wheatley, Khalid Barkaoui, Allyson Bieryla, Matthew R. Burleigh, Ryan Cloutier, Karen A. Collins, Phil Evans, Steve B. Howell, John Kielkopf, Pablo Lewin, Richard P. Schwarz, Avi Shporer, Thiam-Guan Tan, Mathilde Timmermans, Amaury H. M. J. Triaud, Carl Ziegler, Ioannis Apergis, David J. Armstrong, Douglas R. Alves , et al. (34 additional authors not shown)

Abstract: We report the discovery of NGTS-11 c, a transiting warm Neptune ($P \approx 12.8$ d; $M_{p} = 1.2^{+0.3}_{-0.2} M_{\mathrm{Nep}}$; $R_{p} = 1.24 \pm 0.03 R_{\mathrm{Nep}}$), in an orbit interior to the previously reported transiting warm Saturn NGTS-11 b ($P \approx 35.5$ d). We also find evidence of a third outer companion orbiting the K-dwarf NGTS-11. We first detected transits of NGTS-11 c in T… ▽ More We report the discovery of NGTS-11 c, a transiting warm Neptune ($P \approx 12.8$ d; $M_{p} = 1.2^{+0.3}_{-0.2} M_{\mathrm{Nep}}$; $R_{p} = 1.24 \pm 0.03 R_{\mathrm{Nep}}$), in an orbit interior to the previously reported transiting warm Saturn NGTS-11 b ($P \approx 35.5$ d). We also find evidence of a third outer companion orbiting the K-dwarf NGTS-11. We first detected transits of NGTS-11 c in TESS light curves and confirmed them with follow-up transits from NGTS and many other ground-based facilities. Radial-velocity monitoring with the HARPS and FEROS spectrographs revealed the mass of NGTS-11 c and provides evidence for a long-period companion ($P > 2300$ d; $M_{p} \sin i > 3.6 M_{\mathrm{Jup}}$). Taking into account the two additional bodies in our expanded datasets, we find that the mass of NGTS-11 b ($M_{p} = 0.63 \pm 0.09 M_{\mathrm{Sat}}$; $R_{p} = 0.97 \pm 0.02 R_{\mathrm{Sat}}$) is lower than previously reported ($M_{p} = 1.2 \pm 0.3 M_{\mathrm{Sat}}$). Given their near-circular and compact orbits, NGTS-11 c and b are unlikely to have reached their present locations via high-eccentricity migration. Instead, they probably either formed in situ or formed farther out and then underwent disk migration. A comparison of NGTS-11 with the eight other known systems hosting multiple well-characterized warm giants shows that it is most similar to Kepler-56. Finally, we find that the commonly used 10-day boundary between hot and warm Jupiters is empirically well supported. △ Less

Submitted 15 October, 2025; originally announced October 2025.

Comments: 12 pages, 6 figures, submitted to ApJ

MANGOS II: Five new giant planets orbiting low-mass stars

Authors: G. Dransfield, M. Timmermans, D. Sebastian, B. V. Rackham, A. Burgasser, K. Barkaoui, A. H. M. J. Triaud, M. Gillon, J. M. Almenara, S. L. Casewell, K. A. Collins, A. Fukui, C. Jano-Munoz, S. Kanodia, N. Narita, E. Palle, M. G. Scott, A. Soubkiou, A. Stokholm, J. Audenaert, G. Á. Bakos, Y. Beletsky, Z. L. de Beurs, Z. Benkhaldoun, A. Burdanov , et al. (25 additional authors not shown)

Abstract: Giant planets orbiting low-mass stars on short orbits present a conundrum, as in the most extreme cases their existence cannot be reconciled with current models of core accretion. Therefore, surveys dedicated to finding these rare planets have a key role to play by growing the sample to overcome small number statistics. In this work we present MANGOS, a programme dedicated to the search for giant… ▽ More Giant planets orbiting low-mass stars on short orbits present a conundrum, as in the most extreme cases their existence cannot be reconciled with current models of core accretion. Therefore, surveys dedicated to finding these rare planets have a key role to play by growing the sample to overcome small number statistics. In this work we present MANGOS, a programme dedicated to the search for giant objects (planets, brown dwarfs, and low-mass stars) orbiting M dwarfs. We report on the discovery of five new giant planets (TOI-3288 Ab, TOI-4666 b, TOI-5007 b, TOI-5292 Ab, TOI-5916 b) first detected by TESS, and confirmed using ground-based photometry and spectroscopy. The five planets have radii in the range 0.99-1.12 $\mathrm{R_{Jup}}$, masses between 0.49--1.69~$\mathrm{M_{Jup}}$, and orbital periods between 1.43 and 2.91 days. We reveal that TOI-3288 and TOI-5292 are wide binaries, and in the case of TOI-5292 we are able to characterise both stellar components. We demonstrate that the planets presented are suitable for further characterisation of their obliquities and atmospheres. We detect a small but significant eccentricity for TOI-5007 b, although for this to be more robust, more observations are needed to fully sample the orbit. Finally, we reveal a correlation between stellar metallicity and planet bulk density for giant planets orbiting low-mass stars. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Comments: Submitted to MNRAS

Journal ref: Mon Not R Astron Soc (2026)

THYME XIII: Two young Neptunes orbiting a 75-Myr star in the Alpha Persei Cluster

Authors: Anne Dattilo, Andrew M. Vanderburg, Madyson G. Barber, Andrew W. Mann, Ronan Kerr, Adam L. Kraus, Joseph R. Livesey, Cristilyn Watkins, Karen A. Collins, Juliana García-Mejía, Patrick Tamburo, Juliette Becker, Annelies Mortier, Thomas Wilson, Nicholas Scarsdale, Emily A. Gilbert, Alex S. Polanski, Steve B. Howell, Ian Crossfield, Allyson Bieryla, David R. Ciardi, Thomas Barclay, David Charbonneau, David W. Latham, Joseph M. Akana Murphy , et al. (6 additional authors not shown)

Abstract: Young planets with mass measurements are particularly valuable in studying atmospheric mass-loss processes, but these planets are rare and their masses difficult to measure due to stellar activity. We report the discovery of a planetary system around TOI-6109, a young, 75 Myr-old Sun-like star in the Alpha Persei cluster. It hosts at least two transiting Neptune-like planets. Using three TESS sect… ▽ More Young planets with mass measurements are particularly valuable in studying atmospheric mass-loss processes, but these planets are rare and their masses difficult to measure due to stellar activity. We report the discovery of a planetary system around TOI-6109, a young, 75 Myr-old Sun-like star in the Alpha Persei cluster. It hosts at least two transiting Neptune-like planets. Using three TESS sectors, 30 CHEOPS orbits, and photometric follow-up observations from the ground, we confirm the signals of the two planets. TOI-6109 b has an orbital period of P=$5.6904^{+0.0004}_{-0.0004}$ days and a radius of R=$4.87^{+0.16}_{-0.12}$ R$_\oplus$. The outer planet, TOI-6109 c has an orbital period of P=$8.5388^{+0.0006}_{-0.0005}$ days and a radius of R=$4.83^{+0.07}_{-0.06}$ R$_\oplus$. These planets orbit just outside a 3:2 mean motion resonance. The near-resonant configuration presents the opportunity to measure the planet's mass via TTV measurements and to bypass difficult RV measurements. Measuring the masses of the planets in this system will allow us to test theoretical models of atmospheric mass loss. △ Less

Submitted 18 September, 2025; originally announced September 2025.

Comments: 21 pages, 10 figures, 7 tables. Accepted in AJ

The HD 60779 Planetary System: A Transiting Sub-Neptune on a 30-day Orbit and a More Massive Outer World

Authors: Victoria DiTomasso, David Charbonneau, Andrew Vanderburg, Mercedes López-Morales, Shreyas Vissapragada, Annelies Mortier, Thomas G. Wilson, Elyse Incha, Andrew Collier Cameron, Luca Malavolta, Lars A. Buchhave, David W. Latham, Matteo Pinamonti, Stephanie Striegel, Michael Fausnaugh, Luke Bouma, Ben Falk, Robert Aloisi, Xavier Dumusque, A. Anna John, Ben S. Lakeland, A. F. Martínez Fiorenzano, Luca Naponiello, Belinda Nicholson, Emily K. Pass , et al. (15 additional authors not shown)

Abstract: We present the discovery of the planetary system orbiting the bright (V = 7.2), nearby (35 pc), Sun-like star HD 60779, which has a mass of 1.050 +/- 0.044 solar masses and a radius of 1.129 +/- 0.013 solar radii. We report two TESS transits and a subsequent CHEOPS transit of HD 60779 b, a sub-Neptune with a radius of 3.250 (+0.100 / -0.098) Earth radii on a 29.986175 (+0.000030 / -0.000033) day o… ▽ More We present the discovery of the planetary system orbiting the bright (V = 7.2), nearby (35 pc), Sun-like star HD 60779, which has a mass of 1.050 +/- 0.044 solar masses and a radius of 1.129 +/- 0.013 solar radii. We report two TESS transits and a subsequent CHEOPS transit of HD 60779 b, a sub-Neptune with a radius of 3.250 (+0.100 / -0.098) Earth radii on a 29.986175 (+0.000030 / -0.000033) day orbit. Additionally, 286 HARPS-N radial velocity measurements reveal the mass of planet b (14.7 +1.1 / -1.0 Earth masses) and the presence of an outer planet, HD 60779 c, with an orbital period of 104.25 (+0.30 / -0.29) days and a minimum mass (m sin i) of 27.7 +/- 1.6 Earth masses. Both planets' orbits are consistent with being circular, suggesting that they have a dynamically quiet history. The data are not sufficient to determine whether planet c transits. HD 60779's uniquely high systemic radial velocity (129.75 +/- 0.12 km/s) allows its Lyman-alpha emission to avoid absorption by the interstellar medium, making it a prime candidate for probing atmospheric escape from HD 60779 b. HD 60779 is also the third-brightest host of a sub-Neptune with orbital period greater than 25 days and with both mass and radius measured, distinguishing it in terms of accessibility to spectroscopic characterization. △ Less

Submitted 22 August, 2025; originally announced August 2025.

Comments: 18 pages, 12 figures, submitted to AAS Journals

A New Brown Dwarf Orbiting an M star and An Investigation on the Eccentricity Distribution of Transiting Long-Period Brown Dwarfs

Authors: Tianjun Gan, Charles Cadieux, Shigeru Ida, Sharon X. Wang, Shude Mao, Zitao Lin, Keivan G. Stassun, Adam J. Burgasser, Steve B. Howell, Catherine A. Clark, Ivan A. Strakhov, Paul Benni, George R. Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Luc Arnold, Étienne Artigau, David Charbonneau, Karen A. Collins, Neil J. Cook, Zoë L. de Beurs, Sarah J. Deveny , et al. (10 additional authors not shown)

Abstract: The orbital eccentricities of brown dwarfs encode valuable information of their formation and evolution history, providing insights into whether they resemble giant planets or stellar binaries. Here, we report the discovery of TOI-5575b, a long-period, massive brown dwarf orbiting a low-mass M5V star ($\rm 0.21\pm0.02\,M_\odot$) delivered by the TESS mission. The companion has a mass and radius of… ▽ More The orbital eccentricities of brown dwarfs encode valuable information of their formation and evolution history, providing insights into whether they resemble giant planets or stellar binaries. Here, we report the discovery of TOI-5575b, a long-period, massive brown dwarf orbiting a low-mass M5V star ($\rm 0.21\pm0.02\,M_\odot$) delivered by the TESS mission. The companion has a mass and radius of $\rm 72.4\pm4.1\,M_J$ and $\rm 0.84\pm0.07\,R_J$ on a 32-day moderately eccentric orbit ($e=0.187\pm0.002$), making it the third highest-mass-ratio transiting brown dwarf system known to date. Building on this discovery, we investigate the eccentricity distributions of a sample of transiting long-period ($10\leq P\lesssim 1000$ days, $\sim$0.1-1.5 AU) giant planets, brown dwarfs and low-mass stars. We find that brown dwarfs exhibit an eccentricity behavior nearly identical to that of giant planets: a preference for circular orbits with a long tail toward high eccentricities. Such a trend contrasts sharply with direct imaging findings, where cold (5-100 AU) brown dwarfs and giant planets display distinct eccentricity distributions. Our results suggest that transiting long-period brown dwarfs and giant planets probably 1) form in different routes at exterior orbits but undergo analogous dynamical evolution processes and migrate inwards; or 2) both contain two sub-groups, one with widely spread eccentricities while the other has circular orbits, that jointly sculpt the eccentricity distributions. The low-mass-star systems appear to be a distinctive population, showing a peak eccentricity at about 0.3, akin to more massive stellar binaries. △ Less

Submitted 12 July, 2025; originally announced July 2025.

Comments: 18 pages, 8 figures, 4 tables, accepted for publication in ApJL

A Ground-Based Transit Observation of the Long-Period Extremely Low-Density Planet HIP 41378 f

Authors: Juliana García-Mejía, Zoë L. de Beurs, Patrick Tamburo, Andrew Vanderburg, David Charbonneau, Karen A. Collins, Khalid Barkaoui, Cristilyn N. Watkins, Chris Stockdale, Richard P. Schwarz, Raquel Forés-Toribio, Jose A. Muñoz, Giovanni Isopi, Franco Mallia, Aldo Zapparata, Adam Popowicz, Andrzej Brudny, Eric Agol, Munazza K. Alam, Zouhair Benkhaldoun, Jehin Emmanuel, Mourad Ghachoui, Michaël Gillon, Keith Horne, Enric Pallé , et al. (3 additional authors not shown)

Abstract: We present a ground-based transit detection of HIP 41378 f, a long-period ($P = 542$ days), extremely low-density ($0.09 \pm 0.02$ g cm$^{-3}$) giant exoplanet in a dynamically complex system. Using photometry from Tierras, TRAPPIST-North, and multiple LCOGT sites, we constrain the transit center time to $T_{C,6} = 2460438.891 \pm 0.052$ BJD TDB. This marks only the second ground-based detection o… ▽ More We present a ground-based transit detection of HIP 41378 f, a long-period ($P = 542$ days), extremely low-density ($0.09 \pm 0.02$ g cm$^{-3}$) giant exoplanet in a dynamically complex system. Using photometry from Tierras, TRAPPIST-North, and multiple LCOGT sites, we constrain the transit center time to $T_{C,6} = 2460438.891 \pm 0.052$ BJD TDB. This marks only the second ground-based detection of HIP 41378 f, currently the longest-period and longest-duration transiting exoplanet observed from the ground. We use this new detection, along with a recently published transit time from Rossiter-McLaughlin observations, to update the TTV solution for HIP 41378 f. We predict the next two transits will occur at $T_{C,7} = 2460980.793^{+0.098}_{-0.129}$ BJD TDB (2025 November 1) and $T_{C,8} = 2461522.653^{+0.213}_{-0.238}$ BJD TDB (2027 April 27). Incorporating new TESS Sector 88 data, we also rule out the 101-day orbital period alias for HIP 41378 d, and find that the remaining viable solutions are centered on the 278, 371, and 1113-day aliases. The latter two imply dynamical configurations that challenge the canonical view of planet e as the dominant perturber of planet f. Our results suggest that HIP 41378 d may instead play the leading role in shaping the TTV of HIP 41378 f. △ Less

Submitted 2 March, 2026; v1 submitted 25 June, 2025; originally announced June 2025.

Comments: 17 pages, 7 figures. Accepted for publication in The Astronomical Journal

Metallicities from High-Resolution TRES Spectra with uberMS: Performance Benchmarks and Literature Comparison

Authors: Emily K. Pass, Phillip A. Cargile, Victoria DiTomasso, Romy Rodríguez Martínez, David Charbonneau, David W. Latham, Andrew Vanderburg, Allyson Bieryla, Samuel N. Quinn, Lars A. Buchhave

Abstract: As the field of exoplanetary astronomy has matured, demand has grown for precise stellar abundances to probe subtle correlations between stellar compositions and planetary demographics. However, drawing population-level conclusions from the disparate measurements in the literature is challenging, with various groups measuring metallicities using bespoke codes with differing line lists, radiative t… ▽ More As the field of exoplanetary astronomy has matured, demand has grown for precise stellar abundances to probe subtle correlations between stellar compositions and planetary demographics. However, drawing population-level conclusions from the disparate measurements in the literature is challenging, with various groups measuring metallicities using bespoke codes with differing line lists, radiative transfer models, and other assumptions. Homogeneous analyses are thus critical. Here we use the neural-net framework uberMS to measure iron abundances and alpha enrichments from high-resolution optical spectra observed by the Tillinghast Reflector Echelle Spectrograph (TRES), a key resource used for the follow-up of candidate exoplanet hosts. To contextualize these measurements and benchmark our method's performance, we compare to external constraints on metallicity using the Hyades cluster, wide binaries, and asteroids, to external constraints on $T_{\rm eff}$ and $\log g$ using stars with interferometric radii, and to the results of other abundance measurement methods using overlap samples with the APOGEE and SPOCS catalogs, as well as by applying the SPC method directly to TRES spectra. We find that TRES-uberMS provides reliable parameter estimates with errors of roughly 100 K in $T_{\rm eff}$, 0.09 dex in $\log g$, and 0.04 dex in [Fe/H] for many nearby dwarf stars, although [Fe/H] performance is poorer for mid-to-late K dwarfs, with the bias worsening with decreasing $T_{\rm eff}$. Performance is also worse for evolved stars. For [$α$/Fe], our error may be as good as 0.03 dex for dwarfs based on external benchmarks, despite sizable and variable systematic differences when comparing with specific alpha-element abundances from other catalogs. △ Less

Submitted 22 September, 2025; v1 submitted 23 June, 2025; originally announced June 2025.

Comments: Accepted for publication in ApJS; 20 pages, 10 figures, 4 tables

Disentangling Metallicity Effects in Hot Jupiter Occurrence Across Galactic Birth Radius and Phase-Space Density

Authors: Rayna Rampalli, Melissa K. Ness, Elisabeth R. Newton, Andrew Vanderburg, Tobias Buck, Jessica Mills

Abstract: We explore how the correlation between host star metallicity and giant planets shapes hot Jupiter occurrence as a function of Galactic birth radius (\rbirth) and phase-space density in the Milky Way disk. Using the GALAH and APOGEE surveys and a galaxy from the NIHAO simulation suite, we inject hot Jupiters around stars based on metallicity power laws, reflecting the trend that giant planets prefe… ▽ More We explore how the correlation between host star metallicity and giant planets shapes hot Jupiter occurrence as a function of Galactic birth radius (\rbirth) and phase-space density in the Milky Way disk. Using the GALAH and APOGEE surveys and a galaxy from the NIHAO simulation suite, we inject hot Jupiters around stars based on metallicity power laws, reflecting the trend that giant planets preferentially form around metal-rich stars. For \rbirth\ $\geq 5$ kpc, hot Jupiter occurrence decreases with \rbirth\ by $\sim -0.1%$ per kpc; this is driven by the Galaxy's chemical evolution, where the inner regions of the disk are more metal-rich. Differences in GALAH occurrence rates versus APOGEE's and the simulation's at \rbirth\ $< 5$ kpc arise from survey selection effects. APOGEE and the NIHAO simulation have more high-$α$ sequence stars than GALAH, resulting in average differences in metallicity (0.2--0.4 dex), $α$-process element enrichment (0.2 dex), and vertical velocities (7--14 km/s) at each \rbirth\ bin. Additionally, we replicate the result of \cite{Winter20}, which showed that over 92% of hot Jupiters are associated with stars in phase-space overdensities, or "clustered environments." However, our findings suggest that this clustering effect is primarily driven by chemical and kinematic differences between low and high-$α$ sequence star properties. Our results support stellar characteristics, particularly metallicity, being the primary drivers of hot Jupiter formation, which serves as the "null hypothesis" for interpreting planet demographics. This underscores the need to disentangle planetary and stellar properties from Galactic-scale effects in future planet demographics studies. △ Less

Submitted 19 June, 2025; originally announced June 2025.

Comments: 21 pages, 8 figures, 1 table. Accepted in AJ

NIRCam yells at cloud: JWST MIRI imaging can directly detect exoplanets of the same temperature, mass, age, and orbital separation as Saturn and Jupiter

Authors: Rachel Bowens-Rubin, James Mang, Mary Anne Limbach, Aarynn L. Carter, Kevin B. Stevenson, Kevin Wagner, Giovanni Strampelli, Caroline V. Morley, Grant Kennedy, Elisabeth Matthews, Andrew Vanderburg, Maïssa Salama

Abstract: NIRCam and MIRI coronagraphy have successfully demonstrated the ability to directly image young sub-Jupiter mass and mature gas-giant exoplanets. However, these modes struggle to reach the sensitivities needed to find the population of cold giant planets that are similar to our own Solar System's giant planets ($T_{\rm eff} = 60 - 125$ K; $a=5 - 30$ AU). For the first time, we explore the high-con… ▽ More NIRCam and MIRI coronagraphy have successfully demonstrated the ability to directly image young sub-Jupiter mass and mature gas-giant exoplanets. However, these modes struggle to reach the sensitivities needed to find the population of cold giant planets that are similar to our own Solar System's giant planets ($T_{\rm eff} = 60 - 125$ K; $a=5 - 30$ AU). For the first time, we explore the high-contrast imaging capabilities of MIRI imaging rather than coronagraphy. Using data from the JWST GO 6122: Cool Kids on the Block program which targets nearby ($<6$ pc) M-dwarfs with NIRCam coronagraphy and MIRI imaging, we demonstrate that 21$μ$m MIRI imaging can detect planets with the same temperature, mass, age, and orbital separations as Saturn and Jupiter. For systems within 3pc, 21$μ$m MIRI imaging reaches the sensitivity needed to detect planets colder than Saturn ($<95$ K). NIRCam coronagraphy can achieve similar results only in the unlikely case that a cold giant planet is cloud-free. Motivated by these compelling findings, we extend our analysis to evaluate the measured performance of MIRI F2100W imaging versus NIRCam F444W coronagraphy to 70 pc and conclude that MIRI imaging offers the advantage for systems within 20pc. Microlensing surveys predict an occurrence rate as high as 1 - 2 low-mass giant exoplanets per star, suggesting that JWST MIRI imaging surveys of nearby systems may be poised to uncover a substantial population. This breakthrough enables a path towards the first direct characterization of cold giant exoplanets that are analogous to the solar system giant planets. △ Less

Submitted 21 May, 2025; originally announced May 2025.

An Eccentric Sub-Neptune Moving Into the Evaporation Desert

Authors: Sydney Jenkins, Andrew Vanderburg, Ritika Sethi, Sarah Millholland, Joseph E. Rodriguez, Luca Fossati, Andreas Krenn, Emily Pass, Alex Venner, Paul Butler, Hugh Osborn, Aaron Householder, Carl Ziegler, Juliette Becker, Perry Berlind, Allyson Bieryla, Christopher Broeg, Michael L. Calkins, Jeffrey D. Crane, Tansu Daylan, Julien de Wit, Jason D. Eastman, David Ehrenreich, Gilbert A. Esquerdo, Michael Fausnaugh , et al. (9 additional authors not shown)

Abstract: Though missions such as Kepler, K2, and TESS have discovered $>$2,000 sub-Neptune and Neptunian planets, there is a dearth of such planets at close-in (P$\lesssim$3 days) orbits. This feature, called the Neptune desert or the evaporation desert, is believed to be primarily shaped by planetary migration and photoevaporation. However, this region is not completely devoid of planets--a small number o… ▽ More Though missions such as Kepler, K2, and TESS have discovered $>$2,000 sub-Neptune and Neptunian planets, there is a dearth of such planets at close-in (P$\lesssim$3 days) orbits. This feature, called the Neptune desert or the evaporation desert, is believed to be primarily shaped by planetary migration and photoevaporation. However, this region is not completely devoid of planets--a small number of very hot Neptunes reside within the desert. These planets provide an opportunity to directly probe the effects of migration and photoevaporation. We present confirmation of TOI-5800 b, an eccentric sub-Neptune on a $\approx$2.6 day period that is likely actively undergoing tidal migration. We use radial velocity measurements from the Carnegie Planet Finder Spectrograph (PFS) to constrain TOI-5800 b's mass and eccentricity. We find that it has an unusually high eccentricity (0.39$\pm$0.07) for its short orbit. TOI-5800 is therefore currently experiencing high levels of tidal heating as it moves into the desert. Ranked as a top candidate for transmission and emission spectroscopy within its temperature and radius regime, TOI-5800 b is a prime target for atmospheric characterization with JWST. TOI-5800 b presents a unique opportunity to study the atmosphere of a planet undergoing tidal heating and to probe the composition of sub-Neptune planets. △ Less

Submitted 1 July, 2025; v1 submitted 15 May, 2025; originally announced May 2025.

Comments: Accepted for publication in ApJL

Searching for GEMS: Confirmation of TOI-5573b, a Cool, Saturn-like Planet Orbiting An M-dwarf

Authors: Rachel B Fernandes, Shubham Kanodia, Megan Delamer, Andrew Hotnisky, Te Han, Caleb I Canas, Jessica Libby-Roberts, Varghese Reji, Arvind F Gupta, Jaime A Alvarado-Montes, Chad F Bender, Cullen H Blake, William D Cochran, Zoe L de Beurs, Scott A Diddams, Jiayin Dong, Mark E Everett, Eric B Ford, Samuel Halverson, Jesus Higuera, Henry A Kobulnicky, Daniel M Krolikowski, Alexander Larsen, Andrea SJ Lin, Suvrath Mahadevan , et al. (13 additional authors not shown)

Abstract: We present the confirmation of TOI-5573b, a Saturn-sized exoplanet on an 8.79-day orbit around an early M-dwarf (3790 K, 0.59 R$\odot$, 0.61 M$\odot$, 12.30 J mag). TOI-5573b has a mass of $112^{+18}_{-19}$ M$\oplus$ (0.35$\pm$0.06 M$\mathrm{Jup}$) and a radius of $9.75\pm0.47$ R$\oplus$ (0.87$\pm$0.04 R$\mathrm{Jup}$), resulting in a density of $0.66^{+0.16}_{-0.13}$ g cm$^{-3}$, akin to that of… ▽ More We present the confirmation of TOI-5573b, a Saturn-sized exoplanet on an 8.79-day orbit around an early M-dwarf (3790 K, 0.59 R$\odot$, 0.61 M$\odot$, 12.30 J mag). TOI-5573b has a mass of $112^{+18}_{-19}$ M$\oplus$ (0.35$\pm$0.06 M$\mathrm{Jup}$) and a radius of $9.75\pm0.47$ R$\oplus$ (0.87$\pm$0.04 R$\mathrm{Jup}$), resulting in a density of $0.66^{+0.16}_{-0.13}$ g cm$^{-3}$, akin to that of Saturn. The planet was initially discovered by TESS and confirmed using a combination of 11 transits from four TESS sectors (20, 21, 47 and 74), ground-based photometry from the Red Buttes Observatory, and high-precision radial velocity data from the Habitable-zone Planet Finder (HPF) and NEID spectrographs, achieving a 5$σ$ precision on the planet's mass. TOI-5573b is one of the coolest Saturn-like exoplanets discovered around an M-dwarf, with an equilibrium temperature of $528\pm10$ K, making it a valuable target for atmospheric characterization. Saturn-like exoplanets around M-dwarfs likely form through core accretion, with increased disk opacity slowing gas accretion and limiting their mass. The host star's super-solar metallicity supports core accretion, but uncertainties in M-dwarf metallicity estimates complicate definitive conclusions. Compared to other GEMS (Giant Exoplanets around M-dwarf Stars) orbiting metal-rich stars, TOI-5573b aligns with the observed pattern that giant planets preferentially form around M-dwarfs with super-solar metallicity. Further high-resolution spectroscopic observations are needed to explore the role of stellar metallicity in shaping the formation and properties of giant exoplanets like TOI-5573b. △ Less

Submitted 13 May, 2025; originally announced May 2025.

Comments: 16 pages, 8 figures, 3 tables; accepted for publication to AJ

TESS Investigation -- Demographics of Young Exoplanets (TI-DYE) III: an inner super-Earth in TOI-2076

Authors: Madyson G. Barber, Andrew W. Mann, Andrew Vanderburg, Andrew W. Boyle, Ana Isabel Lopez Murillo

Abstract: Young (<500 Myr) multi-planet transiting systems are valuable environments for understanding planet evolution by offering an opportunity to make direct comparisons between planets from the same formation conditions. TOI-2076 is known to harbor three, 2.5-4 $R_\oplus$ planets on 10-35 day orbits. All three are JWST cycle 3 targets (for transmission spectroscopy). Here, we present the detection of T… ▽ More Young (<500 Myr) multi-planet transiting systems are valuable environments for understanding planet evolution by offering an opportunity to make direct comparisons between planets from the same formation conditions. TOI-2076 is known to harbor three, 2.5-4 $R_\oplus$ planets on 10-35 day orbits. All three are JWST cycle 3 targets (for transmission spectroscopy). Here, we present the detection of TOI-2076 e; a smaller (1.35 $R_\oplus$), inner (3.02 day) planet in the system. We update the age of the system by analyzing the rotation periods, Lithium equivalent widths, color-magnitude diagram, and variability of likely co-moving stars, finding that TOI-2076 and co-moving planetary system TOI-1807 are 210 $\pm$ 20 Myr. The discovery of TOI-2076 e is motivation to revisit known transiting systems in search of additional planets that are now detectable with new TESS data and updated search methods. △ Less

Submitted 9 May, 2025; originally announced May 2025.

Comments: Accepted for publication in the Astronomical Journal

A Machine-Learning Compositional Study of Exoplanetary Material Accreted Onto Five Helium-Atmosphere White Dwarfs with $\texttt{cecilia}$

Authors: Mariona Badenas-Agusti, Siyi Xu, Andrew Vanderburg, Kishalay De, Patrick Dufour, Laura K. Rogers, Susana Hoyos, Simon Blouin, Javier Viaña, Amy Bonsor, Ben Zuckerman

Abstract: We present the first application of the Machine Learning (ML) pipeline $\texttt{cecilia}$ to determine the physical parameters and photospheric composition of five metal-polluted He-atmosphere white dwarfs without well-characterised elemental abundances. To achieve this, we perform a joint and iterative Bayesian fit to their $\textit{SDSS}$ (R=2,000) and $\textit{Keck/ESI}$ (R=4,500) optical spect… ▽ More We present the first application of the Machine Learning (ML) pipeline $\texttt{cecilia}$ to determine the physical parameters and photospheric composition of five metal-polluted He-atmosphere white dwarfs without well-characterised elemental abundances. To achieve this, we perform a joint and iterative Bayesian fit to their $\textit{SDSS}$ (R=2,000) and $\textit{Keck/ESI}$ (R=4,500) optical spectra, covering the wavelength range from about 3,800Å to 9,000Å. Our analysis measures the abundances of at least two $-$and up to six$-$ chemical elements in their atmospheres with a predictive accuracy similar to that of conventional WD analysis techniques ($\approx$0.20 dex). The white dwarfs with the largest number of detected heavy elements are SDSS J0859$+$5732 and SDSS J2311$-$0041, which simultaneously exhibit O, Mg, Si, Ca, and Fe in their $\textit{Keck/ESI}$ spectra. For all systems, we find that the bulk composition of their pollutants is largely consistent with those of primitive CI chondrites to within 1-2$σ$. We also find evidence of statistically significant ($>2σ$) oxygen excesses for SDSS J0859$+$5732 and SDSS J2311$-$0041, which could point to the accretion of oxygen-rich exoplanetary material. In the future, as wide-field astronomical surveys deliver millions of public WD spectra to the scientific community, $\texttt{cecilia}$ aspires to unlock population-wide studies of polluted WDs, therefore helping to improve our statistical knowledge of extrasolar compositions. △ Less

Submitted 9 May, 2025; originally announced May 2025.

Comments: 28 pages, 14 figures, 5 tables. Accepted for publication in MNRAS

Thermal Emission and Confirmation of the Frigid White Dwarf Exoplanet WD 1856+534b

Authors: Mary Anne Limbach, Andrew Vanderburg, Ryan J. MacDonald, Kevin B. Stevenson, Sydney Jenkins, Simon Blouin, Emily Rauscher, Rachel Bowens-Rubin, Elena Gallo, James Mang, Caroline V. Morley, David K. Sing, Christopher O'Connor, Alexander Venner, Siyi Xu

Abstract: We report the detection of thermal emission from and confirm the planetary nature of WD 1856+534b, the first transiting planet known to orbit a white dwarf star. Observations with JWST's Mid-Infrared Instrument (MIRI) reveal excess mid-infrared emission from the white dwarf, consistent with a closely-orbiting Jupiter-sized planet with a temperature of $186^{+6}_{-7}$ K. We attribute this excess fl… ▽ More We report the detection of thermal emission from and confirm the planetary nature of WD 1856+534b, the first transiting planet known to orbit a white dwarf star. Observations with JWST's Mid-Infrared Instrument (MIRI) reveal excess mid-infrared emission from the white dwarf, consistent with a closely-orbiting Jupiter-sized planet with a temperature of $186^{+6}_{-7}$ K. We attribute this excess flux to the known giant planet in the system, making it the coldest exoplanet from which light has ever been directly observed. These measurements constrain the planet's mass to no more than six times that of Jupiter, confirming its planetary nature and ruling out previously unexcluded low-mass brown dwarf scenarios. WD 1856+534b is now the first intact exoplanet confirmed within a white dwarf's "forbidden zone", a region where planets would have been engulfed during the star's red giant phase. Its presence provides direct evidence that planetary migration into close orbits, including the habitable zone, around white dwarfs is possible. With an age nearly twice that of the Solar System and a temperature akin to our own gas giants, WD 1856+534b demonstrates JWST's unprecedented ability to detect and characterize cold, mature exoplanets, opening new possibilities for imaging and characterizing these worlds in the solar neighborhood. △ Less

Submitted 23 April, 2025; originally announced April 2025.

Comments: ApJL in press