Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM
South Pole-Aitken basin sample Return and eXploration (SPARX) Science Definition Team Report
Lauren M. Jozwiak, James T. Keane, Robert Citron et al. (+18 more)
Sample return from South Pole-Aitken Basin (SPA) on the Moon has been recognized as the highest priority lunar science mission for well over two decades, appearing as a recommended New Frontiers class mission in the two previous Planetary Science Decadal Survey documents (2003-2012 New Frontiers, 2013-2022
Visions and Voyages), and as a prioritized mission for the Lunar Discovery and Exploration Program (LDEP) in the 2023-2032 Origins, Worlds, and Life Decadal Survey. The South Pole-Aitken basin presents the ideal target destination to test nearly 60 years of lunar science hypotheses owing to a unique combination of its size, antiquity, and location on the lunar farside. Convened by NASA in response to OWL Decadal Survey recommendations, the SPARX report provides analysis on prioritized science objectives, measurement requirements, implementation architectures, and a design reference mission for a South Pole-Aitken basin sample return mission. The mission profiles presented in this report leverage key advancements in remote surface exploration technology, the U.S. commercial space industry, and the programmatic focus on sustained human presence and exploration at the lunar south polar region. The science objectives and measurements presented in this report outline a mission that would transform lunar science, would address multiple high-level Decadal science questions at the only place in the Solar System where they can be credibly addressed, would pioneer a new paradigm for planetary surface exploration in the 21st century, would leverage the burgeoning space economy to pursue ground-breaking science on a more cost-efficient basis, and would unite robotic exploration with human exploration in a model for a future sustained lunar enterprise.
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All authors Lauren M. Jozwiak, James T. Keane, Robert Citron, Natalie Curran, Steve Elardo, Caleb Fassett, Abigail Fraeman, Saira Hamid, Lena Heffern, Peter James, Daniel Moriarty, Kevin Righter, Jennifer Whitten, Hunter Vannier, Zoe Wilbur, Tomokatsu Morota, Hiroshi Nagaoka, Caroline-Emmanuelle Morisset, Patrick Hill, James Carpenter, Francesca MacDonald
Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM
Increasing Sensitivity to Trailed Solar System Objects in Archival JWST NIRCam Imaging with Group Differencing
Anthony Girmenia and Stanimir Metchev
The JWST archive contains thousands of NIRCam exposures distributed across the sky. Small solar system bodies (SSSBs) are present in many of these fields, but are often trailed and more difficult to detect. The standard pipeline produces a single image by fitting a slope to a sequence of $N$ cumulative “up-the-ramp" groups of the detector. Thus, each JWST image comprises a time series of cumulative reads. We demonstrate that transforming the ramp into a series of group difference images reduces the per-image trail length of moving sources, producing an $(N-1)$-group photometrically calibrated time series from an $N$-group integration. This enables higher-cadence trajectory-based searches using as few as a single JWST exposure. A generalized least-squares fit of the group difference images along the trajectory of a moving source recovers the source flux at higher SNR when compared to the ramp fit, with the improvement scaling with the reduction in trailing. We validate our procedure on 13 moving objects detected in archival JWST NIRCam images. To estimate our sensitivity increase, we perform an injection/recovery simulation on the JWST imagery. Trailed moving objects recovered via group differencing show higher SNRs, improving completeness to moving sources compared to standard calibrations. For typical integration lengths of $N=4$ or $6$ for archival JWST/NIRCam exposures in the ecliptic, group differencing yields sensitivity gains between $\sim 1.1$–$1.4$ mag, based on simulation results. This method significantly increases the sensitivity of archival JWST surveys to trailed SSSBs.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR
A Multiband Catalog of Infrared-Excess Sources in the Vela-Carina Region: VVVX, DECaPS, and GLIMPSE
R. M. Torres, R. K. Saito, V. Fermiano et al. (+4 more)
Multiwavelength surveys of the Galactic midplane enable the identification of infrared-excess sources, signatures of circumstellar material, though high extinction and crowding hinder detection. We construct a homogeneous catalog of infrared-excess candidates in a $\sim$7.0 deg$^2$ field of the Vela-Carina region, characterizing their excess emission via spectral energy distribution (SED) analysis. We combine optical photometry from DECaPS, near-infrared photometry from VVVX, and mid-infrared photometry from Spitzer/GLIMPSE using hierarchical positional cross-matching. Candidates are selected via photometric quality and MIR color diagnostics, and their SEDs are analyzed with VOSA using theoretical atmosphere model grids. Photogeometric distances are adopted, while Gaia DR3 and NEOWISE variability provide complementary diagnostics. From the matched 249,719-source VVVX-GLIMPSE-DECaPS catalog, we identify 1,512 MIR-excess objects, of which 191 have complete 12-band photometry with S/N > 10, enabling detailed SED analysis. Photogeometric distances are statistically consistent with
geometric distances for nearly the entire sample. SED analysis independently supports the MIR-excess nature of most sources, indicating emission beyond stellar photospheres. About 15% of sources are flagged variable by Gaia, while NEOWISE light curves reveal MIR variability of a few tenths of a magnitude. Comparisons with published YSO and variability-selected catalogs show limited overlap, particularly with variability-selected samples, indicating that MIR-excess selection complements other approaches to identifying candidate YSOs in the Vela-Carina region. The resulting catalog provides a well-defined MIR-excess sample with homogeneous multiband photometry, SED characterization, distances, and variability diagnostics, forming a foundation for future spectroscopic and time-domain studies.
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All authors R. M. Torres, R. K. Saito, V. Fermiano, P. Esteves, B. W. Borges, D. Quispe, D. Minniti
Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM
Laboratory Evidence that Methanol-Rich Ice Mantles Lower Methyl Formate Binding Energies
Rachel E. Gross, Jeroen Terwisscha van Scheltinga, L. Ilsedore Cleeves et al. (+5 more)
Complex organic molecules are widely detected in
star-forming regions and are important precursors to prebiotic species. Because these molecules are thought to form primarily within icy grain mantles, their desorption is assumed to be regulated by the sublimation of the surrounding H$_2$O ice
matrix. However, observations increasingly reveal gas-phase abundances of methyl formate (MF) at temperatures well below the sublimation temperature of water ice (T ~ 100K), challenging this view. To investigate how ice composition and phase influence MF desorption, we present laboratory temperature-programmed desorption measurements of MF from four astrophysically relevant substrates: amorphous and crystalline H$_2$O and CH$_3$OH. Desorption kinetics were analyzed using pre-exponential factors derived from transition-state theory with leading-edge analysis and non-negative least-squares inversion to recover binding-energy distributions. We find that MF binds more weakly to CH$_3$OH ice than to H$_2$O-rich substrates, with representative binding energies of ~6247K for amorphous H$_2$O, ~6213K for crystalline H$_2$O, and ~5469K for amorphous CH$_3$OH. MF deposited on crystalline CH$_3$OH exhibits coverage-independent leading edges consistent with multilayer or island desorption, yielding an effective binding energy of 5333K. Enhanced surface mobility and reduced trapping efficiency on methanol ice, combined with weaker MF binding, provide a natural explanation for the early appearance of gas-phase MF observed in
star-forming environments, with characteristic desorption temperatures of ~85K on CH$_3$OH and ~95-100K on H$_2$O. Together, these effects support a two-step thermal desorption pathway in which MF associated with CH$_3$OH-rich ice can be released prior to bulk H$_2$O sublimation.
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All authors Rachel E. Gross, Jeroen Terwisscha van Scheltinga, L. Ilsedore Cleeves, Catherine A. Dukes, Robin T. Garrod, Alexia Simon, Shane Sawyer, Adam Woodson
Earth and Planetary Astrophysics
Revisiting planetesimal formation from mm-sized grains in pressure bumps
Tabassum S Tanvir, Jacob B Simon, Daniel Carrera et al. (+1 more)
We present evidence that the streaming instability (SI) can form planetesimals from millimeter grains inside axisymmetric pressure bumps, provided the bump is not too strongly reinforced. We conducted three-dimensional local shearing-box simulations of millimeter grains in a Gaussian pressure bump of amplitude $A = 0.6$, at a resolution of $160/H$. We varied only the Newtonian reinforcement timescale $t_{\rm reinf}$, the timescale on which the imposed bump is restored against particle back-reaction. Our reference run T1 uses $t_{\rm reinf} = 1\,\Omega^{-1}$. Particles pile up in a narrow axisymmetric band at the minimum-headwind point, cross the Roche density, and collapse through direct gravitational instability (GI). In our weakly reinforced run T100 with $t_{\rm reinf} = 100\,\Omega^{-1}$, the outcome is different. Particles drift through the bump roughly three times more slowly, and dense SI-like filaments develop across a wide radial region well before the Roche density is reached. These results are consistent with a residence-time criterion, which states that for the SI to grow, $t_{\rm cross} > t_{\rm grow}$, where $t_{\rm cross}$ is the time a particle spends inside the region where the ratio $Z/\Pi$ of the solid abundance $Z = \Sigma_p/\Sigma_g$ to the headwind parameter $\Pi = \Delta v/c_{\rm s}$ is high enough for strong clumping, and $t_{\rm grow}$ is the SI growth time. T1 violates this criterion, and T100 satisfies it. Our results suggest that the reinforcement timescale matters for millimeter grains because it helps set the crossing time, and therefore whether the SI has time to grow. We caution, however, that our reinforcement scheme is an idealised numerical construction rather than a physical bump-forming mechanism such as a
planet, and a more definitive test of this picture will require simulations with a more physically motivated bump.
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All authors Tabassum S Tanvir, Jacob B Simon, Daniel Carrera, Jeonghoon Lim
Earth and Planetary Astrophysics
M Dwarf Singles and Multis Have Dissimilar Metallicities Indicating Different Origins
Aida Behmard, Sheila Sagear, Yuxi Lu et al. (+3 more)
It is unclear if host
star metallicities differ between systems with one detected transiting
planet ("singles") or multiple detected transiting
planets ("multis") around FGK dwarfs. Here, we find strong evidence that they do for M dwarfs. We use a homogeneous sample of FGK and M dwarf chemical abundances to demonstrate that M dwarf multis are significantly more metal-poor than singles ($p$ = 0.00079), even when we only consider small (<4 $R_{\oplus}$)
planets ($p$ = 0.0013). This result emerges at the late-K to M dwarf transition. We observe that M dwarf multis become more metal-poor as a function of increasing
planet multiplicity. Additionally,
planets in singles have significantly higher eccentricities and shorter orbital periods compared to
planets in multis. We interpret these findings as evidence that M dwarf singles lead relatively active dynamical lives, and the different planetary architectures of singles and multis arise from distinct dynamics influenced by
metallicity. This may not occur in FGK systems because their more massive protoplanetary disks may supply enough
planet-forming material to instigate dynamics that lead to only one transiting
planet, even when the host
star metallicity is low. Another possibility is that multis are less compact around FGK dwarfs because they form from larger disks, which may often cause them to be observed as singles in transit data.
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All authors Aida Behmard, Sheila Sagear, Yuxi Lu, Romy Rodríguez Martínez, Adrian M. Price-Whelan, Soichiro Hattori
Earth and Planetary Astrophysics
Simulated Effects of Radioactive Elements on Magnetic Evolution and Atmospheric Mass Loss of Earth-like Planets
Nathaniel Tanglin and Juliette Becker
Thousands of
exoplanets have been discovered in recent decades, yet Earth remains the only known world with life. To assess the potential habitability of other
planets, we must identify the importance of various physical conditions that may contribute to sustaining life. One such factor is the presence of a planetary
magnetic field. A
planet's
magnetic field can protect its atmosphere from photoevaporation, and its long-term strength depends on interior heat flow driven by radiogenic heating from isotopes such as 40K, 232Th, 235U, and 238U. In this work, we use the VPLanet code to simulate the coupled thermal,
magnetic, and atmospheric
evolution of Earth-like
planets with varying radiogenic heat budgets orbiting G-, K-, and M-dwarf
stars. The range of isotope abundances tested is based on observed stellar elemental distributions for
planet-hosting
stars in the Milky Way. We find that variations in radiogenic heating slightly extend dynamo lifetimes and reduces atmosphere and surface water loss for K- and G-dwarf systems, while its effects are more negligible for M dwarfs. Our results show that, while stellar irradiation and planetary location primarily control photoevaporation rates, radiogenic heating contributes to planetary habitability in a small subset of cases and may help refine target selection for future surveys.
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Earth and Planetary Astrophysics
JWST and HST Confirm Transit Timing Variations for the Ultra-Hot Jupiter TOI-2109 b
Michael Greklek-McKeon, Julie Inglis, Nicole L. Wallack et al. (+9 more)
Ultra-hot Jupiters are a rare yet valuable subset of
exoplanets that can help elucidate both the internal properties of their host
stars as well as the orbital
evolution of close-in
planets. An extreme among extremes, TOI-2109 b is a super-Jupiter ($1.347 \pm 0.047 R_{\rm Jup}$, $5.02 \pm 0.75 M_{\rm Jup}$) with the shortest orbital period (0.67247479 $\pm$ 0.00000028 days) and the fastest predicted orbital decay rate of any known giant
planet. Previous observations hinted at a quadratic long-term trend in the transit timing variations (TTVs) consistent with orbital decay, as well as short-term sinusoidal TTVs consistent with a near-resonant planetary companion that would indicate a dynamically quiescent migration pathway. Here, we combine archival ground-based, TESS, and CHEOPS photometry with new transit and eclipse data from HST and JWST to update the TTV analysis. We find very strong evidence for sinusoidal TTVs over a linear ephemeris ($\Delta$BIC of 33.6), consistent with a nearby planetary companion as suggested by J.-V. Harre et al. 2024, and rule out several non-planetary scenarios that could explain the sinusoidal TTVs. We also find strong evidence of a quadratic TTV trend ($\Delta$BIC of 6.75) consistent with an orbital decay rate of -3.46 $\pm$ 1.17 ms/yr and a stellar tidal quality factor of 2.13$^{+1.18}_{-0.61} \times10^7$, though we cannot rule out line-of-sight acceleration as the cause of the quadratic trend. If our results are confirmed, TOI-2109 b would be the only known
exoplanet besides WASP-12 b with a decaying orbit and the most extreme of an ultra-rare class of close-in giant
planets with nearby companions.
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All authors Michael Greklek-McKeon, Julie Inglis, Nicole L. Wallack, Shreyas Vissapragada, Ian Wong, John R. T. Allen, Yayaati Chachan, Fei Dai, Guangwei Fu, Tiffany Kataria, Thaddeus D. Komacek, Johanna K. Teske
Earth and Planetary Astrophysics
Revealing the Shiny Nature of Lava Worlds: Small Planet Phase Curves with TESS
Brandon Park Coy, Michael Zhang, Fei Dai et al. (+1 more)
Recent thermal emission observations suggest that `lava worlds'–Earth-sized
exoplanets hot enough to melt their silicate surfaces–have atmospheres on a population-level. This evidence comes from measured dayside brightness temperatures much lower than expected for a dark, maximally hot bare rock. However, these results are degenerate between a thick atmosphere advecting heat to the
planet's nightside or a high albedo reflecting incoming radiation. This degeneracy can be resolved through visible light phase curve observations, which can constrain how much light is reflected by the
planet. Here, we present a population-level analysis of the visible-light TESS phase curves of $R\lesssim5\,R_{\oplus}$
exoplanets. We select the population by defining a `Reflection Spectroscopy Metric' meant to quantify the relative signal-to-noise of reflected light observations. We report new $>3\,\sigma$ detections of the TESS phase curve signals of LTT 9779 b and the lava worlds TOI-2431 b, TOI-561 b, 55 Cancri e, K2-141 b, and TOI-1444 b. We use these results and previous results from Kepler and CHEOPS to homogeneously derive
geometric albedos for these
planets, revealing that lava worlds generally show high albedos compared to the low
geometric albedos measured for hot Jupiters at similar temperatures. These results support an emerging picture of reflective silicate clouds on these worlds cooling their daysides. The upcoming PLATO mission is expected to tightly constrain the reflected light phase curves of lava worlds.
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All authors Brandon Park Coy, Michael Zhang, Fei Dai, Qiao Xue
Earth and Planetary Astrophysics
Characterization of Planetary Systems with Astrometry
Gisela N. Ortiz-Leon
Astrometry is the oldest method used to search for extrasolar
planets. This technique provides key information about a planetary system, like the true mass of
planets and its three-dimensional orbital architecture. Nowadays, the space-based mission Gaia, on one hand, and ground-based interferometry at infrared and
radio wavelengths, on the other hand, can achieve astrometric accuracies of tens of micro-arseconds. Thanks to this unprecedented level of accuracy, the number of astrometrically discovered
exoplanets has started to grow. In this chapter, I review the basic principles for orbital characterization of unseen planetary companions using astrometric data. I also review the properties of the
exoplanets discovered so far with astrometric methods and comment on the contributions that this technique can make to the
exoplanet field.
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Earth and Planetary Astrophysics
High-resolution optical spectroscopy reveals the distinctive volatile composition of the interstellar comet 3I/ATLAS
K. Aravind, E. Jehin, C. Opitom et al. (+9 more)
Comets preserve volatile material from the early stages of planetary-system formation. The discovery of the interstellar comet 3I/ATLAS enables a direct comparison between a comet formed around another
star and comets in the Solar System. We characterise the coma composition of 3I/ATLAS across perihelion using homogeneous high-resolution near-UV and optical spectroscopy with UVES on the ESO Very Large
Telescope, from August 2025 (r$_h$=3.14 au) pre-perihelion to February 2026 (r$_h$=4.34 au) post-perihelion. From flux-calibrated spectra, we measured OH, NH, CN, C$_3$, CH and C$_2$ emissions, derived production rates, examined abundance ratios and heliocentric-distance trends, constrained NH$_2$, and compared OH-based water production with estimates from forbidden oxygen lines. Gas production rates show broadly symmetric pre- and post-perihelion behaviour, with steeper heliocentric-distance dependences than typically observed in Solar System comets. NH and NH$_2$ are strongly depleted, indicating a severe deficiency of ammonia-related volatiles. The C$_2$/CN ratio indicates carbon-chain depletion and evolves with heliocentric distance, consistent with coma-driven effects such as hyperactivity rather than intrinsic compositional changes. Water production from forbidden oxygen lines exceeds OH-based estimates except near perihelion, suggesting varying contributions from H$_2$O and CO$_2$ to coma chemistry. Relative abundance correlations place 3I/ATLAS outside the canonical Solar System comet cluster and closest to strongly carbon-chain depleted comets, including G-Z-type comets, while showing strong depletion of NH- and C$_3$-bearing species relative to CN. 3I/ATLAS therefore extends the known diversity of cometary compositions, demonstrating that volatile reservoirs in other planetary systems can differ substantially from those sampled by Solar System comets.
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All authors K. Aravind, E. Jehin, C. Opitom, J. Manfroid, D. Hutsemékers, D. Bodewits, M. Bannister, R. C. Dorsey, L. Ferellec, H. Kawakita, M. Lippi, C. Snodgrass
Earth and Planetary Astrophysics
NGTS clusters survey - VII. An Enigmatic Short-Period Circumsecondary Disk Candidate in Orion
Niamh Mallaghan, Ernst J. W. de Mooij, Christopher A. Watson et al. (+31 more)
Young stellar systems provide key insights into the processes governing
star/
planet formation, often exhibiting complex and evolving photometric variability. In this paper, we present an analysis of the object around NOI 105872, observed by the Next Generation Transit Survey (NGTS) to eclipse a young ($4.1\pm0.4$ Myr) M-type
star in the Orion Nebula Cluster. The system displays deep, asymmetric eclipses with a period of $\sim0.69$ days, alongside variability in morphology. We combine photometric observations spanning approximately a decade from multiple ground- and space-based facilities to investigate the nature of this system. We explore a range of physical scenarios to reproduce the eclipse profiles and their
evolution. After analysis, our preferred explanation is a circumsecondary disk surrounding a companion in orbit around the M-type primary. We adopt a six-parameter disk model and fit the eclipse profiles independently to each
dataset. The best-fitting solution yields a disk radius of $\sim 0.005 \mathrm{au}$ or $0.98 R_{*}$, with broadly consistent orientations across epochs, but with variations that may be attributed to disk precession or intrinsic stellar variability. Constraints from the Hill radius imply a companion mass consistent with a very low-mass stellar companion. These results establish NOI 105872 as a candidate for a circumsecondary disk system in a young stellar environment. Continued photometric monitoring and spectroscopic follow-up will be essential to confirm this interpretation. If confirmed, systems such as NOI 105872 provide valuable
benchmarks for understanding disk dynamics, companion formation, and the origin of complex eclipse phenomena in young
stars.
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All authors Niamh Mallaghan, Ernst J. W. de Mooij, Christopher A. Watson, Edward Gillen, Matthew Kenworthy, Louise D. Nielsen, David R. Anderson, Matthew P. Battley, Edward M. Bryant, Matthew R. Burleigh, Benjamin M. J. Cadell, Sarah L. Casewell, Alexander Chaushev, V. S. Dhillon, Elsa Ducrot, Jorge Fernandez Fernandez, Samuel Gill, Michael Gillon, Michael R. Goad, Faith Hawthorn, Katlyn L. Hobbs, James McCormac, Maximiliano Moyano, Catriona A. Murray, Toby Rodel, Suman Saha, Ramotholo R. Sefako, John Southworth, Mathilde Timmermans, Amaury H. M. J. Triaud, Jose Vines, Richard G. West, Peter J. Wheatley, Tafadzwa Zivave
Earth and Planetary Astrophysics
Molecules in the shadows of the protoplanetary disk HD 143006: Evidence for C/O $\gtrsim 1$ from simultaneously modeling fourteen ALMA lines
S. E. van Terwisga, P. Woitke, A. M. Weiss et al. (+2 more)
The inner disk of the T Tauri
star HD 143006 is inclined and casts a broad shadow on a large portion of the outer disk. We use this extraordinary geometry to study the impact of stellar ultraviolet (UV) irradiation on disk chemistry, temperature, and line formation. We present new ALMA observations of this disk in CO, $^{13}$CO, C$^{18}$O, CN, HCN, HCO$^+$, CS and C$_3$H$_2$ and combine these with previously-published data to get a rich
dataset, which is modeled with ProDiMo models for the illuminated and shadowed side by including an optional inclined inner disk to partially block stellar illumination of the outer disk. The observed line flux contrasts between the illuminated and the shadowed disk sides are small. We explain this by introducing “equilibrated models” which consider a slow heating/cooling relaxation of gas parcels orbiting in and out of the shadow. We fit the radial line intensity profiles of all 14 ALMA lines for both halves of the disk, the SED beyond 20$\,\mu$m, and two ALMA continuum images, with an overall reduced $\chi$ of about 2.3, in one combined model. Line intensities only increase slightly on the illuminated side because the gas warms up slowly, although fast UV photochemistry significantly reduces the observable molecular concentrations. For the lines of N$_2$H$^+$ and CS, which probe deeper layers where the gas and dust temperatures are coupled, slow UV-desorption of ices such as NH$_3$ and H$_2$S plays a crucial role. This can result in a brightening of these lines on the shadowed side. The carbon-to-oxygen ratio in the outer disk of HD 143006 is slightly greater than one ($\sim 1.05$). The disk mass is fitted to be as low as $0.0012 M_{\odot}$, but almost equally well-fitting models with a fixed disk mass of $0.021 M_\odot$ can be obtained after re-adjusting the disk shape, dust, and gas heating/cooling parameters. (abridged)
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All authors S. E. van Terwisga, P. Woitke, A. M. Weiss, A. D. Bosman, L. Trapman
Earth and Planetary Astrophysics
Transport and Thermochemical Kinetics of Alkali Species in Hot Jupiter Atmospheres: Implications for Magnetic Models
D. A. Christie, T. M. Evans-Soma, N. J. Mayne et al. (+4 more)
Interactions between the planetary
magnetic field of a hot Jupiter and the winds within its atmosphere are moderated by the electron and ion abundances. For a solar
metallicity atmosphere at pressures between 10 and $10^{-4}$ bar, the primary sources for these charged species are expected to be the potassium and sodium atoms, and models of
magnetic effects in hot Jupiter atmospheres have typically assumed that charged species exist within the atmosphere in their
equilibrium abundances. In this work, we investigate the thermochemical kinetics of alkali species within a hot Jupiter atmosphere, thus allowing for the thermal ionisation fraction to depart from
equilibrium, and demonstrate that quenching of ions occurs between 1 and 10 mbar. This increase in ionisation fraction on the nightside and at mid-latitudes results in stronger
magnetic interaction, here modelled using the
magnetic drag approximation, further slowing the jet and altering the global circulation. We additionally show that while quenching occurs, large
magnetic resistivities resulting from low electron abundances continue to exist on the nightside between 10 and 100 mbar, in tension with magnetohydrodynamic models that assume horizontally uniform
magnetic resistivities to simplify the explicit integration of the induction equation. At lower pressures ($\sim$ 0.1 mbar) where the electrons have become horizontally homogenised, the
magnetic Reynolds number approaches or exceeds unity, signalling the breakdown of the
magnetic drag approximation. We thus stress that chemical kinetics represents a dynamically important component of modelling hot Jupiter atmospheres while at the same time further complicating the treatment of
magnetic effects.
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All authors D. A. Christie, T. M. Evans-Soma, N. J. Mayne, E. Hébrard, M. Zamyatina, J. E. Owen, K. Kohary
Earth and Planetary Astrophysics
Molecular mapping of an exoplanet with JWST: NH3 detection in the temperate super-Jupiter Epsilon Indi Ab
R. Kravtchenko, O. Berné, I. Schroetter et al. (+2 more)
Epsilon Indi Ab is currently the coldest, and one of the closest, directly imaged
exoplanets (T_eff = 275 K, d=3.6 pc), offering a unique opportunity to test our understanding of the physical and chemical properties of gas giants across the full temperature range spanned by hotter directly imaged
exoplanets and the cooler giants of the Solar System. We aim to characterize the atmosphere of Epsilon Indi Ab using infrared spectroscopic observations. We present JWST spectroscopic observations of Epsilon Indi Ab obtained with MIRI in the Medium Resolution Spectrograph mode (4.9-27.9 microns, October 2025) and NIRSpec in the Integral Field Unit mode (2.87-5.27 microns, May 2026). The data are highly contaminated by the stellar light from the bright host
star. We therefore adopt a high-pass filtering and cross-correlation approach based on petitRADTRANS atmospheric models to detect the planetary signal and specific molecules. The cross-correlation analysis enables a robust detection of the
planet with both instruments (up to S/N = 15.2). Using molecular mapping, we securely identify the presence of NH3 (maximum S/N = 15.6), H2O (maximum S/N = 10.8), CH4 (S/N = 3.8) and marginally detect CO2 (S/N = 2.5). These first results confirm the potential of infrared spectroscopy combined to cross-correlation techniques to characterize the atmosphere of directly imaged
exoplanets with JWST, even the in case where the contamination by the host
star is critical.
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All authors R. Kravtchenko, O. Berné, I. Schroetter, P. Amiot, F. Debras
Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM
Fitting Moving Objects in Up-The-Ramp Data with Applications to the Roman Space Telescope and JWST
Timothy D. Brandt
A moving object breaks the fundamental property of constant per-pixel count rates in an astronomical image read out up-the-ramp. In this paper, we show how to fit a moving object's path across a detector as that detector is read out nondestructively. We write the full likelihood function for every pixel subject to a constant count rate plus a time-dependent count rate due to a moving source. Assuming the moving source to be point-like and assuming the effective point-spread function to be known, we are left with four parameters that enter the likelihood nonlinearly: two for position and two for velocity. All remaining parameters can be optimized using closed-form expressions. Our approach extracts maximal information on a moving source's position and speed and enables the source to be accurately removed from the image. We investigate the dependence of flux, position, and velocity precision on the target's speed and the readout pattern. We also find a small, positive bias on the recovered flux due to the need to fit for an uncertain position and speed. Our approach can be used for space-based images with minor Solar system bodies in the foreground, e.g.~from Roman and JWST, or for ground-based observations with satellites in the foreground. We demonstrate the promise of our method with a fit to an asteroid track observed serendipitously by the NIRISS instrument on JWST, comparing it to the performance of the JWST pipeline. Python code implementing our approach is available at https://github.com/t-brandt/moving_source. The total computational cost to fit the track of a moving object is $\sim$1 second on a 2023 Macbook Pro.
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Earth and Planetary Astrophysics · Cross-listed from math.DS
Identifiable Uniqueness of Impulsively Forced, Inert, and Stabilized Body Trajectories
Bo Pieter Johannes Andrée
An unusual object in the sky raises two related questions: what kind of object it is and what physical process drives its motion. Departures from a
gravity-only trajectory can provide evidence, but the same apparent acceleration may be generated by distinct dynamical mechanisms. We formulate this as an identification problem and establish conditions for identifiable uniqueness among three reference classes: inert dynamics, impulsive forcing, and active stabilization such as a controlled spacecraft. The distinction rests on how each class responds to disturbances. Although different mechanisms can produce similar average trajectories, the specified reference models imply different
stochastic responses around those trajectories. We show when these differences uniquely determine the dynamical class from the observed trajectory and when several classes remain observationally compatible.
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Earth and Planetary Astrophysics
Possible Observational Survey Strategies to Maximize Exoplanet Yields: A Report from the Survey Strategies Task Group in the Exoplanet Science Yields Working Group
Natasha Latouf, Corey Spohn, Kevin Fogarty et al. (+12 more)
We present a variety of possible observational sequences from
planet detection to characterization (i.e., survey strategies) for the initial exoEarth detection and characterization survey phase of the Habitable Worlds Observatory. An array of survey strategies were collated by the HWO
Exoplanet Survey Strategies Task Group; by investigating and comparing expected resultant exoEarth yields for multiple survey strategies, we can better understand the most efficient strategy to characterize multiple
planets in unconventional ways. We present eight varied survey strategies, presented as steps of Detection, Photometry, Orbit Measurement, and/or Characterization, including discussion of possible shortcomings and benefits of each strategy. We present exoEarth yield calculations from the Altruistic Yield Optimizer (AYO) and the
Exoplanet Open-Source Imaging Mission Simulator (EXOSIMS) for select strategies, with initial considerations of thermal emission and detector noise. Herein, a yield is the expectation value given the astrophysical assumptions of the number of
planets that meet the observational criteria during the survey. We find that AYO and EXOSIMS find the highest yields for H2O at 0.9 microns, although the calculated yields vary. When allowing for wavelength optimization within AYO, we find that H2O is most optimal to observe at 0.9 microns when given the full range of VIS and NIR values, with an expected exoEarth yield of 29.1. H2O and O2 dual characterization is possible at the expense of yield
planet loss, with a calculated possible yield of 20.9 in the VIS. The characterization of CH4 and CO2 in the NIR result in the lowest exoEarth yields at 19.9 and 6.4 possible expected
planets, respectively. Future work updating AYO and EXOSIMS is necessary to explore further survey strategies that follow different observation procedures, some of which is currently underway.
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All authors Natasha Latouf, Corey Spohn, Kevin Fogarty, Chris Stark, Dmitry Savransky n=and Eleonora Alei, Anthony Boccaletti, Gagandeep Kaur, Avi Mandell, Rhonda Morgan, Aki Roberge, Jean-Baptiste Ruffio, Jean Schneider, Edward Schwieterman, Armen Tokadijan, Daniel Viudez-Moreiras
Earth and Planetary Astrophysics
Large-scale chaos in restricted hierarchical triples driven by short-range forces
Xiaoyan Leng and Hanlun Lei
Context: The eccentric von Zeipel-Lidov-Kozai effect, which is widely applied to diverse astrophysical settings, can drive the inner binary to extremely high eccentricities, where short-range forces such as general relativity (GR) become prominent. Aims: Poincare surfaces of section show that GR effects reshape phase-space structures, giving rise to a widespread and large-scale chaotic sea. This work aims to uncover the underlying mechanism of GR-enabled chaos. Methods: The dynamical structures are studied within an adiabatic framework, where an adiabatic invariant is constructed. Phase portraits, defined by the level curves of this invariant, establish analytical boundaries for the chaotic domains. Numerical simulations are subsequently performed to map orbital flips, maximum eccentricities, and Fast Lyapunov Indicators (FLI) across the initial eccentricity-inclination parameter space. Results: Phase portrait analysis demonstrates that GR precession introduces an uncertainty zone near polar inclinations, where trajectories crossing this zone inherently become chaotic. Leveraging this framework, the chaotic boundaries across the full parameter space are analytically derived, yielding excellent agreement with numerical maps of flipping orbits, maximum eccentricity, and FLI. Conclusions: In the presence of short-range forces, flipping orbits accompanied by extreme eccentricity excitation are fundamentally chaotic, and the underlying mechanism of large-scale chaos originates from the periodic passage of trajectories through the uncertainty zone in phase space over secular timescales.
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