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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Friday 2 October

Earth and Planetary Astrophysics

Measuring the Age and Initial Composition of Interstellar Objects

Aster G. Barry-Taylor

Measuring the age and composition of interstellar objects is necessary to understand their origins. However, existing methods for measuring the age are either imprecise or require an unusually bright target, while the composition is confounded by the effects of Galactic cosmic rays, which drive chemical reactions in the cometary matrix. As the Vera C. Rubin Observatory expands the census of interstellar objects, measuring these properties will be critical to understanding the overall population. In this work, I derive a new methodology for simultaneously estimating the age and initial composition of an interstellar object from time-series observations of the coma. Measurements of both the composition and its gradient versus depth into the nucleus are shown to fully constrain both properties in most circumstances. A simple model using only CO and CO$_2$ is discussed and used to demonstrate the properties of this inference process. When applied to 3I/ATLAS, this simple model indicates that this object is at least 0.6 Gyr old and has an initial CO/CO$_2$ ratio of 1.5, supporting a formation outside the CO ice line. Further refinement of the chemical network and improved observational strategies will improve the precision and accuracy of these measurements, enabling a deeper understanding of the interstellar object population and extrasolar planet formation.
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Earth and Planetary Astrophysics

The Nearest, Brightest Debris Disk Host Stars: Updated Photosphere Models and Dust Properties for Stars with Saturated 2MASS Photometry

Inbok Yea, Sarah Dodson-Robinson, Cesar Julian Bustos Sanchez et al. (+1 more)

To discover and characterize debris disks, one must obtain high-quality photometry in order to accurately fit photosphere models for the host stars. Since the $K$ band always falls on the Rayleigh-Jeans side of a star's spectral energy distribution (SED), its reliability is particularly important for uncovering mid-infrared excess emission from dust. While Two Micron All Sky Survey (2MASS) photometry is the near-infrared benchmark for most stars that host debris disks discovered by Spitzer and the Wide Field Infrared Survey Explorer (WISE), the brightest stars ($K_s < 5$) saturated the 2MASS detectors. To accurately model debris disks that orbit the nearest, brightest stars, we construct new photosphere models by replacing saturated 2MASS data with $JHK$ photometry from the NASA Catalog of Infrared Observations, archival $R_C I_C$ photometry, and saturation-corrected WISE W1 photometry. We estimate the dust temperature and minimum distance from the star by fitting blackbody and modified blackbody models to infrared photometry from WISE, Spitzer, and Herschel. Our models allow us to identify disks that subtend large angles on the sky; these disks are candidates for follow-up with ground-based angular differential imaging, the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), and NIRCam on JWST. Finally, we find that the disk surrounding $\gamma$~Tri likely has warm dust that could be resolvable with JWST's MIRI instrument at $23$ or $25.5 \micron$. Multiwavelength observations provide benchmarks for collisional cascade models and may reveal planet–disk interactions.
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All authors Inbok Yea, Sarah Dodson-Robinson, Cesar Julian Bustos Sanchez, John E. Gizis

Earth and Planetary Astrophysics

Temporal Variability of Titan's Middle-Atmospheric Zonal Winds from Southern Fall to Late Winter (2016-2023)

Martin A. Cordiner, Yuan Lian, Juan M. Lora et al. (+10 more)

Previous ALMA observations have revealed unexpectedly strong and rapid variations in Titan's high-altitude equatorial zonal winds, which present a challenge to our understanding of this moon's atmospheric dynamics. Here we report further measurements of Titan's zonal wind field at middle atmospheric altitudes $\approx200$-490 km, based on ALMA observations of spatially and spectrally resolved CH$_3$CN emission between 2016-2023 (corresponding to a solar longitude $L_s=81.6^{\circ}$-$156.4^{\circ}$, spanning Titan's late southern autumn to late winter). These observations indicate substantial, ongoing, rapid temporal variability of Titan's zonal winds, on timescales as short as $\approx1$ Earth month ($0.9^{\circ}$ in $L_s$). The strongest variability is at (near-)equatorial latitudes where the zonal winds are fastest (up to $240\pm26$ ms$^{-1}$), with repeated $\sim40$ ms$^{-1}$ fluctuations occurring between $L_s=146.0^{\circ}$-$156.4^{\circ}$. The observed longer-term trends are qualitatively well-reproduced by two independent, state-of-the-art general circulation models (GCMs), which match the observed decrease in zonal wind speeds over a broad range of latitudes between $L_s=81.6^{\circ}$-$146.0^{\circ}$, followed by a more moderate increase between $L_s=146.0^{\circ}$-$156.4^{\circ}$. The wind speeds at mid-to-high latitudes ($\sim-45^{\circ}$ south) are also typically reasonably well reproduced by the GCMs (differing by $\lesssim30$%). However, the equatorial wind speeds are up to a factor of $\sim2$ faster than model predictions (with the greatest discrepancy around solstice; $L_s\approx90^{\circ}$). Rapid temporal variability of the retrieved zonal winds indicates the presence of strong atmospheric instabilities that are not well reproduced by models, suggesting a need for future GCM improvements.
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All authors Martin A. Cordiner, Yuan Lian, Juan M. Lora, Nicholas A. Lombardo, Lucy Wright, Jonathon Nosowitz, Richard Cosentino, Nicholas A. Teanby, Conor A. Nixon, Alexander E. Thelen, Claire E. Newman, Steven B. Charnley, Eliot F. Young

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

Plato benchmark stars I. The initial benchmark sample

T. Merle, P. F. L. Maxted, O. L. Creevey et al. (+23 more)

The ESA PLATO mission aims to detect and characterise Earth-size exoplanets orbiting bright, late-type stars using high-precision photometry and asteroseismology. Precise stellar parameters of host stars are essential for exoplanet characterisation and model benchmarking. This work defines the PLATO benchmark stars (PBS) catalogue, a comprehensive sample of well-characterised stars designed to support all mission phases. We compiled data from eclipsing and spectroscopic binaries, interferometry, asteroseismology, and large spectroscopic and photometric surveys. Fundamental and atmospheric stellar properties (mass, radius, luminosity, age, effective temperature, surface gravity, density, and limb darkening) were assigned quality levels (B1, B2, B3) reflecting their degree of model dependence. Homogenized ancillary parameters (including Gaia DR3 bias-corrected parallaxes, metallicities, bolometric fluxes, extinction, rotation periods, and X-ray fluxes for M dwarfs) are also provided. The PBS catalogue contains 1090 FGKM main-sequence and subgiant stars, divided into three quality tiers based on model-independent (B1) parameters: gold (15 stars with B1 mass, radius, and luminosity), silver (195 with B1 mass and radius), and bronze (416 with at least one B1 property). The remaining stars feature well-characterised model-dependent (B2) or empirical (B3) properties. About 40% of the sample lies within the PLATO fields of view (285 in LOPN1 and 143 in LOPS2). The PBS sample represents the largest catalogue of benchmark stars assembled to date, providing a key resource for validating automated pipelines, testing evolutionary models, and cross-survey calibration. The catalogue is available online at https://astro.ulb.ac.be/pbs and will be updated regularly.
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All authors T. Merle, P. F. L. Maxted, O. L. Creevey, U. Heiter, D. B. Palakkatharappi, K. G. Hełminiak, C. C. Aguilera Gómez, M. Bazot, S. Cassisi, N. Ebrahimkutty, R. E. Giribaldi, P. Jofré, F. Kiefer, M. N. Lund, N. Miller, T. Morel, D. Mourard, N. Nardetto, J.-D. do Nascimento, Jr., T. Olander, G. N. Pawar, A. Rebassa-Mansergas, R. Raddi, B. Rojas-Ayala, J. Southworth

Earth and Planetary Astrophysics

Joint RV-Astrometric Analysis of two-planet system HD 65216: Prospects for Gaia DR4

Alexander L. Wallace, Robert A. Wittenmyer and Jonathan Horner

We provide updated mass and orbital constraints on the planetary system around HD 65216, consisting of at least two giant planets on eccentric orbits. We first analyse new RV data to constrain the periods and eccentricities of both planets, before applying the Hipparcos-Gaia proper motion anomaly to constrain the inclination of HD 65216 c. From this joint analysis, we find that HD 65216 c is most likely in an eccentric orbit ($e$ = 0.42$\pm$0.05) with a longer period (7007$^{+192}_{-161}$ days) than previously determined. The proper motion anomaly is consistent with a bimodal distribution of inclinations, with peaks at sin$i\sim$0.5, producing true masses of 2.23$^{+0.96}_{-0.77}$ M$_{\mathrm{J}}$ and 3.32$^{+1.40}_{-1.16}$ M$_{\mathrm{J}}$ for HD 65216 b and c respectively, assuming the planets are co-planar. Finally, we simulate Gaia DR4 epoch astrometry and the DR3-DR4 proper motion anomaly. We find that these methods will be sensitive enough to further constrain orbital parameters and true mass.
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Earth and Planetary Astrophysics

Performance of AutoRegressive Planet Search methodology on simulated PLATO lightcurves

Eric D. Feigelson, Marco Montalto, Geert Jan Talens et al. (+4 more)

AIM. This study examines the PLATO mission sensitivity to small transiting planets (radii between 0.5 and 2.0 R$_\oplus$) using Autoregressive Planet Search (ARPS) methodology based on simulated lightcurves. Methods. Several thousand simulations of PLATO-like lightcurves from magnetically active stars expected from the PLATO Long Observation Phase South 2 (LOPS2) field with injected transiting planets smaller than 2.0 R$_\oplus$ radius are examined. The lightcurves are analyzed with ARPS that uses autoregressive modeling for filtering of nonplanetary signals and the Transit Comb Filter periodogram for planetary transit detection. False alarms of nonexistent periodic signals are reduced by thresholds on two ARPS parameters, peak periodogram power, and transit duration. Results. When applied to PLATO's simulated first three months observations of bright stars (P1 and P2 samples), at least 50% of Earth-size planets are recovered for periods shorter than 40 d. In two years of LOPS2 observation, 25% are recovered for periods less than 240 d. Methodological implications on detrending, periodograms, False Alarms, vetting, and catalog evaluation are discussed. The utility of a positive predicted value heat map after detection and vetting is demonstrated. Conclusions: While the ARPS planet detection procedure is not entirely well-suited for PLATO analysis, this study provides methodological insight into the sensitivity and reliability of small transiting planet detection.
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All authors Eric D. Feigelson, Marco Montalto, Geert Jan Talens, Suzanne Aigrain, Luca Malavolta, Valerio Nascimbeni, Tiziano Zingales

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

The 200-300 GHz Survey for 18 Class II Disks in the Ophiuchus Star-Forming Complex

Chia-Ying Chung, Hauyu Baobab Liu, Chuan-Yung Lin et al. (+4 more)

We measured the 198-310 GHz flux densities of 18 Class II protoplanetary disks in the Ophiuchus star-forming complex using the Submillimeter Array (SMA). The $\sim$200-300 GHz spectral indices ($\alpha_{200-300}$) of these disks are $2.3^{+0.2}_{-0.5}$. In this observed frequency range, emission properties of the Ophiuchus disks are very similar to the 48 spatially compact Class II disks in the Taurus-Auriga region observed in a previous SMA survey. Combining the Ophiuchus and Taurus-Auriga samples, the Pearson correlation coefficient between $\alpha_{200-300}$ and the flux density at 250 GHz ($F_{250\,\mathrm{GHz}}$) is 0.27 ($p=0.02$). We do not find a convincing correlation between $\alpha_{200-300}$ and the $R_{95\%}$ radius of the disks. Our interpretation for the $\alpha_{200-300}$ values being close to 2 in the spatially compact disks is that at $\gtrsim 200$ GHz frequencies, the continuum emission in these disks is dominated by optically thick dust thermal emission, independent of $F_{250\,\mathrm{GHz}}$ and $R_{95\%}$. As a result, the (sub)millimeter luminosity and the apparent disk size are positively correlated, which has been found in numerous resolved emission surveys of Class II disks. In young clusters with ages of $\sim$1-2 Myr, Class II disks with smaller radii or lower (sub)millimeter luminosities are not necessarily those in which the dust mass budget has been consumed or dispersed.
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All authors Chia-Ying Chung, Hauyu Baobab Liu, Chuan-Yung Lin, Linjing Feng, Sean M. Andrews, Mark A. Gurwell, Melvyn Wright

Thursday 1 October

Earth and Planetary Astrophysics

Pressure-induced desalting of NaCl-bearing ice VII: A compositional filter in water-rich planets

Alasdair Nicholls, Tomasz Poreba, Xi Zhu et al. (+6 more)

Sodium chloride is a major component of extraterrestrial oceans, but it is generally assumed to be excluded from the high-pressure ice mantles of water-rich planets. Here we show that a concentrated NaCl solution, when quenched in an amorphous state before compression, crystallises in a metastable NaCl-bearing ice VII phase. Synchrotron x-ray diffraction and neutron diffraction reveals an expanded and strongly disordered ice VII lattice with no detectable crystalline NaCl. Ab initio calculations reproduce lattice expansion by substituting water molecules for Na$^+$ and Cl$^-$ ions and show that the structural response increases strongly with salt concentration. Upon decompression at 300 K, the phase expels crystalline NaCl at $5.1 \pm 0.3$ GPa and does not reform upon recompression, demonstrating that its formation is controlled by the thermodynamic pathway. Despite an 8.5% larger unit-cell volume, NaCl-bearing ice VII has a density close to that of pure ice VII and is substantially less dense than an equivalent mechanical mixture of ice and halite. These properties suggest that salty ice may be transported through deep convecting mantles but release salt near the 5 GPa boundary, where the denser products could inhibit further upward transport. Pathway-dependent salt trapping may therefore provide a previously unrecognised control on chemical exchange between rocky interiors and subsurface oceans.
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All authors Alasdair Nicholls, Tomasz Poreba, Xi Zhu, Richard Gaal, Stefan Klotz, Gabriel Tobie, Henrik M. Ronnow, Razvan Caracas, Livia Eleonora Bove

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

Post-Training Quantization of Autoregressive Weather Models

Ananyo Bhattacharya, Swastik Bhattacharya and Christiane Jablonowski

Advancements in high-resolution numerical weather prediction (NWP) and data assimilation (DA) have shaped the developments in deep learning (DL) architectures emulating atmospheric dynamics. Emulators for weather forecasting exhibit forecast quality comparable to physics based models at forecast horizon scaling from few days to subseasonal time scales. The emulators are driven by hardware-accelerated matrix multiplication in autoregressive inferences, significantly reducing the computation time and resources required for NWP. Optimization of the matrix multiplication processes in GPU architectures provides opportunities to scale towards high-resolution domain, and offers implementation of out of the box solutions. Post-training quantization (PTQ) has been demonstrated across multiple DL architectures to accelerate and increase the number of computations in unit time while consuming less power, enabling applications on edge hardware. In this study, we investigate the effect of PTQ on pre-trained AI emulators for global-scale weather forecasting. We implement PTQ algorithms in Deep Learning Weather Prediction (DLWP) and FourCastNet (FCN) models as a proof of concept for geophysical fluid dynamics applications. We systematically investigate the effect of PTQ on emulator inferences over short-range forecast horizons. Evaluation of PTQ configurations using simulated quantization hints at qualitatively meaningful forecasts over short-time horizons. These results provide a first benchmark of PTQ for autoregressive weather emulators and a basis for quantization-based optimization of DL models for dynamical systems.
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Earth and Planetary Astrophysics

TOI-1408: the limb darkening models, photometric and Doppler noises, and the exoplanetary system

Roman V. Baluev

We perform a self-consistent analysis of Doppler and photometric TESS and ground-based transit observations available for TOI-1408, known to host a system with two planets orbiting near 2:1 mean-motion commensurability and a distant companion. In general we confirm its orbital configuration derived in previous studies, however we found that the likelihood function contains multiple local maxima spread over a wider parametric domain, thus making some model uncertainties significantly larger than deemed before. In particular, the planet b radius still appears poorly constrained (from $\sim 1.2$~$R_{\rm Jup}$ to $\sim 3.5$~$R_{\rm Jup}$) because of the near-tangential transit geometry. We also show that the derived model is very prior-dependent regarding the astrophysical (spectrum-derived) constraints on the stellar mass $M_\star$ and radius $R_\star$. While such estimations may potentially contribute a significant information to the fit, their prior distribution must be accurately specified to be useful. Presently so accurate characterization (e.g. the correlation between $M_\star$ and $R_\star$) is not available in the literature.
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Earth and Planetary Astrophysics

Interpreting effective homogeneous rheologies through a local differential map with application to the Moon

Yeva Gevorgyan

Layered viscoelastic interiors control the frequency dependence of planetary tidal dissipation, but repeated layered Love-number calculations are expensive in long-term orbital and spin integrations. Equivalent homogeneous rheologies provide a cheaper representation of the same response, but their effective parameters do not by themselves identify the interior layers they represent. We develop a local interpretation of such parameters by differentiating the layered-to-homogeneous construction about a fixed-geometry baseline, perturbing only selected layer rigidities and viscosities. We use the pole-residue representation of the degree-two Love number to construct a physical-to-effective transfer matrix. We then use its singular values, resolution matrix, and mode-dominance matrix to determine which physical perturbations are visible in the Love-number response and how they appear in effective-rheology coordinates. Applied to a five-layer lunar model, the full degree-two response is sensitive to seven of eight solid-layer rheological parameters. The single near-null direction is the inner-core rigidity, consistent with shielding by the fluid outer core and with the weak dependence of Love numbers on core elastic structure. Over the LLR frequency interval, fewer physical directions are visible. To first order, the elastic spring, isolated dashpot, and two Voigt elements reproduce the nine-pole response over this interval. Finite perturbations confirm the tangent prediction to within a few percent, with the validity radius limited by a nearly degenerate pair of long-timescale modes.
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Earth and Planetary Astrophysics

Constraining Particle Stiffness in Asteroid Regolith from Early-Time High-Speed Penetrator Dynamics under Local Granular Variability

Zichen Wang, Yang Yu, Chenyang Huang et al. (+4 more)

Mechanical properties of rubble-pile asteroid regolith remain poorly constrained because contact responses depend on both material properties and local particle configuration. This study examines whether early-time high-speed penetrator dynamics can constrain particle stiffness, represented by the particle Young's modulus E, within a controlled discrete-element model. A bidirectionally coupled EDEM-Adams discrete-element-multibody model is used to screen six parameters: Young's modulus, Poisson's ratio, coefficient of restitution, static friction coefficient, rolling friction coefficient, and adhesion strength. Five Young's-modulus levels are then tested at the same 17 spatial locations in one settled granular bed, giving 85 simulations with location-matched comparisons across modulus levels. Within the 75-90 m s^-1 speed range, varying Young's modulus yields the clearest and most systematic differences in probe deceleration, whereas the other parameters have weaker effects over the tested ranges. Validation by withholding all modulus cases at one location in turn indicates that the early response is more informative for distinguishing broad modulus ranges than adjacent modulus levels. Mesoscale analysis links the response differences to concentrated interface load sharing and spatially extended three-dimensional high-capacity contact paths as Young's modulus increases. The results provide a numerical basis for narrowing the particle Young's-modulus range from high-speed penetration responses despite local granular variability. Quantitative application to real asteroid regolith requires further experimental validation.
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All authors Zichen Wang, Yang Yu, Chenyang Huang, Zhijun Song, Yutian Wu, Xiaojing Zhang, Xuhui Zhang

Earth and Planetary Astrophysics

Planetary eccentricity enhances inward comet transport but suppresses gentle impacts

Qunfeng Jiang

Comets can supply volatile and prebiotic material to rocky planets, but survival of fragile molecules depends on atmospheric entry and impact. Compact planet chains can transfer comets inward at low velocity. We test whether modest planetary eccentricity preserves this route. We follow 64,000 comets from the region between the two outermost planets of an eight-planet chain to an Earth-mass planet on a temperate orbit around a $0.1 M_\odot$ star. A second suite of simulations isolates the last transfer to the innermost planet across initial planet eccentricities $e_{p,0}=0$–$0.05$ and separations of 10 and 30 mutual Hill radii; a $\Delta=12$ comparison tests the influence of the near-3:2 period ratio at $\Delta=10$. At $e_{p,0}=0.05$, the fraction of comets intercepted by the outermost planet falls by 11 per cent and 6 per cent more reach the inner region. The innermost planet's impact probability changes by less than 3 per cent, while the fraction of impacts below 15 km s$^{-1}$ falls from 25 to 18 per cent. The fraction of all injected comets producing impacts below 15 km s$^{-1}$ consequently decreases by 30 per cent. Measurements of the comet-planet speed before the final close encounter show that eccentricity preferentially removes the slowest approaches. Applying an impact-chemistry model gives a 31 per cent lower HCN survival-equivalent yield. Modest planetary eccentricity can therefore increase inward transport while reducing the prebiotic material delivered under chemically favourable impact conditions.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Comparing Optimized Systematic Error Correction Methods on Selected TESS Light Curves

David Rapetti, Jon Jenkins, Joseph Twicken et al. (+2 more)

The correction of systematic errors in TESS light curves is crucial for all astrophysical analyses employing these observations. Here we present a data analysis and a software package, SysCoCoPy, to investigate and directly compare the performance of the Presearch Data Conditioning (PDC) correcting method from the Science Processing Operations Center (SPOC) pipeline and three correctors developed by the community. We incorporate these three correctors based on their implementations in Lightkurve and are particularly interested in the ability of the four correctors to remove scattered light contamination from the Earth and the Moon, which is a key systematic for TESS. We implemented these correctors in SysCoCoPy with a framework that allows an automatic optimization of their parameters to scale the analysis towards increasingly larger samples. SysCoCoPy provides qualitative and quantitative products for the comparison of individual cases as well as statistical results for selected samples. We currently find that while our automatic parameter optimization provides a significant number of successful scattered-light corrections for two of the correctors with a design that favors this purpose, an statistical analysis of our largest sample indicates that PDC is presently more robust, with a larger overall success level of the metrics used.
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All authors David Rapetti, Jon Jenkins, Joseph Twicken, Douglas Caldwell, Jeffrey Smith

Wednesday 30 September

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

A Missing Latent, Not a Missing Simulator: Radius-Augmented Inference for Real JWST Retrieval

Angshuman Chakravertty and P V V Raj

Amortized simulation-based inference (SBI), which is trained on radiative-transfer simulators, recovers exoplanet atmospheres accurately on synthetic James Webb Space Telescope (JWST) spectra but collapses when it comes to real reduced spectra. The flow posterior collapsed on real WASP-39b (importance-sampling effective sample size (ESS) = 1, best-fit ḩi}2/N = 301), and such a failure is usually blamed on missing the forward-model physics, but ruling these levers out with nested sampling first (a temperature gradient, SO2 opacity, and a high-fidelity opacity set) leaves the fit unchanged, meaning the collapse is not from the simulator misspecification but instead from a missing latent, the planet radius. To fix this, we build MIRAGE, a radius-augmented flow-matching posterior calibrated against an independent nested-sampling reference with importance sampling and an optimal-transport map, which yields a physical and literature-consistent retrieval of real WASP-39b (with ḩi}2/N from 301 to 0.06). This same method transfers unchanged across two instruments and three real JWST targets, including one spectrum self-reduced end-to-end from raw Mikulski Archive for Space Telescopes(MAST) data. The lesson is cross-domain, as a latent the simulator encodes but the inference omits can masquerade as misspecification.
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Earth and Planetary Astrophysics

Correlations between the Carbon-to-Oxygen Ratio and the Orbital and Physical Properties of Exoplanets

Noah Ferich, Robert Royer III, Cody Shakespeare et al. (+1 more)

Studies suggest that protoplanetary disks around stars with high carbon-to-oxygen (C/O) ratios can produce terrestrial planets with carbon-dominated compositions instead of silicon-dominated ones. While previous work studied the evolution of these disks and the planets that form within them, none analyze in detail how the differences in the surface density profiles of these disks could affect the architectures and iron and siderophile contents of exoplanetary systems. Here, we present a new study that uses the N-body integrator REBOUND and data from a sequential dust condensation model to simulate the formation of planets in systems with varying C/O ratios. We find that bulk density could be used to distinguish between silicon-rich and carbon-rich planets, though it may not be a reliable metric on its own.
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All authors Noah Ferich, Robert Royer III, Cody Shakespeare, Jason H. Steffen

Earth and Planetary Astrophysics

How eccentric is the debris disk of epsilon Eridani? ALMA reveals a near-circular belt

Oto Ulrich, Joshua B. Lovell, David J. Wilner et al. (+2 more)

The nearby (3.2 pc) K2V star $\epsilon$ Eridani hosts the closest detected debris disk and an exo-Jupiter analog ($\epsilon$ Eridani b). In this work, we reanalyse ALMA Band 6 (1.29 mm) observations of $\epsilon$ Eridani to assess whether its outer debris belt exhibits a non-zero eccentricity, potentially induced by planet-disk interactions. Considering two models, one that accounts for the disk's forced eccentricity ($e_\mathrm{f}$) and another that accounts for a proper eccentricity ($e_\mathrm{p}$), we place stringent (99.7th-percentile) upper limits of $e_\mathrm{f} < 2.6\%$ and $e_\mathrm{p} < 6.8\%$, respectively, and find tentative evidence for a non-zero forced eccentricity of $e_\mathrm{f} = 1.62^{+0.39}_{-0.40}\%$ at the $4\sigma$ level. This corresponds to the lowest millimeter-derived upper limit on the forced eccentricity of any debris disk to date, which, together with the low upper limit on the proper eccentricity, suggests that the outer belt is nearly circular and dynamically cold. We further explore planetary system architectures that are consistent with these ALMA-based results in combination with Spitzer/IRAC, JWST/NIRCam F444W, and JWST/MIRI F2550W data. Together, these analyses provide insight into potential planet-disk interactions in this nearby system, constraining any additional planet beyond $\epsilon$ Eridani b to masses ranging from $\sim 2\times10^{-4}$ to $0.3\,M_\mathrm{Jup}$ at orbital separations of $\sim 6$-$60$ au.
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All authors Oto Ulrich, Joshua B. Lovell, David J. Wilner, Antranik A. Sefilian, Mark Booth

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

Water enhances the formation of refractory sulfur in interstellar ices

Carlos del Burgo Olivares, Hector Carrascosa, Guillermo M. Muñoz Caro et al. (+3 more)

Sulfur is the tenth most abundant element in space, yet it is strongly depleted in the gas phase of dense interstellar regions, suggesting sequestration in dust grain components that are difficult to detect. We study whether UV irradiation and thermal processing of H2S-containing interstellar-ice analogues can produce refractory sulfur species, and whether water-dominated ice enhances their formation. We performed UV irradiation and warm-up experiments on H2S-containing ice analogues with and without water, and the resulting refractory residues were analysed ex situ. Refractory sulfur species, including the sulfur allotropes S6-S8, are formed during UV irradiation and thermal processing of H2S-containing interstellar-ice analogues. Water enhances the formation of these sulfur allotropes by two orders of magnitude. We propose a formation mechanism in which ionic intermediates stabilised by the water-ice matrix promote chain growth and cyclisation, yielding predominantly S8. The combined detection in our residues of sulfur allotropes and polythionic species, also reported in meteorites and samples returned from asteroids, supports their formation in pre-cometary ice mantles covering dust grains. Because these species can incorporate multiple sulfur atoms per molecule, they constitute an efficient solid-phase reservoir for the missing sulfur in dense cloud environments where young stars are born. Refractory sulfur can therefore serve as a tracer of water-ice environments in space.
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All authors Carlos del Burgo Olivares, Hector Carrascosa, Guillermo M. Muñoz Caro, Rafael Lebron-Aguilar, Jose E. Quintanilla-Lopez, Yao-Jen Chen

Earth and Planetary Astrophysics

Flow dynamics of cryolava or impact melt on Titan's surface

Daniel Cordier, Bastien Bodin, Stephane Le Mouelic et al. (+1 more)

Titan, a unique body in the solar system, resembles a life-size Miller-Urey experiment where pockets of liquid water might interact with abundant organic matter. Its young surface (less than a billion years) shows signs of material exchange with the interior, and an isotopic signature is detected in the atmosphere. Cryovolcanism and meteor impacts represent potential high energy mechanism for these exchanges. Although cryolava or impact melt properties are largely unknown, Titan's internal structure makes a significant water content in these fluids highly probable. The temperature of these fluid mixtures at the onset of the flows is above 0~$^\circ$C. The primary objective of this work is to investigate the dynamical and thermal properties of potential Titanian flows, while ensuring their spatial extents remain broadly consistent with the few available observations. We also aim to assess whether their evolution could enable the hydrolysis of encountered organic material. On Earth, in the context of lava flow risk assessment, numerical techniques based on cellular automata have been developed for many years. This approach allows simulating the flow of Bingham fluids over distance scales of several tens of kilometers. In the context of Titan's surface, and within the explored parameter space, flows with a spatial extent of several tens of kilometers can be produced with our model. The resulting flow thickness is about a meter. The flow extent is primarily controlled by the total erupted volume and the terrain topology. As expected, the rheology and thermo-physical properties of the erupted fluid have significant influence on the flow's extent and the cooling rate of the cryolava. We predict hydrolysis reactions between an aqueous cryolava and the organic matter likely ubiquitous on Titan's surface. Our model code is publicly available.
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All authors Daniel Cordier, Bastien Bodin, Stephane Le Mouelic, Ashley G. Davies

Earth and Planetary Astrophysics

Project CERES: Nuclear Thermal Transportation and In-Situ Propellant Production A Foundational Architecture for Solar System Logistics

S.P. Worden and F.G. Kennedy

Project CERES proposes a reusable deep-space transportation architecture centered on the dwarf planet Ceres, combining nuclear thermal propulsion (NTP) with in-situ production of water, hydrogen, oxygen and ammonia. Its first flight, a Pathfinder that surveys Ceres and returns samples, also bears on the question of life: Dawn found the ingredients of prebiotic chemistry there, and returned material would show just how far that chemistry went. We survey every direct Earth-Ceres opportunity from 2032 through 2042 with ephemeris-based Lambert analysis and compare chemical, gravity-assisted, nuclear-electric and nuclear thermal vehicles under one parametric mass model. Impulsive requirements vary from 10.2 to 14.1 km/s across the decade. A 900 s NTP stage delivering 35 t closes near 220 t in low Earth orbit and does so at every surveyed window; chemical delivery is marginal and sensitive to opportunity and staging, and nuclear-electric propulsion requires multi-megawatt power to match one-to-two-year trip times. Refueling at Ceres reduces the launch mass of an Earth-Ceres-Earth sortie by 61%, and the specific impulse of the propellant the node produces decides whether Ceres water becomes cargo or tanker mass. We conclude that Ceres uniquely combines abundant volatiles, exceptionally low gravity and a strategic Main Belt position, and that nuclear thermal propulsion is the only propulsion class that closes mass, time and the return leg together. Together they convert deep-space exploration from independent expeditions into a network operating on a timetable.
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Earth and Planetary Astrophysics

Early Planet Formation in Embedded Disks (eDisk). XXV. Inclination-Induced Minor-Axis Brightness Asymmetries Reveal Limited Dust Settling in Embedded Protostellar Disks

Sidhant Kumar Suar, Zhe-Yu Daniel Lin, Zhi-Yun Li et al. (+9 more)

How and when dust settles in young protostellar disks is a key open question for the dust concentration needed to form planetesimals and, ultimately, planets. However, directly measuring the vertical dust distribution in embedded (Class 0/I) systems remains challenging. We show that brightness asymmetry along the minor axis of highly inclined disks provides a simple, powerful geometric diagnostic of vertical dust structure. Using radiative transfer modeling with RADMC-3D, we generate synthetic continuum images showing that the observed asymmetry arises naturally from disk inclination, optical depth, and dust scale height. We apply this framework to nine Class 0 and I disks from the ALMA Large Program, Early Planet Formation in Embedded Disks (eDisk), using Markov Chain Monte Carlo (MCMC) fitting. Outflow observations independently validate the inferred near- and far-side geometries: all eight sources with useful outflow constraints agree with the orientations predicted by the dust continuum modeling. Our results indicate that most embedded disks show no strong evidence of significant dust settling, with dust scale heights comparable to the gas scale height. Given that the literature indicates Class II disks tend to be well settled, our results reinforce the notion that significant dust settling occurs during the Class I phase, when deeply embedded Class 0 disks transition to their more revealed Class II counterparts. Intriguingly, the timing of dust settling appears to broadly coincide with the development of widespread dust substructures, suggesting that gravitationally driven vertical dust concentration may have triggered substructure formation.
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All authors Sidhant Kumar Suar, Zhe-Yu Daniel Lin, Zhi-Yun Li, Nagayoshi Ohashi, Shigehisa Takakuwa, John Tobin, Leslie Looney, Mayank Narang, Youngwoo Choi, Woojin Kwon, Patrick Sheehan, Ilseung Han

2609.39501 · 30 Sep · 27 pages, 16 figures. Accepted for publication in The Astrophysical Journal after addressing referee comments. In this arXiv version, the full set of source-by-source modeling figures is included in the Appendix; the journal version may instead present these figures as an online figure set (for more information on a figure set, see https://journals.aas.org/graphics-guide/)

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Earth and Planetary Astrophysics

Planetesimal Formation under Realistic Gas Dynamics: Dust Concentration in Turbulent and Windy Protoplanetary Disks

Pinghui Huang and Xue-Ning Bai

Planetesimals are a key intermediate stage of planet formation and originate from dust concentration in protoplanetary disks, which is strongly regulated by gas dynamics. In this study, we use the multifluid dust module of Athena++ to investigate dust concentration in 2D axisymmetric global non-ideal MHD (ambipolar diffusion, AD) simulations of outer disks. Our simulations simultaneously launch large-scale MHD disk winds and resolve both streaming instability (SI) and vertical shear instability (VSI). We systematically explore the effects of magnetic field strength, cooling timescale, ambipolar Elsasser number, and dust size on dust concentration. We find that strong dust clumping persists across a broad range of magnetized and wind-launching disk conditions. MHD winds also enhance dust clumping by modifying background conditions in the following ways: (1) secular gas depletion by MHD wind mass loss, and (2) dust trapping in zonal flows as a result of magnetic flux concentration (which occurs in more strongly magnetized cases). Overall, our results demonstrate that strong dust clumping can persist in global magnetized disks with AD and large-scale MHD winds, leading to conditions favorable for planetesimal formation.
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Tuesday 29 September

Earth and Planetary Astrophysics

A Probabilistic Trajectory and Dispersion Study of Martian Tumbleweed Rover Swarms in Global Dust Storm Conditions

Emma-Catherine Belhadfa and Gabriele MT D'Eleuterio

Global Dust Storms (GDSs) dominate the Martian climate, yet the mechanisms of dust lifting, transport, and deposition remain poorly constrained because in situ observations are limited: landers are stationary, and their Radioisotope Thermoelectric Generators (RTGs) contaminate local measurements. Our solution is a swarm of lightweight, wind-propelled spherical rovers – Dust Rovers (DRs) – that follow natural wind patterns to collect high-spatial-resolution in situ dust data during storms. Here, we quantify the dispersion and communication connectivity of this robotic architecture. Using 625 wind states calculated using the Mars Climate Database (MCD) for the MY34 storm at the Curiosity site, we build a bivariate-normal model of the near-surface wind velocity and characterise its diurnal structure. Rover trajectories and swarm dispersion are propagated with three integrators: the Euler and fourth-order Runge-Kutta schemes for the deterministic dynamics, and a stochastic Ornstein-Uhlenbeck formulation that simulates turbulent gust forcing. Dispersion is controlled by the unmeasured gust correlation time: with a static rolling threshold enforced, the white-gust case (tau_g = Delta t = 1 s) provides a two-rover separation below 1 m over an hour (0.44 km over a sol), whereas correlation times of 10-60 s yield 6-25 m over an hour (1.4-3.3 km over a sol). We demonstrate that a 20-rover swarm needs only a 1.6-4.1 km per-rover range to remain connected over a sol, and stays connected across the plausible envelope – for gust amplitudes up to twice the nominal value with tau_g <= 60 s, and at the nominal amplitude up to tau_g ~ 150 s.
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Earth and Planetary Astrophysics

aRieL - Reinforcement Learning for the Ariel Space Telescope Scheduling

James Kostas Ray, Kai Hou Yip, Alexandra Thompson et al. (+2 more)

The Ariel mission will conduct a population level survey of hundreds of exoplanet atmospheres, requiring observations to be scheduled across a large and diverse catalogue of potential targets. By framing Ariel scheduling as a long-horizon optimisation problem in which individual decisions affect both mission time and the scientific opportunities available later in the survey, Reinforcement Learning (RL) can be utilised as a framework for target selection. We introduce aRieL, a simulated observing environment coupled to a Set Transformer Proximal Policy Optimisation (PPO) agent that is trained to generate a scheduling policy. The RL policy consistently finds a strong compromise between competing survey objectives, producing large Tier~1 samples while maintaining high Tier~3 completion, population coverage, and observing efficiency when compared to a set of baseline heuristic polices. This behaviour is retained when the candidate catalogue is substantially expanded, while modifications to the reward function produce corresponding changes in the learned observing strategy. We further show that a policy trained on the baseline mission scenario can generalise without retraining to a modified scenario requiring repeated Tier~3 observations, revealing the resulting trade-off with the wider survey. These results demonstrate that reinforcement learning provides a flexible approach to large-scale astronomical scheduling, in which the observing strategy can respond directly to changes in mission state and to the scientific priorities, and motivate its wider exploration for observatories with similarly complex, state dependent scheduling problems.
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All authors James Kostas Ray, Kai Hou Yip, Alexandra Thompson, Luís F. Simões, Nikolaos Nikolaou

Earth and Planetary Astrophysics

Modeling of the Yarkovsky effect. I. Thermal dependence

O. Golubov, O. Mikhalchenko, V. Lipatova et al. (+1 more)

We investigate how the Yarkovsky effect created by one flat surface element on the asteroid depends on the thermal parameter. Then we integrate the Yarkovsky force over the surface of a spherical asteroid. In the next articles of the series, we will investigate the Yarkovsky force for bodies of more complicated shape and compute the change of the asteroid's orbit. Using perturbation theory, we analytically solve the one-dimensional heat conduction equation under the surface element and use the solution to analytically compute the Yarkovsky effect in the limiting cases of big and small thermal parameters. Then we analytically sew the two solutions to obtain an approximate expression for the Yarkovsky effect valid for both large and small thermal parameters. We verify it by comparing it to the results of the numerical solution of the heat conduction equation. Finally, we fit the parameters in an approximate analytical expression to improve the agreement with the numerical results. We obtain a fully analytical expression for the Yarkovsky effect of one surface element, which is composed of 4 terms and is precise for any value of the thermal parameter up to the accuracy of 15%. We also propose a fitted expression of the same form, which is precise up to 0.15%. They both much supersede the traditionally used 3-parameter fit, which produces an error up to 50% and, in particular, is about a factor of 2 wrong for small values of thermal parameters. Finally, we apply the new formalism to evaluate an analytical expression for the Yarkovsky force acting on a spherical asteroid, ending up in a 0.1%-accurate fitted expression for an asteroid with 0 obliquity on a circular orbit and a less accurate expression for the general case.
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All authors O. Golubov, O. Mikhalchenko, V. Lipatova, D. J. Scheeres

Earth and Planetary Astrophysics

Migration and Evolution of giant ExoPlanets (MEEP). III. Twenty-Nine Giant Planets from the TESS Mission

Jack Schulte, Joseph E. Rodriguez, David W. Latham et al. (+97 more)

We present the discovery and characterization of 29 hot and warm Jupiter systems transiting bright ($G < 12.8$) FGK stars using TESS data and ground-based photometry and spectroscopy. Through the use of high angular resolution imaging, we discovered three bound stellar companions, named TOI-3988 B, TOI-6171 B, and TOI-7266 B. The planets that we confirmed span an orbital period range of $1.28 - 16.9$ days, a mass range of $0.35 - 8.7$ $\mathrm{M}_{\mathrm{J}}$, and an orbital eccentricity range of $0 - 0.6$, and add to the growing self-consistent sample of hot and warm Jupiter systems detected using TESS and analyzed using the Markov-Chain Monte Carlo code EXOFASTv2. By performing two-sample Kolmogorov-Smirnov tests on a set of host star and planetary parameters, we find that this growing self-consistent sample of giant planets has a different distribution of host star masses, surface gravities, and metallicities, compared to the hot Jupiter and warm Jupiter systems in the literature, likely due to the additional constraint on the host star density from the planetary transits included in our global fits. We find that seven of the 29 newly confirmed planets have significant orbital eccentricity, and that one of these, TOI-3365 b, is in a system which likely hosts a massive outer companion. The continued confirmation of hot Jupiter and warm Jupiter systems and the follow-up RV monitoring on these systems to identify outer companions will pave the way for important investigations of giant planet migration.
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All authors Jack Schulte, Joseph E. Rodriguez, David W. Latham, Allyson Bieryla, Karen A. Collins, Samuel N. Quinn, Xian-Yu Wang, Rafael Brahm, Abdullah Al-Haji, Robert Aloisi, Caitlyn Altermatt, Nikola Antonov, David Baker, Pavel Balanutsa, Khalid Barkaoui, Özgür Baştürk, Slawomir Bednarz, Paul Benni, Krzysztof Bernacki, Mario Billiani, Ventsislav Bodakov, Pau Bosch-Cabot, Valerio Bozza, Ahmet Cem Kutluay, David R. Ciardi, Catherine A. Clark, Jerome de Leon, Jason D. Eastman, İpek Aleyna Ertürk, Thomas M. Esposito, Phil Evans, Miranda Felsmann, Raquel Forés-Toribio, Isaac Fournier, Akihiko Fukui, Tianjun Gan, Cristilyn Gardner-Watkins, Purvi Garg, Eric Girardin, Tateki Goto, Ferran Grau Horta, Thomas Henning, Eric G. Hintz, Keith Horne, Kai Ikuta, Jon M. Jenkins, Andrés Jordán, Jenson Keen, Adam Kraus, Valentina Kuzmina, Artem Kuznetsov, Adam Lark, Rodrigo Leiva, Vladimir Lipunov, Michael B. Lund, Franck Marchis, Joshua Margherone, Robert Massey, Kim McLeod, Edward Michaels, Mayuko Mori, J. A. Muñoz, Felipe Murgas, Norio Narita, Takaya Okada, Shane Painter, Enric Palle, Ivan Panchenko, Hannu Parviainen, Anastasiia Pechko, Adam Popowicz, Don Radford, Fabian Rodriguez Frustaglia, Sylvain Roux, Subhroja Roy, Matthew Ryno, Gülben Şanc{\i}, Richard P. Schwarz, Victor Senik, Lauren A. Sgro, Avi Shporer, Gregor Srdoc, Denise Stephens, Chris Stockdale, Ashley Stone, Ivan Strakhov, Marcelo Tala Pinto, Thiam-Guan Tan, Suzanne Taylor, Neil Thomas, Nataly Tiurina, Julian C. van Eyken, Songhu Wang, Noriharu Watanabe, Levi R. Webb, Francis P. Wilkin, Joe Williams, Selçuk Yalç{\i}nkaya, Mesut Y{\i}lmaz, Carl Ziegler

Earth and Planetary Astrophysics

Space Journey Beyond Earth: Exploring the properties of exoplanets and multi-planetary systems

Alexandra Muresan

In contrast to the observed exoplanet diversity, planets within many multi-planetary systems exhibit intra-system similarities in their radii, masses, and orbital spacings. This thesis investigates the planetary properties and system architectures, focusing on the intra-system similarities, the inferred planetary interior compositions, and the differences between single- and multi-planetary systems. Paper A shows that planets within the same system tend to have similar orbital spacings even when their sizes or masses differ. The spacing similarity is more pronounced in orbital period ratios than in mutual Hill separations, while the period ratios are more strongly correlated with the masses than with the radii of adjacent planets. These results indicate that uniform orbital spacings represent a common architectural property and are not necessarily associated with similarities in planetary size or mass. Paper B compares transiting planets in observed single- and multi-planetary systems. After excluding hot Jupiters, the distributions of planet types and radii of singles and multis orbiting FGK stars show no significant differences, suggesting a common underlying planet population. Around FGK host stars, however, an overabundance of multis is identified within a specific planet radius range. Paper C finds that non-gas-giant planets in systems hosting detected gas giants are, on average, larger, more massive, and more irregularly spaced than planets in systems without detected gas giants. Adjacent planets exhibit significant similarities in radius, mass, and bulk density, whereas their inferred core and water mass fractions show substantial scatter and no strong correlations. These results indicate that similarities in bulk properties do not necessarily translate into similarities in compositions. These studies place new constraints on the processes governing planet formation and evolution.
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Earth and Planetary Astrophysics

An Infant Sub-Saturn in Scorpius-Centaurus

Gurmeher Kathuria, Luke G. Bouma, Andrew W. Boyle et al. (+25 more)

We report the discovery and validation of TIC 88297141 Ab, a transiting planet orbiting a pre-main-sequence M dwarf (0.31 solar masses, 0.74 solar radii) in the Scorpius-Centaurus OB association. Group membership implies an age of $15.6 \pm 1.6$ Myr, supported by lithium and isochrone age-dating. We detected the TESS transits using a custom pipeline designed for variable stars and used ground-based photometry (LCO/Swope and LCOGT/Sinistro) to confirm the on-target nature of the signal. Our global fit of the transits and stellar activity gives an orbital period of 4.64 days and a planet radius of $7.21 \pm 0.32$ Earth radii (0.64 Jupiter radii). The star has a comoving M-dwarf companion (0.4 solar radii) at a projected separation of $260$ au; speckle imaging (Gemini-S/Zorro) reveals no additional stellar companions, and radial velocities from Magellan/PFS are consistent with stellar activity, giving $M_p \sin i < 4.7$ Jupiter masses at $2\sigma$. A statistical validation analysis yields a false positive probability of $10^{-5}$, validating the planet. A mass measurement will determine whether TIC 88297141 Ab is a low-density super-puff, like other comparably sized planets at these ages, or an unusually massive planet for its radius.
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All authors Gurmeher Kathuria, Luke G. Bouma, Andrew W. Boyle, Roberto Tejada Arevalo, Andrew W. Mann, Nidia Morrell, Karen A. Collins, R. Paul Butler, Stephen A. Shectman, Johanna Teske, Jeffrey D. Crane, Shreyas Vissapragada, Madeleine Mckenzie, Khalid Barkaoui, Norio Narita, Akihiko Fukui, Jerome P. De Leon, Toshi Suganuma, Madyson G. Barber, Francis P. Wilkin, Victoria Zaledonis, Sophia Garcia-Gallet, Glauk Hizmo, Steve B. Howell, David R. Ciardi, Colin Littlefield, Sarah Deveny, Douglas A. Caldwell

Earth and Planetary Astrophysics

Atmospheric dynamics and variability of periodically irradiated tidally locked planets

Deepayan Banik, Vasilii Pustovoit, Thaddeus D. Komacek et al. (+1 more)

Time-variable stellar heating may create new climate states, such as permanently hot or cold hemispheres, on asynchronous planets. Planets on eccentric orbits, circumbinary planets and planets on polar orbits around gravity-darkened stars all receive variable irradiation, yet variably irradiated planets (VIPs) have not been studied from a fundamental dynamical perspective. We present the first generalized study of the atmospheric response of variably irradiated tidally locked planets, using a 1.5-layer shallow-water model forced towards a time-dependent radiative equilibrium. We derive linearized analytic expressions for the mean, amplitude and phase lag of the response, which is that of a forced damped harmonic oscillator, and recover the established trends of tidally locked planets in the limit of steady forcing. When the instellation variation and wave timescales match and the damping is weak, a resonance occurs because waves propagate and interfere freely. The resonance produces a global standing wave mode and consequently a temporarily warmer nightside. Linear and nonlinear simulations reproduce these results and show that the hotspot oscillates longitudinally at the forcing frequency and reaches the antistellar point at resonance. The oscillation is eastward or westward of the substellar longitude depending on the rotation rate and the nonlinearity of the system. Synthetic phase curves carry signatures of this variability and invert in shape at resonance because of nightside warming. Among observed systems, we find 11 planets with at least 10% phase curve modulation from variable irradiation. Eccentric, pseudo-synchronous giants are the most promising targets, with HAT-P-2b having the largest predicted modulation.
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All authors Deepayan Banik, Vasilii Pustovoit, Thaddeus D. Komacek, Marta L. Bryan

Earth and Planetary Astrophysics

Radiation Hydrodynamics of Self-gravitating Protoplanetary Disks II. Accretion, Migration, Spin, and Internal Structure of GI Fragments

Yang Ni, Hongping Deng and Xue-Ning Bai

In the first paper of this series, we showed that gravitational instability (GI) in protoplanetary disks can produce fragments of planetary rather than brown-dwarf mass, leaving the subsequent evolution and ultimate fates of such fragments an open question. Here, we follow every bound object in a global three-dimensional radiation hydrodynamic simulation of a fragmenting $0.196\,M_\odot$ disk around a $1\,M_\odot$ star: seven surviving fragments, one disrupted clump, and one merged clump, followed for $1.2$\,kyr. The fragments form at $1.4$–$3.0\,M_\mathrm{J}$, consistent with the normalized initial-mass distribution of Paper~I. Mass growth follows a single Hill-limited scaling $\propto \Sigma \Omega R_\mathrm{H}^2$, regulated by the delivery of gas into draining feeding zones, while the latest-forming fragments experience supply starvation. Migration is bidirectional and governed by gravitational interactions with both the disk and neighboring clumps. Accretion supplies most of the fragments' spin, which aligns with their orbits and provides roughly a tenth of the support against gravity. The interiors are entropy-stratified, largely convectively stable, and accumulate mass far faster than they can radiatively cool: compression is quasi-adiabatic, and central entropies near $12\,k_\mathrm{B}$ per baryon favor hot-start initial conditions for fragments that evolve into gas giants. Integrating the measured growth law against the measured gas budget, we predict that the disk produces gas giants, brown dwarfs, and a possible low-mass stellar companion, while one scattered fragment may become a free-floating planet: the outcome of disk fragmentation is determined not merely at birth, but by the subsequent mass supply and dynamics.
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