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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Monday 14 September

Earth and Planetary Astrophysics

What the Solar System Can Teach Us About Rocky Exoplanets

Paul K. Byrne, Claire Marie Guimond, Peter A. Cawood et al. (+9 more)

The number of rocky extrasolar planets being discovered continues to increase, but so too does the apparent diversity of such worlds. As we work to understand the likely bulk properties and thermal, geological, and climatological attributes we might expect of rocky exoplanets, we can look to the Solar System for guidance. Here, we review the interior, surface, and atmospheric characteristics of modern Earth, and discuss how our homeworld has changed through Solar System history. We then visit in turn Venus, Mars, Mercury and Earth's Moon, and Io, noting how these terrestrial planets are alike, how they are different, and how they have evolved through time. Finally, we consider some examples of the types of rocky worlds known or suspected to exist without direct Solar System counterparts — but we argue that even then, for all the variety we might expect, they are still variations on a common theme. Perhaps the most important lesson the Solar System can teach us is that terrestrial bodies change through time, sometimes dramatically, and that rocky worlds of similar size and mass can have vastly different planetary outcomes.
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All authors Paul K. Byrne, Claire Marie Guimond, Peter A. Cawood, Michael J. Way, Doris Breuer, Tilman Spohn, João C. Duarte, Diogo L. Lourenço, Francesca Miozzi, Maëlis Arnould, Nicolas Coltice, Stephanie L. Olson

Earth and Planetary Astrophysics

Rescuing Kepler's False Positives: A Possible Habitable Zone Exoplanet in the Triple Star System KOI-1623

Rita Lanxuan Wang, Daniel Huber, Daniel Hey et al. (+6 more)

The Kepler mission has significantly advanced our understanding of exoplanet demographics. However, Kepler planet candidates showing centroid shifts are often classified as false-positives and thus excluded from demographic analyses. Some of these systems may be erroneous false positives, resulting from unresolved binary stars with planets orbiting one of the stars, thereby introducing biases into past exoplanet demographic studies. Here, we present updated Kepler centroid offset values derived from Gaia Data Release 3 (DR3) and analyze KOI-1623.01, a Kepler centroid offset false positive (COFP) with a clear transit signal and an orbital period of 111 days. High-contrast imaging with Keck/NIRC2 reveals that KOI-1623A has a close companion with a separation of $0.704 \pm 0.002$ arcsec, consisting of a slightly evolved G-type primary and a K-dwarf secondary, while Gaia detects a tertiary companion with common proper motion at a separation of $\sim 8.4$ arcsec. By combining transit photometry, Kepler pixel level data, direct imaging, and Gaia DR3, we find that the transit signal is consistent with a $10.02 ^{+0.44}_{-0.31} R_{\oplus}$ giant planet located in the habitable zone of the secondary. We furthermore use resolved companions from Gaia to estimate that another $\approx 70$ out of $515$ of Kepler's centroid false positives were misclassified and instead are real planets that belong to binary systems.
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All authors Rita Lanxuan Wang, Daniel Huber, Daniel Hey, Nathanael Burns-Watson, Alexander Larsen, Adam Kraus, Trent J. Dupuy, Steven Giacalone, Justin R. Crepp

Earth and Planetary Astrophysics

Inhomogeneous Cloud Coverage and Altitude-Dependent Heat Transport on the Hot-Jupiter NGTS-10 Ab from its Optical-to-Infrared Phase Curve

Louis-Philippe Coulombe, Vivien Parmentier, Kevin B. Stevenson et al. (+15 more)

Hot-Jupiters, gas giant planets with equilibrium temperatures above 1,000 K, host large temperature gradients between their permanent day- and nightsides, resulting in circulation regimes that have no Solar System analogs. Past Kepler and Spitzer measurements show that the phase curves of these objects typically peak westward of the substellar point at optical wavelengths and eastward in the infrared, indicative of an interaction between circulation and cloud coverage. However, few hot-Jupiters have joint reflected light and thermal emission measurements, preventing a definitive statement as to the link between these phenomena. Here, we present the first phase curve of a hot-Jupiter that separates thermal emission and reflected light through JWST observations of NGTS-10 Ab with the NIRSpec PRISM instrument ($\lambda$=0.5-5.5 $\mu$m). Using the spectrally-resolved phase curve, we jointly retrieve the planet's thermal and reflected light maps. We show that the temperature and reflectance distributions are anti-correlated, best explained by clouds evaporating from the eastern substellar region ($\varphi\approx$-17 to 48$^\circ$) where temperatures are highest. This is confirmed by comparisons of the phase-resolved spectra with three-dimensional circulation models, which show that NGTS-10 Ab's atmosphere hosts inhomogeneous cloud coverage, likely made-up of $\mu$m-sized silicate particles, and weak atmospheric drag ($\tau_\mathrm{drag}\gt 10^6$ s). Finally, by measuring the spectral variation of the thermal phase curve offsets, we infer a slope of 7.1$\pm$1.9 degrees per pressure dex, indicative of heat transport that becomes more efficient at depth. Future optical and infrared hot-Jupiter phase curve measurements over a wide range of equilibrium temperatures will enable a complete mapping of the interplay between heat transport and cloud formation in highly-irradiated exoplanet atmospheres.
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All authors Louis-Philippe Coulombe, Vivien Parmentier, Kevin B. Stevenson, Xianyu Tan, Everett Schlawin, Luis Welbanks, Jake Taylor, Yao Tang, Mike Line, Hinna Shivkumar, Jacob L. Bean, Jean-Michel Désert, Jonathan J. Fortney, Peter Gao, Mark Hammond, Eliza M.-R. Kempton, Thaddeus D. Komacek, Megan Weiner Mansfield

Earth and Planetary Astrophysics

Thermophysical characterization of the potentially hazardous near-Earth object 2024 YR4

T. G. Müller, E. M. MacLennan, A. Y. Burdanov et al. (+7 more)

The asteroid 2024 YR4 is a potentially hazardous Apollo-type near-Earth object. Its highly eccentric orbit produces close Earth-Moon encounters roughly every 4 years. A collection of light curves, including JWST-NIRCam data, allowed us to constrain the rotation period, spin pole, and convex shape solutions for the object. We analyzed two sets of JWST-MIRI observations obtained in three filters on 26 March 2025. The extracted photometry reveals rotationally driven thermal flux variations. The combination of a spin-shape model from light-curve inversion and the absolutely calibrated 3-band MIR light curves is well reproduced by a convex spin-shape solution with a spin pole at (l,b) = (232, -11), a sidereal period of 19.4633 min, and axis ratios of a/b ~1.28 and b/c ~1.45. The corresponding equivalent-volume diameter is 60.8 +1.8/-3.6 m (pV= 0.11 +0.05/-0.03, assuming HV = 24.14+/-0.25 mag). A high thermal inertia and low surface roughness are required to explain the observed MIRI data. The near-Earth asteroid thermal model has limited reliability for this object, requiring an extreme beaming parameter >3, whereas the fast-rotating model and a full thermophysical model provide consistent and reliable estimates of the size and albedo. The combination of high eccentricity and high thermal inertia implies seasonal skin depths of up to ~3 m and radiative timescales of weeks to months. Although seasonal heating is negligible for the March 2025 observations because of the near-equator-on viewing geometry, the seasonal Yarkovsky drift is expected to be dominant over the diurnal component and might become measurable during future encounters. Although JWST astrometry from February 2026 rules out any possible impact on the Earth or the Moon for at least 100 years, the spin, shape, and radiometric constraints presented here provide an important benchmark for future potentially hazardous objects.
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All authors T. G. Müller, E. M. MacLennan, A. Y. Burdanov, B. J. Holler, A. S. Rivkin, J. de Wit, P. Pravec, M. Micheli, K. Muinonen, D. Farnocchia

Earth and Planetary Astrophysics

Detecting transiting exoplanets in simulated PLATO data: A comparison of light curve filter and transit search algorithms

Geert Jan Talens, Leigh C. Smith, Luca Malavolta et al. (+3 more)

Aims: Our goal is to test and compare transit search methodologies, and provide recommendations as to the best practices to be implemented by the upcoming ESA PLATO mission, in order to achieve its goal of detecting Earth-like planets in the habitable zones of Sun-like stars. Methods: We generate simulated two-year PLATO light curves with injected planets with sizes 0.5–2.0 $R_\oplus$, and compare the performance of the CETRA, umbra, and nuance transit search methods. CETRA and umbra require pre-filtered light curves and we test the biweight, Huber spline, Lowess, and YSD-Lowess filters. nuance uses a Gaussian process to model the stellar variability at all proposed transit parameters. Results: nuance achieves the best performance, recovering 61.2% signals using a simple harmonic oscillator Gaussian process kernel, and it performs especially well for both hot and fast-rotating stars. However, when multiple Huber spline filter windows are considered, both CETRA and umbra can match nuance's performance. CETRA matches nuance with four windows, recovering 61.3% of signals. umbra matches nuance with two windows, recovering 61.7% of signals. Recovery rates exceeding nuance are possible by using more windows. The computational cost of running nuance is so high that running CETRA or umbra on multiple windows is preferred. Conclusions: The PLATO pipeline should use the Huber spline with a range of window sizes as its primary light curve filter. CETRA should be updated to use the warped least-squares templates implemented in umbra. The use of nuance should be considered for hot, rapidly rotating stars.
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All authors Geert Jan Talens, Leigh C. Smith, Luca Malavolta, Lionel Garcia, Simon Hodgkin, Suzanne Aigrain

Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

SPAMMS: 3D spectroscopic modeling of stellar surfaces. II. Implementation of Kurucz and TLUSTY model atmospheres

D. Galán-Diéguez, M. Abdul-Masih, C. Allende Prieto et al. (+3 more)

Context. Accurate stellar spectra are essential to derive stellar properties. Traditional model atmospheres often oversimplify phenomena that break spherical symmetry, such as rotational deformation or multiplicity. The Spectroscopic PAtch Model for Massive Stars (SPAMMS) accounts for these effects, but its applicability has been limited by the spectral types covered by its model atmosphere grids. Aims. We aim to extend the parameter space of the model atmosphere grids available to SPAMMS, enabling spectral synthesis across a broader range of stellar types. Methods. We computed specific intensities, $I\left(\lambda,\mu\right)$, for $101$ emergent angles using PRISMAS (Pipeline of Radiative Intensity Synthesis for Meshed Atmospheric Surfaces), and pre-computed LTE and non-LTE atmospheres from two ATLAS9-Kurucz grids and the TLUSTY-based OSTAR2002 and BSTAR2006 models. Results. The intensity grids cover effective temperatures from $3500$ to $55000\,\mathrm{K}$ and surface gravities from $0.0$ to $5.0\,\mathrm{dex}$, spanning O- to K-type stars. They include metallicities from $0$ to $30\,\mathrm{Z_\odot}$ and microturbulent velocities of $1$, $3$, $5$, and $10\,\mathrm{km\,s^{-1}}$. The spectral range extends from $3000$ to $9000\,\mathring{\mathrm{A}}$ with $\Delta\lambda=0.01\,\mathring{\mathrm{A}}$. As a proof of concept, we modelled with SPAMMS a rapidly rotating B-type star and an eclipsing Algol-type binary. Conclusions. The new LTE-Kurucz and NLTE-TLUSTY grids substantially expand the parameter space accessible to SPAMMS. The code can now generate synthetic spectra for a broader range of stellar types and geometries, including rapidly rotating and multiple systems – providing a more comprehensive framework for modelling non-spherical stellar surfaces.
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All authors D. Galán-Diéguez, M. Abdul-Masih, C. Allende Prieto, S.R. Berlanas, A. Herrero, H. Sana

Earth and Planetary Astrophysics · Cross-listed from gr-qc

Testing the equivalence principle with lunar laser ranging residuals from different planetary and lunar ephemerides

Jun Ke, Jie Luo, Qin Li et al. (+2 more)

Lunar laser ranging (LLR) provides a sensitive test of the equivalence principle (EP) through a possible synodic perturbation in the Earth–Moon distance. In this work, we develop an independent LLR data-reduction framework and investigate this signature in the post-fit O–C residuals obtained with the EPM21, INPOP21, and DE430 planetary and lunar ephemerides. The same observation model and parameter-adjustment procedure are applied to the three ephemerides, allowing their residual-based results to be compared within a consistent framework. To account for the nonuniform distribution of LLR observations over the synodic angle $D$, the residuals are fitted with cosine and sine harmonics up to the third order. Signal-injection tests are also performed to quantify the attenuation of a possible $\cos D$ signal during the parameter adjustment. After correcting for signal attenuation, solar radiation pressure, and the thermal response of the lunar retroreflectors, the preferred EPM21, INPOP21, and DE430 solutions yield $\Delta(m_g/m_i)_{\rm EM}=(0.900\pm3.183)\times10^{-14}$, $(0.496\pm3.624)\times10^{-14}$, and $(2.669\pm7.048)\times10^{-14}$, respectively. The EPM21 and INPOP21 results are based on observations from 1970 to 2024, whereas the DE430 solution was obtained using observations up to 2016. All three estimates are consistent with zero within their uncertainties. This work demonstrates that residual-based analysis can provide an independent and transparent EP test, while also offering guidance for assessing sampling and ephemeris-dependent effects in future high-precision LLR studies.
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All authors Jun Ke, Jie Luo, Qin Li, Yu-Jie Tan, Cheng-Gang Shao

Earth and Planetary Astrophysics

Spectral Evolution of Ceres' Surface and Implications for Space Weathering

Qing Zhang, Jian-Yang Li, Yazhou Yang et al. (+2 more)

The surface of Ceres exposed to the space environment will be gradually altered, but the evolution of its spectral properties remains poorly understood. Here we analyze visible and infrared spectra acquired by the Dawn mission to investigate spectral variations across different surface units. We identify local shifts of a few nm toward shorter wavelengths in the 2.7 $\mu$m band center, predominantly associated with freshly exposed slumping and impact materials. Our analysis suggests that compositional variations in Ceres' regolith are unlikely the explanation for the band center shift, and therefore it may represent a spectral evolution within 10$^6$ years. Combining previous studies about the spectral reddening on Ceres, we propose a two-stage spectral evolution on Ceres. The blue-shifted regions are interpreted as the youngest materials. Within 10$^6$ years after exposure, these materials become spectrally bluer, the 2.7 $\mu$m band weakens, and its center shifts toward longer wavelengths. Then the evolution is characterized by spectral reddening and strengthening of the 2.7 $\mu$m band without the band center shift. Based on the previous laboratory work and observations on other C-complex asteroids, we suggest that the observed spectral variations may be attributed to the chemical and/or physical changes of the regolith, possibly associated with space weathering.
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All authors Qing Zhang, Jian-Yang Li, Yazhou Yang, Minge Liu, Yang Liu

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Nii-MALA: A Fast Metropolis-Adjusted Langevin Sampler with Radial Velocity Benchmarks

Jian Jiao, Sheng Jin, Wenxin Jiang et al. (+1 more)

Markov chain Monte Carlo is widely used for model assessment and parameter fitting in astronomy and astrophysics, leading to numerous ready-to-use packages implementing various sampling techniques. For large-scale analyses involving many individual targets, computational efficiency becomes paramount, as it dictates the overall runtime. We introduce Nii-MALA, a high-performance C implementation of the Metropolis-Adjusted Langevin Algorithm, which leverages Message Passing Interface for parallelization and incorporates automatic differentiation backends for gradient evaluation. The code offers flexible control via a configuration file, allowing users to specify the proposal step sizes for all model parameters across parallel chains. We validate its effectiveness on 15- and 30-dimensional Gaussian distributions and a bimodal distribution, and further benchmark it against several other codes using radial velocity data from 51 Pegasi b. Our benchmarks confirm the efficiency of Langevin sampling over random-walk sampling in obtaining the effective sample size, particularly as the dimensionality of the target function increases. This algorithmic advantage can be effectively leveraged when paired with an efficient automatic differentiation library. However, for complex functions commonly encountered in astronomy—such as radial velocity orbital fitting—the derivative-dependent Langevin sampler shows lower efficiency than parallel tempering or alternative sampling approaches, as revealed by effective sample size analysis.
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All authors Jian Jiao, Sheng Jin, Wenxin Jiang, Dong-Hong Wu

Sunday 13 September

Earth and Planetary Astrophysics

Second Generation Planet Formation in Post-AGB Discs - II: Dust Coagulation and Core Accretion

Ali Pourmand, Orsola De Marco, Devika Kamath et al. (+1 more)

Observations have established that the circumbinary discs formed around post-asymptotic giant branch (post-AGB) binaries have striking similarities to protoplanetary discs around young stars. In this study, we examine the feasibility of the different stages of growth in the core accretion framework of planet formation in post-AGB discs, in order to assess whether planet formation is possible in these systems. We find that dust coagulation up to mm sizes is possible within the lifetimes of post-AGB discs, consistent with observations. We then investigate the subsequent growth of planetesimals through pebble and planetesimal accretion. If the streaming instability operates in these discs, the resulting planetesimals formed in higher-mass post-AGB discs ($M_{\rm disc}\sim0.1M_\odot$) can enter rapid pebble accretion and reach their isolation mass within the estimated disc lifetime. By contrast, in lower-mass post-AGB discs ($M_{\rm disc}\sim0.01M_\odot$), planetesimal accretion is too inefficient to produce substantial further growth. We also show that the larger aspect ratios of post-AGB discs compared to protoplanetary discs around young stars imply high pebble isolation masses and therefore potential formation of rocky planets with masses extending up to Jupiter masses. After assessing gas accretion and concurrent migration in these discs, we conclude that second generation planet formation in post-AGB discs is theoretically possible within their estimated lifetimes ($10^4$–$10^5$yr) provided that local dust-to-gas ratio enhancements and sufficiently high disc masses are achieved.
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All authors Ali Pourmand, Orsola De Marco, Devika Kamath, Daniel J. Price

Earth and Planetary Astrophysics

WINERED Detects a Strong Atmospheric Outflow on the Sub-Neptune GJ 3090b

Shreyas Vissapragada, Zifan Lin, Annabella Meech et al. (+12 more)

Sub-Neptunes are the most common short-period ($P<100$ d) planets known. A major goal for the field is to build a comprehensive understanding of their compositions and evolutionary histories, and an important tool for achieving this goal is metastable helium (He$^*$) transmission spectroscopy, which traces atmospheric escape. In this paper, we report the detection of He$^*$ in the atmosphere of the sub-Neptune GJ 3090b at high spectral resolution. We observed two consecutive transits of this planet with Magellan II/WINERED, and detected peak He$^*$ absorptions during transit of $2.033\pm0.086\%$ (23.6$\sigma$) and $1.619\pm0.122\%$ (13.3$\sigma$), respectively. The first transit was affected by a stellar flare near egress while the second transit was unaffected. The signal is variable in amplitude and deeper than anticipated by the JWST/NIRISS observations of Ahrer et al. (2025). We do not observe a significant Doppler shift, and the signal has a FWHM of $25$ km s$^{-1}$, implicating photoevaporation. Our outflow modeling suggests that $Z_\mathrm{atm}\lesssim100\times$ solar, as the observed He$^*$ amplitudes are challenging to achieve in a metal-rich atmosphere. To match the muted transmission spectra from JWST and VLT/CRIRES+, GJ 3090b's lower atmosphere is likely covered by aerosols. Finally, we found that GJ 3090b has an atmospheric lifetime of $\sim300$ Myr, much shorter than previously reported. This adolescent ($\sim1$ Gyr) sub-Neptune is currently in a transformative phase of photoevaporative evolution.
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All authors Shreyas Vissapragada, Zifan Lin, Annabella Meech, Collin Cherubim, Leonardo A. Dos Santos, Aaron Householder, Krishna Kanumalla, Mercedes Lopez-Morales, Andrew McWilliam, William Misener, Ava Morrissey, Morgan Saidel, Jessica J. Spake, Johanna Teske, Nicole L. Wallack

Saturday 12 September

Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Reconstruction of pretelescopic and early telescopic solar activity cycles from auroral records

Kristof Petrovay, Laura G. Magyar and Hisashi Hayakawa

The historical record of low-latitude aurorae is essentially a poorly sampled record of the largest space weather events (SWEs). Its use for the identification of individual solar cycles is hindered by the low event rate and by the fact that the solar cycle profile of the occurrence of SWEs does not closely follow the variation of sunspot numbers. Based on recent studies of the solar cycle dependence of the occurrence rates of large SWEs, here we construct Monte-Carlo simulations of a large number of activity cycles to identify the optimal procedure to infer the characteristics of underlying solar cycles from the sparse record. We find that a reliable reconstruction of the cycle phase ($>90$% of reconstructed minima corresponding to actual minima within $\pm 2$ years) is possible whenever the long-term mean event rate (annual mean number of space weather events resulting in low-latitude auroral sightings) reaches or exceeds a value around 3. This condition is found to be satisfied during most of the the Early Modern Active Period (EMAP), a century-long period of normal solar activity between the Spörer and Maunder Minima. For the numbering of solar cycles in the EMAP we introduce the "telescopic era", where T$n$ denotes the $n$th cycle from the first telescopically observed cycle, T$0$, ongoing in 1610. Using our optimal procedure we reconstruct a series of 8 solar activity cycles from T$-5$ to T$2$ (1560-1640). Earlier cycles starting from 1540 can be reconstructed with a somewhat lower degree of reliability. Comparing our results with radionuclide-based reconstructions and sunspot observations we find a good overall correspondence, with the exception of the last cycle before the Maunder Minimum.
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Earth and Planetary Astrophysics · Cross-listed from cs.CG

The optimal-transport cartogram: world population as a Brenier map

Philipp Bogdan

A contiguous cartogram is a map whose area is proportional to a quantity such as population. The defining condition, that the Jacobian determinant of the deformation equals the density, is one equation for two unknown functions, so every cartogram method adds a tie-breaker, usually implicitly. Optimal transport makes the tie-breaker explicit: among all density-equalising maps of the frame onto itself, take the one that moves the population least in the mean-square sense. By Brenier's theorem that map is the gradient of a convex potential, so it has no local rotation anywhere and cannot fold. We compute this map for the world population of 2025 on a 4096 by 4096 Mercator grid (10 km cells) from the GHS-POP raster, using the fixed-point Monge-Ampère iteration of Benamou, Froese and Oberman with spectral Poisson solves, continuation in the population share and an ocean-only buffer, on a laptop GPU. Against a Gastner-Newman diffusion cartogram of the same density we find the same transport cost to within 0.4 per cent and density errors of a few per cent for both, but a median local rotation of 8.8 degrees for diffusion against 0.01 for transport, and a median anisotropy of 6.30 against 3.93. The construction extends to local refinement, by transporting a city's 100 m population onto the area measure the global map assigns to it, and to a semi-discrete counterpart: 8,192 Laguerre cells of 1.00 million people each. Code, data provenance and every figure's inputs are public.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Investigating Variability in Long-lived Protoplanetary Disks (>10 Myr) using NEOWISE

Gregory Mathews Ben, Jessy Jose and Jesús Hernández

We present the mid-infrared variability study of 120 long-lived disk candidates (ages 10-100 Myr) and 13 confirmed "Peter Pan" disks using NEOWISE to constrain the longevity of dynamic disk processes beyond the standard 10 Myr dispersal threshold. We identified 32 sources exhibiting significant variability by combining stochastic flux metrics and the Stetson $J$ index. The majority of these variables belong to the 10-25 Myr age range, suggesting a sharp decline in disk brightness variability after 25 Myr. Morphologically, the variability is characterized by irregular fluctuations with mean amplitudes of $\Delta W2 \approx 0.5$ mag, consistent with variable extinction or inner disk warping induced by embedded planetesimals. We also report a strong correspondence between mid-infrared and optical variability for the Peter Pan disks, with all 9 mid-IR variables confirmed as optical variables in the literature. Our findings reveal a population of 23 new long-lived disk candidates that retain active, gas-rich environments, supporting the existence of a rarefied class of systems that survive well into the debris disk era.
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Friday 11 September

Earth and Planetary Astrophysics

Incompatibility of iron in post-perovskite and the stability of basal magma oceans in super-Earths

Francis Dragulet and Lars Stixrude

Post-perovskite is expected to dominate much of the solid mantles of rocky exoplanets, yet iron partitioning between post-perovskite and silicate melt, which controls the compositional evolution and buoyancy of crystallizing magma oceans, is unconstrained at these pressures. We use first-principles molecular dynamics and thermodynamic integration to compute the Fe–Mg distribution coefficient $K_D$ between post-perovskite and (Mg,Fe)SiO$_3$ liquid at 150–600~GPa and 6000–10000~K. Iron is strongly incompatible in post-perovskite and becomes increasingly so with pressure. Combining $K_D$ with equations of state, we find that iron enrichment of residual liquid reverses the solid–liquid density contrast, causing post-perovskite to become buoyant. Basal magma oceans are therefore gravitationally stable in super-Earth exoplanets up to 4 M$_{\oplus}$.
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Earth and Planetary Astrophysics · Cross-listed from cs.LG

Operational Range Bounding in Spectroscopy: A Safety Cage Framework for Machine Learning Models

Nikki Grens, Luís F. Simões, Kai Hou Yip et al. (+1 more)

Ensuring the reliability of black-box machine learning models in safety-critical space missions remains a significant challenge, particularly when ground-truth is unavailable for validation. Although machine learning models offer a powerful means to augment standard pipelines by extracting transmission spectra from complex exoplanetary light curves, their susceptibility to unmodelled instrument anomalies, stellar activity, and domain shifts introduces unquantified risks. This study evaluates a modular safety cage architecture that operates as a parallel monitoring layer to assess the validity of a prediction without modifying the underlying estimator. By monitoring different runtime indicators, including uncertainty quantification, out-of-domain detection, and influence functions, the framework constrains the model's operational domain to a verified region. A controlled evaluation is conducted under both in-domain and cross-domain conditions, using datasets from the 2019 and 2021 editions of the Ariel Data Challenges. The results reveal that model failure is multifaceted and that no single indicator captures all failure modes, demonstrating the need for indicator fusion. The application of safety-driven rejection strategies shows that a modest 20% reduction in data coverage results in error reductions between 45% and 65% across different domains and evaluation metrics. Using a formalised coverage-risk framework, a systematic analysis of indicator combinations is performed to identify configurations that maximise risk-ranking accuracy and optimise the trade-off between data coverage and scientific performance. Safety cages provide a transparent mechanism for detecting unreliable predictions and represent a critical step towards the safe deployment of data-driven models in scientific applications, such as astrophysics, where ground truth is seldom available.
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All authors Nikki Grens, Luís F. Simões, Kai Hou Yip, Theresa Lueftinger

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Photonic Integrated Circuits for the Habitable Worlds Observatory: Science Drivers, Material Platforms, Arrayed-Waveguide Spectrographs, and a Space-Qualification Roadmap

Kalaga Madhav

NASA's Habitable Worlds Observatory (HWO) will require ultraviolet, optical, and near-infrared instruments that are simultaneously compact, mechanically and thermally stable, high-throughput, and replicable at large channel counts. Space-qualified photonic integrated circuits (PICs) and optical fibres are key platforms that can deliver these properties: they manipulate light at the diffraction limit within micron-scale single-mode waveguide circuits. An astrophotonic instrument fully guides the starlight from focal plane to detector, eliminating scatter and ghosts and offering excellent stability with no moving parts. This paper examines how astrophotonics can address the principal science drivers of HWO through four topics: (I) the HWO observing modes best implemented with photonic instruments; (II) the waveguide and fibre materials that can span the demanding 100nm-2.5{\mu}m HWO wavelength range; (III) the potential of arrayed-waveguide-grating (AWG) spectrographs to reach the resolving powers and throughputs HWO science requires; and (IV) the steps needed to space-qualify PICs and fibres against radiation, thermal cycling, vacuum, and launch loads. For each topic, concrete technical requirements are extracted and the current Technology Readiness Level (TRL) is assessed. The main contribution of this paper is to unify these science drivers, candidate-aperture photon budgets, UV-to-near-infrared material platforms, AWG architectures, and space-qualification requirements within a single photon-budget framework that pairs each claimed benefit with a measurable requirement, a TRL, and an environmental test that can retire it. A phased roadmap advances the critical photonic components from their present TRL~2 to -5, depending on platform and application, to the TRL~6 needed at HWO's instrument-definition gate.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Sinking Silicates I: Characterizing the benchmark system containing the T0 brown dwarf CWISE J210640.16+250729.0 using JWST

Austin Rothermich, Jacqueline K. Faherty, Ben Burningham et al. (+16 more)

In this study, we present the full (97.3% complete) 0.8–12.5 $\mu$m spectral energy distribution (SED) of an L/T transition object, CWISE J210640.16+250729.0 (CW2106), using the James Webb Space Telescope (JWST). We provide a full characterization of the host star's elemental abundances and age. We empirically derive the bolometric luminosity ($L_{\rm bol}\approx-4.825$ $\textup{L}_\odot$) of CW2106, and obtain estimates of its mass (M$\approx50-62$ M$_{\rm Jup}$), radius (R$\approx0.83-0.87$ R$_{\rm Jup}$), effective temperature ($T_{\rm eff}$$\approx1213$ K), and surface gravity ($\log~g$$\approx5.28$ dex). We find the near-infrared (near-IR) spectrum ($0.8-2.5 ~\mu$m) is best reproduced with cloudy atmospheric models while the mid-infrared (mid-IR) spectrum ($5-12.5 ~\mu$m) is best reproduced with cloudless models. This suggests a cloud layer restricted to only the deepest observable parts of the atmosphere and is qualified by the lack of a 9 $\mu$m silicate feature. Making use of the Mg/Si ratio of the primary, alongside thermochemical models, we predict the clouds in CW2106 to be composed primarily of enstatite (MgSiO$_3$), removing $\sim23\%$ of the bulk oxygen out of the atmosphere. Future retrieval studies will be able to help investigate the existence and full impact of these cloud species.
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All authors Austin Rothermich, Jacqueline K. Faherty, Ben Burningham, Catherine Manea, Emily Calamari, Genaro Suárez, Daniella C. Bardalez Gagliuffi, John M. Brewer, Kelle L. Cruz, Josefine Gaarn, Jonathan Gagné, Eileen C. Gonzales, Marina E. Gemma, Viktória Kecskeméthy, Mark S. Marley, Caprice L. Phillips, Channon Visscher, Johanna M. Vos, Niall Whiteford

Earth and Planetary Astrophysics

The core-mantle mode of gravitational oscillation

Mathieu Dumberry

We present the characteristics of a mode of axial oscillation between Earth's mantle, fluid core and solid inner core that has not been previously reported. The mode involves a quasi-rigid rotation of the fluid core outside the tangent cylinder (TC) exchanging its angular momentum with the mantle via a three step process. First, by a magnetic torque with the fluid inside the TC; second by a magnetic torque between the latter and the inner core; and finally by a gravitational torque between the inner core and mantle. Although the gravitational torque is purely between the mantle and inner core, the mode involves an oscillation of the whole of the core, and we refer to it as the core-mantle gravitational (CMG) mode. This form of gravitational oscillation occurs when the magnetic field within the core is sufficiently strong that the propagation time of Alfvén waves is shorter than the mode period, which is the case for Earth. We show how the period, quality factor $Q$ and structure of the CMG mode depends on the strength of the gravitational torque and viscous relaxation time $\tau_i$ of the inner core. For Earth, the CMG mode period should be in the range of 40 to 100 years, but viscous relaxation of the inner core likely implies a small $Q$, below 1 if $\tau_i<10$ years. Our results suggest that the CMG mode may act to amplify resonantly, though only modestly, multi-decadal changes in the length of day driven by zonal accelerations in the fluid core.
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Earth and Planetary Astrophysics

JWST/MIRI Imaging Search for Kinematically Detected Protoplanetary Candidates

G. Cugno, M. Benisty, R. Teague et al. (+32 more)

Kinematic perturbations observed with ALMA in CO line emission provide evidence for a population of embedded giant protoplanets shaping the structure of protoplanetary disks. We present JWST/MIRI F1140C ($\lambda = 11.3~\mu$m) coronagraphic observations of five protoplanetary disks, HD163296, RXJ1615.3-3255, RXJ1842.9-3532, SY Cha, and LkCa 15, with the goal of directly detecting candidate protoplanets orbiting at $\gtrsim$ 70 au previously inferred from gas kinematics. The data were analyzed using a bespoke methodology that combines reference PSF subtraction with forward modeling of partially resolved inner disk emission, which otherwise dominates the diffraction pattern in the images. This approach improves the sensitivity to young companions at small separations. No point source consistent with an embedded protoplanet is detected in any of the systems. Instead, in three systems we detect extended emission at $11.3~\mu$m tracing the outer disk out to radii comparable to those probed by CO. Injection tests indicate upper mass limits of roughly $3-20$ M$_J$ at separations of a few hundred au, assuming no additional thermal contribution from circumplanetary environment. Even with space-based observations, these limits remain mostly above the $\sim1-5$ M$_J$ masses inferred from disk kinematics, largely due to the limitations imposed by emission (and/or scattered light) contributions from both the inner and outer disk. These observations highlight the challenges of observing protoplanets embedded in their forming environment at large separation with JWST/MIRI. Lessons learned can inform future studies with the Extremely Large Telescope, which will probe separations where the occurrence rate of gas giants is expected to be higher.
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All authors G. Cugno, M. Benisty, R. Teague, A. Boccaletti, L. Pueyo, M. Perrin, M. Mâlin, J. Girard, V. Christiaens, P. Patapis, K. Lawson, S. M. Andrews, J. Bae, M. Barraza-Alfaro, M. J. Bonse, M. Courtoux, S. Facchini, M. Fukagawa, G. Guidi, R. Helled, T. Henning, J. Huang, J. Kammerer, C. Law, G. Lodato, F. Long, F. Ménard, M. Meyer, D. J. Price, C. Rab, I. Rebollido Vazquez, L. M. Stapper, T. Stolker, D. Wilner, A. J. Winter

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Spectro-polarimetry of HAbitable Planet Earth (SHAPE) on Chandrayaan-3: Instrument characteristics, calibration and onboard performance

Bhavesh Jaiswal, Swapnil Singh, Ravishankar B T et al. (+20 more)

The orbiter of the Chandrayaan-3 mission of the Indian Space Research Organisation (ISRO) carries an experimental payload called SHAPE (Spectro-polarimetry of HAbitable Planet Earth). This payload makes disc-integrated observations of Earth as an exoplanet, from the Moon as well as from the high altitude Earth orbit. The instrument consists of an Acousto-Optic Tunable Filter (AOTF) based near-infrared spectro-polarimeter making the measurements in the two orthogonally polarized directions using a pair of Indium-Gallium-Arsenide (InGaAs) detectors. The laboratory characterization of the flight model of the instrument included a relative measurement of the response of the two channels of the instrument. The field measurements of the instrument revealed a non-uniformity in the field response. In the light of non-identical response of the two channels and the non-uniformity of the field response, a theoretical model of such a polarimeter is developed to gain insights into the performance of a polarimeter. Analysis of lunar observations obtained within the SHAPE field of view indicates that the transmission ratio between the two polarized channels lies in the range 0.8-1.2. Such deviations from unity can introduce offsets in the measured polarization of up to about 10%. The suitability of SHAPE for studying the band polarization, defined as the relative polarization within a spectral absorption band, is studied. Using the Moon observations and the theoretical instrumental model, the suitability of measuring the relative band polarization is demonstrated. A study of systematic biases in the band polarization demonstrates a maximum offset of less than 1% in the measured value of the band polarization. The initial results of Earth observations, spectra and flux measurements across phase angles, and the methodology for retrieving the band polarization from these observations are also discussed.
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All authors Bhavesh Jaiswal, Swapnil Singh, Ravishankar B T, Anand Jain, Smrati Verma, Reenu Palawat, Brajpal Singh, Bijoy Raha, Sathyanarayana Raju, Bhavesh Mendhekar, Srinivasa Rao Kondapi, Priyanka Das, Rahul Waghmare, Supratik Bose, Supriya Verma, Yogesh Prasad K R, Praloy Karmakar, Abhishek Kumar Singh, Honey Gupta, Balaraman Prabakaran, Motamarri Srikanth, Sankarasubramanian Kasiviswanathan, Anuj Nandi

Earth and Planetary Astrophysics

The atomic C/O ratio of KELT-9b

Stefan Pelletier, Nicholas W. Borsato, Jacob L. Bean et al. (+12 more)

The carbon-to-oxygen (C/O) ratio of a giant planet's atmosphere has long been theorised to hold compositional information that can be traced back to its formation history. Typically, the C/O ratio of an exoplanetary atmosphere is inferred from abundance measurements of major C- and O-bearing molecules such as CO, CO$_2$, H$_2$O, and OH. However, some exoplanets have such elevated temperatures that molecules can be nearly completely thermally dissociated at the pressure levels that observations probe, making it difficult to measure their C/O ratio via these traditional tracers. Here, rather than using molecules, we aim to retrieve the C/O ratio of KELT-9b (T$_\mathrm{eq} = 4000$K) directly from atomic C and O, which are detected in its atmosphere. We analysed two transits of KELT-9b observed with the MAROON-X high-resolution spectrograph, finding absorption cross-correlation signals from atomic C and O as well as refractory metals. From this, we inferred the vertical temperature structure, the relative proportions of volatile and refractory species, and the C/O ratio of KELT-9b using a 1D local thermodynamic equilibrium atmospheric retrieval framework applied only to spectral regions mostly unaffected by non-local thermodynamic equilibrium effects. We measure the atomic C/O ratio of the atmosphere of KELT-9b to be $0.20_{-0.07}^{+0.13}$, which is slightly lower than the stellar value of $0.38\pm0.15$ and significantly below the solar value of $0.59\pm0.07$. We otherwise confirm previous investigations of the terminator region, finding KELT-9b's atmosphere to be thermally inverted and slightly metal-rich. We measure the volatile-to-refractory ratio, a proxy for the ice-to-rock ratio, to be $1.24_{-0.78}^{+1.93}$ $\times$ solar ($[$M$_{\mathrm{vol}}$/M$_{\mathrm{ref}}]$ = $0.09_{-0.20}^{+0.19}$), which is consistent with both KELT-9 and the Sun.
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All authors Stefan Pelletier, Nicholas W. Borsato, Jacob L. Bean, Andreas Seifahrt, David Kasper, Julian Stürmer, Ana Rita Costa Silva, David Ehrenreich, Luca Fossati, Jens Hoeijmakers, Bibiana Prinoth, Michal Steiner, Brian Thorsbro, Valentina Vaulato, Daniel B. Zucker

Earth and Planetary Astrophysics

Limits on a Host Star around a Saturn-mass Free-floating Planet Candidate KMT-2024-BLG-0792/OGLE-2024-BLG-0516

Przemek Mróz, Klara Piotrowska, Antoine Mérand et al. (+2 more)

Recent studies found a number of short-timescale microlensing events that are thought to be produced by free-floating or wide-orbit planets. The microlensing event KMT-2024-BLG-0792/OGLE-2024-BLG-0516 is currently the only free-floating planet candidate with a directly measured mass ($0.73^{+0.25}_{-0.15}$ Saturn masses), derived from joint ground-based and Gaia satellite observations. However, it remains unclear whether the lens is truly isolated or bound to a widely separated host star. Here, we report high-angular-resolution interferometric observations of the event obtained with the Very Large Telescope Interferometer/GRAVITY instrument two years after peak magnification. We detect no luminous host star up to a projected separation of 90 au, supporting the hypothesis that the lens is indeed a free-floating planet. We derive a 5 sigma upper limit on the mass of a putative host star of approximately 0.5-0.6 M_solar. This work demonstrates that interferometry provides a powerful method for directly searching for or constraining host stars in short-duration and planetary microlensing events.
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All authors Przemek Mróz, Klara Piotrowska, Antoine Mérand, Subo Dong, Zexuan Wu

Earth and Planetary Astrophysics

Terminal instability of the Solar System triggered by stochastic solar mass loss

Konstantin Batygin, Jim Fuller and Fred C. Adams

From its birth, celestial mechanics has been deeply intertwined with the question of the Solar System's dynamical stability. For the inner planets, this question is now statistically settled: Mercury's orbit carries a $\sim$1% chance of destabilization before the Sun leaves the main sequence. The outer Solar System has seemed more secure, with its intrinsic dynamical lifetime estimated at $\sim10^{18}$ years. Even accounting for the Sun's mass loss and stellar flybys, the orbital architecture of the giant planets had been expected to persist for $\sim$100 Gyr. Here we show that these estimates rest on the assumption that solar mass loss is smooth. The recently measured white dwarf recoil demands asymmetric mass loss that is most readily attributed to discrete, independently directed ejections that impulsively perturb stellar motion. As the Sun sheds its envelope in such parcels, the planets' orbits random-walk with amplitude set by the mass-loss granularity. At a coarseness corresponding to observationally permitted kicks, this stochastic forcing restructures the outer Solar System concurrently with the Sun's death. In particular, our numerical experiments reveal that orbit crossings can commence on the red giant branch, with $\sim$40% of realizations undergoing disruption or violent scattering before the white dwarf forms and $\sim$90% self-destructing within 3 Gyr. The outer Solar System's dynamical lifetime thus collapses from $10^{18}$ years to approximately a gigayear after white dwarf formation.
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Earth and Planetary Astrophysics

KMT-2026-BLG-0083L: A Two-Jovian-Planet System Orbiting an M Dwarf Discovered by Microlensing

Cheongho Han, Chung-Uk Lee, Zhixing Li et al. (+65 more)

We present the analysis of the microlensing event KMT-2026-BLG-0083, which was independently detected by the KMTNet, OGLE, and PRIME surveys and also monitored by the DREAMS survey. The combined data provide dense coverage of two distinct short-duration anomalies in the light curve that cannot be reproduced by a standard binary-lens model. Independent analyses of the two anomalies indicate that each is produced by a planetary companion to the lens, motivating a triple-lens interpretation. The modeling yields two pairs of degenerate solutions arising from the well-known inner–outer degeneracy, with each pair exhibiting two local solutions depending on whether the source passes above or below the distant planetary companion. The preferred model indicates two giant planets with mass ratios $q_2=(5.25\pm 0.08)\times 10^{-3}$ and $q_3=(3.04\pm 0.24)\times10^{-3}$ orbiting a common host. Bayesian analysis indicates that the host is an M-dwarf star with a mass of $0.48^{+0.36}_{-0.28}~M_\odot$, hosting two giant planets with masses of $2.65^{+1.96}_{-1.55}~M_{\rm J}$ and $1.54^{+1.14}_{-0.90}~M_{\rm J}$. The projected planet–host separations are $10.6^{+1.7}_{-2.2}$~au and $1.7^{+0.3}_{-0.3}$~au, placing the inner planet near the host's snow line and the outer planet at a substantially larger separation. Thus, KMT-2026-BLG-0083L becomes the seventh confirmed multiple-planet system discovered through gravitational microlensing, providing another example of a cold giant planetary system orbiting a subsolar-mass star.
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All authors Cheongho Han, Chung-Uk Lee, Zhixing Li, Weicheng Zang, Andrzej Udalski, Ian A. Bond, Yoon-Hyun Ryu, Steve Heathcote, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Youn Kil Jung, Kyu-Ha Hwang, Hongjing Yang, Yossi Shvartzvald, In-Gu Shin, Doeon Kim, Dong-Jin Kim, Byeong-Gon Park, Richard W. Pogge, Qiyue Qian, Yaosong Yu, Yuchen Tang, Yuxin Shang, Tomas Ahumada, imothy Abbott, Guillermo Damke, Konstantina Boutsia, Alfredo Zenteno, Shude Mao, Andong Xu, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radosław Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, David P. Bennett, Aparna Bhattacharya, Kotaro Daimon, Ryusei Hamada, Yuki Hirao, Shuma Makida, Stela Ishitani Silva, Shota Miyazaki, Tutumi Nagai, Seiya Nakayama, Kansuke Nunota, Ryo Ogawa, Ryunosuke Oishi, Hideaki Ose, Nicholas J. Rattenbury, Yuki K. Satoh, Takahiro Sumi, Daisuke Suzuki, Motohide Tamura, Takuto Tamaoki, Sean K. Terry, Chihiro Ueda, Aikaterini Vandorou, Hibiki Yama

Earth and Planetary Astrophysics

High water D/H ratio of the interstellar object 3I/ATLAS is consistent with a low-metallicity origin

Kenji Furuya, Martin Cordiner, Dominique Bockelée-Morvan et al. (+5 more)

Recent JWST observations have revealed unusually high $^{12}$C/$^{13}$C ratios in carbon-bearing molecules of the interstellar object 3I/ATLAS, consistent with formation in a lower-metallicity environment than the present-day local interstellar medium (ISM). 3I/ATLAS also exhibits an exceptionally high water D/H ratio, exceeding those in Solar System comets and nearby low-mass star-forming regions. Here we investigate whether this high water D/H ratio can be reproduced in a low-metallicity formation scenario, using gas-ice astrochemical models. Assuming that the water observed in 3I/ATLAS was inherited from the parent molecular cloud and core, we perform a grid of astrochemical models covering the cloud to core stages, varying the gas density, ultraviolet radiation field ($\chi$), cosmic-ray ionization rate ($\zeta$), and metallicity, while solving thermal balance for the gas temperature. We find that lower metallicity enhances H$_3^+$ deuteration and, more importantly, its transfer to water ice. In contrast, water D/H ratio depends non-monotonically on $\chi$ and $\zeta$, because of competing chemical and thermal effects. In our models, the observed water D/H ratio is most readily reproduced at subsolar metallicities, $\lesssim0.5Z_\odot$, and relatively high cloud densities of $\sim$10$^4$ cm$^{-3}$ without strong constraints on either $\chi$ or $\zeta$, as long as $\zeta<10^{-15}$ s$^{-1}$. The D/H ratio of methane normalized by that of water is not sensitive to the metallicity, being consistent with the similar values observed in 67P/Churyumov-Gerasimenko and 3I/ATLAS. These results suggest that water deuteration may provide a complementary probe of the metallicity and physical condition of the parent molecular cloud and dense core of interstellar objects.
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All authors Kenji Furuya, Martin Cordiner, Dominique Bockelée-Morvan, Dennis Bodewits, Colin Orion Chandler, Maria N. Drozdovskaya, Nathan X. Roth, Geronimo Villanueva

Thursday 10 September

Earth and Planetary Astrophysics

OSIRIS-REx Returned a Pristine Sample of Asteroid Bennu: Takeaways from the Mission's Contamination Control and Knowledge Program

Jason P. Dworkin, Scott A. Sandford, Nicole G. Lunning et al. (+81 more)

NASA's OSIRIS-REx mission had the objective of delivering a pristine sample from asteroid (101955) Bennu to Earth for scientific analysis–where "pristine" signifies the absence of foreign materials that could affect sample measurements. OSIRIS-REx returned 121.6 g of regolith in September 2023; this study documents the systematic investigation of suspected contaminants encountered during the mission's sample analysis phase. Most suspected contaminants did not originate from the spacecraft or sample curation. Some were introduced during laboratory analyses, reinforcing the importance of procedural blanks and a strategic approach to sharing samples across laboratories with different analytical targets. Several suspected contaminants, such as phosphate and sodium fluoride particles, were ultimately identified as indigenous to Bennu, highlighting the critical role of contamination knowledge in preventing the dismissal of valuable scientific data. We find that the returned sample meets the definition of pristine, except for an isolated 1.24% (by mass) that escaped the sample container and was thereby contaminated with spacecraft particulates. These findings demonstrate the effectiveness of systematically applied contamination science and engineering practices and provide lessons and approaches to help maximize the scientific integrity of future planetary sample return missions.
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All authors Jason P. Dworkin, Scott A. Sandford, Nicole G. Lunning, Kevin Righter, Charles C. Lorentson, Daniel P. Glavin, Kathie L. Thomas-Keprta, Loan Le, Catherine M. Corrigan, Timothy J. McCoy, Edward B. Bierhaus, Jose C. Aponte, Angel Mojarro, Hannah L. McLain, Eric T. Parker, Denise K. Buckner, Frédéric Seguin, Radford L. Perry, Heather V. Graham, Havishk Tripathi, Pierre Haenecour, Piers Koefoed, Kun Wang, Cody Schultz, Takahiro Hiroi, Ralph E. Milliken, Simon J. Clemett, Bumsoo Kim, Christopher J. Snead, Eve L. Berger, Michael Liss, Jessica J. Barnes, Sandra Freund, Zoe A. Wilson, Ryan D. Dubisher, Natasha V. Almeida, Kimberly K. Allums, Erika H. Blumenfeld, Joseph E. Aebersold, Rachel C. Funk, Carla P. Gonzales, Julia L. Plummer, Maritza Montoya, Daniel J. Rohmer, Erika V. Rivera, Jannatul Ferdous, Gabriel C. Garcia, Melissa Rodriguez, Jose L. Ponce, Ronald Bastien, Wayland D. Connelly, Jemma Davidson, Marghaleray Amini, Vivian Lai, Dominique Weis, Josh Wimpenny, Jan Render, Gregory A. Brennecka, Yoshihiro Furukawa, Toshiki Koga, Yoshinori Takano, Hiroshi Naraoka, Yasuhiro Oba, Kenneth J. Domanik, Yao-Jen Chang, Zoe Zeszut, Thomas J. Zega, George D. Cody, Conel M. O'D. Alexander, Ian A. Franchi, Monica M. Grady, Danielle N. Simkus, Jamie E. Elsila, Philippe Schmitt-Kopplin, Allison A. Baczynski, Katherine H. Freeman, Amy E. Hofmann, Aaron S. Burton, Lindsay P. Keller, Sara S. Russell, Anjani T. Polit, Francis M. McCubbin, Harold C. Connolly Jr., Dante S. Lauretta

Earth and Planetary Astrophysics

Steepening Optical Slopes in Exoplanet Transmission Spectra with Charged Hazes

Masayuki Inai, Kazumasa Ohno and Shota Notsu

Observations of exoplanetary atmospheres have revealed the ubiquity of aerosols, yet their microphysics remain largely uncertain. Haze charging is a key microphysical process in aerosol-rich Solar System atmospheres, but it has been ignored in exoplanetary haze models. Here we develop a microphysical framework that includes haze charging for exoplanet atmospheres and investigate its effects on transmission spectra. Electrostatic repulsion suppresses coagulation, maintaining smaller particle radii and higher mixing ratios in the upper atmospheres. We find that particle charging steepens the optical spectral slopes when vertical mixing is weak. This behavior arises from the combination of reduced particle sizes and a steepened vertical gradient in haze opacity. Furthermore, we find distinct spectral responses to charging for different haze analogs, owing to the different contributions of scattering and absorption. For absorption-dominated materials such as soot, particle-size reduction has little impact on opacity profiles, leading to only minor charging-induced spectral changes. By contrast, scattering-dominated materials such as tholin and diamond show a stronger spectral signature of particle charging because of the strong dependence of scattering opacity on particle size. While previous studies have invoked haze formation under vigorous vertical mixing as a mechanism for producing super-Rayleigh optical slopes, we demonstrate that highly charged scattering haze can produce such slopes even under weak-to-moderate vertical mixing. Our results highlight haze charging as a previously neglected microphysical process that can affect particle growth and leave observable signatures in transmission spectra, providing a quantitative framework for assessing atmospheric electrical conditions.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

An unresolved extreme warm infrared excess toward a nearby low-mass star

Sahin Torlakcik

Gaia DR3 2981818948336660224 is a nearby low-mass star with a substantial warm mid-infrared excess. Identified in a Gaia-2MASS-WISE search, it lies at approximately 127 pc and has an AllWISE W3 signal-to-noise ratio of 33.1. We recover the emission in all 16 available cryogenic exposures over 1.26 d; removing any one exposure leaves the signal intact. The W3 emission is centred close to the propagated stellar position, and the known neighbour 6.1 arcsec away fails to reproduce its morphology. Nominal scene fits place 97-98 per cent of the W3 flux at the target position. This provides strong spatial support for association, although template uncertainty and a nearly coincident hidden source prevent a definitive decomposition. The excess can be described by a roughly 300-350 K component with L_IR/L_star ~ 0.022, assuming stellar association and retaining the weaker W4 detection. If produced by circumstellar dust, it falls in the extreme warm-debris regime around a dwarf with no established evidence of youth. Its origin remains unresolved. The repeatable excess and close spatial association make this a useful target for subarcsecond MIR imaging and spectroscopy to test the warm-dust interpretation.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Continuous Learning of Gravity Field Irregularities Around Small Bodies via Neural Hamiltonian ODEs

Giacomo Acciarini and Dario Izzo

We propose to learn the unknown dynamics in the proximity of a small body directly from tracking data, representing them as a feed-forward neural network embedded in the system Hamiltonian. The equations of motion form a Neural Hamiltonian Ordinary Differential Equation, whose variational equations provide exact training gradients: estimation uses position and velocity arcs at realistic noise levels, without acceleration or potential labels, and a continual learning approach warm-starts the network as new data are acquired. The known part of the Hamiltonian carries whatever is available, from the central term and spin state to the constant-density model of the imaged shape. We assess the method against a normalized spherical harmonics expansion estimated from identical arcs through the same machinery, on scenarios built on the shapes of Itokawa, 67P, Bennu and Eros. The network remains usable inside the Brillouin sphere: it plans ballistic descents at Itokawa to \SI{4.6}{m} median touchdown error from tracking alone, against 5.1–\SI{48.9}{m} for harmonics of degree 4–12, and to \SI{0.9}{m} with the imaged shape as prior, a configuration that also recovers localised density anomalies invisible to any harmonics degree. The two representations are complementary, and we discuss their combined use across the phases of a small-body mission.
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