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

Monday 28 September

Earth and Planetary Astrophysics

Energy distributions of precipitating electrons in Jupiter's auroral regions from combined Juno/JADE and Juno/JEDI measurements

B. Benmahi, V. Hue, N. André et al. (+17 more)

Jupiter's auroras are produced by magnetospheric electrons precipitating into its atmosphere. Juno/JADE and Juno/JEDI together measure these electrons from 100 eV to 1 MeV. However, their auroral spectra are poorly reproduced by the widely used kappa distribution, hereafter the classical single-kappa distribution. We aim to statistically characterize the energy flux distributions of precipitating auroral electrons and to derive a new phenomenological 4-kappa distribution better suited to JADE+JEDI data. We build mean energy flux distributions in six auroral sub-regions (polar, main, and outer emissions in both hemispheres), combining JADE and JEDI data from PJ3 to PJ35, mapped to the SIII frame with the JRM33 model including the current sheet. We fit them using MCMC with the classical single-kappa and 4-kappa distributions. The mean distributions show a monotonic power-law decay with an energy cutoff beyond ~500 keV in most sub-regions, although some individual spectra depart from it at intermediate energies. Mean energies range from ~21 to ~119 keV, and energy fluxes from ~9.5 to ~28.7 mW/m$^2$. The classical single-kappa fit fails in all sub-regions, with $\kappa$ converging to the lower bound of its prior range. We therefore introduce the 4-kappa distribution, a linear combination of four classical single-kappa distributions modulated by an exponential high-energy cutoff, which accurately fits all six sub-regions. At equal energy flux and mean energy, transport simulations show that the 4-kappa distribution deposits energy at lower altitude than the classical one and distributes it differently along the vertical, with implications for the UV color ratio, atmospheric chemistry and thermal structure, and ionospheric conductances. This distribution provides an analytical framework for realistic modeling of electron precipitation and UV auroral emissions at Jupiter.
Read the full abstract

All authors B. Benmahi, V. Hue, N. André, B. Bonfond, M. Blanc, Z.-Y. Liu, B. H. Mauk, F. Allegrini, G. Clark, M. Devinat, G. Gronoff, T. Le Liboux, M. Barthélémy, C. Lefour, T. Cavalié, B. Benne, T. Gautier, T. Briand, J. A. Noble, J. A. Sinclair

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

P2D - A Two-Dimensional Multi-Spacecraft Solar Wind Persistence Model

Daniel Milošić, Manuela Temmer, Stephan G. Heinemann et al. (+2 more)

The background solar wind is a key component in space weather forecasting, as it contains geoeffective high-speed streams and provides the medium through which coronal mass ejections propagate and evolve in interplanetary space. Due to the solar rotation and the slow evolution of large-scale solar wind structures, solar wind properties exhibit an autocorrelation with a period of roughly 27 days, particularly at solar minimum. We made use of this property to develop a solar wind persistence model with input from multiple spacecraft (Solar Orbiter, Parker Solar Probe, STEREO-A, STEREO-B and the OMNI database). The model ballistically propagates in-situ data from the position of their measurement radially away from the Sun, as well as longitudinally with the solar rotation rate, producing 2D maps of solar wind parameters. These can be extracted at any point in the heliosphere for a solar wind reconstruction. From Earth's perspective, the reconstruction performs with an MAE of 65.41 km/s and 3.51/cm^3 for speed and density, respectively. During high-speed streams, the peak hit rate is 50% and 48% for speed and density. It performs best during times when there are spacecraft located between Earth and Lagrange point L5. During these times, the mean absolute error of the predicted solar wind speed decreases by roughly 35% in comparison to the benchmark 27-day persistence model. Therefore, future L5 missions like Vigil are expected to provide a robust basis for reliable persistence forecasts.
Read the full abstract

All authors Daniel Milošić, Manuela Temmer, Stephan G. Heinemann, Mathew Owens, Stefan J. Hofmeister

Earth and Planetary Astrophysics

Beyond gas dwarfs and water worlds: hybrid envelopes among the M-dwarf sub-Neptunes characterised with JWST

Juan F. Pagés Navarrete

Sub-Neptunes orbiting M dwarfs are commonly interpreted either as rocky cores beneath primordial H/He envelopes (gas dwarfs) or as volatile-rich bodies formed beyond the water-ice line (water worlds). Because the two are degenerate in mass and radius once envelope evolution is treated self-consistently, the atmospheric mean molecular weight $\mu$ is the more direct discriminant. We compile the eight M-dwarf sub-Neptunes with published JWST transmission spectra and a constraint on $\mu$, grade each constraint by the quality of the underlying evidence, and combine it with the restricted Jeans parameter and with energy-limited escape integrated over the system lifetime, using XUV histories from M-dwarf activity-age relations. Planets are classified by what their present composition implies about their origin. At the $\mu = 3.8$ amu threshold adopted in the gas-dwarf literature, four planets fit neither end-member: their envelopes ($3.8 < \mu \le 18$ amu) are too heavy for primordial H/He, yet neither their composition nor their escape history requires a volatile-rich origin. Two of these assignments rest on molecular detections (LP 791-18 c and TOI-270 d) and two on bounded or conditional metallicities. One planet, LHS 1140 b, requires a volatile-rich origin; one, TOI-776 c, is tentatively a gas dwarf; two remain ambiguous. We propose the term hybrid worlds for the intermediate class, whose envelopes can be produced by magma-ocean equilibration, supercritical miscibility, preferential hydrogen loss or accretion interior to the ice line. The count depends on the adopted threshold (three planets at 5 amu, one at 10 amu), but no threshold leaves both end-member classes physically consistent. The sample is set by JWST target selection, so these fractions are not occurrence rates; a homogeneous survey testing whether $\mu$ is bimodal would test the proposed class directly.
Read the full abstract

Earth and Planetary Astrophysics

Resolved Structure and Orbital Motion of a Localized 1 au-scale Dust Accumulation in the Protoplanetary Disk around TW Hya

Takashi Tsukagoshi, Takayuki Muto, Hideko Nomura et al. (+6 more)

We present the results of high-resolution ($\sim1$~au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the TW~Hya protoplanetary disk in the Band 6 dust continuum, as well as the \ce{^13CO} and \ce{C^18O} J=2–1 emission lines. The primary focus of this study is to investigate the kinematics, internal morphology, and local gas environment of the prominent dust blob at a radius of 52~au. By comparing our 2021 data with archival observations from 2017, we detect the proper motion of the blob. The measured azimuthal velocity of 3.3$\pm$0.9~km~s$^{-1}$ is fully consistent with local Keplerian rotation. Combined with the lack of significant radial migration over the four-year baseline, this confirms that the structure is robustly co-moving with the disk system. Crucially, our high-resolution continuum map resolves the blob into a distinct double-peaked morphology separated by $\sim$1.7~au azimuthally. We robustly validate this double-peaked substructure by reproducing it in the independent 2017 dataset using a sparse-modeling image reconstruction technique. We discuss potential physical origins for this double-peaked morphology, including an inclined circumplanetary disk with an inner dust cavity, the roots of planet-induced spiral arms, or alternative hydrodynamic scenarios that do not involve an actively accreting planet such as the U-turn trajectory of secondary dust or a short-lived hydrodynamic gas vortex. We detect no compact gas emission counterparts associated with the continuum blob. Since these CO lines likely trace optically thick upper atmospheric layers, the absence of localized vertical gas perturbations suggests that if an embedded planet is responsible for the dust structure, its mass must be exceptionally low.
Read the full abstract

All authors Takashi Tsukagoshi, Takayuki Muto, Hideko Nomura, Ryohei Kawabe, Satoshi Okuzumi, Shigeru Ida, Jun Hashimoto, Taichi Uyama, Motohide Tamura

Earth and Planetary Astrophysics

Planets Around Solar Twins/Analogs (PASTA) III: Chemical Clock Relations in Planet-Hosting Solar Analogs

Qinghui Sun, Serat M. Saad, Yuan-Sen Ting et al. (+10 more)

Context. Abundance ratios between elements synthesized on different nucleosynthetic timescales provide empirical chemical clocks for estimating stellar ages, but robust calibrations require homogeneous samples with precise stellar parameters and elemental abundances. Aims. We aim to investigate whether the presence of planets modifies empirical chemical clock relations. Methods. We present high-precision stellar parameters and elemental abundances for 52 new planet-hosting targets observed with Keck/HIRES, LBT/PEPSI, and Subaru/HDS. Combined with PASTA I and II, the full sample comprises 94 stars, of which 81 are identified as planet-hosting solar twins and analogs, and is used to characterize Galactic chemical evolution and derive empirical chemical clock relations. Results. We recover the expected Galactic chemical evolution trends, with $\alpha$-elements such as Mg and S increasing with stellar age, while s-process elements such as Y, Ba, and Sr show negative age correlations. In contrast, Fe-peak elements and the r-process element Eu show little or no significant age dependence. These trends give rise to tight chemical clock relations based on [Y/Mg], [Y/Al], [Ba/Mg], [Ba/Al], and [Sr/Mg], with [Y/Mg] and [Y/Al] providing the strongest correlations. [Ba/Al] shows the steepest age dependence, and the Ba-based ratios are generally more sensitive to age than their Y-based counterparts. Conclusions. Planet-hosting solar analogs follow chemical-clock relations consistent with those of nearby solar twins, with no evidence for a significant planet-related effect. The derived relations are primarily applicable to local solar twins and analogs in the Galactic thin disk.
Read the full abstract

All authors Qinghui Sun, Serat M. Saad, Yuan-Sen Ting, Jiayue Zhang, Chenyang Ji, Fei Dai, Sharon Xuesong Wang, Bryant Randolph, Yunzhe Gu, Ilya Ilyin, Yaguang Li, Jie Yu, Fan Liu

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

Numerical analysis of electron density and response time delay during solar flares in mid-latitudinal lower ionosphere

Sayak Chakraborty and Tamal Basak

Impacts of solar flare vary at different parts of the lower ionosphere depending on its proximity to the direct exposure of incoming solar radiation. The quantitative analysis of this phenomenon can be attributed to the solar zenith angle (chi(t)) profile over the ionosphere. We numerically solve the electron continuity equation to obtain the lower ionospheric electron density profile (Ne(t)). The electron production rate (q(t)) is governed by the (i) X-ray profile (phi(t)) of the flare, (ii) chi(t)-values during the flare occurrence, etc. For analyzing the X-ray profile during flares, we use the GOES-15 satellite observations. Since we are working on an electron continuity equation based simplified ionospheric model, we confined our analysis to the comparatively stable mid-latitude ionosphere only. We choose three flares each from C, M, and X-classes for Ne(t)-profile computation. We observe that temporal Ne(t)-profiles differ when computed for the lower ionosphere over different discrete latitudes. Further, we compute the spatial Ne(t)-profile across the mid-latitude region at the time when phi(t) = phi_max. Now we assume that these flares repeat themselves every day of a year (DoY) at the same time of a day and we compute Ne(t)-profiles for each day. We found a seasonal effect on the Ne(t)-profile due to solar flare. Further, we investigate the response time delay (Delta t) of the lower ionosphere, which is the time difference between incidence of X-ray and the respective change in Ne(t)-profiles during solar flares. Strong seasonal effects on Ne(t)-profile and Delta t are the unique results of this work.
Read the full abstract

Earth and Planetary Astrophysics

A JWST Study of Stardust. II. Polycyclic Aromatic Hydrocarbons in Comet 81P/Wild 2 and Implications for Primitive Solar System Carbon

Nathan X. Roth, Stefanie N. Milam, Diane H. Wooden et al. (+11 more)

We report observations of comet 81P/Wild 2, target of the Stardust sample return mission, on UT 2023 March 20 and 24 at a heliocentric distance ($r_H$) of 1.85 au using the NIRSpec and MIRI integral field unit spectrographs on board the James Webb Space Telescope (JWST). This study is the first compositional comparison between JWST remote-sensing spectroscopy of a solar system object against terrestrial analysis of its returned samples. Recent work determined contributions of molecular emission from coma volatiles and thermal emission from the nucleus and coma dust grains to these spectra. Subtracting the molecular and thermal emission models produces a residual spectrum with a clear resonance near 3.37 $\mu$m and multiple others spanning the $6 - 12$ $\mu$m region. Analysis of these residuals provides strong evidence for the presence of polycyclic aromatic hydrocarbons (PAHs) in the coma of 81P/Wild 2. The resulting PAH populations reflect material incorporated into the nucleus of 81P/Wild 2 that was inherited from the diffuse interstellar medium, the interstellar medium, and the protoplanetary disk. The PAHs sensed by JWST are compared to those detected in laboratory analyses of the Stardust mission returned samples.
Read the full abstract

All authors Nathan X. Roth, Stefanie N. Milam, Diane H. Wooden, Els Peeters, Charles E. Woodward, Dominique Bockelee-Morvan, Michael S. P. Kelley, Steven B. Charnley, Simon J. Clemett, Martin A. Cordiner, Perry A. Gerakines, David E. Harker, Ella Sciamma-O'Brien, Geronimo L. Villanueva

Earth and Planetary Astrophysics

Dynamical Impacts of Accretion Streamers on Protoplanetary Disks

Han-Gyeol Yun, Jeong-Eun Lee, Jaehan Bae et al. (+1 more)

Recent observations suggest that accretion streamers are common in protoplanetary disks, yet their dynamical impact on disk evolution remains poorly understood. Using three-dimensional hydrodynamic simulations with mass infall rates of $10^{-8}$–$10^{-6} \ M_{\odot}\ \mathrm{yr}^{-1}$, we investigate how streamer accretion influences the structure and evolution of protoplanetary disks. We find that a prograde streamer can excite disk eccentricity globally to values as high as $\sim0.4$. The resulting eccentric disk develops prominent spiral arms and crescent-shaped overdensities whose spatial structures agree remarkably well with analytic eccentric-disk theory. It also undergoes significant warping, and exhibits enhanced and variable stellar accretion. In contrast, retrograde streamer accretion efficiently removes disk angular momentum, producing a compact disk and, in extreme cases, triggering disk breaking. Using synthetic ALMA molecular-line observations, we show that streamer-driven perturbations generate observable kinematic signatures, including Doppler flips in moment maps and wiggles in position–velocity diagrams. Remarkably, these signatures can persist for up to $100\ \mathrm{kyr}$ after infall has ceased, suggesting that some kinematic disturbances observed in disks without currently detected streamers may be relics of past infall events. Finally, we discuss the implications of streamer-driven disk evolution for planet formation and planet–disk interactions.
Read the full abstract

All authors Han-Gyeol Yun, Jeong-Eun Lee, Jaehan Bae, Woong-Tae Kim

Sunday 27 September

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

An autonomous approach to model daytime behavior of sub-ionospheric VLF signals over short and medium propagation paths in India

Sayak Chakraborty, Tamal Basak, Sourav Palit et al. (+1 more)

We present an autonomous model to simulate the daytime variation of sub-ionospheric Very Low Frequency (VLF) signal amplitude, beginning with the computation of the D-region electron density by numerically solving the electron continuity equation (ECE). From the resulting altitude-dependent electron density profile (Ne), we extract Wait's ionospheric parameters (h' and beta) using a log-linear fitting method. The study focuses on two VLF propagation paths (one short and one medium in length) in India, originating from the VTX (18.2 kHz) transmitter. The model employs the Long Wave Propagation Capability (LWPC) framework to reproduce the daytime VLF signal amplitude profile. It accurately captures the daytime variations observed at the Bengaluru (BAN) station, where the ground-wave component is dominant, as well as at Khukurdaha, WB (KHK). A quantitative comparison between the simulated (Asim) and observed (Aobs) amplitudes shows good agreement, supporting the physical consistency and potential predictive capability of the proposed approach.
Read the full abstract

All authors Sayak Chakraborty, Tamal Basak, Sourav Palit, Sandip K. Chakrabarti

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

Synthesis of organo-phosphorous species in space: the reaction of P$^+$ with C$_2$H$_2$

Matteo Michielan, Jorge Alonso de la Fuente, Roland Thissen et al. (+8 more)

Despite its low cosmic abundance, phosphorus is a bioessential element whose prebiotic availability and incorporation into biomolecules remain open questions. Only a few phosphorous containing molecules with P to C bonds have been detected in astronomical environments (CP, CCP, HCP). More complex species have been proposed, but their formation and destruction pathways remain poorly constrained. Gas-phase ion molecule chemistry involving P cations may contribute to organophosphorus formation, particularly in protostellar shocks and outflows, while reactions of ground state P cations with closed-shell neutrals provide benchmarks for spin-forbidden mechanisms. We investigate the reaction of P+ with C$_2$H$_2$ through a joint experimental and theoretical study aimed at revising astrochemical database rate coefficients. Absolute cross sections and branching ratios were measured as a function of collision energy and complemented by high-level electronic structure calculations and a refined capture model accounting for higher-order long-range interactions and intermediate complex formation. Channel-specific rate coefficients were derived in the range from 10 to 5000 K. The reaction produces predominantly HCCP$^+$ + H (branching ratio 99%), while CCP$^+$ + H$_2$ is a minor channel (branching ratio 1%) arising from intersystem crossing from the triplet to the singlet potential energy surfaces. The total rate coefficient at 300 K agrees well with the SIFT value, but it increases with decreasing temperature, deviating from a pure Langevin trend. The reaction should be included in astrochemical models where phosphorus is released as P+, such as during energetic processing of icy grains in shocks. It provides a pathway to linear HCCP$^+$, a potentially relevant precursor to the observed CP and CCP species through dissociative recombination
Read the full abstract

All authors Matteo Michielan, Jorge Alonso de la Fuente, Roland Thissen, Christian Alcaraz, Nicolas Solem, Cristina Sanz Sanz, Susana Gómez Carrasco, Miroslav Polášek, Alexandre Zanchet, Marcelino Agúndez, Daniela Ascenzi

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

Modeling of the variability of D-region ionospheric electron density during solar cycle-24

Sayak Chakraborty, Sourav Palit, Semontee Deb et al. (+1 more)

Solar cycle variation of earth's atmosphere, particularly the ionosphere is of particular interest in the field of space science and space weather studies. In this article, we present the outcome of our detailed quantitative study on solar cycle variation of lower ionospheric properties using numerical investigation. First, we seek to model and compare the collective D-region ionization rates (q's) due to the individual contributions from the ionizing sources, namely, (a) solar extreme ultraviolet (EUV) radiation including the Lyman-alpha irradiation and (b) solar X-ray irradiation throughout the 24th solar cycle (C24). Then, we compute the electron density (Ne) profiles using the ionization rates. We report significant solar cycle variation in ionization rate and electron density profiles for the entire span of C24. We use the sunspot number (SPN) profile to substantiate the finer details of Ne profile during C24. For the segments of the D-region above two different geographic coordinates, we report that Ne profiles show a consistent "dual peak" nature. It is very similar to the SPN profile during C24. As a next-order validation, we compare our modeled Ne profiles with their IRI-2020 counterpart (Ne,iris). Their overall trends are found to be in agreement. Finally, we discuss the response of the D-region in terms of Ne due to C24. The work lays the foundation for our upcoming studies on D-region response to solar cycle variation with Very Low Frequency (VLF) observation.
Read the full abstract

All authors Sayak Chakraborty, Sourav Palit, Semontee Deb, Tamal Basak

Earth and Planetary Astrophysics

The July 2023 Outburst of Comet 12P/Pons-Brooks: Observations and Modeling of Dust Coma and Arc Structure

Hitoshi Hasegawa, Mitsunori Tsumura, Shin-ichi Watanabe et al. (+2 more)

We conducted continuous imaging observations of comet 12P/Pons-Brooks, which has experienced multiple outbursts since 2023 July. Among these, we determined the dust coma expansion velocities and the occurrence times for three outbursts. The outburst on 2023 July 20.39$\pm$0.05 had an expansion velocity of 207.5$\pm$0.1 m s$^{-1}$. The outburst on 2023 November 14.52$\pm$0.10 had an expansion velocity of 305.8$\pm$13.7 m s$^{-1}$, and the outburst on April 2.23$\pm$0.06, 2024 had an expansion velocity of 408.9$\pm$14.3 m s$^{-1}$. During the July outburst, in addition to the isotropically expanding dust coma, a semicircular structure (arc structure) was observed. This structure expanded without changing shape over two months, until mid-September, at a slower velocity of 52.0$\pm$1.7 m s$^{-1}$ compared to the outer coma. We hypothesize that this arc structure consists of dust ejected over a certain period during the outburst from an active region at mid-latitudes on the comet's nucleus, with a rotation axis near the line of sight. We performed model calculations to reproduce the structure. As a result, we found that the observations were well reproduced by assuming a rotation axis direction of RA = $85^\circ$, Dec = $-30^\circ$ to $-35^\circ$ and an active region latitude of $70^\circ$ during the July outburst. The active period of the outburst was shorter than the rotation period, approximately 0.7 times the rotation period. Since the dust particles comprising the arc structure escaped dissipation due to solar radiation pressure, we infer that they are dust with a ratio of radiation pressure to gravity of $\beta \sim 0.1$, which corresponds to a dust particle size of about $10\,\mu\mathrm{m}$.
Read the full abstract

All authors Hitoshi Hasegawa, Mitsunori Tsumura, Shin-ichi Watanabe, Hiroki Akisawa, Jun-ichi Watanabe

Earth and Planetary Astrophysics

On the Secular Evolution of Inclinations Among the Classical Belt TNOs

Dallin Spencer, Darin Ragozzine, Kat Volk et al. (+1 more)

Proper orbital elements have been used in diverse ways to study the dynamical architecture of transneptunian objects (TNOs), providing insights into Solar System evolution and migration theories. In this paper, we present the numerically-computed proper elements of all known TNOs. We then compare their distribution with the distribution of proper elements of a large synthetic sample generated to study the secular behavior of TNOs in the Classical belt region in an effort to better understand certain observed features, particularly features appearing in the inclination distribution of these TNOs. Our analysis indicates the presence of an inclination-dependent instability in the Classical belt from 42 < a < 45 au, which we find is caused by the g+s-g8-s8 = 0 secular resonance. The coincidence of this instability with the previously-noted inclination boundary of the Cold Classical belt near proper inclination of Ifree = 4 (deg) could suggest that the primordial Classical belt may have originally been more continuous between 4 < Ifree (deg) < 6 than we observe today. However, our analysis to account for the impact of secular resonant instabilities finds a best-estimate of the inclination width of the primordial Cold Classical belt near 1.5(deg), well below 4(deg), and slightly thinner than previous works have suggested. We conclude that the inclination boundary of the Cold Classical belt is not set directly by secular resonance or instability, and that this belt is generally unaltered by resonance or instability since the end of planetary migration.
Read the full abstract

All authors Dallin Spencer, Darin Ragozzine, Kat Volk, Renu Malhotra

2609.33080 · 27 Sep · 26 pages, 10 figures, and 2 tables. Submitted to The Astronomical Journal, pending review as of 09/26/2026. Data will be published in a Zenodo repository with the reserved doi:10.5281/zenodo.22285391. The datasets are also accessible at this presently publicly available GitHub repository: https://github.com/dallinspencer/TNO-Secular-Dynamics-Catalog/

Abstract PDF $EVO ×2

Saturday 26 September

Earth and Planetary Astrophysics

Worlds Next Door. V. A Candidate Solar System Scale Super-Jupiter in the 61 Cygni Binary System

Aniket Sanghi, Billy Quarles, Andrea S. J. Lin et al. (+16 more)

We present new constraints on a candidate third companion in the 61 Cygni binary system-one of the closest neighbors to our solar system (3.5 pc), the first stars to have a measured parallax, and two of the most favorable targets for habitable zone exo-Earth searches with future direct imaging missions. Kervella et al. (2022) first identified the candidate based on a 4.4$\sigma$ tangential velocity anomaly in the system determined using Hipparcos and Gaia DR3 astrometry of the A and B components. We combine this astrometric evidence with constraints from Gaia DR3 RUWE, MMT/Clio Lp imaging, nearly four decades of radial velocity (RV) measurements (including $\sim$2 years of new NEID RVs presented here), and N-body dynamical stability calculations of both stars in a Monte Carlo framework to estimate the candidate companion's mass and semi-major axis. Our analysis reveals that all of the available data are compatible with an $\approx(8 \pm 3)\;M_{\rm Jup}$ super-Jupiter in an $\approx(8 \pm 3)$ au orbit, with a broad range of allowed eccentricities and mutual inclinations. Using the Sonora Flame Skimmer evolutionary models, given the system's mature age of $(6.0 \pm 1.0)$ Gyr, we estimate a companion effective temperature of $(282 \pm 55)$ K and radius of $(1.02 \pm 0.02)\;R_{\rm Jup}$. Finally, we evaluate the stability of terrestrial planets in the habitable zone (HZ) of 61 Cygni AB in the presence of the giant planet candidate using N-body simulations. A companion semi-major axis $\lesssim$5 au, irrespective of the planet-planet mutual inclination, and between $\approx$5 au and 10 au, for misaligned orbits ($40^o \lesssim i_{\rm mut} \lesssim 140^o$), severely disrupts the HZ. Our results highlight the need to confirm the planet candidate and characterize its orbit to inform future exo-Earth searches with missions such as SHERA, HWO, and LIFE.
Read the full abstract

All authors Aniket Sanghi, Billy Quarles, Andrea S. J. Lin, Cheyanne Shariat, Pierre Kervella, James Mang, Dimitri Mawet, Mark R. Giovinazzi, Arvind F. Gupta, Charles Beichman, Bertrand Mennesson, Mathilde Mâlin, Jerry W. Xuan, Liton Majumdar, Jack J. Lissauer, Mark Wyatt, William O. Balmer, Eduardo Bendek, Kevin Wagner

Earth and Planetary Astrophysics

Pre-accretional irradiation of comet 67P/Churyumov-Gerasimenko constituents

Inès Sansberro, Nicolas Fray, Hervé Cottin et al. (+11 more)

Comets are thought to have largely preserved the primordial material from which they formed. Therefore, cometary studies provide important clues about the processes involved in the formation of the Solar System. During the last weeks of ESA's Rosetta mission, the COSIMA (COmetary Secondary Ion Mass Analyser) instrument performed a series of measurements, which involved long-term sputtering of dust particles captured from comet 67P/Churyumov-Gerasimenko. These post-sputtering analyses revealed the subsurface composition of 8 particles, which we compare here with surfaces composition measured on 59 un-sputtered particle fragments for 9 elements. We found that the analysed surfaces are strongly depleted in metals, such as Mg and Fe, compared to solar abundances, while the subsurface material is consistent with solar values. Because the dust captured by COSIMA fragmented upon impact with the collection targets, this metal depletion cannot reside exclusively on the outer surface of the bulk particles. Instead, these depletion layers must coat the surface of smaller, unfragmented mineral subunits. Such depletion layers, which are often called 'rims', are common at the surface of small regolith dust particles found on airless bodies in our solar system and are attributed to space weathering. We suggest that these mineral cometary subunits experienced pre-accretional solar wind irradiation in the inner regions of the solar nebula during the early stages of Solar System formation. The small irradiated dust constituents must then have been transported to the outer regions of the solar nebula, where they mixed with ices to form the nucleus of the comet.
Read the full abstract

All authors Inès Sansberro, Nicolas Fray, Hervé Cottin, Cécile Engrand, Donia Baklouti, Christelle Briois, Anaïs Bardyn, Henning Fischer, Klaus Hornung, John Paquette, Jouni Ryno, Olivier J. Stenzel, Laurent Thirkell, Martin Hilchenbach

Earth and Planetary Astrophysics

Application and Evaluation of the Material Point Method for Low-Velocity Asteroid Collisions Involving Large Deformations

Haru Fukuta, Tomoaki Ishiyama and Shu-ichiro Inutsuka

The collisional lifetimes of asteroids larger than $\sim 10$ km in the present-day main belt are estimated to exceed the age of the solar system, suggesting that their shapes may preserve memories of the collisional environment in the primordial solar system. Recent studies performed systematic simulations of equal-mass and low-velocity ($50$–$400\,\mathrm{ms}^{-1}$) collisions between 50-km-radius asteroids using Smoothed Particle Hydrodynamics (SPH), identifying the impact conditions that produce irregular shapes. As an alternative approach, we here employ the Material Point Method (MPM), a particle-grid method well suited to large deformation of solids and free from tensile instability, and we assess its applicability to such systems by direct comparison with the established SPH results. We integrate a previously established rock model combined with a fracture model, the Tillotson equation of state, and Drucker-Prager friction, with the efficient non-associative Drucker-Prager plasticity solver originally developed for granular flows. We perform 135 collision simulations of equal-mass rocky asteroids spanning 15 impact velocities ($50$–$400\,\mathrm{ms}^{-1}$) and 9 impact angles ($5$–$45^\circ$), following the setup of the previous SPH simulations. The mass, axis ratio, and shape classification of the largest remnants closely reproduce the trends of the previous SPH simulations. Since most material transitions into a granular state early in the collision, this agreement appears to depend primarily on the validity of the frictional treatment of the granular material, rather than on the details of the fracture model. These results demonstrate the applicability of MPM to low-velocity asteroid collision simulations and support cross-validation between MPM- and SPH-based approaches.
Read the full abstract

Earth and Planetary Astrophysics

COSINE (Cometary Object Study Investigating their Nature and Evolution) II: Colors and Sizes of Comet Nuclei

Yuna G. Kwon, Dar W. Dahlen, Joseph R. Masiero et al. (+6 more)

Comet nuclei preserve a record of planetesimal formation, but their sizes are difficult to measure because the nucleus is usually blended with its coma. We present a catalog of nucleus sizes for 523 comets (235 long-period and 288 short-period comets; LPCs and SPCs) from the 14.5-year WISE/NEOWISE archive, supplemented by Spitzer photometry. A coma-nucleus decomposition of the radial profiles yields conservative upper limits for all 523 comets and diameters with uncertainties for 301 (107 LPCs and 194 SPCs), with median diameters of 5.3 and 2.5 km, respectively. Nucleus colors across the four WISE bands follow the heliocentric trend expected from the transition between reflected and thermal emission, with no measurable difference between the two dynamical classes. The cumulative size-frequency distribution of the SPCs has a slope of $\gamma = 1.45_{-0.13}^{+0.15}$ (68% confidence interval) over $D = 2$–15 km, steepening to $2.05_{-0.38}^{+0.47}$ for the perihelion $q < 2$ au subset. The LPC distribution is smoothly concave down: a broken power law places a break near 35 km, with slopes of $0.92_{-0.12}^{+0.13}$ below and $3.68_{-1.24}^{+1.96}$ above, while the $q < 2$ au subset gives $1.39_{-0.28}^{+0.35}$ over $D = 4$–20 km. All distributions flatten below the fitted ranges and level off near 1 km. We discuss the implications of our results and their connection with models of the destabilized trans-Neptunian population.
Read the full abstract

All authors Yuna G. Kwon, Dar W. Dahlen, Joseph R. Masiero, Yanga R. Fernández, Adeline Gicquel, James M. Bauer, Yoonyoung Kim, Frank Masci, Amy K. Mainzer

Earth and Planetary Astrophysics

The NEID Earth Twin Survey. VI. Discovery of a Low-Mass Planet Orbiting HD 126053 and RV Signals Near the Rotation Periods of HD 168009 and HD 10780

Arvind F. Gupta, Sarah E. Logsdon, Jacob K. Luhn et al. (+19 more)

Extreme precision radial velocity (EPRV) spectrographs are making strides in extending the limits of radial velocity exoplanet detection. Perhaps the best evidence for this is how readily EPRV instruments are facilitating the discovery and detailed characterization of small-amplitude planetary signals around stars that have already been intensively monitored for decades with less stable instruments. In this paper, we use data from the ongoing NEID Earth Twin Survey (NETS) to detect and confirm the planet HD 126053 b (P=10.91 d), which is among the least massive planets (m sin i = 3.60 m M_\oplus) around solar-type stars within 25 pc. We then jointly characterize the known planet HD 168009 b (P=15.14 d; m sin i = 8.64 M_\oplus) orbiting a solar analog along with a previously unreported signal at 27.8 d which we tentatively attribute to rotational modulation of stellar activity (P_rot = 30.1 d). We also analyze and discuss periodic RV variations in HD 10780 arising from a combination of rotationally-modulated activity and a long-term activity cycle. We discuss HD 126053 b and HD 168009 b in the context of the broader small planet population and our sensitivity to long-period planets in these systems, and we comment on our capacity to disambiguate planet-induced and activity-induced radial velocity signals. HD 126053 is exceptionally RV-quiet, making it a promising target for continued RV monitoring in search of low-mass exoplanets in the habitable zone.
Read the full abstract

All authors Arvind F. Gupta, Sarah E. Logsdon, Jacob K. Luhn, Evan Fitzmaurice, Suvrath Mahadevan, Paul Robertson, Eric B. Ford, Chad F. Bender, Mark R. Giovinazzi, Samuel Halverson, Te Han, Daniel M. Krolikowski, Andrea S.J. Lin, Joe P. Ninan, Michael L. Palumbo III, Leonardo A. Paredes, Jayadev Rajagopal, Arpita Roy, Christian Schwab, Gudmundur Stefansson, Ryan C. Terrien, Jason T. Wright

Friday 25 September

Earth and Planetary Astrophysics

Investigating potential causes for high inferred intrinsic temperatures of warm transiting Neptune and Sub-Neptune planets

Saugata Barat, Jean-Michel Désert, Allona Vazan et al. (+7 more)

Atmospheric characterization of a warm 10-30 Myr old sub-Neptune progenitor (V1298 Tau b) and a $\sim$3.4 Gyr old warm super-Neptune (WASP-107b) using JWST have revealed extremely low methane abundance. Atmospheric forward models find higher than expected inferred intrinsic temperatures (450~K and 500~K) — inconsistent with theoretical planet formation and core-envelope evolution predictions (70K and 150K respectively) assuming a convective interior. We explore three hypotheses to reconcile the high intrinsic temperatures with evolutionary models — tidal heating, silicate rainout and heat trapping due to deep cloud condensation. Tidal heating requires high planetary obliquity ($\gtrsim70^{\circ}$) and low reduced tidal quality factor ($\sim$100) for V1298 Tau b, implying an extremely short obliquity damping timescale ($<$10$^{4}$ years). Although high obliquity may be maintained by spin–orbit resonant locking, it requires fine-tuning and is therefore unlikely. Silicate rainout can increase the temperature in the deep atmosphere of the young V1298 Tau b (0.1-1 bar) by $\sim$700K, without requiring extremely high intrinsic temperature, but is unlikely to explain WASP-107b, as silicate rainout timescales are expected to be much shorter than its age. Including cloud condensation in self-consistent atmospheric models reduces the inferred intrinsic temperature for V1298 Tau b from 500K to 300K, still exceeding the core-envelope prediction (150K). Future measurements of thermal emission from young transiting planets such as V1298 Tau b, combined with methane abundances as a function of age, will be needed to distinguish between these scenarios.
Read the full abstract

All authors Saugata Barat, Jean-Michel Désert, Allona Vazan, Ritika Sethi, Sagnick Mukherjee, Sarah Millholland, Jonathan J. Fortney, William Misener, Hilke E. Schlichting, Sara Seager

Earth and Planetary Astrophysics

The First Hubble Detection of a Secondary Eclipse from a Rocky Exoplanet: the 5.4-hour planet TOI-2431 b

Sebastian Zieba, Billy Edwards, Samuel N. Quinn et al. (+18 more)

We present an HST/WFC3 G141 phase-curve observation of the ultra-short-period rocky planet TOI-2431 b and detect its secondary eclipse in the near infrared. Combined with the TESS optical eclipse, these measurements constrain the planet's dayside brightness temperature, reflected light contribution, albedo, and heat redistribution. We detect the eclipse in the optical and near infrared wavelengths of TESS and HST/WFC3 G141, with a planet-to-star flux ratio of 37+/-10 ppm and 69(+14/-13) ppm, respectively. Assuming negligible reflected light, the joint TESS+HST fit yields a brightness temperature T_b,joint=2524(+77/-84) K and a brightness temperature ratio of R_joint=T_b,joint/T_p,max=0.980(+0.032/-0.034) consistent with the zero-albedo, no-redistribution limit T_p,max=2574(+36/-35) K. The HST phase curve is consistent with zero nightside emission and no measurable hotspot offset, consistent with inefficient day-night heat distribution. Under this thermal-dominated interpretation, TOI-2431 b lies at the zero-albedo, no-redistribution limit and contrasts with previously observed lava worlds. At optical and near-infrared wavelengths, however, thermal emission is degenerate with reflected light. For a geometric albedo of A_g=0.1, reflected light would contribute approximately 11 ppm in each bandpass, reducing the temperature to T_b,joint(A_g=0.1)=2407(+91/-102) K. Longer-wavelength observations are required to isolate the thermal component. Planned JWST/MIRI LRS observations are expected to substantially reduce this degeneracy and provide more direct constraints on heat redistribution and possible silicate-atmosphere spectral features. This marks the first secondary eclipse detection of a rocky exoplanet using HST and establishes TOI-2431 b as a benchmark target for studying properties of lava worlds.
Read the full abstract

All authors Sebastian Zieba, Billy Edwards, Samuel N. Quinn, Leoni J. Janssen, Nicolas B. Cowan, Laura Kreidberg, Mercedes Lopez-Morales, Lisa Dang, Luca Malavolta, Yamila Miguel, T. Giang Nguyen, Andrew Vanderburg, Thomas G. Wilson, Mantas Zilinskas, Nicholas J. Connors, Ian J. M. Crossfield, Oliver Herbort, Adam L. Kraus, Tim Lichtenberg, Mariana Sastre, Joost P. Wardenier

Earth and Planetary Astrophysics

JWST Reveals the Kuiper Belt-like Compositions of the Uranian Rings and Small Moons

Matthew Belyakov, M. Ryleigh Davis, Zachariah Milby et al. (+2 more)

We present the JWST NIRSpec 1–5 micron spectra of the Uranian rings and four ringmoons: Puck, Perdita, Portia, and Juliet. We find that the compositions of the rings and moons strongly resemble water-type Kuiper belt objects, showing deep 3.0 micron O–H and water ice features as well as the CO$_2$ band at 4.27 micron. The volatiles show a radial trend of decreasing volatile abundance at closer radial distance to the planet, consistent with recent estimates of the densities of the innermost moons. Given the observed compositional signatures, we suggest two ways to reconcile the history of the small inner moons with that of the regular ones. The first is that the Uranus-tilting collision produced a disk from an impactor formed out of material similar to that which comprises water-rich Kuiper belt objects, and the ringmoons are small undifferentiated remnants of that process. Alternatively, the rings and ringmoons postdate the formation of the regular moons, and formed from the later tidal disruption of a several hundred kilometer sized undifferentiated water-type Kuiper belt object.
Read the full abstract

All authors Matthew Belyakov, M. Ryleigh Davis, Zachariah Milby, Ian Wong, Michael E. Brown

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

Negative and Positive Cascade Rates of Slow Alfvénic Turbulence in Switchback and Non-switchback Intervals: Wind Observations

Sofiane Bourouaine

We estimate the turbulent cascade rate in imbalanced Alfvénic turbulence in the slow solar wind using a Politano–Pouquet-based approach that does not require an isotropic assumption. We analyze selected 8-hour intervals provided by Wind spacecraft. These intervals are characterized by near-homogeneity, weak velocity shear, and imbalanced Alfvénic fluctuations, and are classified as switchback or non-switchback depending on the angular spread of the magnetic field relative to the mean field. Switchback intervals are identified by large magnetic-field rotations, whereas non-switchback intervals exhibit only small angular deviations. Our results show that non-switchback intervals exhibit a positive total cascade rate and power spectra consistent with a $-3/2$ scaling, indicative of a forward energy cascade. In contrast, switchback intervals are characterized by a negative total cascade rate (inverse cascade), and by steeper power spectra with a spectral index of approximately $-1.6$. This indicates that large magnetic-field rotations can substantially modify the scale-to-scale energy transfer in Alfvénic slow solar wind. The results suggest that switchbacks may be associated with additional physical processes, such as local instabilities, or reconnection-related structures, that alter the direction and magnitude of the turbulent cascade. These findings may help explain previous reports of negative cascade rates in imbalanced Alfvénic solar-wind turbulence.
Read the full abstract

Earth and Planetary Astrophysics

Variable X-ray flux may explain variable helium escape from the habitable-zone exoplanet LHS 1140b

Collin Cherubim, Tim Cunningham and Jason A. Dittmann

A central goal in exoplanet science is to understand the conditions under which potentially habitable worlds retain atmospheres. This question is of special interest for worlds orbiting M stars, whose habitable-zone planets are more readily observable, but which also emit prolonged high-energy radiation that can erode planetary atmospheres. For one such world, LHS 1140b, a rocky planet orbiting in the habitable zone of an inactive star, time-variable helium absorption has been observed as the planet transited in front of its host star, consistent with atmospheric escape. We present X-ray/ultraviolet flux observations with the XMM-Newton space telescope, which serve to test whether the observed helium absorption variability can be explained by stellar XUV flux variability. We detect X-ray flux variability with an amplitude of $F_\mathrm{max}/F_\mathrm{min} = 8.5^{+9.4}_{-4.4}$ within the 18-hour observing window. We do not detect variability in the UV or visible flux. The integrated X-ray flux is fully consistent with the X-ray flux measured in 2018, suggesting stable XUV flux over years-long timescales. We find that the 2018 observation was not sensitive to the level of variability observed in 2026. We explore several models that fit both datasets and conclude that short-term XUV variability and/or small flares are more likely to explain the helium variability than long-term XUV variability. Simultaneous observations of the planet-transit in the near-infrared and stellar activity indicators like XUV flux are critical to confirm the link between the observed helium signal variability and the observed X-ray variability.
Read the full abstract

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

Electric Potential Patterns Forecasting in the Southern Hemisphere with Deep Learning Techniques

Francesco Pio Ramunno, Simone Mestici, Igino Coco et al. (+5 more)

Space weather disturbances driven by the solar wind can degrade satellite navigation, disrupt radio communications, and threaten power infrastructure, making accurate forecasting of the high-latitude ionosphere's response a critical operational need. Existing approaches, empirical climatological models and physics-based magnetohydrodynamic simulations, either smooth out the ionosphere's time-dependent, non-linear response or are too computationally expensive for real-time use, while prior machine learning efforts have mostly targeted scalar indices rather than the full spatial structure of ionospheric convection. Here we train and compare three deep learning architectures, a probabilistic diffusion model conditioned on multi-variate solar wind and interplanetary magnetic field measurements at the L1 Lagrange point, an unconditioned diffusion ablation, and a deterministic U-Net baseline, to forecast Southern Hemisphere high-latitude electric potential maps derived from SuperDARN radar observations. Using five years (2020–2025) of SuperDARN data synchronised with DSCOVR L1 measurements, we evaluate the models under a single-pass regime, an extended autoregressive rollout of up to 350 frames, and an out-of-distribution case study on the intense March 2015 St.\ Patrick's Day storm, unseen during training. We find that the relative advantage of the deterministic and probabilistic approaches is not fixed: the deterministic model is competitive over short horizons and calm conditions, while the diffusion model's advantage grows and eventually dominates as the forecast horizon lengthens and the event becomes more dynamic, evidence that probabilistic, sample-based generative models are the more promising direction for operational, long-horizon space weather forecasting.
Read the full abstract

All authors Francesco Pio Ramunno, Simone Mestici, Igino Coco, Maria Walach, Stefano Massetti, Maria Federica Marcucci, Brandon Panos, André Csillaghy

Earth and Planetary Astrophysics

Inclination of Miranda as a Constraint on the Tidal Dissipation of Uranus

Maryame El Moutamid and Matija Ćuk

The five major moons of Uranus record a complicated geological history characterized by both tectonic resurfacing and heavy impact cratering, connecting their evolution to dynamical processes in the Solar System. Miranda, the smallest and closest major moon to Uranus, has an unusually large orbital inclination ($4.3^\circ$) and an remarkable surface geology dominated by coronae and tectonic structures. In this paper we explore whether Miranda's inclination and geological history can be explained through past orbital resonances within the Uranian satellite system. Using direct $N$-body integrations with the code SIMPL, we explore the tidal and dynamical evolution of the five major moons while assuming a fast tidal dissipation of Uranus and varying the internal responses of the satellites. Our simulations confirm that Miranda's inclination can be excited through resonant interactions involving Ariel and Umbriel, even when Miranda mean motion is not involved in that resonance. The Ariel-Umbriel 5:3 mean-motion resonance appears to be the most recent major dynamical event capable of driving Miranda's inclination to its current value. We compute the tidal heating associated with these resonance encounters and show that, for a strongly dissipative Uranus ($Q_U\sim600$), the resonance could cause heat fluxes in Miranda approaching those required to form its coronae. These results could provide new constraints on Uranus's tidal dissipation.
Read the full abstract

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

Physics-induced impact on the properties of Kepler/K2 solar analogs in the light of PLATO's requirements

Saniya Khan, Gaël Buldgen, Jérôme Bétrisey et al. (+2 more)

Solar analogs are useful laboratories for tests of stellar structure and evolution, particularly in the context of the upcoming PLATO mission. Our study focuses on six seismic solar analogs observed by Kepler and K2. We investigate the impact of the model physical ingredients on these six targets in order to evaluate how well one can satisfy the PLATO precision requirements for stellar parameters with the data quality that is currently available to us. We used as reference values the stellar mass, age, and chemical composition obtained with the Forward and Inverse COmbination (FICO) procedure, based on OPAL opacities and a combination of NACRE II and Solar Fusion II (SFII) nuclear reaction rates. The efficiency of macroscopic transport is calibrated on lithium abundances derived from the analysis of HERMES spectra. From there, we carried out extensive tests of the physical ingredients with the help of a Levenberg-Marquardt local minimisation method using both classical and seismic constraints. In particular, we investigated the impact induced by the use of OPLIB opacities and SFIII nuclear reaction rates on the stellar fundamental properties, as well as the use of various seismic constraints. We quantify the potential differences that changes in the modelling input physics may lead to, and compare their extent with the requirements expected for the PLATO mission (15% in mass, 2% in radius, and 10% in age), providing crucial constraints on the accuracy and robustness with respect to systematics of the determination of fundamental properties for PLATO. For our sample of solar analogs, we are able to accurately retrieve stellar masses within 2.5%. As for stellar ages, we quantify systematics of the order of 10-14% at most, but there are also very promising cases for which deviations remain within 4% depending on the stars and constraints considered.
Read the full abstract

All authors Saniya Khan, Gaël Buldgen, Jérôme Bétrisey, Rafael A. García, Savita Mathur

Earth and Planetary Astrophysics

N-Body Dynamics as a Mechanism for Mean Motion Resonance Formation in the Post-Gas Era

Kai Sun, Sheng Jin, Dong-Hong Wu et al. (+1 more)

Mean motion resonances (MMRs) are traditionally thought to form during the gas-rich phase of protoplanetary disks via disk-driven migration. Whether MMRs can form solely through collisional damping after disk dispersal has not been systematically investigated. To study MMR formation in the post-gas-disk era, we perform a large suite of N-body simulations, each containing 10,000 planetesimals around an M-dwarf star and evolving over 10 Myr. We compare two groups of simulations that differ only in their initial mass distributions. Each group consists of 10 runs with statistically identical initial planetesimal orbital distributions, generated using different random seeds. One group adopts a uniform planetesimal mass distribution, whereas the other features a bimodal distribution with massive embryos embedded in a swarm of smaller planetesimals. At 1 Myr, 40% of systems (8/20) exhibit near-resonant period ratios, but this fraction drops to 25% (5/20) by 10 Myr as higher-order commensurabilities dissolve. Resonant-angle tracking shows that all persistent systems have circulating resonant angles at 10 Myr, although one system undergoes a transient libration phase between about 2 and 7 Myr before returning to circulation. These results demonstrate that collisional merging can drive MMR formation even without a gas disk, although in this scenario near-resonant configurations are strongly favored over true resonances. Furthermore, this mechanism produces similar MMR fractions in both groups, suggesting that MMR formation is insensitive to the initial mass distribution, although the latter may modulate the formation pathway to a limited extent.
Read the full abstract

All authors Kai Sun, Sheng Jin, Dong-Hong Wu, Meijuan Wang

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

From Image Morphology to Multiphysics Earth Posteriors

Ziye Yu, Xin Liu and Yuqi Cai

Structural learning and physical-property inference can draw on different sources of knowledge. We learn morphology from 33,140 natural, satellite, and texture images, without geological training models, then infer Earth properties from physical observations. Identical frozen weights map 128 coordinates into each $256\times256$ compressional-velocity, shear-velocity, or density field. Fixed adapters assign physical meaning; observation-specific likelihoods determine new posteriors without retraining. Across 256 unseen Earth models, image coordinates reduce projection error fourfold relative to a dimension-matched cosine basis. Matched inversions favor image coordinates for the tested curved-velocity targets and a smooth radial basis for the tested faulted targets. A simplified 2.5-dimensional application with 915 measured observations along one 120.9-km southern-California profile constrains a velocity–density contrast. Grouped arrival-time and gravity errors fall by 43% and 44% relative to the pretrained image prior, although the matched smooth radial basis predicts better. Direct layered-Rayleigh updating reduces blind phase-velocity error by 28% at five sites, whereas P-and-gravity-only sharing worsens it, distinguishing reusable morphology from beneficial cross-property coupling. These results establish a practical separation: images supply structural alternatives, and heterogeneous physical observations determine their experiment-specific posterior probabilities.
Read the full abstract

Earth and Planetary Astrophysics

JWST detection of methane emission from a young brown dwarf

K. L. Luhman, C. Alves de Oliveira, J. K. Faherty et al. (+1 more)

In recent studies, we have used low-resolution spectroscopy (R~100) with the James Webb Space Telescope (JWST) to uncover low-mass brown dwarfs (2-10 MJup) in the young cluster IC 348 that exhibit the so-called 3.4um absorption band from aliphatic hydrocarbons. Atmospheric models have not predicted the presence of that band in brown dwarfs at any age. Instead, methane absorption was expected in the coolest newborn brown dwarfs, but it was not detected. We have performed JWST spectroscopy at higher resolution (R~1000) on one of the brown dwarfs in IC 348, LRL 11001 (~6 MJup). The new measurement of the 3.4um band is fit well with four Gaussians that represent the CH stretching modes of CH2 and CH3 groups, indicating that the carrier is a large alkane (CnH2n+2). In addition, the spectrum contains emission lines at 3.324 and 3.333um, which we attribute to Q branches of CH4 hot bands between the octad and dyad regions (primarily nu3+nu4->nu4) and the tetradecad and pentad regions. This is the first detection of 3.33um CH4 emission from a young brown dwarf. The emission probably arises from the photosphere rather than a circumstellar disk given that no disks around stars or brown dwarfs are known to exhibit emission in these transitions. Modeling of the emission is needed to constrain the excitation mechanism, which could be either thermal (e.g., an accretion shock) or pumping by external radiation (e.g., neighboring cluster members). We speculate that vertical mixing has suppressed CH4 and enhanced large alkanes in the photosphere, but CH4 survives in the upper atmosphere, where it is available to experience the observed emission.
Read the full abstract

All authors K. L. Luhman, C. Alves de Oliveira, J. K. Faherty, B. C. Smith

Earth and Planetary Astrophysics

TS23/McDonald and FIES/NOT strike again. Two new warm Jupiter systems and outer companions in a third

E. Knudstrup, D. Gandolfi, W. D. Cochran et al. (+29 more)

Warm Jupiters (gas giant planets with orbital periods of P$\sim$8-200 d) are thought to be largely unaffected by the tidal interactions that can erase information about the dynamical histories of hot Jupiters. Their orbital eccentricities ($e$) and stellar obliquities are therefore expected to be preserved, making them valuable probes of giant-planet formation and migration. Our aim is to identify and characterise transiting warm Jupiters in order to expand the sample of well-characterised systems and enable further studies of giant-planet formation and migration. We analyse TESS transit photometry together with ground-based radial velocity measurements and perform a joint fit of the photometric and spectroscopic data from the TS23 and FIES spectrographs to determine the planetary and orbital parameters. We report on the discovery and characterisation of two new, transiting warm Jupiters; TOI-5120 b ($M_p = 1.23\pm0.05$ M$_{\rm Jup}$, $R_p = 0.969\pm0.017$ R$_{\rm Jup}$, $P = 24.91645\pm0.00002$ d, $e = 0.10\pm0.02$) and TOI-5699 b ($M_p = 0.25\pm0.03$ M$_{\rm Jup}$, $R_p = 0.996\pm0.015$ R$_{\rm Jup}$, $P = 22.01850\pm0.00004$ d, $e = 0.30^{+0.09}_{-0.08}$). We also refine the parameters of the known warm Jupiter TOI-2158 b ($M_p = 0.87\pm0.04$ M$_{\rm Jup}$, $R_p = 0.899\pm0.015$ R$_{\rm Jup}$, $P = 8.60079^{+0.00002}_{-0.00001}$ d, $e = 0.028^{+0.013}_{-0.014}$). In addition, we detect an outer planetary companion, TOI-2158 c ($M_p \sin i = 1.62\pm0.13$ M$_{\rm Jup}$, $P = 414.5^{+1.5}_{-1.6}$ d, $e = 0.54\pm0.04$), and identify a long-term radial velocity trend that may indicate another planetary companion on a wide orbit. The diverse architectures of these systems, in particular the presence and absence of outer companions, highlight the range of dynamical pathways leading to warm Jupiters.
Read the full abstract

All authors E. Knudstrup, D. Gandolfi, W. D. Cochran, M. Endl, P. MacQueen, T. Pugh, M. S. Lundkvist, C. M. Persson, A. Stokholm, M. L. Winther, J. R. Larsen, J. L. Rørsted, S. H. Albrecht, K. A. Collins, C. Watkins, B. Edwards, D. R. Ciardi, C. A. Clark, A. S. Polanski, C. Ziegler, C. Briceño, A. W. Mann, M. Everett, S. Howell, B. Safonov, T. Gan, K. Barkaoui, P. Benni, R. P. Schwarz, K. Horne, R. Sefako, D. Muthukrishna