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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Tuesday 29 September

Earth and Planetary Astrophysics

Improved Constraints on the Surface of LHS 3844 b from its Mid-Infrared Spectrum

Kimberly Paragas, Heather A. Knutson, Renyu Hu et al. (+4 more)

The thermal emission spectra of terrestrial exoplanets provide a window into their surface compositions and corresponding geological processes. Close-in, rocky planets orbiting M dwarfs are ideal targets for these studies, as observations have shown that most have little to no atmosphere. LHS 3844 b is an ultra-short period super-Earth orbiting a nearby M dwarf, and is the most favorable target that does not have a dayside magma ocean. We present an updated JWST MIRI/LRS emission spectrum ($5-12$ $\mu$m) of this planet, derived from eight new and three archival eclipse observations. We combine these visits to obtain the highest SNR emission spectrum for any rocky exoplanet thus far, with a median SNR of 29 across 12 wavelength bins. Our data are sensitive to the predicted Si-O stretching feature (the strongest mid-infrared silicate feature) for a wide range of common materials and the transparency feature, which is relatively insensitive to composition and constrains the grain size and porosity of surface materials. We find that LHS 3844 b's emission spectrum resembles a blackbody shortward of 10 $\mu$m disfavoring the presence of a transparency feature, and identify a tentative feature ($1.9-3.5\sigma$) between $10-12$ $\mu$m. If this feature is astrophysical and not instrumental in nature, it can be matched by a fayalite (the iron end-member of olivine) surface, but might also be consistent with other candidate planet-forming materials like spinel or silicon carbide. We discuss possible biases introduced by the wavelength-dependent instrumental ramp, and outline several strategies to mitigate this effect in future observations of LHS 3844~b that would establish the surface composition of this rocky exoplanet.
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All authors Kimberly Paragas, Heather A. Knutson, Renyu Hu, Bethany L. Ehlmann, Aishwarya R. Iyer, Sebastian Zieba, Laura Kreidberg

Earth and Planetary Astrophysics

Constraining exoplanet population parameters with Kepler and simulation-based inference

Chloé Padois, Friedrich Anders and Daniel del Ser

In the context of the rapidly growing field of galactic exoplanet population studies, we present an exoplanet simulator capable of generating synthetic populations for millions of stars in a few seconds (Padois et al., 2025). Our framework combines observed exoplanet detections with the latest planetary formation models, incorporating dependencies between host star properties and planet occurrence rates, orbital period distributions, and other key demographic features. However, many model parameters remain uncertain and model-dependent. To constrain some of the most critical ones, we couple our simulator with simulation-based inference (SBI): we define a set of 44 free parameters describing the population of different planet types (occurrence rates, mass-period distribution, mass-radius relation, etc.), run millions of simulations sampling from broad prior distributions, simulate their detectability by Kepler, and train a machine-learning algorithm to learn the relationships between input parameters and the resulting "observed" synthetic populations. The best-fit parameters are then inferred by comparing model outputs to real observations, for which we adopt the Kepler confirmed planet catalogue as our reference dataset, since it provides the largest homogeneous sample from a single facility. We present preliminary results for the planet occurrence rate as a function of stellar mass and metallicity, across different planet types, along with constraints on several key simulation parameters such as the orbital period distribution and the inclination dispersion within planetary systems. These refined parameters enable us to refine our yield predictions for upcoming exoplanet detection missions, including PLATO, Roman, and HAYDN.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Detection of fine-structured radio bursts during a superflare on EQ Peg

Zhanhao Zhao, Xin Cheng, Yuankun Kou et al. (+6 more)

Superflares are frequently observed on magnetically active stars, particularly on active M-dwarfs, thereby influencing the habitability of nearby exoplanets. However, the causes of superflares remain unclear. Here, combining FAST and TESS, we detected a finely structured decimetric radio burst appearing as groups of spikes during a white-light superflare (total bolometric energy $\sim 10^{33} \ \mathrm{erg}$) on the M-dwarf binary EQ Peg on September 8th, 2022. The most significant ones appeared near the peak time of the optical flare and lasted for about $100 \ \mathrm{s}$. The radio spikes present extremely high brightness temperatures ($\gtrsim 10^{13} \ \mathrm{K}$) and high degrees of circular polarization ($\sim 0.84 \pm 0.16$), indicating the origin of a coherent emission process, most likely the electron cyclotron maser. Based on Zeeman-Doppler Imaging measurements of EQ Peg, we further locate the sources of the radio spikes, including their heights and latitudes, under the assumption of a large-scale dipolar magnetic field configuration. The results provide strong evidence for finely structured decimetric radio bursts generated by stellar flares and shed light on the origin of superflares.
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All authors Zhanhao Zhao, Xin Cheng, Yuankun Kou, Guoyin Chen, Hao Ning, Yao Chen, Baolin Tan, Keping Qiu, Mingde Ding

Earth and Planetary Astrophysics

Detecting atmospheres in the presence of stellar contamination: an empirically calibrated framework applied to four JWST/NIRSpec PRISM transits of TRAPPIST-1c

Alexander D. Rathcke and Lars A. Buchhave

Transmission spectroscopy of rocky exoplanets orbiting late M dwarfs is limited by stellar contamination rather than photon noise. We present a framework for this contamination-dominated regime, fitting all transit epochs jointly with a Gaussian process per epoch for the time-varying stellar contamination and a single atmospheric model shared across epochs. We use pure CO$_2$, H$_2$O, and CH$_4$ models scaled by their peak-to-trough amplitude, allowing us to measure how large a signal must be to be recovered. We calibrate this framework using injection-recovery tests and 17 archival JWST/PRISM transits of the airless sibling TRAPPIST-1 b to quantify the spurious signals that stellar contamination alone produces. Applied to four JWST/NIRSpec PRISM transits of TRAPPIST-1 c, our framework recovers injected CO$_2$ signals without bias and reaches detection thresholds of 146 (171) ppm for moderate (strong) evidence, compared with 96 ppm if there were no stellar contamination. CO$_2$ and CH$_4$ produce no spurious signals on the airless control planet, whereas H$_2$O shows a persistent stellar floor of $+55 \pm 34$ ppm. TRAPPIST-1 c is consistent with a featureless, airless baseline for all three molecules. Our 95 per cent upper limit of 90 ppm for CO$_2$-shaped signals effectively rules out clear, isothermal pure-CO$_2$ atmospheres ($\geq$0.1 bar) and N$_2$-dominated atmospheres with 1 per cent CO$_2$ ($\geq$1 bar) at the equilibrium temperature. An empirical scaling study using 2 to 10 transits of TRAPPIST-1 b shows the CO$_2$ detection threshold decreasing with the number of transits $k$ as $k^{-0.6}$, reaching 80 ppm at ten transits, while water searches become limited by the stellar floor beyond about six transits. CO$_2$ atmospheres, by contrast, are detectable when we utilize our framework to account for stellar activity at the cost of roughly 1.5 to 2 times as many transits.
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Earth and Planetary Astrophysics

TOI-6981 b: a transiting sub-Neptune at the water ice line

Madison G. Scott, Amaury H.M.J Triaud, Emily K. Pass et al. (+42 more)

We present TOI-6981 b, a cold (Teq= 170.0 +/-4.5 K, assuming an Earth-like albedo) sub-Neptune (Rb=2.40+/-0.10 R_oplus) on a 60.8 day orbit around around its M4-type host star (R*=0.304 +/- 0.012 R_odot, M*=0.296 +/- 0.026 M_odot, Teff = 3215+/-58K), part of the SPECULOOS TEMPOS program. We validate the planetary nature of TOI-6981 b using ground-based follow-up photometry, statistical validation and high-resolution spectroscopy. At such cold temperatures, TOI-6981 b sits roughly at the location of the water ice line (approx 170 K). Given its orbital period and high transmission spectroscopy metric (TSM=51 +/- 9), it is one of the only planets in the sparsely populated cold planet regime amenable for atmospheric studies with JWST. Therefore, TOI-6981 b could. possibly become a crucial benchmark in cold chemistry studies, tests of Hycean world hypotheses, and drawling parallels to the Solar System's ice giants. Additionally, given its current orbit, it may provide insight into planetary formation and migration at or beyond the water ice line.
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All authors Madison G. Scott, Amaury H.M.J Triaud, Emily K. Pass, Aleyna Adamson, Karen A. Collins, Khalid Barkaoui, Allyson Bieryla, Adam J. Burgasser, Mark E. Everett, Steve B. Howell, David W. Latham, Benjamin V. Rackham, Boris S. Safonov, Miquel Serra-Ricart, Abderahmane Soubkiou, Georgina Dransfield, Katharine Hesse, Pipa Fernandez de Diego, Emma Softich, Gregor Srdoc, Mathilde Timmermans, Jeroen Audenaert, Roi Alonso, Artem Y. Burdanov, Yasmin T. Davis, Fatemeh Davoudi, Julien de Wit, Shishir Dholakia, Elsa Ducrot, Michaël Gillon, Yilen Gomez Maqueo Chew, Matthew J. Hooton, Clàudia Janó-Muñoz, Emmanuel Jehin, Akanksha Khandelwal, Thomas R. Marriott, Peter P. Pedersen, Manuel Pichardo Marcano, Francisco J. Pozuelos, Rafael Rebolo-López, Manu Stalport, Alexander Venner, Selçuk Yalçinkaya, Francis Zong Lang, Sebastián Zúñiga-Fernández

Earth and Planetary Astrophysics

The Occurrence Rate of Planets Around Subgiant Stars from TESS Photometric Survey

Arkaprova Dutta and Priyanka Chaturvedi

Subgiant stars represent a critical phase in stellar evolution, offering an opportunity to investigate how planetary systems respond to the early stages of post-main-sequence expansion. Despite their importance, systematic occurrence-rate studies of this population remain sparse compared with those of main-sequence and red-giant hosts. In this work, we present a uniform analysis of planet occurrence around a sample of 282,904 subgiant stars selected from the Gaia DR3 catalogue. We perform an independent reanalysis of TESS light curves for transit-signal detection and refinement, followed by multi-stage vetting including visual inspection and statistical false-positive assessment. We quantify the detection sensitivity of the survey through injection-and-recovery experiments, with 565,808 synthetic transit signals injected across the stellar sample. Over the period range of 1–10 days and the planet-radius range for which the detection completeness is well characterised, we measure a completeness-corrected planet occurrence rate of 0.644^{+0.048}_{-0.041}. The occurrence rate is strongly dependent on planet radius, with the highest occurrence contributed by planets in the 1-4 R_earth range and a secondary enhancement at 12-15 R_earth. These results provide a demographic baseline for studying the population of close-in planets around stars undergoing early post-main-sequence evolution.
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Earth and Planetary Astrophysics

Homogeneous Nucleation of Water Vapor Evidenced by Elongated Clouds on Mars

J. Hernandez-Bernal, A. Maattanen, A. Spiga et al. (+1 more)

It is widely accepted that water vapor forms clouds by heterogeneous nucleation (condensation on pre-existing dry nuclei). Homogeneous nucleation (directly from water vapor, without a pre-existing nuclei) is theoretically possible, but it requires high levels of supersaturation and so it is not considered a viable cloud formation process under real atmospheric conditions. Here, we show that introducing homogeneous nucleation in a meteorological model of Mars allows to successfully reproduce the unique characteristics of the Arsia Mons Elongated Cloud, a remarkable water ice cloud that occurs recurrently on Mars and which had remained impossible to model under conventional cloud microphysics. This finding demonstrates that homogeneous nucleation happens on Mars, provides the first evidence of homogeneous nucleation of water vapor in a planetary atmosphere, and challenges current assumptions about cloud formation processes, which is also relevant for certain clouds on Earth and potentially on other planets.
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All authors J. Hernandez-Bernal, A. Maattanen, A. Spiga, F. Forget

Earth and Planetary Astrophysics

Chondrule size averaging in two and three dimensions

Emmanuel Jacquet

Chondrule sizes are an important discriminant of chondrite groups and chondrule formation theories. Yet most studies report 2D sizes without attempting the somewhat tedious corrections to 3D proposed in the past literature. I show here that 3D size averages can be simply calculated directly from 2D averages of appropriate powers of sizes (and vice-versa), without having to reconstruct 3D distributions, although explicit formulas to that end are also provided. This illuminates the comparison between 3D and 2D arithmetic size averages, which are confirmed to be little different for the published datasets. Yet I suggest another type of average, the "sphere-weighted average" (i.e. weighted by the chondrule equal-volume sphere area), a measure of the surface/volume ratio of the chondrule population, which is more robust against omission of small chondrules. While larger than the arithmetic averages, it is best in line with previous literature estimates based on less exhaustive surveys of chondrules.
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Earth and Planetary Astrophysics

Astrometric Evidence for Outer Giant Planets in Known Exoplanet Systems

Clarissa R. Do Ó, William Thompson, Dori Blakely et al. (+19 more)

Outer giant planets can influence the formation and dynamical evolution of their planetary systems. However, their long orbital periods make them difficult to detect using transit and radial velocity (RV) techniques. Measurements from Hipparcos, Gaia DR2 and DR3 (G23H) can detect the stellar reflex motion induced by distant companions before the release of Gaia DR4 epoch astrometry. Using the G23H catalogue, we identify 29 outer companion candidates ($a_{median}$ $>$ 8.4 AU) in known transiting and RV systems. Starting from 170 exoplanet hosts with $P(\mathrm{companion})>0.75$ and posterior support for $0.3$–$13\,M_{\rm J}$ companions, we retain 29 systems where each selected component has a median semi-major axis beyond the outermost known planet with every known planet outside its 95% highest posterior density region in mass and semi-major axis. We incorporate published RV and imaging data from the literature to further constrain the outer candidate's mass and semi-major axis. In eight systems present in the sample, an RV variation or trend has already been reported in the literature. The reported candidates could potentially explain these RV variations, but joint astrometric and RV fits are needed to establish whether the same companions produce both signals. These results provide a set of high priority targets for further RV monitoring and joint orbit analysis with Gaia DR4. If these companions are confirmed, their orbital constraints will provide a starting point for studies of their influence on the dynamical evolution of the known inner planets.
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All authors Clarissa R. Do Ó, William Thompson, Dori Blakely, Aniket Sanghi, Jerry W. Xuan, Dimitri Mawet, Jessica Speedie, Sarah Blunt, Simon Blouin, Jingwen Zhang, Doug Johnstone, Jean-Baptiste Ruffio, Eric Nielsen, Brendan P. Bowler, Alexandre Bouchard-Côté, Kyle Franson, William Roberson, Ryan Cloutier, Andre Fogal, Kaitlyn Hessel, Christian Marois, Alexandra Rochon

Earth and Planetary Astrophysics

Detecting Extragalactic Exoplanets With Fast Radio Burst Nanolensing

Kenneth F. Olibrice and Dylan L. Jow

Fast Radio Bursts (FRBs) are spatially and temporally compact sources at cosmological distances. As background sources, they will be uniquely sensitive to the gravitational lensing of exoplanets outside of our own galaxy. We present a method to detect extragalactic exoplanets using planetary echo nanolensing-periodic, nanosecond-scale variations in the relative time of arrival (ToA) between an initial FRB and its microlensed echo as the planet orbits its host star. For a simple binary lens model, we demonstrate that measuring the amplitude and period of these ToA fluctuations enables a determination of the exoplanet mass and orbital parameters. FRBs will be most sensitive to echo nanolensing by lenses within ten megaparsecs of the Milky Way as well as within ten megaparsecs of the FRB host, opening the door to detections of planets at a range of redshifts. We estimate that at least one in a million FRBs will exhibit this phenomenon (i.e. an optical depth of $\tau_l = 10^{-6}$). While current burst rates and low repeating-FRB fractions make a detection challenging in the immediate term, upcoming high-volume surveys and next-generation arrays (such as the SKA Phase 2) will bring the unambiguous detection of extragalactic exoplanets across cosmological redshifts into possibility.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.GA

Testing KMTNet–PRIME Optical–Near-Infrared Source-Color Constraints in KMT-2024-BLG-0211 and KMT-2024-BLG-1522

Kansuke Nunota, Jennifer C. Yee, Takahiro Sumi et al. (+37 more)

We present analyses of two 2024 microlensing events, KMT-2024-BLG-0211 and KMT-2024-BLG-1522, jointly observed by KMTNet in the optical and PRIME in the near-infrared. For KMT-2024-BLG-0211, the KMTNet–PRIME $I-H$ color provides a useful constraint on the angular source radius for a short-timescale finite-source event with a giant source. The event is consistent with a low-mass stellar lens, although the weak parallax constraint leaves the lens mass and distance uncertain. For KMT-2024-BLG-1522, we compare the results obtained from $V-I$, $I-H$, $V-H$, and $J-H$ color constraints. The microlensing parameters are nearly identical among the four analyses, yielding a robust binary-lens solution with nearly equal masses. However, the inferred source properties and lens physical parameters depend on the adopted source color because the different color estimates imply different angular source radii. Comparing the $(V-I)_{\rm KMT}$ versus $(I-H)_{\rm KMT,PRIME}$ plane shows that the inferred source colors lie off empirical color–color relations but within the scatter of observed stars. The prevalence of such deviations should be tested with a larger sample of KMTNet–PRIME events and this specific case can be further tested with future adaptive-optics follow-up, which can directly measure the lens–source relative proper motion and lens flux.
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All authors Kansuke Nunota, Jennifer C. Yee, Takahiro Sumi, Ryusei Hamada, Ian A. Bond, Andrew Gould, Weicheng Zang, David P. Bennett, Aparna Bhattacharya, Kotaro Daimon, Yuki Hirao, Stela Ishitani Silva, Shuma Makida, Shota Miyazaki, Tutumi Nagai, Seiya Nakayama, Ryo Ogawa, Ryunosuke Oishi, Hideaki Ose, Nicholas J. Rattenbury, Yuki K. Satoh, Daisuke Suzuki, Takuto Tamaoki, Motohide Tamura, Sean K. Terry, Chihiro Ueda, Aikaterini Vandorou, Hibiki Yama, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Hongjing Yang, Dong-Jin Kim, Chung-Uk Lee, Byeong-Gon Park

Earth and Planetary Astrophysics

High-CO2 Climates and Observables in the Outer Habitable Zone

Daria Pidhorodetska, Edward W. Schwieterman, Thomas J. Fauchez et al. (+1 more)

The habitable zone (HZ) is a fundamental concept used to guide our search for temperate exoplanets with stable surface liquid water that would sustain remotely detectable biosignatures. So far, most advanced 3D climate studies and prospective spectral simulations of HZ planets have focused on inner HZ planets that receive stellar radiation similar to Earth and would consequently maintain relatively low (e.g., hundreds of parts per million) atmospheric CO2. Here, we present a systematic investigation of outer HZ (OHZ) planets, which require high CO2 for habitability, using the 3D Generic Planetary Climate Model (PCM). Our 3D climate results are compared with previous 1D predictions that show strong agreement between models. Simulated spectra of the modeled planets indicate that high overlying CO2 levels affect remote signatures of habitability. We also determine substantial spectral differences that would distinguish habitable versus nonhabitable high-CO2 worlds with future direct-imaging observations for solar analogs and with transmission and emission spectroscopy for M dwarfs. Our results demonstrate that 3D models that include CO2 condensation are necessary to understand the potential planetary habitability and spectral impacts of clouds on terrestrial worlds in the OHZ.
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All authors Daria Pidhorodetska, Edward W. Schwieterman, Thomas J. Fauchez, Martin Turbet

Earth and Planetary Astrophysics

A Bayesian Inference Framework for Binary Lens Events Fully Incorporating Higher-Order Effects

Kansuke Nunota and Kento Masuda

Higher-order effects, such as microlensing parallax and lens orbital motion, are essential for characterizing the physical properties of microlensing planetary systems including their masses and distances. In practice, higher-order effects are often included in light-curve modeling only when their signals are strong, because their inclusion in weakly constrained cases tends to drive the inferred parameters toward regions of parameter space that are disfavored by standard Galactic models. This binary choice over physically continuous effects introduces an event-dependent selection function that complicates population-level interpretation and prevents strong and weak detections from being combined within a single uniform framework. In this work, we investigate the origin of instabilities associated with higher-order effects, and show that such instabilities can arise from a mismatch between commonly adopted uninformative priors in the light-curve parameter space and the distributions predicted by Galactic models. Motivated by this, we develop a new Bayesian framework that enables higher-order effects to be incorporated in a stable and uniform manner. As part of this framework, we introduce Galactic Prior Modeling Engine (gapmoe), a dedicated tool that enables efficient evaluation of the Galactic prior density and allows it to be incorporated directly into the light-curve inference. Using simulated events, we demonstrate that our framework robustly recovers the true physical parameters while fully accounting for microlensing parallax and lens orbital motion. This framework eliminates the need for ad-hoc model selection and provides a scalable and statistically consistent pathway for analyzing the large samples expected from next-generation surveys such as the Roman Space Telescope.
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Monday 28 September

Earth and Planetary Astrophysics

Whole-disk Photometric and Colorimetric Phase Curves of Earth with the Clementine Lunar Orbiter

Chase Cooper, Tyler D. Robinson, L.C. Mayorga et al. (+2 more)

The phase curve on a planetary object can reveal key details about its atmosphere and surface, including the presence of surface liquid oceans. Phase curves for Earth can inform the search for habitable surface environments on terrestrial exoplanets, but such phase curves are quite rare. The Clementine lunar orbiter made 3,744 observations of the Earth between February and May of 1994. These observations spanned phase angles between 3.4 and 139.1 degrees. From these data, we produce phase curves of Earth in 5 distinct bands with wavelengths between 400 nm and 1000 nm. We extrapolate fits to the phase curves to derive the geometric albedo of Earth in each filter. We examine the Earth's color as a function of phase angle and find the observed values are best fitted by models that include contributions from ocean glint. We also find a number of observations where contributions from glint are minimal but the disk-integrated color is in line with the glinting model predictions; we propose that this can be explained by the presence of optically clouds on the disk. These findings stress the importance of high-phase Earth observations for high-fidelity Earth models and for future efforts to characterize terrestrial exoplanets via direct imaging.
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All authors Chase Cooper, Tyler D. Robinson, L.C. Mayorga, Jason W. Barnes, Lily Robinthal

Earth and Planetary Astrophysics

Cool, Cloudy Nights on an Ultrahot Neptune: A Panchromatic NIRISS/NIRSpec Transmission Spectrum of LTT 9779 b

Sarah Stamer, Diana Dragomir, Annabella Meech et al. (+13 more)

Studies of planets that reside in the hot Neptune desert allow us to gain insight into how their atmospheres survive the intense flux from their host stars. One such member of that population, LTT 9779 b, is unique in that it has a confirmed atmosphere across various multi-wavelength studies, although results regarding the planet's atmospheric content differ. We present a panchromatic ($\lambda = 0.63 - 5.165$ $\mu$m) JWST transmission spectrum of LTT 9779 b's atmosphere, including a re-reduction of previously obtained NIRISS/SOSS data and a reduction of recent NIRSpec/G395H data. Through atmospheric retrievals, we find muted spectral features consistent with the presence of clouds and a low terminator temperature ($\sim560 \ \mathrm{K}$ for free chemistry, and $\sim910-950 \ \mathrm{K}$ for equilibrium chemistry), with a range of possible atmospheric metallicity values dependent on atmospheric temperature and cloud coverage. Forward modeling suggests that, if clouds are present, small sub-micron particle sizes, moderate-to-high sedimentation efficiency ($f_{\rm sed} = 1 - 3$, corresponding to a relatively compact vertical cloud extent), low particle column densities, and high eddy diffusion coefficients ($k_{zz} \geq 10^{10}$ cm$^{2}$s$^{-1}$) are preferred. Probing silicate cloud absorption features in the mid-infrared is needed to confirm the cloud species, allowing us to break the cloud-metallicity degeneracy that is present in this panchromatic transmission spectrum.
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All authors Sarah Stamer, Diana Dragomir, Annabella Meech, Joshua D. Lothringer, Reza Ashtari, Jonathan Brande, Vivien Parmentier, Ian J. M. Crossfield, Tansu Daylan, Suman Saha, K. Angelique Kahle, Kevin B. Stevenson, David R. Coria, Jared E.J. Splinter, Nicolas B. Cowan, Emma Esparza-Borges

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

PHAROS: Panchromatic spectral energy distributions of solar-like stars across evolutionary stages

Viktor Sumida, Raissa Estrela, Eric Mamajek et al. (+2 more)

Panchromatic stellar spectral energy distributions (SEDs) provide the wavelength-dependent irradiation fields required for studies of exoplanet atmospheres, photochemistry, atmospheric escape, and habitability. We present PHAROS, the Panchromatic Habitable-world Archive of Radiation from Observed Solar-like stars, a first release of fifteen component-traceable SEDs for nearby FGK stars spanning adopted ages of 0.26–6.5\,Gyr. The catalogue covers 0.5–5000\,nm and combines archival XMM-Newton and Chandra high-energy constraints, semiempirical extreme-ultraviolet (EUV) reconstructions, HST and IUE ultraviolet spectra, Gaia DR3 XP and ancillary optical spectrophotometry, and PHOENIX photospheric extensions. When X-ray data support spectral modelling, target-specific coronal plasma models define the high-energy segment and anchor the EUV normalisation; otherwise, empirical high-energy templates are scaled to literature luminosity constraints. Each SED preserves segment-level provenance, distinguishing directly observed intervals from reconstructed components, empirical templates, bridges, and model-derived extensions. The largest diversity occurs at X-ray, EUV, and ultraviolet wavelengths. Younger age-context groups generally show stronger high-energy output relative to their photospheric continua, although the dispersion within each group shows that age alone does not uniquely determine the irradiation environment. PHAROS provides traceable panchromatic irradiation fields for studies of planetary atmospheres, photochemistry, atmospheric escape, forward modelling, retrievals, and interpretation of future direct-imaging observations, including those anticipated for NASA's Habitable Worlds Observatory.
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All authors Viktor Sumida, Raissa Estrela, Eric Mamajek, Pin Chen, Adriana Valio

Earth and Planetary Astrophysics

Binary tidal evolution as a sculptor of circumbinary planet architectures

Mario Sucerquia, Nicolás Cuello and Gaspard Duchêne

Circumbinary planets (CBPs) are expected to form in circumbinary discs and migrate towards the disc inner cavity, often near the binary stability boundary. Yet the observed population is not strictly marginally stable: excluding extreme systems, the typical offset is $\Delta \equiv a_{\rm p}/a_{\rm crit}=1.22^{+0.18}_{-0.07}$, suggesting post-formation evolution may shape present-day architectures. We test whether secular evolution of close binaries can contribute to this displacement. Using high-accuracy $N$-body simulations, we follow coplanar CBPs initially placed near $a_{\rm crit}$ while prescribing binary contraction and eccentricity damping along a track that approximately conserves orbital angular momentum. We quantify how the retreat of $a_{\rm crit}(t)$ affects planetary offsets and survival across binary mass ratios. The moving stability boundary filters the near-boundary population, adding a contraction-driven loss component dominated by ejections. Survivors remain quasi-fossilised, with median changes in $a_{\rm p}$ and $e_{\rm p}$ close to zero and semimajor-axis drifts of only a few per cent. For all valid synthetic survivors, the final offset has median $\Delta_f=1.86^{+0.18}{-0.26}$. Applying the same damping prescription to the observed sample shifts the median from $\Delta{\rm now}=1.22^{+0.18}{-0.07}$ to $\Delta{\rm damp}=1.44^{+0.32}_{-0.10}$. Near-equal-mass binaries undergo stronger filtering, with enhanced ejections and collisions. Binary tidal evolution can therefore shape non-marginal circumbinary architectures. By removing planets close to marginal stability while leaving survivors nearly fossilised, the retreat of $a_{\rm crit}$ can widen the inner gap and increase offsets from the present-day stability boundary. This links binary orbital evolution, dynamical filtering, and transit detectability in a multi-channel interpretation of the CBP desert.
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Earth and Planetary Astrophysics

The Dense, Rocky Core of Haumea Revealed by Satellite Dynamics

Benjamin Proudfoot, Darin Ragozzine, Will Grundy et al. (+2 more)

The icy dwarf planets in the outer solar system are among the most enigmatic bodies known, showing activity ranging from atmospheric resurfacing to possible cryovolcanism. Yet the study of their interiors remains largely theoretical, with few empirical measurements to guide our understanding. The orbits of their moons offer a way to break this deadlock, providing a direct probe of dwarf planet interiors. Here we present a detailed investigation of Haumea's interior derived from the motion of its satellite system. Fitting a new dynamical model to two decades of precise Hubble Space Telescope astrometry, we simultaneously measure Haumea's dynamical oblateness, $J_2$, and the masses of its satellites. Our analysis of the $J_2$ measurement combined with occultation-derived shape models conclusively shows that Haumea has a dense rocky core overlaid with an ice-rich mantle. However, the current dataset is not constraining enough to fully determine the detailed internal structure (core/mantle density, two-layer vs. three-layer, etc.). We do find a slight preference for models where Haumea retains a frozen-in fossil figure, but more data are needed to statistically confirm this. Future observations of the satellite system, as well as observations of stellar occultations, are needed to fully test this hypothesis and should substantially tighten constraints on Haumea's interior. Taken together with other recent evidence for geophysical and geochemical evolution of dwarf planets, our work shows that dense rocky cores and subsurface oceans are likely to be ubiquitous among the trans-Neptunian dwarf planets.
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All authors Benjamin Proudfoot, Darin Ragozzine, Will Grundy, Flavia Rommel, Bryan Holler

Earth and Planetary Astrophysics

Toddlers in Resonance I: low masses and eccentricities of the 17 Myr giant planets HIP 67522 bc from transit timing variations

Hannah R. James, Madyson G. Barber, Andrew W. Mann et al. (+28 more)

Infant ($<$100\,Myr) transiting planet systems provide glimpses into the processes that shape the observed mature planet population. Masses for these planets are powerful data points for testing theories of planet formation and evolution. Because young systems tend to be in mean-motion resonances (MMR) and show higher rates of transit timing variations (TTVs), we can take advantage of deviations in the expected versus observed transit timings due to gravitational interactions between the planets to determine the planetary masses and orbital eccentricities. Here we report the TTV analysis of HIP\,67522, a 17\,Myr two-planet system near a 2:1 orbital resonance. The analysis is based on 55 transit observations (50 epochs) of planet b and 29 transit observations (22 epochs) of planet c, taken across 11 facilities. Assuming circular orbits, we determine masses of $M_b=25.0^{+7.6}_{-7.8}M_\oplus$ and $M_c=11.2\pm1.4M_\oplus$. Allowing for eccentric orbits, we find $M_b=23.1^{+15.4}_{-12.4}M_\oplus$ and $M_c=11.8^{+3.0}_{-2.3}M_\oplus$, and low eccentricities ($<0.1$) for both planets. Adopting a Gaussian prior on $M_b$ from the JWST transmission spectrum tightens the eccentric-solution mass for planet c to $9.7^{+1.9}_{-1.6}M_\oplus$, which is our recommended solution. The low masses and large radii are consistent with a contracting atmosphere planet formation model, such as Gas Dwarf formation. Given the challenge of radial-velocity masses and the high rate of TTVs seen in young systems, TTV-masses will be essential for testing theories of the formation and evolution of super-Earths and sub-Neptunes and determining the conditions that create the most common types of planets in the Galaxy.
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All authors Hannah R. James, Madyson G. Barber, Andrew W. Mann, Pa Chia Thao, Adam L. Kraus, Benjamin M. Tofflemire, Andrew Vanderburg, Lyu Abe, Tristan Guillot, Olga Suarez, Djamel Mekarnia, Amaury H. M. J. Triaud, Vincent Deloupy, Mayuko Mori, Jerome P. de Leon, Norio Narita, Akihiko Fukui, John H. Livingston, George Zhou, Camille M. L. Guenée, Juliette Becker, Ana Isabel Lopez Murillo, Karen A. Collins, Richard P. Schwarz, Chris Stockdale, Thiam-Guan Tan, Keith Horne, Leah J. Boff, Mackenna L. Wood, Nidia Morrell, Luke G. Bouma

Earth and Planetary Astrophysics

GameDev: GPU-accelerated model for dust evolution

Jiaqing Bi

Grain growth and fragmentation through dust collisions in protoplanetary disks are strongly coupled with dust dynamics. This is because the spatial and velocity distributions of dust set the collision rates and outcomes, while dust grain sizes set the aerodynamic coupling with gas. However, existing dust evolution codes often rely on prescribed dust velocities and are mostly restricted to one or two spatial dimensions. In this work, we present GameDev, a dust evolution model accelerated by graphics processing units (GPUs) that couples independently evolved three-dimensional dust dynamics with Monte Carlo collisional evolution of dust. In GameDev, we model dust as Lagrangian representative particles in a prescribed gas disk. We integrate particle trajectories with the staggered semi-analytic method, which remains accurate for both tightly and weakly coupled dust grains. We estimate collision rates from each particle's nearest neighbors rather than on a grid, preventing physically close particles from being excluded from collision sampling because they lie across a grid boundary. Most importantly, we sample collision events against neighborhoods that remain frozen over adaptive intervals, enabling massive parallelization across particles. These implementations make GameDev an accurate and efficient tool for studying dust evolution in protoplanetary disks. GameDev supports both NVIDIA CUDA and AMD ROCm platforms, provides a smaller-scale standalone Eulerian dust fluid model, and is publicly available on GitHub.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

SIFARI: Self-Supervised Interferometric Fitting for Astronomical Radio Imaging

Shunyuan Mao, Andrea Isella, Paris Perdikaris et al. (+2 more)

Radio-interferometric images are reconstructed from sparsely sampled visibilities, and CLEAN-based imaging can struggle with spatial filtering, complex morphologies, and uncertainty quantification. Alternative methods that fit visibilities directly can address some of these limitations but often require manual choices of image priors and model hyperparameters. We present SIFARI (Self-Supervised Interferometric Fitting for Astronomical Radio Imaging), a self-supervised neural network workflow that represents sky brightness as a continuous function of position and fits measured visibilities without an external image training set or explicit spatial regularizer. An empirical rule sets the Fourier feature scale from the visibilities before training, controlling how readily the network fits fine structure. Sampling network weights with Stochastic Weight Averaging-Gaussian (SWAG) gives approximate brightness uncertainty estimates, which we combine with a thermal-noise floor to construct spatially resolved signal-to-noise maps. In synthetic ALMA tests, SIFARI yields an effective point-source response about eight times narrower than the natural-weighting CLEAN restoring beam and recovers more extended flux than CLEAN when short baselines are missing. It also achieves higher image fidelity than the restored CLEAN images in all three morphology benchmarks. Applied to ALMA observations of PDS 70, SIFARI recovers the bright outer ring together with faint compact emission in the central cavity. For long-baseline-only WISPIT 2 data, SIFARI supplies a sky model for phase self-calibration where the CLEAN model is inadequate. The restored, self-calibrated SIFARI image has approximately 30% lower RMS noise than the CLEAN image made from the original visibilities without self-calibration.
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All authors Shunyuan Mao, Andrea Isella, Paris Perdikaris, Li-Ta Lo, Hui Li

Earth and Planetary Astrophysics

A temperate sub-Neptune transiting the M4 Dwarf TOI-210 identified by NIRPS and TESS – Uncovering hidden M-dwarf planetary systems in the near-infrared

C. Cadieux, B. N. Skinner, F. Bouchy et al. (+63 more)

Super-Earths and sub-Neptunes dominate the exoplanet population, yet their compositions, formation mechanisms, and capability of retaining atmospheres remain poorly understood. M-type stars offer a unique opportunity to investigate these questions, thanks to their favorable planet-to-star radius and mass ratios and the diversity of planetary systems they host. We aim to characterise the planetary system of the M4 dwarf TOI-210, in which TESS during its primary mission identified one transiting exoplanet candidate at $P= 9.01$ days. We combine multi-technique observations, including transits from 40 sectors of TESS and ground-based follow-up with LCOGT and ExTrA, and radial velocities (RV) from NIRPS obtained as part of its Guaranteed Time Observations program. These data were analysed using a Bayesian framework to constrain stellar, planetary, and orbital parameters. We confirm TOI-210 b, a temperate sub-Neptune ($T_{\rm eq} = 368 \pm 9$ K) with a mass of 6.75 $\pm$ 1.25 M$_{\oplus}$ and a radius of 2.234 $\pm$ 0.074 R$_{\oplus}$. Its bulk density implies a volatile-rich composition, either as an extended H/He atmosphere with mass fraction of approximately 1% (gas dwarf), a substantial water reservoir comprising at least 29% of the mass (2$\sigma$ lower limit; water world), or a mixture of both. The NIRPS RVs show moderate evidence ($\Delta \ln Z = 5.9$) for at least one non-transiting exoplanet interior to TOI-210 b. In a targeted search, we identify two Keplerian signals at 2.15 and 3.76 days, with minimum masses of 3.2 $\pm$ 0.8 M$_{\oplus}$ and 4.4 $\pm$ 1.0 M$_{\oplus}$, respectively, that provide a plausible explanation for the observed RV variations. If these signals are planets, the absence of transits in the TESS photometry implies mutual inclinations with TOI-210 b above 2.3-3.5$^{\circ}$.
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All authors C. Cadieux, B. N. Skinner, F. Bouchy, E. D. Gillis, V. Bourrier, R. Doyon, L. Y. Messamah, B. L. Canto Martins, A. L'Heureux, Y. S. Messias, J. M. Almenara, A. K. Stefanov, X. Bonfils, K. A. Collins, H. M. Relles, C. Rodríguez, P.-A. Roy, A. Shporer, G. Srdoc, S. Taylor, C. Ziegler, R. Allart, K. Al Moulla, É. Artigau, F. Baron, S. C. C. Barros, F. Bélanger, B. Benneke, M. Bryan, T. Ciolak, R. Cloutier, N. J. Cook, N. B. Cowan, E. Cristo, L. Dang, J. R. De Medeiros, X. Delfosse, E. Delgado-Mena, X. Dumusque, D. Ehrenreich, D. O. Fontinele, T. Forveille, J. Gagné, M. J. Hobson, P. Lamontagne, I. C. Leão, R. de Lima Gomes, C. Lovis, L. Malo, C. Melo, L. Mignon, C. Mordasini, N. Nari, L. Parc, R. Rebolo, R. Rosener, J. Rowe, N. C. Santos, D. Ségransan, A. Srivastava, A. Suárez Mascareño, S. Udry, D. Valencia, G. Wade, J. P. Wardenier, D. Weisserman

Earth and Planetary Astrophysics

Correcting stellar contamination in transmission spectroscopy with contemporaneous monitoring: Application to GJ 1214 b

Ò. Porqueras-León, M. Perger, J. C. Morales et al. (+19 more)

Transmission spectroscopy has emerged as an essential tool for characterising the atmospheres of transiting exoplanets. However, stellar surface inhomogeneities contaminate transmission spectra, posing a major challenge to high-precision observations such as those from the James Webb Space Telescope (JWST). We develop and apply methods to correct for stellar contamination, improving the accuracy of exoplanet atmospheric characterisation. We obtained coordinated multi-band photometry and high-resolution spectroscopy around JWST observations of GJ 1214 b and applied two frameworks: (i) a StarSim inversion, which infers stellar activity parameters from the monitoring data and propagates them to corrections; and (ii) UnSPOTTER, in which neural networks trained on StarSim simulations learn the mapping from monitoring data to corrections. Both frameworks agree within uncertainties and indicate that the JWST observations of GJ 1214 occurred at a favourable rotation phase with low stellar contamination. For UnSPOTTER, the inferred corrections can be constrained at approximately 15 ppm across the JWST wavelength range, implying post-correction residuals of the same order. If the same system were observed near activity maximum, the predicted contamination would be strongly chromatic and affect atmospheric retrievals, highlighting the importance of coordinated monitoring and robust activity correction techniques. The two approaches are complementary but serve different roles. The inversion yields physically interpretable parameters and surface maps, whereas UnSPOTTER marginalises over surface-configuration degeneracies and provides tighter predictive corrections within its validated simulation domain. Our pipeline can be generalised to other active stars: with multi-band and multi-technique monitoring around JWST visits, it can provide activity forecasts for scheduling and activity corrections.
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All authors Ò. Porqueras-León, M. Perger, J. C. Morales, I. Ribas, J. Blanco-Pozo, H. Tabernero, E. Herrero, E. Pallé, H. Parviainen, F. Murgas, C. Rodríguez-López, P. H. Hauschildt, A. Schweitzer, N.-E. Nèmec, D. Baroch, N. R. C. Gomes, G. Anglada-Escudé, J. Aceituno, N. Narita, A. Fukui, M. Mori, Y. Smolyarova

Earth and Planetary Astrophysics

K-dwarf starspot hunters: how to directly characterize spot and faculae properties with UV-IR panchromatic transit spectra

Joanna K. Barstow, Caitlyn Cullen, Yvonne Unruh et al. (+7 more)

Transmission spectroscopy of exoplanets provides an important window into their atmospheric composition, structure and dynamics, especially in the JWST era. As the quality of the observational data and therefore the precision of our constraints improves, we become increasingly sensitive to sources of systematic bias in our models and observations. One significant example of this is the Transit Light Source Effect, in which heterogeneous features in the stellar photosphere - spots and faculae - imprint additional spectral signatures onto exoplanet transmission spectra. The effects of this stellar contamination must be accounted for or removed in order to accurately recover the planet's atmospheric properties. Including parameterized models of spots and faculae within spectral retrieval analysis is increasingly adopted as a solution to this problem, but is limited by the accuracy of models of stellar spectra. In this paper, we outline an observational strategy combining simultaneous data from JWST and the Hubble Space Telescope that would enable us to further constrain these models. We perform synthetic retrievals to demonstrate how we could constrain starspot and faculae parameters; we test the impact of using different model spectra in the retrieval; and we consider the impact of variable stellar activity on coadding transits to achieve the desired signal-to-noise. We find that ultraviolet and optical wavelengths are key for breaking degeneracies between stellar contamination and planetary parameters.
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All authors Joanna K. Barstow, Caitlyn Cullen, Yvonne Unruh, Hannah Wakeford, Eva-Maria Ahrer, Lili Alderson, Charlotte Fairman, Ulrich Kolb, Nikole Lewis, Cinta Vidante

Earth and Planetary Astrophysics

JWST NIRSpec G395H Transmission Spectra of Two Similar Sub-Neptunes in the TOI-125 System

Yiwei Chai, Néstor Espinoza, Chloe Fisher et al. (+10 more)

The James Webb Space Telescope (JWST) has enabled the first in-depth characterisations of sub-Neptune atmospheres, revealing a diversity of chemical compositions and cloud properties that challenge current models. Multi-planet systems provide an opportunity to compare planetary atmospheres while controlling for formation conditions within the same protoplanetary disk. We present JWST NIRSpec G395H 3-5 um observations of two similarly-sized sub-Neptunes orbiting a sun-like star within the TOI-125 system: TOI-125 b ($P=4.65$ d, $R_p=2.7~R_\oplus$, $M_p=10~M_\oplus$, $T_\mathrm{eq}=1100$ K) and TOI-125 c ($P=9.15$ d, $R_p=2.85~R_\oplus$, $M_p=6.8~M_\oplus$, $T_\mathrm{eq}=825$ K), comprising of one full transit of TOI-125 b but only 70% of TOI-125 c's transit due to larger than predicted TTVs. We obtain precise R~100 transmission spectra for both planets, with median errorbars of 50 ppm for TOI-125 b and 85 ppm for TOI-125 c. Atmospheric retrievals are compatible with a ~150x solar metallicity atmosphere or clouds above ~3 mbar for TOI-125 b, and a ~100x solar metallicity atmosphere or clouds above ~10 mbar for TOI-125 c. Our results may support recent evidence for metal enrichment in sub-Neptunes, while also further complicating the proposed trend in atmospheric feature size with planet temperature. However, shorter wavelength follow-up observations of both planets are needed to establish whether their spectra are truly muted or feature-rich, with implications for the nature of sub-Neptunes around sun-like stars.
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All authors Yiwei Chai, Néstor Espinoza, Chloe Fisher, Erik Meier Valdes, Matthew Hooton, Brett Morris, Natalie H. Allen, Adam J. Burgasser, Brice-Olivier Demory, Amélie Gressier, Kevin Heng, Mercedes López-Morales, Meng Tian

Earth and Planetary Astrophysics · Cross-listed from physics.space-ph

Spectral Properties of Solar Wind Charge Exchange from Earth's Magnetospheric Boundaries: MHD and Test Particle Simulations

A. Ramachandran, R. T. Desai, H. L. Norman et al. (+6 more)

The Solar Wind Charge Exchange (SWCX) mechanism, where X-rays can be generated through interactions between heavy, highly charged solar wind ions and neutral atoms, offers an opportunity to observe the large-scale transfers of energy and momentum through the Sun-Earth system. In this study, we simulate SWCX signatures from Earth's outer boundaries using Gorgon global magnetohydrodynamic (MHD) simulations combined with kinetic particle-based simulations which we call the X-ray Imaging of the Magnetosphere (XIM) framework. The XIM-predicted emissivities agree with the predictions of the MHD model, producing enhanced emissions from the magnetosheath and cusp regions, but several differences are apparent. Compared with MHD, XIM shows enhanced structuring in the magnetosheath and notable enhanced emissions along the magnetopause associated with betatron acceleration. The results also evidence species-specific spatial variations, which are shown to vary compared to anticipated relative abundances in the solar wind and ion-specific properties. These simulations provide new insights into the underlying dynamics of SWCX at the Earth's outer boundaries, which can be used to understand what might be observed using X-ray observatories in space, such as the recently launched SMILE mission.
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All authors A. Ramachandran, R. T. Desai, H. L. Norman, Y. Tong, D. Bewicke, S. Nitti, J. A. Carter, J. P. Eastwood, J. P. Chittenden

Earth and Planetary Astrophysics

Surveying exogenous species in Saturn with ALMA. II. Detecting and Mapping HCN

T. Fouchet, T. Cavalié, R. Moreno et al. (+3 more)

Several external sources (the rings, the satellites, cometary impacts, interplanetary dust particles) supply material to the upper atmosphere of Saturn. The signature of this external influx has been documented on the ionospheric electronic and ionic densities, and in the stratosphere on oxygenated molecules (CO, CO2, H2O). We search for the chemical signature of the external sources in nitrogen-bearing species in Saturn's stratosphere. We have targeted the HCN(4-3) rotational line and mapped its emission line at the planet limb with ALMA in 2018 with configuration C43-3, providing a synthetic beam of 0.61"x0.50". HCN was detected at all observable latitudes from 20{\deg}S to 60{\deg}N. The HCN abundance was measured at two independent pressure levels, 0.1 and 1 hPa. The measured volume mixing ratios are latitudinally uniform within uncertainties at both pressure levels. The mean vmr is $(7\pm 2)\times 10^{-11}$ and $(4\pm 1)\times 10^{-12}$ at 0.1 and 1 hPa respectively. This corresponds to a mean column-density of $(4\pm 1)\times 10^{12}$ cm$^{-2}$, and a total nitrogen mass of $(3.7 \pm 0.9)\times 10^{10}$ g. The steep vertical profile suggests that another loss mechanism, possibly sticking or heterogeneous chemistry on aerosols, is active besides photodissociation. The huge influx of material detected in the ring plane by Cassini left no detectable chemical signature on HCN. The detected HCN mass seems compatible with several sources: the ring rain at mid-latitudes, Enceladus, or an old cometary impact. The detected HCN could also be a chemical product of internal N2 transported from the deep atmosphere up to the stratosphere.
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All authors T. Fouchet, T. Cavalié, R. Moreno, S. Guerlet, E. Lellouch, D. Bardet

Earth and Planetary Astrophysics

Planetesimal formation facilitated by streaming instability in weak pressure bumps

Magnus S. Sørensen-Taylor, Anders Johansen and Troels Haugbølle

Planetesimal formation via the streaming instability of small pebbles in protoplanetary discs requires enhanced solid concentrations relative to the solar metallicity, $Z\simeq 0.01$. We investigate here whether pile-ups in weak axisymmetric pressure bumps are sufficient to trigger strong particle concentrations via the streaming instability. Using high-resolution 2D shearing box simulations with millimetre-to-centimetre pebbles, we explore the behaviour of the streaming instability in the presence of a non-reinforced pressure bump. We find that even very weak bumps, with gas density amplitudes as low as $A = 0.04$ relative to the background, produce dense particle filaments via the streaming instability for all tested Stokes numbers at solar metallicity in the inner disc. Outer disc regions require slightly stronger bumps ($A \geq 0.14$) to form filaments at a solar metallicity, though the necessary bump amplitude is substantially lowered when the metallicity is increased to $Z = 0.02$. Our results suggest that weak, non-reinforced pressure bumps can act as focal points for planetesimal formation via the streaming instability in small pebbles, in contrast to previous studies which used reinforcement to maintain the pressure bump. Additionally, we introduce a pressure-bump-dependent clumping criterion, $(Z/\chi)_\mathrm{crit} \approx 0.3$, where $\chi = \Pi_\mathrm{min}^2/\Pi_0$ reduces to the background pressure gradient $\Pi_0$ in the absence of a pressure bump. This criterion encapsulates the scale of solid pile-ups at lower pressure gradients and accurately predicts the onset of strong clumping based on the results of our simulations. With pressure bump signatures being common features of observed young discs and magnetohydrodynamical simulations, the results of our 2D simulations imply that weak pressure bumps may be major cradles for planetesimal formation in protoplanetary discs.
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Earth and Planetary Astrophysics

Activity in White Dwarf Debris Disks II: WISE Mission Traces a Decade of Disk Evolution and Persistence

Hiba Tu Noor, Jay Farihi and Scott J. Kenyon

This study presents multi-epoch photometry from the Wide-field Infrared Survey Explorer to investigate variability in white dwarf debris disks, utilizing the full 14.5 yr mission datasets pre- and post-cryogen. Unambiguous variations are detected across the bulk of the 52 confirmed dusty white dwarfs and are consistent with universal variability after correcting for the sensitivity of WISE relative to Spitzer. Some disk light curves exhibit trends such as possible oscillations, sudden brightening, and steadily decaying fluxes, but all infrared excesses persist utterly. On baselines longer than 0.5 yr, flux changes are significantly skewed toward decreases, in contrast to the symmetric distribution found at shorter baselines with Spitzer, consistent with gradual dust depletion over time. Disk emission generally becomes redder when dimmer and bluer when brighter, consistent with changes in the grain size distribution following collisions, although five disks exhibit the opposite trend possibly due to dust production near apastron. A moderate positive correlation is observed between disk luminosity and photospheric Ca abundance, consistent with the accretion of disk material in an optically thin configuration. Taken together with the Spitzer legacy of dusty white dwarfs, these results provide a comprehensive view of debris disk variability and provide empirical constraints on models of disk structure and evolution.
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Earth and Planetary Astrophysics

The precipitation of protons and electrons in Jupiter's auroral regions: a statistical comparison based on Juno/JEDI data

B. Benmahi, N. André, V. Hue et al. (+8 more)

Energetic electrons dominate the energy precipitated into Jupiter's auroral regions, but protons precipitate along the same field lines, with a contribution that remains poorly constrained. We statistically compare the precipitating energy flux of protons and electrons in two of Jupiter's auroral sub-regions, the polar (PE) and main (ME) emission regions. We use Juno/JEDI data from PJ3 to PJ66. The magnetic footprint of the spacecraft, computed with the JRM33 and CON2020 field models, is assigned to one of the two sub-regions, and the precipitating energy flux of each species is obtained by integrating over the loss cone the mean differential intensity measured within it. In both sub-regions, the median proton energy flux is 52 to 223 times lower than that of the electrons, and the total precipitated proton power is less than 2% of the electron power. Proton fluxes are broadly distributed across the sub-regions, with higher values in the ME than in the PE. Protons play a secondary role in Jupiter's auroral energy budget, radiating an estimated 5 to 9 GW in the UV per sub-region, pending a dedicated proton transport modelling. Their Doppler signature in the red wing of the Lyman-$\alpha$ line, undetected by HST and difficult to access with Juno/UVS, is a key observable for the upcoming Juice and Europa Clipper missions.
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All authors B. Benmahi, N. André, V. Hue, Z.-Y. Liu, G. Gronoff, B. Mauk, B. Bonfond, T. Stallard, M. Blanc, M. Devinat, M. Barthélémy