Peer Revenue Publish or profit

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Thursday 8 October

Earth and Planetary Astrophysics

Dust-driven vertical shear instability in an isothermal shearing box: I. Turbulence and gas dynamics without dust feedback

Jip Matthijsse, Hossam Aly, Sijme-Jan Paardekooper et al. (+1 more)

The classical vertical shear instability (VSI) is a baroclinic instability that arises from height-dependent azimuthal velocities and is a leading candidate for driving anisotropic turbulence in discs with extended vertical modes. The classical VSI requires fast cooling times and radial temperature gradients, which are absent in an isothermal stratified (barotropic) setup. We investigate the dust-driven vertical shear instability in an isothermal, stratified shearing box, where the VSI is generated by drag forces acting on the gas due to dust rather than radial thermal stratification. We construct two-fluid (gas+dust) vertically stratified equilibria including dust diffusion and use these profiles to initialise 2D (radial-vertical) hydrodynamical simulations with FARGO3D. To separate dust-driven vertical shear instability (DVSI) from drag instabilities, we employ a dust-analogue model in which dust-induced drag on the gas is prescribed as a time-invariant and height-dependent acceleration, such that the underlying spatial distribution of the dust is assumed to be constant. The DVSI grows from regions of strongest vertical shear away from the midplane, exciting predominantly radially short, vertically extended disturbances (large k_x/k_z) and producing banded structures in the perturbed azimuthal and vertical velocities during the linear phase. In the nonlinear regime, the instability saturates via a Kelvin-Helmholtz-like parasitic instability that breaks the coherent vertical-shear modes into smaller-scale eddies, which balance the growth of the vertically extended modes, driving sustained vertical stirring. Dust-driven vertical shear can drive anisotropic turbulence and vertical mixing in an isothermal model without invoking global thermal gradients and could play an important role in the stratified streaming instability.
Read the full abstract

All authors Jip Matthijsse, Hossam Aly, Sijme-Jan Paardekooper, Richard P. Nelson

Earth and Planetary Astrophysics

The Fast & Fourier: Using neural operators to speed up radiative modeling of protoplanetary disks

Lukas Welzel and Melissa K. McClure

Edge-on protoplanetary disks provide a spatially resolved view of the vertical distribution of icy planetary building blocks, but inferring their relative abundances requires radiative-transfer (RT) modeling with multiple anisotropic scattering. Each model costs $10^{1}$-$10^{3}$ CPU hours, which precludes principled Bayesian inference and homogeneous, population-scale analyses. We develop and validate a fast and reusable surrogate for Bayesian inference with ice-bearing edge-on disk models. We train a Fourier Neural Operator on a grid of RADMC-3D spectra. The network maps disk parameters and analytic physical input fields to the spectrum, using mixed-resolution spectra. We use the surrogate in an explicit-likelihood nested sampler and validate it on held-out simulations and synthetic recovery tests with TARP coverage. Finally, we use it to retrieve the disk structure and ice abundances of ESO-H$\alpha$ 569 from its spectral energy distribution. The surrogate reproduces the RADMC-3D spectra with a median error of 4.84%. We recover synthetic parameters without detectable bias and with nominal coverage. For ESO-H$\alpha$ 569, the posterior favors a massive ($M_{\rm gas}=0.028^{+0.015}_{-0.011}\,M_\odot$), nearly edge-on ($i=79.8^{+5.2}_{-2.4}$ deg) disk consistent with the image-plus-SED model of Wolff et al. (2017). Its ice abundances and cavity size remain weakly constrained by broadband data alone. The marginal spectrum-evaluation speed-up is $\sim10^{9}$-$10^{10}$. Neural-operator emulation makes full posterior inference feasible within the adopted model and training prior. Key posterior points should still be checked with high-fidelity RT models. By drastically cutting evaluation time, this approach enables for the first time homogeneous population studies of ices in disks, which new JWST surveys can capitalize on to map the range of compositions within planetary nurseries.
Read the full abstract

Earth and Planetary Astrophysics

"Mega-Earths" are likely an artifact of stellar activity

Casey L. Brinkman and Nicolas Cowan

Empirical relations and planet formation simulations suggest an upper mass limit for rocky planets of $\sim$10M$_{\oplus}$, as cores above this will almost certainly undergo runaway gas accretion. Nevertheless, a small number of planets appear to have densities consistent with rocky Earth-like compositions above this threshold, indicating that unusual formation and evolutionary scenarios are capable of producing extremely massive rocky planets called "Mega-Earths." However, all of these planets orbit active stars with log$R'_{HK}$ $>$-4.75. We find a <1$\%$ probability that all literature ultra-massive rocky planets would coincidentally orbit such active stars, and find no astrophysical reason to expect Mega-Earths to preferentially form around active stars. We therefore conclude that Mega-Earths are artifacts of stellar activity, and we question the reliability of Gaussian Processes to enable mass measurements for rocky planets around active stars.
Read the full abstract

Earth and Planetary Astrophysics

The accretionally heated atmospheres of protoplanets and brown dwarfs

Nick Choksi, Peter Gao, Jerry Xuan et al. (+2 more)

The ranks of accreting planets and brown dwarfs are growing. To help interpret their spectra, we study how accretion affects a planet's atmosphere. The atmosphere is irradiated from above by whatever nonthermal radiation from the accretion shock does not directly escape into space. This accretional heating drives a temperature inversion. Even relatively slow accretion, corresponding to mass doubling times longer than system ages, can raise temperatures by many hundreds of Kelvin at ambient pressures of order millibars. The heated atmosphere radiates an optical/infrared excess. For environments that are not too dusty, the excess concentrates in molecular lines that trace the heated layer. Thus an accretionally heated atmosphere may be distinguished by its muted absorption bands. Irradiation from the accretion shock also changes the chemical composition of the atmosphere, further altering spectra. Atmospheric retrievals promise to map out the deposition of accretional energy, helping to decide between ”hot” and ”cold” start modes of planet formation.
Read the full abstract

All authors Nick Choksi, Peter Gao, Jerry Xuan, William Balmer, James Mang

Earth and Planetary Astrophysics

Longitudinal distribution of Io's dayside atmospheric density

R. S. Giles, J. R. Spencer, T. K. Greathouse et al. (+3 more)

Since 2001, we have used the TEXES high resolution mid-infrared spectrograph at NASA's Infrared Telescope Facility to study the density of Io's SO$_{2}$-dominated atmosphere. The spectra cover several SO$_{2}$ absorption lines near 530 cm$^{-1}$ and are used to retrieve the equatorial SO$_{2}$ column density. In addition to covering a long time period, our 191 independent observations also cover the full range of Io central longitudes, allowing us to study the longitudinal variability of Io's dayside atmosphere in more depth than has previously been possible. By improving our modeling of longitudinal variability and using a seasonal model to apply a temporal normalization to the retrieved SO$_{2}$ densities, we produce two complete longitudinal distributions of Io's equatorial SO$_{2}$ column abundances, one representing perihelion and one representing aphelion. Both show the same hemispheric asymmetry that has been observed in previous studies, with the highest densities near 200W and the lowest densities near 305W. We find that the contrast between the maximum and minimum densities is a factor of ~27 at aphelion and a factor of ~16 at perihelion. Both longitudinal distributions are asymmetric, with a sharper drop-off on Io's trailing hemisphere than on the leading. We compare these longitudinal distributions to the distributions expected if the spatial variability were primarily driven by volcanic activity, SO$_{2}$-ice inhomogeneity or the effects of eclipses. We conclude that the effect of eclipses is important, but insufficient to explain the shape of the observed longitudinal variability, and frost distribution is likely to also be important.
Read the full abstract

All authors R. S. Giles, J. R. Spencer, T. K. Greathouse, C. C. C. Tsang, E. Lellouch, M. A. López-Valverde

Earth and Planetary Astrophysics

Gen-EBM: an energy balance model for terrestrial planets. Climate multistability from snowball to post-runaway greenhouse climates

Siddharth Bhatnagar, Emeline Bolmont, Maura Brunetti et al. (+6 more)

Climate multistability and tipping points are fundamental properties of planetary climates that depend sensitively on climate feedbacks. We introduce the Geneva Energy Balance Model (Gen-EBM), a new 1-D latitudinal EBM for rapid exploration of terrestrial planet climates, and use it to investigate how planetary rotation, eccentricity, and thermal inertia shape climate attractors and multistability. Gen-EBM is implemented in Rust and builds on previous exoplanet EBMs by incorporating a temperature-dependent outgoing longwave radiation prescription spanning Earth-like, runaway-onset, and post-runaway greenhouse regimes. We construct bifurcation diagrams from ensembles of simulations and explore the effects of rotation rate, orbital eccentricity under the mean-flux approximation, and surface thermal inertia. Including post-runaway greenhouse states substantially enlarges the parameter space over which multiple climate states coexist. Within our model framework, slow rotators approach the spatially homogeneous limit and maintain broader temperate stability ranges, whereas fast rotators develop strong equator-to-pole temperature gradients that narrow the temperate branch. Under the mean-flux approximation, increasing eccentricity enhances climate variability and can alter the attractor structure itself. The critical eccentricity at which temperate climates disappear depends strongly on thermal inertia, with ocean-rich planets remaining stable to larger eccentricities than land-dominated planets. Gen-EBM therefore broadens rapid parameter-space exploration to climates spanning temperate, runaway-onset, and post-runaway regimes. Its computational efficiency and flexibility make it a valuable bridge between simple climate models and 3-D general circulation models.
Read the full abstract

All authors Siddharth Bhatnagar, Emeline Bolmont, Maura Brunetti, Jérôme Kasparian, Tim Kallioinen, Marine Leyvraz, Guillaume Chaverot, Yonatan Birhanu Haile, Dóra Takács

Earth and Planetary Astrophysics

Size, Shape, and Geometric Albedo of Dwarf Planet Quaoar's Largest Satellite Weywot

Cameron Collyer, Estela Fernandez-Valenzuela, Benjamin Proudfoot et al. (+3 more)

The small satellites of dwarf-planet size worlds in trans-Neptunian space are thought to be produced through giant impacts, and are typically observed to have bright water-ice-dominated surfaces. Here we focus on Quaoar's small primary satellite, Weywot. We build on previous work by re-analyzing the June 2023 stellar occultation by Weywot using results from 11 orbits of HST imaging with the Wide Field Camera 3. Weywot's rotational lightcurve was constrained along with its independent photometric phase curve, which we used to obtain more robust measurements of Weywot's size, shape, and geometric albedo. We found Weywot's volume-equivalent radius to be req = 73+-5 km, with principal axes a = 82+5-3 , b = 73+5-3, c = 65+8-12 km, indicating a triaxial shape. This shape is consistent with a Roche-ellipsoid rubble-pile interpretation requiring only moderate internal friction at Weywot's current semimajor axis, and Weywot can retain this shape down to Quaoar's co-rotation radius. We also found Weywot's geometric albedo to be quite low, pV = 0.036+0.010-0.006, akin to that of Eris's satellite Dysnomia, but over an order of magnitude lower than Pluto's minor satellites and Haumea's satellites. We propose this may indicate that Weywot's ice-mass fraction < 100%, and that Weywot is not sourced from the water-ice mantle of a differentiated pre-impact progenitor as suggested for Pluto's minor satellites and Haumea's satellites.
Read the full abstract

All authors Cameron Collyer, Estela Fernandez-Valenzuela, Benjamin Proudfoot, Bryan J Holler, Jose Luis Ortiz, Ishan Sharma

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

Metallicity does not reorder line-to-line sensitivity to granulation in solar-like stars

Dušan Vukadinović, Sowmya Krishnamurthy, Valeriy Vasilyev et al. (+2 more)

Stellar granulation imprints line-dependent wavelength shifts and profile variations that limit the precision of radial velocity (RV) measurements used for exoplanet detection and characterization. Understanding how the sensitivity of individual spectral lines to granulation depends on stellar parameters is therefore essential for mitigating granulation-induced RV signals. Here, we investigate the effect of metallicity using MURaM 3D magnetohydrodynamic simulations of stellar granulation including a small-scale dynamo for metallicities $\mathrm{M/H}=\{-1.0,-0.5,0.0,0.3,0.5\}$. We synthesize spectra of neutral and ionized lines spanning a broad range of lower excitation potentials and transition probabilities using the MPS-ATLAS code, assuming local thermodynamic equilibrium. We quantify the sensitivity to granulation using the continuum-intensity-weighted standard deviations of the line centre-of-gravity wavelength and equivalent width, denoted by $\sigma_\lambda$ and $\sigma_W$, respectively. Both metrics increase systematically with metallicity at disc centre owing to the combined effects of more vigorous convection and metallicity-dependent changes in the line opacity. We find that the correlation between the solar ($\mathrm{M/H}=0.0$) and non-solar sensitivity metrics remains high from the disk center to the stellar limb. This indicates that the relative ordering of line sensitivities is robust against changes in viewing angle and metallicity. Consequently, line masks calibrated on the solar spectrum can be reliably applied to radial-velocity measurements of stars with non-solar metallicities, provided they have solar effective temperature and surface gravity.
Read the full abstract

All authors Dušan Vukadinović, Sowmya Krishnamurthy, Valeriy Vasilyev, Veronika Witzke, Andrew Collier Cameron

Earth and Planetary Astrophysics

Gravitational Microlensing

Aikaterini Vandorou and Stela Ishitani Silva

Gravitational microlensing is a unique planet-detection method that does not rely on detecting light from the host star or planet. Instead, planets are discovered when their gravitational field perturbs the light coming from a distant source. The mechanics of this method offer several advantages. It has the ability to detect wide-orbit planets of various masses around host stars of different types, at and beyond the system's snow line. Thus, microlensing complements the other detecting techniques that are more sensitive to close-orbit or high-mass planets. In this Chapter, we review the microlensing method and discuss how the physical properties, such as mass and distance, can be extracted from the microlensing light curve or from additional high-angular resolution observations. Microlensing is essential for the broader context of exoplanet demographics, as it can place constraints on planets, in wide orbits, beyond the snow line. Studying this parameter space can help us unravel the details of planet formation and how our own Solar System formed. Lastly, we provide an example of how to model a light curve and obtain accurate physical parameters for the host and planet.
Read the full abstract

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

Gaseous SiO and Silicate Clouds in Three Benchmark Early-L Dwarfs

Zhijun Tu, Shu Wang, Xiaodian Chen et al. (+2 more)

Tracing silicon from gaseous SiO into silicate condensates provides a direct view of the condensation process that forms silicate clouds in L-dwarf atmospheres. Here we present evidence for gaseous SiO in three benchmark early-L dwarfs, HD 89744B, GJ 1048B, and LSPM J0632+5053B, using JWST/NIRSpec and MIRI spectroscopy. Atmospheric retrievals with and without SiO under multiple cloud prescriptions identify the strongest SiO signatures at 4.0–4.2 and 7.7–8.2 $\mu$m, with the local likelihood diagnostic reaching $4.6\sigma$. In the physical cloud retrievals, the 8 $\mu$m band probes lower pressures than the 4 $\mu$m overtone, reaching atmospheric layers where equilibrium SiO is more strongly depleted by silicate condensation. All three objects also show compact Fe opacity at pressures of a few bar. Their inferred gas-phase C/O ratios are consistent with expectations from the host-star compositions after accounting for refractory oxygen sequestration. Within the adopted Mie treatment of amorphous silicate grains, the silicate mineralogies favor Mg$_2$SiO$_4$ for HD 89744B and a mixed Mg$_2$SiO$_4$+MgSiO$_3$ cloud for GJ 1048B. Extending this framework to cooler L dwarfs will trace the coupled evolution of gaseous SiO depletion and silicate-cloud formation along the L-dwarf sequence.
Read the full abstract

All authors Zhijun Tu, Shu Wang, Xiaodian Chen, Haomiao Huang, Jifeng Liu

Wednesday 7 October

Earth and Planetary Astrophysics

Stochastic Snowball States in Planetary Climate

Duc Thach Son Vu and John S. Wettlaufer

Motivated by the recent finding of Ji and Abbot (2025) that at moderate eccentricity (0.2–0.3) the planetary Snowball bistability vanishes, we have introduced stochasticity of the orbital eccentricity into a simplified version of the energy balance model of Eisenman and Wettlaufer (2009) to study a general Earth-like planet. The stochastic eccentricity is approximated by two dominant time scales, annual and daily, and is introduced through an analysis of the Kepler equation. We find that, apart from mean eccentricities less than 0.1, the stochastic dynamics are quantitatively and qualitatively different than the deterministic dynamics. For a fixed mean eccentricity, fluctuations in eccentricity amplify the asymmetry and intermittency in radiative flux forcing, thereby increasing the time it takes to reach a stable seasonal cycle. As the mean eccentricity increases above 0.1, the stochastic transition from the Snowball to non-Snowball state occurs over a range of mean stellar flux $\Delta S^*$ rather that at a particular stellar flux $S^*$ for the deterministic case. Moreover, as the mean eccentricity increases from 0.1 and the variance of the annual eccentricity fluctuations increases, $\Delta S^*$ increases and the probability of the system reaching a steady state and experiencing a Snowball to non-Snowball bifurcation decreases. This implies that there may be many high eccentricity planetary systems in a perpetually transient state.
Read the full abstract

Earth and Planetary Astrophysics

Systematic non-compliance of satellite megaconstellations with IAU brightness limits

Jack Rayworth, Denis Vida, Pauline Barmby et al. (+7 more)

Satellite megaconstellations in low Earth orbit interfere with ground-based optical astronomy, but the scale of that interference has been hard to measure. Here we report an uncued photometric survey from a mid-northern latitude site in late 2024 which recorded some 25,000 tracks of 5,118 individual satellites to a limiting visual magnitude of +9.0. The observed population is systematically brighter than the altitude-adjusted limit of order seventh magnitude recommended by the International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS). Starlink satellites exceeded that limit on roughly a quarter of all geometrically possible passes, rocket bodies on about a fifth, and the emerging Guowang/Hulianwang constellation on more than half. OneWeb was the most compliant major operator (exceeding the IAU CPS limit on only about one in twenty possible passes), which shows that effective brightness mitigation is achievable with current technology. Satellite visibility is concentrated into the two hours after sunset and before sunrise and into limited regions of the sky. From the measured plane-of-sky satellite flux we predict that of order one in three 30 s twilight exposures at the Vera C. Rubin Observatory will carry a satellite trail.
Read the full abstract

All authors Jack Rayworth, Denis Vida, Pauline Barmby, Peter G. Brown, Sarah Gallagher, Michael J. Mazur, David L. Clark, Maximilian Vovk, Stanimir Metchev, Lauchie Scott

Earth and Planetary Astrophysics

EK Cha b: multi-tracer detection of a protoplanet candidate in a gas-rich environment

Felipe Alarcón, C. Swastik, Stefano Facchini et al. (+2 more)

Despite sustained community efforts and advances in instrumentation and high-contrast imaging, the search for protoplanets remains difficult, with only two widely accepted systems to date in Class II systems (PDS 70 and WISPIT 2). Here we present the detection of EK Cha b, a new protoplanet candidate, identified through CO emission, millimeter continuum and 0.82 micron broadband photometry, linked to EK Cha, a young late-type M star. The detection of a new protoplanet candidate offers an additional opportunity to advance our understanding of planet formation. By exploiting the wealth of archival data available for nearby star-forming regions, we aim to place EK Cha b in context, characterize its properties, and motivate future campaigns targeting similar systems. We analyzed high-spatial-resolution archival observations of EK Cha from HST, VLT/NACO, VLT/MUSE, and ALMA. We searched for EK Cha b in broadband continuum and gas tracers, reporting the measured flux with uncertainties, and upper limits for non-detections. EK Cha b shows a spectrally-resolved footprint that matches the CO J=2–1 emission, together with 0.82 micron and millimeter continuum emission. EK Cha b is spectrally resolved in CO J=2–1 emission, kinematically consistent with a circumplanetary disk. Best fits from evolutionary models place EK Cha b as a planetary mass companion, although deeper observations are required to fully confirm its nature. Although giant planets are uncommon around M dwarfs, these stars host the highest planet occurrence rate while remaining severely underrepresented in protoplanet searches. EK Cha b demonstrates that such systems are now within reach, and the advent of extremely large telescopes and improved high-contrast imaging – where the lower host luminosity relaxes the required contras– will open this overlooked regime to systematic exploration.
Read the full abstract

All authors Felipe Alarcón, C. Swastik, Stefano Facchini, Edwin A. Bergin, Gabriele Cugno

Earth and Planetary Astrophysics

Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169

Kansuke Nunota, Andrew Gould, Takahiro Sumi et al. (+56 more)

We present an analysis of two planetary microlensing events, KMT-2021-BLG-0247 and MOA-2023-BLG-169, both of which exhibit high magnifications and low planet–host mass ratios, but with markedly different levels of parameter constraint. For KMT-2021-BLG-0247, the finite-source effect and microlens parallax are both clearly detected, leading to unusually tight constraints on the physical properties of the lens system. The host mass and lens distance are approximately $M_{\rm L}=0.9\pm0.1\,M_\odot$ and $D_{\rm L}=6.7^{+1.0}_{-0.3}\,\mathrm{kpc}$, respectively, and the planet mass is $M_{\rm p}=41\pm5\,M_\oplus$. The projected planet–host separations are $a_\perp=3.4^{+0.7}_{-0.3}\,\mathrm{au}$ and $3.0^{+0.6}_{-0.3}\,\mathrm{au}$ for the wide and close solutions, respectively. In contrast, MOA-2023-BLG-169 involves an extremely faint source, with $I_{S,{\rm OGLE}}=26.73$, such that the light curve permits a broad family of strongly correlated solutions. We therefore construct the physical-parameter likelihood using approximate invariant combinations of the light-curve parameters and supplement it with post-event Euclid/VIS imaging from the Euclid Q2 Galactic Bulge Survey (Beaulieu et al. 2026). The Euclid data reveal a component at the event position with ${\rm VIS}_{\rm AB}=23.05\pm0.09\,{\rm mag}$. Interpreting this component as the combined light from the source and any luminous lens, the resulting posterior gives $M_{\rm L}=0.48^{+0.23}_{-0.17}\,M_\odot$, $D_{\rm L}=3.50^{+2.82}_{-1.20}\,\mathrm{kpc}$, $a_\perp=1.62^{+0.77}_{-0.43}\,\mathrm{au}$, and $M_{\rm p}=143^{+103}_{-63}\,M_\oplus$. MOA-2023-BLG-169 demonstrates that, for an extreme faint-source event, even the event timescale and angular Einstein radius can remain strongly dependent on the Galactic prior and independent flux constraints.
Read the full abstract

All authors Kansuke Nunota, Andrew Gould, Takahiro Sumi, Ian A. Bond, Jennifer C. Yee, Valerio Bozza, Fumio Abe, David P. Bennett, Aparna Bhattacharya, Kotaro Daimon, Ryusei Hamada, Yuki Hirao, Takuto Inoue, Stela Ishitani Silva, Shuma Makida, Shota Miyazaki, Yasushi Muraki, Seiya Nakayama, Ryo Ogawa, Ryunosuke Oishi, Greg Olmschenk, Hideaki Ose, Clément Ranc, Nicholas J. Rattenbury, Yuki K. Satoh, Daisuke Suzuki, Takuto Tamaoki, Sean K. Terry, Paul J. Tristram, 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, Weicheng Zang, Dong-Jin Kim, Chung-Uk Lee, Byeong-Gon Park, Andrzej Udalski, Przemek Mróz, Radosław Poleski, Jan Skowron, Michał K. Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz

Earth and Planetary Astrophysics

A Recurrent Infrared Modulation in the Warm Post-impact Debris Disk NGC 2547 ID8

Xiaodian Chen, Shu Wang and Zhuochao Huang

Extreme debris disks are signposts of violent rocky collisions, but it remains unclear whether their mid-infrared variability traces transient dust clouds or longer-lived post-impact reservoirs. We analyze a 19 yr mid-infrared record of the young solar analog NGC 2547 ID8, combining four spectra from 2007-2024 with 3-5 micron monitoring through 2026. The optically thin mineral surface remains compositionally stable: broad fits spanning multiple grain sizes give 550-577 K, and a common-basis decomposition with T_surf fixed at 560 K is dominated by 1 micron olivine/Mg-olivine and 0.1 micron forsterite. The W2-equivalent 4.5 micron excess, traced across six recurrent high states, is instead driven mainly by changes in the hot-base continuum component and defines a 956.8 d infrared recurrence timescale with cycle-to-cycle variations in timing and amplitude. This combination supports the interpretation of ID8 as an early post-impact stage in which material on eccentric orbits repeatedly interacts with a warm rocky reservoir, preserving the impact's mineral fingerprint while the interaction geometry evolves. Material on eccentric orbits can persist for decades, and possibly longer, while interacting with debris disks. Longer-baseline, higher-cadence infrared monitoring of ID8 will further constrain the stability of its recurrence timescale and the detailed evolution of its infrared variability.
Read the full abstract

Earth and Planetary Astrophysics

Astrometric planet search around southern ultracool dwarfs: V. Discovery of the exoplanet candidate PALTA-1 b

J. Sahlmann, P. F. Lazorenko, E. L. Martín et al. (+3 more)

We report the discovery of PALTA-1 b, a sub-Jupiter mass exoplanet candidate orbiting the nearby early-L dwarf DENIS-P J1253108-570924 (DE1253-57) located at a distance of ~17 pc. The exoplanet was discovered by monitoring the L dwarf's astrometric motion with FORS2 at the Very Large Telescope over more than eight years and characterising the deviations from the expected single-source motion. The estimated planet mass is between 0.54 MJup and 0.77 MJup, depending on the uncertain mass of the ultracool dwarf host. The system's mass ratio is about 0.010, and the relative separation is estimated at 1.6-3.4 au. If confirmed, PALTA-1 b would be one of the very few known examples of a giant planet orbiting a nearby ultracool dwarf. This discovery finalises a larger astrometric planet search survey that targeted 20 nearby ultracool dwarfs and previously discovered three new ultracool binary systems.
Read the full abstract

All authors J. Sahlmann, P. F. Lazorenko, E. L. Martín, D. Ségransan, M. Mayor, S. Udry

Earth and Planetary Astrophysics

The GAPS Programme at TNG. LXXX. Characterisation of the 400 Myr old multi-planet system K2-233

V. Fardella, S. Benatti, R. Spinelli et al. (+27 more)

Understanding exoplanet physical properties is crucial for characterising their atmospheres and internal composition. Precise planetary masses are essential for constraining bulk densities and interiors, particularly in young systems hosting planets within or near the radius valley, where atmospheric mass loss may strongly shape their evolution. Here we revise the masses of the three transiting planets orbiting K2-233, a young ($\sim 400$ Myr) active K-type star. We combine 70 HARPS-N observations from the GAPS/ArMS Large Programme with 124 archival HARPS observations, K2 light curves, and TESS photometry obtained during our radial-velocity monitoring. We explore several Multi-GP configurations to mitigate the strong stellar activity and find that the inferred planetary masses depend significantly on the adopted activity-modelling strategy, yielding several physically viable solutions rather than a uniquely preferred one. We model the long-term atmospheric evolution of K2-233 d and find significant atmospheric mass loss. Depending on its internal composition and atmospheric properties, the planet is expected to evolve towards either a low-mass sub-Neptune retaining a thin envelope ($R_p \sim 1.71$-$1.84\ R_{\oplus}$) or a bare-core super-Earth ($R_p \sim 1.95\ R_{\oplus}$) on Gyr timescales. Our interior-structure models suggest that K2-233 b and c are likely iron-dominated, while K2-233 d retains a substantial H/He atmosphere.
Read the full abstract

All authors V. Fardella, S. Benatti, R. Spinelli, D. Locci, G. King, M. Baratella, K. Biazzo, S. Desidera, D. Barbato, M. C. D'Arpa, L. Naponiello, A. Petralia, M. Damasso, O. Barragán, C. Di Maio, A. Maggio, G. Piccinini, A. Bonomo, I. Carleo, R. Claudi, M. Gonzales, A. Harutyunyan, A. F. Lanza, L. Malavolta, L. Mancini, G. Mantovan, D. Nardiello, M. Rainer, A. Sozzetti, T. Zingales

Earth and Planetary Astrophysics

A faint dust ring beyond the compact disk of Sz 76

Giulia Ricciardi, Anna Miotello, Karina Mauco et al. (+9 more)

We report new ALMA Band 7 high-resolution ($\sim$0.05$^{''}$) continuum and $^{12}\text{CO}\ (J=3\text{--}2)$ observations of the disk around the young low-mass star Sz 76. Visibility-plane modeling reveals a previously undetected, faint outer dust ring centered at $\sim$45 au surrounding the compact central disk. Including this low-surface-brightness feature increases the characteristic dust radius from $R_{\text{dust,68}} \approx 7$ au to $41$ au. Combined with an outer gas extent of $R_{\text{CO,68}} \approx 77$ au, the resulting gas-to-dust size ratio decreases from an extreme value of $\sim$11 to $\sim$2, placing Sz 76 in line with typical protoplanetary disks and contradicting a scenario of unimpeded inward radial drift. These results demonstrate that spatial filtering or limited surface-brightness sensitivity can severely underestimate disk sizes, highlighting the necessity of multi-scale observations to properly identify dust traps and accurately constrain disk evolution.
Read the full abstract

All authors Giulia Ricciardi, Anna Miotello, Karina Mauco, Carlo F. Manara, Stefano Facchini, Agnes Kóspál, Juan M. Alcalá, Jochen Eislöeffel, Catherine C. Espaillat, Miguel Vogue, Jonathan P. Williams, Zhen Guo

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

A Jupiter-like radio aurora in the L3.5 dwarf LSPM J0036+1821

D. Martín-Carrero, J.B. Climent, P.A. Miles-Páez et al. (+6 more)

Ultracool dwarfs exhibit radio emission revealing strong magnetic fields and complex magnetospheric processes. Their auroral emission resembles that observed in magnetized Solar System planets, providing a framework to investigate their magnetic topology. We aim to characterize the magnetic activity, rotation, and atmospheric variability of the L3.5 dwarf LSPM J0036+1821 through a multiwavelength analysis. We conducted a long-term monitoring campaign combining radio observations from the Very Large Array and very long baseline interferometry arrays with TESS optical photometry, spanning 2019-2023. We analyzed time-series data to derive precise rotation periods and constructed light curves and radio dynamic spectra. The radio lightcurves were modeled using an auroral framework analogous to Jupiter's magnetosphere, incorporating main oval and active field line components. We detect persistent, compact radio emission with significant variability and high circular polarization. Periodogram analysis yields a rotation period of 3.07941 $\pm$ 0.00020h from radio data, consistent with the TESS optical period (3.07908 $\pm$ 0.00038h). The radio light curves display stable morphology characterized by asymmetric, rotationally modulated pulses. Our modeling reproduces the emission using a hybrid auroral scenario, with the main oval contributing a stable component and an active field line producing dominant, variable bursts. Short-term variability is explained by small changes in emission cone geometry or longitude of the active field line. The radio emission of LSPM J0036+1821 is consistent with auroral processes driven by the electron cyclotron maser instability in a structured magnetosphere. The behavior is consistent with a Jupiter-like auroral system, possibly involving companion-driven or internally-driven magnetospheric interactions analogous to those observed in the Solar System.
Read the full abstract

All authors D. Martín-Carrero, J.B. Climent, P.A. Miles-Páez, J.Balmón-Antón, J.C. Guirado, M.M. Kao, C. O'Toole, J.S. Pineda, J.M. Vos

Earth and Planetary Astrophysics

A comparison between particle and fluid approaches for streaming instability in global patch simulations

Dominik Hetzel Ostertag, Mario Flock, Paul Rosendahl et al. (+3 more)

Identifying the process relevant to planet formation is still a major task. Mechanisms have been identified that can trap dust, preventing it from migrating inwards. A particular hydrodynamic instability, known as the streaming instability, is of high interest because it may be responsible for the formation of dust clumps from which the first planetesimals form. We aim to compare the outcome of non-linear streaming instability simulations using both fundamental approaches in a more realistic global disk model. The results will not be used to identify or disentangle the effect of, e.g., numerical diffusion in fluid simulations or the possibility of having crossing particle streams. Instead, they will enable us to determine whether the Lagrangian particle approach is the most suitable for numerical studies of the streaming instability. Methods: We perform 2D, axisymmetric, global, and isothermal hydrodynamic simulations using the two codes FARGO3D (dust fluid) and PLUTO (fluid, particles) to investigate the temporal evolution of dust scale height, midplane dust-to-gas ratio, and maximum dust density as well as to study velocity distributions and vorticities. For PLUTO particle simulations, we also investigate the influence of the gas Riemann solver and spatial reconstruction orders. Our results from a resolution study up to 5120 cells per gas scale height indicate convergence between PLUTO fluid and FARGO3D. Both yield a Gaussian profile dominated by small-scale, dust-depleted voids. Particle simulations with PLUTO have not yet converged, as a transient midplane dust component persists, indicating the need for even higher resolution or more particles. Using a more accurate Riemann solver or a higher-order spatial reconstruction scheme helps to bring the dust density profile closer to the converged structure.
Read the full abstract

All authors Dominik Hetzel Ostertag, Mario Flock, Paul Rosendahl, Andrea Mignone, Jeonghoon Lim, Jacob B. Simon

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

The Fast Transient Foreground Fog of LSST

G. Megias Homar, S. R. Kulkarni, C. S. Lage et al. (+3 more)

Studies with 1-m class telescopes have now established that glints from satellites and space debris are the main obstacles to searches for sub-minute optical transients. Here, we report a study of this foreground using observations from the Legacy Survey of Space and Time (LSST) with the Simonyi 8.4-m telescope at the Vera C. Rubin Observatory. From 2,955 pairs of consecutive 30-s exposures, spanning 4,755 deg$^2$ of unique sky area and an area-time coverage of 472 deg$^2$ hr, we identified a population of faint, PSF-like, sub-minute events, including isolated events with no linear sequences of repeated flashes (tracklets) indicative of a tumbling satellite. We extended measurements of this population to the faintest magnitudes yet probed, finding a lower-bound to the occurrence rate of $(9.55 \pm 0.14) \times10^6\,$sky$^{-1}\,$day$^{-1}$ to $\sim23$ mag (median of $\sim22.3$ mag). The large aperture of the Simonyi 8.4-m telescope provides an additional discriminator: orbital debris in low-Earth orbit are sufficiently out of focus that they are filtered out. We find that, for a $1^{\prime\prime}$ PSF, unresolved events are constrained to distances beyond 1,732 km, and identify a previously unreported population of glints consistent with medium-Earth-orbit altitudes with estimated sizes of order $\sim1$-3 mm. We also report two isolated events observed along sight lines deep within the Earth's shadow, for which a sunlit-debris origin is disfavored. The scant evidence is consistent with an eclipsing binary and a stellar flare. The robust way forward for sub-minute transients is simultaneous observations of the same field by two (or more) widely separated telescopes. The resulting measurement of parallax will cleanly eliminate local (primarily orbital) debris, clarifying the nature of this transient foreground. This understanding will help astronomers probe truly celestial optical bursts.
Read the full abstract

All authors G. Megias Homar, S. R. Kulkarni, C. S. Lage, J. A. Tyson, S. M. Kahn, F. A. Harrison

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

Constrained Diffusion for Data-Scarce Orbital Monte Carlo in Constellation Tasking

Omar Ramadan, Sam Siavoshian, Amir Kashif Saeed et al. (+3 more)

Constellation Monte Carlo results depend on the orbital population used to evaluate a tasking policy. With scarce reference trajectories, replay limits geometric diversity, while independent orbital-element jitter can violate physical constraints. We study constrained diffusion for orbital-population augmentation. A force-conditioned diffusion model learns a 13-dimensional orbital prior, recovering semimajor axis from perigee altitude and eccentricity; Basilisk propagates each sample under one of five force-model tiers. Using 800 reference trajectories, we compare diffusion with jittered bootstrap, per-tier Gaussian mixtures, and a conditional variational autoencoder, and evaluate distributional fidelity, support shift, classical astrodynamics diagnostics, and 4,000 paired GoDSAT-compatible campaigns. The largest diffusion model achieves held-out trajectory MMD of 0.0171 +/- 0.0239, similar to bootstrap (0.0170) and the mixture (0.0198), but samples farther from training priors (median nearest-training distance 2.7 versus 0.10 standardized units). All generators fail to match the shifted-blind population (classifier AUC 0.991-0.998). Endpoint-conditioned samples satisfy Lambert boundaries but have greater interior error than the matched Lambert reference (29.2 versus 5.7 km mean RMSE). Residual diffusion improves selected sparse forecasts and catalog-mode recall but does not outperform classical estimators on custody ranking. In a fixed 16-satellite configuration, diffusion yields similar mean custody to replay and bootstrap, while the force-tier mixture shifts custody by about 5.5 percentage points. Constrained diffusion supports local, in-support augmentation but cannot replace orbital dynamics or serve as an operational posterior. Orbital-population construction is a consequential source of uncertainty in constellation analysis.
Read the full abstract

All authors Omar Ramadan, Sam Siavoshian, Amir Kashif Saeed, Benjamin A. Johnson, Amin M. E.-A. Diab, Benjamin M. Rodriguez

Tuesday 6 October

Earth and Planetary Astrophysics

Detection of escaping magnesium in the upper atmosphere of WASP-76b

Lakeisha M. Ramos Rosado, Leonardo A. Dos Santos, Joshua D. Lothringer et al. (+8 more)

Near-ultraviolet (NUV) observations can uniquely probe low-density, high-altitude gas in ultra-hot Jupiters (UHJs) via strong resonance lines of metals. WASP-76b is a well-studied UHJ with prior detections of refractory metals and complex day-night chemistry, making it a prime target for atmospheric escape diagnostics in the NUV. We present HST/STIS E230M (2274 - 3119 $\mathring{\mathrm{A}}$) transmission spectroscopy of WASP-76b. While broad- (~ 200 $\mathring{\mathrm{A}}$) and narrow-band (4 $\mathring{\mathrm{A}}$) transmission spectra do not show spectral features, a velocity-resolved single line analysis reveals clear excess absorption in both components of the Mg II doublet (2796 $\mathring{\mathrm{A}}$ and 2803 $\mathring{\mathrm{A}}$, $k$ and $h$ lines). The Mg II signal is localized to the blue wing (Doppler velocities [-50, -10] km s$^{-1}$) and is recovered with narrower 0.5 $\mathring{\mathrm{A}}$ bins; the inferred absorption exceeds both the optical continuum radius and the Roche-lobe scale, suggesting a highly extended upper atmosphere. We estimate a mass-loss rate of $\dot{M}\sim10^{12.14}\,\mathrm{g\,s^{-1}}$ from ATES. The present NUV data do not improve constraints on lower-atmosphere properties, and a comparison with upper-atmosphere forward models disfavor scenarios with extreme Mg enrichment. Together with the near-solar metallicity inferred from optical+IR spectra, this suggests that the Mg II absorption can arise in an escaping upper atmosphere without requiring extreme Mg enrichment, qualitatively consistent with hydrodynamic escape. Ongoing HST programs expanding the sample of UHJs focused on NUV observations will enable comparative tests of composition and kinematics in escaping atmospheres.
Read the full abstract

All authors Lakeisha M. Ramos Rosado, Leonardo A. Dos Santos, Joshua D. Lothringer, David K. Sing, Johanna Teske, Aline A. Vidotto, David Ehrenreich, Julia V. Seidel, H. Jens Hoeijmakers, Munazza K. Alam, Monika Lendl

Earth and Planetary Astrophysics

Polarimetric Behaviour of (3200) Phaethon: New Observations with Implications for Surface Heterogeneity

Zuri Gray, Mikko Vuori, Eric MacLennan et al. (+4 more)

The near-Earth asteroid (3200) Phaethon exhibits unusually high linear polarisation at large phase angles. Previous observations revealed a significant difference between apparitions: measurements obtained in 2016 showed a polarisation up to $\sim10$ percentage points higher than those obtained in 2017 at comparable phase angles. The distinct surface regions and viewing geometries sampled during the two apparitions have been suggested as possible explanations for this difference. Here, we present new R-band polarimetric observations obtained with the Nordic Optical Telescope, covering phase angles $32^\circ<\alpha<103^\circ$. The 2019 measurements show polarisation intermediate between higher and lower values measured in 2016 and 2017, respectively. Using a recent shape model, we calculate the distribution of reflected flux across the surface during the three individual apparitions and find that the 2019 observations sample the surface more similarly to 2016 than to 2017. We explore several possible explanations for the different polarisation behaviours, including differences in regolith grain size, related surface albedo, and observing geometry. While the available observations do not allow these effects to be uniquely disentangled, our results and analysis suggest that surface heterogeneity is the most plausible underlying cause, with viewing geometry potentially contributing to the observed polarimetric differences.
Read the full abstract

All authors Zuri Gray, Mikko Vuori, Eric MacLennan, Mikael Granvik, Karri Muinonen, Antti Penttilä, Mikael Turkki

Earth and Planetary Astrophysics

Searching for hot water world candidates with CHEOPS: II. A low-density super-Earth orbiting the K dwarf TOI-2211

J. A. Egger, P. Cortés-Zuleta, D. Kubyshkina et al. (+98 more)

Small exoplanets on close-in orbits are exposed to high levels of stellar irradiation, which can effectively remove low-mass primordial H/He envelopes through atmospheric escape. Under these conditions, planets whose masses and radii are incompatible with both bare rocky interiors and extended H-dominated atmospheres are therefore expected to host high mean molecular weight atmospheres, making them promising candidates for volatile-rich hot water worlds. We present the first detailed characterisation of the low-density super-Earth TOI-2211 b (P~3.09 d), a recently validated transiting planet orbiting a K type star (G mag: 9.1). Combining TESS and CHEOPS photometry with radial velocity measurements from HARPS, ESPRESSO, and KPF, we precisely constrain the planet's radius and mass to $1.457 \pm 0.047$ R$_\oplus$ and $2.69 \pm 0.56$ M$_\oplus$. We also identify an outer, non-transiting planetary candidate (P~15.6 d, Msin(i) $ = 8.53 \pm 1.04$ M$_\oplus$) in the radial velocity data. We investigate the internal structure of the transiting planet and assess the stability of the inferred volatile envelopes through a detailed evaporation analysis, thereby identifying TOI-2211 b as a promising hot water world candidate. TOI-2211 b therefore joins the small but growing sample of these close-in low-density super-Earths, which represent particularly interesting targets for testing current planet formation and evolution theories. Additionally, we investigate the full architecture of the planetary system using a generative model of planet formation and evolution, with the resulting posterior distributions showing a clear over-density consistent with the observed orbital period and minimal mass of the non-transiting planetary candidate identified in the radial velocity data.
Read the full abstract

All authors J. A. Egger, P. Cortés-Zuleta, D. Kubyshkina, H. P. Osborn, S. Marques, I. Crossfield, A. Deline, S. Ulmer-Moll, A. E. Simon, G. Scandariato, A. C. M. Correia, Y. N. E. Eschen, D. Gandolfi, V. Adibekyan, A. Bonfanti, C. Pezzotti, P. H. Premnath, S. G. Sousa, T. G. Wilson, L. Fossati, R. Eltschinger, Y. Alibert, D. Degen, G. Lacedelli, T. Zingales, B. Akinsanmi, R. Alonso, T. Bárczy, D. Barrado, S. C. C. Barros, W. Baumjohann, W. Benz, N. Billot, L. Borsato, A. Brandeker, C. Broeg, M. Buder, A. Castro-González, A. Collier Cameron, C. Corral Van Damme, Sz. Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, O. D. S. Demangeon, B.-O. Demory, A. Derekas, B. Edwards, D. Ehrenreich, A. Erikson, A. Fortier, M. Fridlund, K. Gazeas, M. Gillon, M. Güdel, M. N. Günther, J. Hasiba, A. Heitzmann, Ch. Helling, K. G. Isaak, L. L. Kiss, D. Kitzmann, J. Korth, K. W. F. Lam, J. Laskar, A. Lecavelier des Etangs, A. Leleu, M. Lendl, M. Lund, D. Magrin, P. F. L. Maxted, B. Merín, C. Mordasini, M. Munari, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, A. Peel, G. Peter, D. Piazza, G. Piotto, D. Pollacco, D. Queloz, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, N. C. Santos, D. Ségransan, A. M. S. Smith, M. Stalport, S. Sulis, Gy. M. Szabó, S. Udry, V. Van Grootel, J. Venturini, E. Villaver, N. A. Walton, S. Wolf

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

Coronal Mass Ejections from the Young Sun: Deceleration-Powered Solar Energetic Particles as a Self-Extinguishing Forcing of the Early Earth

Olga A. Panasenco

At $\sim$3.9~Ga (stellar age $\sim$0.6~Gyr), the young Sun was far more magnetically active than today. It launched $\sim$$10^2$ large, fast coronal mass ejections (CMEs) per year into a denser, more magnetized wind. We follow these eruptions to Earth's atmosphere with a semi-analytic model chain. We find that a CME launched at $v_0\sim3\text{--}4\e{3}\unit{km\,s^{-1}}$ dissipates $\Delta E_k\sim6\e{25}\unit{J}$ as it decelerates, an amount set only by its launch and final speeds. Diffusive shock acceleration converts $\sim$10% of this energy into solar energetic particles (SEPs), whose deposition depth depends mainly on a spectral break energy $E_b$. We show that the stronger field moves the Alfvén surface, inside which the magnetic field controls the wind, from $\sim$10–25$\,\Rsun$ to $\sim$40–60$\,\Rsun$, so CME shocks deliver over ten times the particle fluence of flares. Because the forcing is powered by deceleration, it follows the measured wind history ($\dot M\propto t^{-2.3}$) and declines as $\sim t^{-3}$. It was $\sim$50–100 times stronger at 3.9~Ga than at 2~Ga and several hundred times today's level. This decline, strongest when the Sun was faintest, is what greenhouse solutions of the faint young Sun (FYS) problem usually impose by hand. The magnitude is small: SEP-driven $\mathrm{N_2O}$ adds at most a few $\unit{W\,m^{-2}}$ to a 20–40$\unit{W\,m^{-2}}$ greenhouse requirement, and only if a fractal organic haze extends its lifetime. Counting energy deposited below a survival level near 1~hPa, we find the particles fix $\sim$$4\e{10}$–$4\e{11}\unit{mol\,N\,yr^{-1}}$, which could supply prebiotic feedstock to surface pools. The largest uncertainties are $E_b$, the event rate, the survival depth, and the $\mathrm{N_2O}$ lifetime.
Read the full abstract

Earth and Planetary Astrophysics

SOPHIE and TESS characterization of fourteen TESS Objects of Interest: nine planetary systems and five low-mass stellar companions

N. Heidari, G. Hébrard, S. Sousa et al. (+61 more)

We present fourteen TESS Objects of Interest (TOIs) from the SOPHIE-TESS follow-up program. Combining TESS photometry, SOPHIE radial velocities (RVs), ground-based photometry, and high-resolution imaging, we establish the nature of all targets. Nine systems (TOI-6457, TOI-6883A, TOI-6649, TOI-6842A, TOI-5217A, TOI-6893A, TOI-7025, TOI-7176, and TOI-5893) host planets. TOI-6649 b, TOI-6842A b, and TOI-5217A b are transiting hot Jupiters with periods of 4.4-6.0 d, radii of 1.3-1.6 RJ, masses of 0.3-1.3 MJ, and densities of 0.1-0.6 g/cm3. TOI-5217A also hosts an outer companion, TOI-5217A c, with a period of about 1761 d, a minimum mass of about 13 MJ, and an eccentric orbit (e = 0.53 +/- 0.02). TOI-5893 b, TOI-6893A b, TOI-6457 b, TOI-7176 b, and TOI-7025 b are transiting warm Jupiters with periods of 40.4-67.0 d, radii of 0.8-1.2 RJ, and masses of 0.5-1.0 MJ. TOI-6883A b, a recently reported warm Jupiter, is further characterized with new photometry and SOPHIE and TRES RVs. The other five systems (TOI-5621AB, TOI-5321AB, TOI-3678AB, TOI-5906AB, TOI-5308AB) show large RV amplitudes indicating eclipsing binaries (companions of 0.1-0.6 Msun and 0.1-0.6 Rsun). TOI-6842A b is a super-puff (density 0.08 +/- 0.01 g/cm3), among the nine lowest-density planets known, and with a transmission spectroscopy metric of about 250 it is an excellent target for atmospheric characterization. The six warm Jupiters, with equilibrium temperatures of 377-846 K, are low-irradiation benchmarks for hot-Jupiter inflation models. TOI-7025 b has an eccentricity of 0.82 +/- 0.02, one of the largest known for a planet orbiting a single star. Finally, using Gaia astrometric excess noise, we detect TOI-5906 B, the first object identified by transit, RV, and astrometry.
Read the full abstract

All authors N. Heidari, G. Hébrard, S. Sousa, T. Forveille, F. Destriez, J. D. Eastman, J. M. Almenara, D. W. Latham, B. S. Safonov, R. Brahm, K. G. Stassun, K. A. Collins, D. Dragomir, J. Janík, I. Boisse, J. G. Barrientos, J. Serrano Bell, F. Kiefer, A. Bieryla, X. Bonfils, Z. Balkóová, G. Conzo, M. Deleuil, O. D. S. Demangeon, X. Delfosse, R. F. Díaz, Z. Essack, J. Eberhardt, Y. N. E. Eschen, A. C. Frommer, F. R. Frustagia, D. Feliz, A. F. Gupta, N. Hara, T. Henning, S. B. Howell, A. Jordán, J. Köhler, J. F. Kielkopf, H. A. Knutson, J. Lipták, C. R. Mann, E. Martioli, C. Moutou, F. Murgas, B. Nicholson, P. Pintr, M. Tala Pinto, S. N. Quinn, H. M. Relles, P. Rowden, R. P. Schwarz, R. Sefako, A. Shporer, G. Srdoc, C. Stockdale, I. A. Strakhov, B. Skinner, B. M. Tofflemire, T. Trifonov, S. Ulmer-Moll, L. Vanzi, F. P. Wilkin, C. Ziegler

Earth and Planetary Astrophysics

Reflex instabilities II: The reflex motion of the central object drives at least seven instabilities in accretion discs

Nathan Magnan, Michel Tagger, Clément Baruteau et al. (+3 more)

This series of papers studies the stability of accretion discs to the reflex motion of the central object under the gravitational pull of the disc itself. In this second paper, we use linear analysis to reproduce or discover seven distinct instabilities. We outline their defining characteristics and propose a classification. Of the four instabilities that had already been discovered, three are artificial: one does not survive the transition to modern surface density profiles such as power-laws, one is due to the location of the domain's boundaries, and one is due to the use of damping layers near the domain's boundaries. Only the SLING instability of Adams et al. (1989) and the three new 'cavity' instabilities seem capable of affecting accretion discs. All four can be described to a high degree of precision by WKB methods. They may drive eccentricity growth, affect planet migration, create spiral and crescent substructures in the absence of any planet, and boost accretion onto the central object. The issue is that the three artificial instabilities are extremely hard to avoid in simulations, and would bias the same observables. This suggests that our community may not have the tools to model the reflex motion of the central object yet.
Read the full abstract

All authors Nathan Magnan, Michel Tagger, Clément Baruteau, Aurélien Crida, Jean-François Gonzalez, Héloïse Méheut

Earth and Planetary Astrophysics

Reflex instabilities I: Boundaries makes grid-based disc simulations frame-dependent

Nathan Magnan, Michel Tagger, Clément Baruteau et al. (+3 more)

If the mass distribution within an accretion disc is asymmetric, it will exert a gravitational pull on its central object. The central object must then move away from the origin of the reference frame, resulting in atypical gravitational pulls on the disc. The goal of the present series of papers is to investigate the stability of this feedback loop. In this first paper, we report a surprising finding: the choice of reference frame affects the number and nature of the waves and instabilities contained in the analytical equations. To show this, we use a simple example: the modes discovered by Sanchez et al. (2025, Appendix A.3). We provide the first analytical description of those modes, we explain their physical mechanism, and propose to call them 'bracket modes' because they arise from the bracket side of an integration by parts. We show that the same disc can be stable in the stellocentric reference frame but unstable in the barycentric reference frame. This is because the boundaries of the simulation domain are frame-dependent. To avoid this, one must model the entire disc all the way from the central cavity to the outer edge. But this is prohibitively expensive, and some discs do not have a central cavity anyway. Our results suggest that extreme caution is required when interpreting simulations of asymmetric discs, and that our community may not have the tools to model the reflex motion of the central object yet.
Read the full abstract

All authors Nathan Magnan, Michel Tagger, Clément Baruteau, Aurélien Crida, Jean-François Gonzalez, Héloïse Méheut

Earth and Planetary Astrophysics · Cross-listed from cs.CV

Decoy and disclosure radii of invariant shape descriptors

Tanush Shaska and Lubjana Beshaj

A recognizer that compares rotation-invariant descriptors sees a surface only up to the fiber of the descriptor. We measure this fiber by its radius in the orbit distance from the enrolled surface. A large radius admits decoys, that is, distant shapes that pass the matcher. A small radius discloses the enrolled shape to anyone who captures the stored value. For star-shaped surfaces truncated to spherical harmonics of degree at most $L$, with $n$ coefficients, a descriptor of generic rank $r$ has generic fibers of dimension $n-3-r$ modulo rotations. The standard pool of band powers, even bispectra, and three invariants of the degree-three band therefore admits decoy families of dimension $5$, $13$, $20$ at $L=4,6,8$. Its rank first reaches $n-3$ at $L=16$, and a mirror decoy remains at every $L$. The odd bispectra remove the mirror decoy generically for $L \geq 4$. Yet at fixed mean radius the same pool determines the enclosed volume exactly, and it does not determine whether a surface meets a clearance requirement. We certify two cases by exact and interval arithmetic. At $L=6$ a decoy matches all $32$ invariants to relative precision $2 \cdot 10^{-18}$ at orbit distance at least $0.87$ times the norm of the enrolled tuple. For the radar shape model of asteroid (101955) Bennu, the pool recovers the modeled volume, misses the handedness, and leaves the keep-out radius uncertain by more than $7 \, \mathrm{m}$.
Read the full abstract