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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Monday 31 August

Earth and Planetary Astrophysics

Where planetary solids survive sublimation around young and hot white dwarfs

Dimitri Veras, Keiji Ohtsuki, Rafael Martinez-Brunner et al. (+2 more)

All observed planetary systems orbiting single white dwarfs have lived through the hot stellar transition from an asymptotic giant branch star. In this post-nebular transition period, the initial conditions for planetary system evolution throughout white dwarf cooling are established. The hottest ($\gtrsim$ 20,000 K) and youngest ($\lesssim$ 20 Myr-old) white dwarf planetary system host stars differ significantly from their canonical older and colder counterparts by failing to support solid body accumulation in the immediate vicinity (a few $R_{\odot}$) of the white dwarf. Here, we analyse the likely locations of both solid-body survival and the sublimated gaseous content during this pivotal epoch, and the consequences. We find that (i) reservoirs of iron-rich, rocky and water-rich asteroids of radius $R$ that later observably enrich, or pollute, the white dwarf need to remain parked for the first tens of Myr of white dwarf cooling beyond critical distances of (16 au)$\times(1 {\rm km}/R)^{1/2}$ (for iron), (30 au)$\times(1 {\rm km}/R)^{1/2}$ (for rock) and (130 au)$\times(1 {\rm km}/R)^{1/2}$ (for snow), (ii) sublimation acts much more quickly than radiatively-driven orbital drifts from Poynting-Robertson drag or the Yarkovsky effect, and (iii) although large asteroids ($R \approx$ 10-1000 km) that are kicked on highly eccentric orbits around newly born white dwarfs could survive sublimation, they may fragment into debris which will sublime before the white dwarf cools. These results support, but do not necessitate, dynamical origin scenarios of polluted white dwarfs that feature delayed gravitational instability subsequent to the host star's asymptotic giant branch phase at Kuiper Belt-like distances, and beyond.
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All authors Dimitri Veras, Keiji Ohtsuki, Rafael Martinez-Brunner, Takato Nishio, Ryo Tamon

Earth and Planetary Astrophysics

Three-dimensional circumplanetary flows in a PDS 70c-inspired system: hydrodynamic simulations with FARGO3D and analysis with FARGOpy

Alejandro Murillo-Gonzalez, Jorge I. Zuluaga and Matias Montesinos

The detection of circumplanetary material around the forming planet PDS~70c provides a valuable setting for studying three-dimensional gas accretion during giant-planet formation. We present three-dimensional hydrodynamic simulations with FARGO3D for a locally isothermal protoplanetary disk, adopting system-motivated stellar, orbital, and disk parameters and planetary masses of $2$, $4$, and $8,M_{\rm Jup}$, all above the local thermal mass. The locally isothermal prescription provides a controlled prescribed-temperature limit that isolates the hydrodynamic organization of the flow, without modeling self-consistent thermal evolution or radiative observables. Gas enters the planetary environment through meridional flows from the upper disk layers and streams near the midplane. With increasing planetary mass, the flow changes from a vertically extended, envelope-like configuration to a more compact and stratified circumplanetary structure. The inferred CPD radius increases from $R_{\rm CPD}\simeq0.31$ to $0.40,R_{\rm Hill}$, while the flow remains sub-Keplerian, reaching $v_\phi/V_{K,p}\sim0.79$–$0.85$. Most enclosed gas mass lies within a few tenths of the Hill radius, whereas the outer Hill sphere is dominated by anisotropic inflow, outflow, and recirculation. The analysis was performed with FARGOpy, a Python post-processing framework developed in this work to reconstruct three-dimensional fields, compute integrated fluxes, and characterize circumplanetary kinematics from FARGO3D outputs. This study therefore provides both a hydrodynamic baseline for a PDS~70c-like environment and a reproducible framework for analyzing three-dimensional FARGO3D simulations.
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Earth and Planetary Astrophysics

A JWST transiting survey of FGK stellar limb darkening: empirical evidence for quadratic laws and atmospheric model comparisons

David K. Sing, Joshua D. Lothringer, Jeff A. Valenti et al. (+11 more)

We present a study of stellar limb-darkening using JWST transit observations of seven exoplanets orbiting FGK host stars, spanning 4200-6800 K. The wide wavelength coverage and high S/N of NIRISS/SOSS and NIRSpec/PRISM enable precise constraints on the wavelength-dependent limb-darkening. Using Bayesian model selection, we find that the quadratic limb-darkening law is statistically preferred over higher-order laws for most FGK stars, recovers consistent intensity profiles for $>$95% of the stellar disk area, and introduces a minimal bias in the derived transit depths of only $\sim$14 ppm (1$\sigma$) for 6/7 targets. This contrasts with previous studies relying on stellar models. We compare the empirically derived quadratic coefficients to predictions from the PHOENIX, MPS-ATLAS, MURaM, and Stagger stellar atmosphere grids. We introduce a quadratic limb-darkening parameterization in terms of limb intensity ($\ell$) and curvature at mid-$\mu$ ($\delta$), finding that empirical FGK limb darkening is generally more linear than models predict ($\delta \lesssim 0.1$). We identify wavelength-independent offsets between data and model quadratic coefficients, minimized by adopting $\mu_{\rm min} = 0.2$ in intensity calculations; we attribute this in part to models overpredicting limb-darkening near the limb where the plane-parallel approximation breaks down. For spherical PHOENIX models, we derive a $\mu$ rescaling method using a $\tau = 1$ photospheric radius. With these corrections, residual offsets are minimized and all stellar models achieve statistically acceptable fits. We provide recommended limb-darkening offset priors for use in JWST transit analyses, enabling more accurate constraints on exoplanet transmission spectra while accounting for residual stellar model uncertainties.
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All authors David K. Sing, Joshua D. Lothringer, Jeff A. Valenti, Natalie H. Allen, Katherine A. Bennett, Carlos Gascón, Mei Ting Mak, Patrick McCreery, Sagnick Mukherjee, Lakeisha M. Ramos Rosado, Stephen P. Schmidt, Kevin B. Stevenson, Daniel P. Thorngren, Le-Chris Wang

Earth and Planetary Astrophysics

Self-induced edge rings in protoplanetary disks

Massimiliano Bolchini, Haochang Jiang and Jiaqing Bi

Observations with a high angular resolution by ALMA have revealed that substructures are ubiquitous in protoplanetary disks. Axisymmetric dust rings are the most common morphology. The profiles of some observed disks, including young disks, are smooth overall, with a localized dip or bump near the outer edge of the continuum disk that manifests as an edge ring. While embedded planets might contribute to these structures, their physical origin remains unclear. We investigated the possibility that these edge rings arise purely from radiative transfer effects at the outer edge of a protoplanetary disk. A steep surface density dust gradient at the outer edge of the disk allows stellar irradiation to penetrate more efficiently beyond the disk edge, producing a non-monotonic temperature profile characterized by a dip that is followed by a bump. We tested whether this non-monotonic temperature structure can generate and maintain a localized continuum enhancement. We coupled radiative transfer and dust evolution by iterating between the Monte Carlo radiative transfer code RADMC-3D and the dust evolution code DustPy. This framework self-consistently follows the coupled evolution of temperature, grain growth, and dust dynamics. Thermodynamic feedback at the disk edge can naturally generate and maintain localized dust enhancements resembling the edge rings that are observed in some extremely young disks. Without invoking planets or additional dynamical perturbations, this mechanism offers a plausible explanation for the first-generation ring formation. Our results highlight the importance of coupling thermodynamics and dust evolution when modeling protoplanetary disks, suggesting that thermodynamic feedback probably plays a role in shaping disk substructures.
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Earth and Planetary Astrophysics

The Venus Benchmark: Resolving Degeneracies in Terrestrial Exoplanet Spectra with DAVINCI

Stephen R. Kane, David S. Alexander, Shahid Aslam et al. (+8 more)

The characterization of terrestrial exoplanets with thick, CO$_2$-dominated atmospheres via transmission and emission spectroscopy is limited by degeneracies between atmospheric composition, cloud structure, and surface conditions. These degeneracies are particularly acute for planets in or near the Venus Zone, where sulfuric acid aerosol layers and deep-atmosphere opacity render the lower atmosphere and surface spectroscopically inaccessible via many optical/IR wavelengths. Venus provides the only accessible analog to such worlds, yet current knowledge of its full atmospheric profile relies on decades-old in situ data with known limitations. Here we demonstrate that the forthcoming DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) mission will provide the comprehensive, high-fidelity atmospheric profile data necessary to resolve many of these degeneracies. We quantify how atmospheric profile uncertainties translate into uncertainties in modeled transmission and thermal emission spectra of CO$_2$-dominated terrestrial worlds, and show that the spread in the modeled Venus benchmark spectrum arising from current atmospheric profile uncertainties will decrease by factors of $\sim$4–5 for transmission and $\sim$5–15$\times$ for thermal emission after DAVINCI, providing a correspondingly improved benchmark and prior for the modeling of exoplanets with Venus-like atmospheres. We further demonstrate that these improvement factors are larger for the cloud-free atmospheric case, where the opacity floor is set by gas-phase processes rather than aerosols, because the pre-DAVINCI data are most discrepant in the sub-cloud region. Our results highlight the importance of Venus for the atmospheric characterization of rocky exoplanets in the JWST and HWO era, and demonstrate how DAVINCI measurements will directly improve exoplanet atmospheric modeling.
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All authors Stephen R. Kane, David S. Alexander, Shahid Aslam, Giada N. Arney, James B. Garvin, Stephanie A. Getty, Amy E. Hofmann, Noam R. Izenberg, Natasha M. Johnson, Erika Kohler, Emma L. Miles

Earth and Planetary Astrophysics

Using Ringed Disks to Determine Fundamental Parameters of Planet Formation

Olivia Wu, Luca Camarra and Eve J. Lee

Two non-dimensional parameters, Stokes number (St) and turbulent $\alpha$, critically control the early stage of planet formation. In spite of their importance, these two numbers are notoriously difficult to obtain and remain largely unconstrained, except in ringed disks. In particular, E. J. Lee (2024) showed that ringed disks can be uniquely leveraged to derive local St and $\alpha$ through a simple model combining dust radial equation of motion with the measured distribution of dust masses in Class 0/I disks. We apply their model to the currently known census of ringed disks, finding 19 viable rings in 10 systems, which more than doubles the previous sample. Similar to previous findings, we obtain generally low St$\sim 10^{-4}$–$10^{-2}$ and $\alpha \sim 10^{-5}$–10$^{-2}$ across a wide range of system parameters, consistent with all the disks that we study to be rich in gas and the dust-to-gas ratio of the rings to be too low to generate planetesimals. Disks around low mass host stars likely have leakier traps, broadly consistent with massive, gap-carving giants to be rare around low mass hosts, if the rings are generated by planets.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Conspicuous Gas, Cryptic Dust: Spectroscopy and Chromaticity of Complex Periodic Variables

Luke G. Bouma, Facundo Perez Paolino, Lynne A. Hillenbrand et al. (+17 more)

Complex periodic variables (CPVs) are young low-mass stars whose light curves show periodic dips indicative of transiting corotating material. The origin and composition of this material are unclear. Here we present new optical and near-infrared spectroscopy and photometry of four CPVs from Magellan, Keck, Hale, MuSCAT1, MuSCAT2, Tierras, KeplerCam, and TESS. The spectra imply that CPVs host magnetically bound circumstellar plasma clumps, on the basis of sinusoidal-in-time Balmer emission out of transit, and Balmer dimming during transit. Yet large night-to-night changes in circumstellar hydrogen emissivity occur without clear changes in light curve morphology, suggesting that the sharp flux dips are caused not by circumstellar plasma but by dust. Optical chromaticities (depth proportional to $\lambda^{-\beta}$, with $\beta$ = 0.79 $\pm$ 0.16) support this, but the power law breaks in the near-infrared, where a single power law under-predicts the depths observed at 2.1 microns. We therefore favor dips caused by dusty plasma clumps with opaque cores and optically thin halos, though we cannot rule out models in which the dust properties vary per-star or per-epoch. Observations at wavelengths greater than 2 microns and less than 0.4 microns would test this interpretation and clarify the dust's origin.
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All authors Luke G. Bouma, Facundo Perez Paolino, Lynne A. Hillenbrand, Juliana Garcia-Mejia, Allyson Bieryla, Patrick Tamburo, David Charbonneau, John H. Livingston, Keisuke Isogai, Norio Narita, Akihiko Fukui, Enric Palle, Felipe Murgas, Adolfo S. Carvalho, Howard Isaacson, Jessica J. Spake, Luisa M. Rebull, Moira M. Jardine, David R. Ciardi, Jeff A. Valenti

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

Accretion Rates and Thermohaline Convection in Polluted White Dwarfs

J. R. Fuentes, Matias Castro-Tapia, Jim Fuller et al. (+1 more)

Polluted white dwarfs provide a unique window into the composition of exoplanetary material, but interpreting their surface abundances requires a quantitative understanding of the mixing processes in their envelopes. Accretion of metal-rich debris onto hydrogen-rich white dwarfs drives thermohaline (fingering) convection in the underlying radiative zone. Previous studies have modeled this as enhanced diffusive transport, often inferring mass accretion rates, $\dot{M}_{\rm acc}$, that exceed constraints from X-ray observations. Here we develop a time-dependent model that treats thermohaline mixing as a propagating front whose evolution is coupled self-consistently to the surface abundance of heavy elements. We perform hydrodynamical simulations which demonstrate that thermohaline mixing drives the composition gradient towards marginal stability. Using this condition, we derive analytic solutions in shallow and deep stratification regimes, finding that the mixed layer depth, $h$, and surface abundance, $X_{\rm surf}$, both scale as $t^{1/2}$ at early times, transitioning to $h \propto t^{4/27}$ and $X_{\rm surf} \propto t^{10/27}$ at later times. The mixed layer reaches depths of only $\sim 100$ km over $10^5$ yr and, without gravitational settling, never reaches a steady state. Including settling leads to an equilibrium surface abundance scaling as $X_{\rm surf, eq} \propto \dot{M}_{\rm acc}^{30/43}$. Applied to G 29–38, the model matches the observed heavy-element abundance for $\dot{M}_{\rm acc} \sim 2\times 10^9$–$4\times 10^{9}~\mathrm{g~s^{-1}}$, in better agreement with X-ray constraints than prior estimates incorporating thermohaline mixing. We also present a general scaling relation for inferring accretion rates directly from observed surface abundances and stellar properties, giving a practical prescription for other polluted white dwarfs.
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All authors J. R. Fuentes, Matias Castro-Tapia, Jim Fuller, Marcus King

Earth and Planetary Astrophysics

Öpik-type collision frequency for Kozai-driven projectiles: Target bodies on eccentric and inclined orbits

Youpeng Liang and Xiaodong Liu

For high-inclination projectiles undergoing Lidov–Kozai secular evolution, coupled variations in eccentricity and inclination complicate estimates of long-term collision frequencies with a target body. Previous collision-frequency studies for Kozai-driven projectiles have considered target-body orbits that are either circular or confined to the reference plane. The present study considers the general case in which the target body's orbit has both non-zero eccentricity and non-zero inclination. For each complete Lidov–Kozai cycle, the initial relative nodal longitude and the target body's initial argument of periapsis serve as two independent orientation variables. The single-cycle collision frequency is evaluated for each pair of initial values. Under the incommensurability condition considered here, the long-term mean is then obtained by explicitly averaging these values over both orientation variables. For the special cases in which the target body's orbit is circular or lies in the reference plane, the method is shown analytically to reduce to the corresponding formulations of previous studies. Numerical comparisons confirm these reductions. For the general eccentric and inclined case, the resulting collision frequency predicts a projectile survival curve that agrees well with the fraction of projectiles remaining in independent direct dynamical integrations. Finally, it is shown that, for a fixed dynamical setup and under the incommensurability condition, the long-term mean collision frequency associated with a given closed Hamiltonian level curve is independent of both the projectile's initial secular state along that level curve and its initial longitude of ascending node.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

Joint Observations of PTPS Targets (JOTA). Combined spectroscopic and photometric analysis of 16 SB1 systems

Robert Jaros, Andrzje Niedzielski, Sohaib Ali et al. (+9 more)

Context. The Pennsylvania-Toruń Planet Search, which operates on a sample of $\sim$1000 northern-hemisphere stars, has been underway since 2004. Stars with radial velocity (RV) amplitudes exceeding 2 km s$^{-1}$ represent a backup subprogram sample dedicated to monitoring binary stars with multiple instruments. Aims. We used almost 21 years of combined RV measurements to search for Doppler signals consistent with stellar or brown dwarf companions and to produce a catalog of both known and previously unpublished binary stars in our planet-search sample. Methods. We analyzed the combined RV measurements, searching for stellar companions and obtaining orbital solutions for both known and new binary systems. We also searched for periods in available long-term photometric monitoring data from All Sky Automated Survey (ASAS), and applied Gaia astrometric data whenever available. Results. We report the results of long-term RV monitoring of 16 systems: new detections of low-mass companions to 11 stars and updated orbital elements based on combined sets of our new and literature data for five systems. For two objects (TYC 3318-00789-1 and TYC 3318-01538-1), we find evidence of activity or the influence of another unseen companion, possibly due to line-profile variations or unresolved spectral contamination. We present true masses for three systems in our sample: TYC 1931-1040-1, TYC 3451- 1449-1, and TYC 3667-1636-1. We obtained these masses using Gaia DR3 non-single star data.
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All authors Robert Jaros, Andrzje Niedzielski, Sohaib Ali, Divyansh Srivastava, Julia Sierzputowska, Monika Adamów, Jorge Lillo-Box, Dmytro Orikhovskyi, Aleksander Wolszczan, Eva Villaver, Theodor Pribulla, Martin Vaňko

Earth and Planetary Astrophysics

Planar Three-Body Problem: theoretical predictions and simulation results

Yogesh Dandekar, Ethan Springer, Shoval Zard et al. (+3 more)

We investigate the statistical properties of the non-hierarchical planar three-body problem, relevant to astrophysical systems with nearly planar dynamics, including protoplanetary disks and AGN disks. Using the Flux-based statistical theory of the three-body problem, previously studied in three dimensions, we derive theoretical predictions for several statistical observables in the planar case. Focusing on ergodic disintegration outcomes, we compare these predictions directly with numerical simulations and contrast the results with the corresponding unconstrained three-dimensional case. Our analysis is based on one million simulations for each of eight distinct mass sets. We examine escape probabilities, properties of marginal escape events, eccentricity distributions, lifetime distributions, and relative prevalence of prograde and retrograde escapes. While several of the theoretical predictions are in good agreement with the simulations, others exhibit unexpected discrepancies. We discuss possible explanations for these deviations.
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All authors Yogesh Dandekar, Ethan Springer, Shoval Zard, Alessandro Alberto Trani, Barak Kol, Ofek Birnholtz

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

Systematic and Statistical Properties of Prominence Eruptions on the M-dwarf YZ CMi

Yuto Kajikiya, Kosuke Namekata, Yuta Notsu et al. (+4 more)

M-dwarfs produce frequent flares, and their associated mass ejections are expected to significantly affect the habitability of close-in exoplanets. Recent spectroscopic observations have revealed several prominence eruptions-indicative of stellar mass ejections-on M-dwarfs through Doppler shifts of the H$\alpha$ line. However, systematic and statistical studies, particularly regarding their association with white-light flares, have been limited due to the lack of intensive and continuous simultaneous photometric and spectroscopic monitoring of the same target star. We conducted one month of continuous spectroscopic observations of the active M-dwarf YZ CMi using the 3.8-m Seimei telescope with an unprecedentedly high time cadence of $\sim$1 min, simultaneously with TESS. We detected four prominence eruptions, among which two events showed rapid, short-duration eruptions with velocities of $\sim$300-500 km s$^{-1}$ and durations of $\sim$5 min. Such short-duration events may have been missed in previous observations due to insufficient time cadence. We further performed a systematic analysis using 35 H$\alpha$ flares on YZ CMi observed simultaneously with TESS. Notably, most prominence eruptions (6 out of 7) were not associated with detectable white-light flares. This result suggests that most observed prominence eruptions on M-dwarfs may have occurred near the stellar limb, where white-light flares are difficult to detect, which may imply a potential observational bias in their detectability due to low contrast with the background emission. These first statistical constraints, together with the discovery of rapid, short-duration prominence eruptions, indicate that previous observations may have underestimated both the frequency and velocities of mass ejections on M-dwarfs due to observational biases and highlight the necessity of reassessing their impact on close-in exoplanets.
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All authors Yuto Kajikiya, Kosuke Namekata, Yuta Notsu, Kai Ikuta, Hiroyuki Maehara, Bunei Sato, Daisaku Nogami

Earth and Planetary Astrophysics

Empirical Constraints on the CO Snowline Transition in HD 163296: The Local CO Column and $^{13}$C$^{18}$O Optical Depth

Chunhua Qi, Takahiro Ueda, David J. Wilner et al. (+1 more)

CO isotopologue emission is widely used to infer gas masses and volatile carbon abundances in protoplanetary disks, but converting line emission into a CO column depends on optical depth, temperature structure, linewidth, and isotope ratios. Inferring CO/H$_2$ additionally requires an independent constraint on the local hydrogen column. We use high-resolution $^{13}$C$^{18}$O $2$-$1$ observations of HD 163296 to derive a spatially localized empirical constraint on the CO column at the resolved CO snowline edge. We focus on the 70-75 au annulus, on the inner, high-column side of the observed profile steepening near 75 au. Using RADEX slab calculations conditioned on a two-dimensional temperature structure, we infer an effective beam-averaged CO column from the absolute integrated intensity. Across representative temperatures, isotope-ratio pairs, and effective local linewidths of 0.30 and 0.50 km s$^{-1}$, we find $N_{\rm CO}^{\rm beam}=(1.6-2.4)\times10^{20}$ cm$^{-2}$ and $^{13}$C$^{18}$O line-center optical depths $\tau=0.39-0.97$. Thus, even this rare isotopologue is not safely optically thin at the snowline edge. Adopting $N_{\rm H2}=2.5\times10^{24}$ cm$^{-2}$ from a published parametric gas surface-density profile gives the conditional abundance ${\rm CO/H_2}=(6.4-9.5)\times10^{-5}$. A beam-forward radial-profile analysis gives consistent columns, and a physical disk model with a near-canonical warm-layer CO abundance supplies a comparable CO column. The measurement is consistent with the higher C$^{17}$O-based MAPS estimate. For the adopted hydrogen column, the inferred CO/H$_2$ ratio is consistent with a near-canonical abundance on the warm side of the snowline.
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All authors Chunhua Qi, Takahiro Ueda, David J. Wilner, Catherine C. Espaillat

Earth and Planetary Astrophysics

Atmospheric escape fractionates secondary but not primary atmospheres

Mara Attia and Tim Lichtenberg

A planet's atmosphere, heated by starlight, can flow off as a wind, taking some gases and leaving others in unknown proportions. Yet this selection wrote the noble-gas records of the terrestrial planets, and decides which gases hot exoplanets keep. We solve this fractionated escape problem for arbitrary composition: a wind sorts gases only for secondary, hydrogen-poor atmospheres, and removes primary, hydrogen-rich atmospheres wholesale. The algebraic solution recovers every published formula as special cases. It provides a unified interpretation of atmospheric evolution across the Solar System and exoplanets. Fractionating argon on Mars stripped carbon while sparing krypton, Venus' retained argon constrains the wind intensity that removed its water, Earth's xenon record excludes a neutral wind. The same solution ranks the rocky exoplanets under JWST observation by the gases they can keep.
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Sunday 30 August

Earth and Planetary Astrophysics

The $\gamma$ Cephei System: Updated Orbits, Dynamical Architecture, and Limits on Additional Companions

Judah Van Zandt, Brendan P. Bowler, Michael Endl et al. (+18 more)

The $\gamma$ Cephei system hosts one of the first exoplanets discovered and is orbited by one of the closest known stellar companions to a planet-hosting star. Here, we derive updated orbital fits for $\gamma$ Cep AB, the stellar binary, and Ab, the planet, by combining literature data with Hipparcos-Gaia astrometry, new radial velocities (RVs), and adaptive optics imaging. We acquired 328 RVs of $\gamma$ Cep A with Keck/HIRES, AFP/Levy, McDonald/Tull, and Whipple/TRES, and eight adaptive optics imaging epochs with Keck/NIRC2, including the earliest spatially resolved image of $\gamma$ Cep B in 2003. These observations extend the precision RV baseline of $\gamma$ Cep to 45 years and the direct imaging baseline to 23 years, improving inferred orbital parameter precisions by a factor of 2–10 compared to previous work. For $\gamma$ Cep B, we derive a semi-major axis of $a_B=20.07 \pm 0.06$ AU, a mass of $M_B=415 \pm 2$ $M_{Jup}$ ($0.396 \pm 0.002$ $M_{\odot}$), an eccentricity of $e_B=0.422 \pm 0.002$, and an inclination of $i_B=119.8^{\circ}\pm0.1^{\circ}$. For $\gamma$ Cep Ab, we find a separation of $a_{Ab}=1.978 \pm 0.007$ AU, a minimum mass of $M_{Ab} \sin i = 1.62 \pm 0.04$ $M_{Jup}$, and an eccentricity of $e_{Ab}=0.07 \pm0.03$. Using the RV residuals and dynamical constraints, we rule out additional Jovians between 2.5–20 AU, and companions more massive than Neptune for $a<1$ AU, both at $>90\%$ confidence. The absence of additional giant planets over a broad range of orbital separations is consistent with a dynamically sculpted system in which the close stellar companion limited the formation or long-term survival of other distant companions.
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All authors Judah Van Zandt, Brendan P. Bowler, Michael Endl, William D. Cochran, Phillip MacQueen, Artie Hatzes, Guillermo Torres, David W. Latham, Andrew W. Howard, Benjamin Fulton, Howard Isaacson, Michael C. Liu, Samuel A. U. Walker, Jerry W. Xuan, Jingwen Zhang, Rebeca E. Soto Armendariz, Lauren I. Biddle, Kyle Franson, Lillian Jiang, Marvin Morgan, Quang H. Tran

Earth and Planetary Astrophysics

Probing Triton's Space Environment and Internal Structure: An Integrated Detection-and-Interpretation Framework

Jiansen He, Chuanpeng Hou, Haoen Xie et al. (+10 more)

Triton, Neptune's largest moon, is a prime ocean-world target. Constraining ocean thickness, composition, and conductivity is essential for habitability assessment, but magnetic induction alone cannot resolve the thickness-conductivity degeneracy, and magnetic perturbations from Triton's space currents can obscure the internal induction signal. We present an integrated detection-and-interpretation concept linking four physically consistent calculations. Using `PlanetProfile', we construct a common radial interior structure (temperature, density, conductivity, seismic-wave speed). We then use `MoonMag' to compute the degree-one magnetic-induction response from that conductivity profile at the synodic, rotational, and orbital periods. We perform a multi-fluid `SWMF' simulation with the induced dipole as the inner-boundary condition and develop a Coulomb-gauge Poisson reconstruction to isolate space-current magnetic fields. Finally, we develop the `TritonSeis' workflow, three-dimensional seismic forward modeling plus hierarchical travel-time inversion, to constrain the ice-ocean and ocean-rock interface depths. We find that induction is substantially more sensitive to ocean conductivity than to layer thickness, and that space-current fields are comparable in amplitude to the internal induction signal. A five-station synthetic recovery test resolves both interfaces to first order, with errors of +8.4% for the ice shell and -12.5% for the ocean. Under a conservative noise assumption, the minimum detectable magnitudes are approximately 3.8-4.6 at epicentral distances of 100-1000 km. The Poisson reconstruction and end-to-end seismic recovery are, to our knowledge, the first such quantitative demonstrations for Triton. Coordinated magnetic, plasma, and seismic measurements are complementary and can break the conductivity-thickness degeneracy, providing a framework for future Triton exploration.
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All authors Jiansen He, Chuanpeng Hou, Haoen Xie, Jiaqi Li, Tianhang Chen, Hong Zou, Xuzhi Zhou, Hui Li, Yan Li, Fuchuan Pang, Bingkun Yu, Hui Huang, Tong Wang

Earth and Planetary Astrophysics

Gemini and Apache Point Multi-band Optical Imaging Characterization of Fragmenting Long-period Comet C/2025 K1 (ATLAS)

Carl Ingebretsen, Bryce T. Bolin, Meredith A. MacGregor et al. (+8 more)

We present results from multi-band g, r, and i, observations of C/2025 K1 (ATLAS) taken with the Gemini North 8.1-m/GMOS imager on 2025 December 6 and December 24, and u, g, r, i, and z observations with the Astrophysical Research Consortium (ARC) 3.5-m/ARCTIC imager on 2025 December 8. We identify at least four distinct fragments in the Gemini and ARC images, designated as A, C, D, and E in these data taken between 2025 December 6 and 24. Color indices are determined from the December 8 ARC observations of fragments A and C, and from the Gemini observations on December 24 for A, C, and D. K1 has an unusually blue g-r color of $\sim$0.40. The color difference between the comet and its fragments at the two epochs may be explained by particle size and light-scattering effects. We used the Gemini observations to calculate dust mass-loss rates for fragments A, C, and D. We conclude that C/2025 K1 has moderate dust mass-loss rates for millimeter-sized dust of $\sim$50 kg/s for the A and C fragments.
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All authors Carl Ingebretsen, Bryce T. Bolin, Meredith A. MacGregor, Carey M. Lisse, Matthew Belyakov, Gracyn Jewett, Mukremin Kilic, Marco Micheli, Davide Farnocchia, Brian Lemaux, Hyewon Suh

Saturday 29 August

Earth and Planetary Astrophysics

A semi-analytical surrogate model for giant planet evolution: bypassing ordinary differential equation solvers with localised thermodynamics, softplus asymptotes, and B-spline photometry

Christian Wilkinson, Jonas Wehrung-Montpezat, Benjamin Charnay et al. (+7 more)

Context. Evolutionary models translate the observable luminosity, temperature, and colours of giant planets and brown dwarfs into mass and age. Generating their cooling tracks normally requires integrating the internal energy over time with an ordinary differential equation (ODE) solver coupled to pre-computed atmospheric grids, which becomes numerically stiff at sharp transitions such as cloud condensation and the onset of electron degeneracy, and is fragile inside Bayesian retrievals. Aims. We aim to generate continuous cooling tracks and photometric light curves directly from discrete atmospheric grids, without an ODE solver. Methods. We mapped the grids into a logarithmic thermodynamic space and extracted localised surrogate models with Gaussian-weighted regressions at fixed planetary parameters. We fitted the entropy and cooling rate against the internal temperature using bounded piecewise softplus functions to capture structural and cooling-rate transitions; the radius was fitted on the same temperature axis; and band photometry was represented with fixed-knot cubic B-splines. The age followed from numerical integration of these analytic functions, and uncertainties were propagated from the residual scatter of each fit. Results. The surrogate, CoolTrack, reproduces the transition into electron degeneracy and the L-to-T spectral-type transition in the colour-magnitude diagram, converges on Solar System benchmarks, and evaluates a full evolutionary track in milliseconds on a standard desktop CPU. Conclusions. By removing the forward-modelling bottleneck, CoolTrack is suitable for direct use in Bayesian retrieval pipelines, where the age, mass, and formation entropy of a planet can be inferred jointly with its atmospheric properties.
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All authors Christian Wilkinson, Jonas Wehrung-Montpezat, Benjamin Charnay, Mathilde Mâlin, Lukas Delaye, Anne-Marie Lagrange, Vito Squicciarini, Johan Mazoyer, Stéphane Mazevet, Baptiste Perrier

Earth and Planetary Astrophysics

The refractory fraction of phosphorus in planet-forming discs

Sandipan P. D. Borthakur, Mihkel Kama, Luca Fossati et al. (+3 more)

Context. Phosphorus (P) is an essential element for life on Earth and a potential tracer of planet formation history. However, there has been no detection of P-bearing molecules in protoplanetary discs so far. Herbig Ae/Be stars constantly accrete matter from their pro- toplanetary disc, which alters the composition of the stellar photosphere due to their shallow convective, or fully radiative, envelope. The altered surface composition reflects the composition of the accreting matter, and thus that of the inner protoplanetary disc. This accretion contamination of stellar photosphere can persist after accretion has ended in young A and B-type stars (age < 50 Myr). Aims. We aim to quantify the fraction of P locked in dust (the refractory fraction of P) compared to gas in the inner protoplanetary disc around Herbig Ae/Be stars. Methods. We measure the stellar parameters and abundance of 5 Herbig Ae/Be stars using optical and UV spectra, to compare their P and Fe abundances. We also used a 20 Myrs old main sequence B-type star, which has P and Fe abundance estimated from optical spectrum. Fe is assumed to be completely locked in refractory reservoirs in the inner disc. A parameterised relationship between the stellar P and Fe abundance gives the fraction of P locked in refractory reservoirs. Results. We find the refractory fraction of P in the inner protoplanetary disc to be > 96 % within 95th percentile of the posterior distribution. Conclusions. Consistent with a previous finding in the HD 100546 system, we conclude most of the P in the inner protoplanetary disc is locked in dust, likely in refractory minerals like schreibersite or apatite. Our result, combined with the low cosmic abundance of P, is also consistent with the lack of infrared and mm-wavelength observations of P-bearing molecules in protoplanetary discs to date.
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All authors Sandipan P. D. Borthakur, Mihkel Kama, Luca Fossati, Colin P. Folsom, Anna Aret, Christiane Helling

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

Evolution of Stellar Activity and Habitable Zone (EATEN): III. X-ray Activity of Dwarfs in Open Clusters and Field Stars

Xue Li, Song Wang, Henggeng Han et al. (+3 more)

Stellar X-ray emission serves as a direct diagnostic of coronal activity, which is fundamentally linked to coronal heating processes. It also strongly influences the atmospheres and long-term habitability of orbiting exoplanets. Investigating how this high-energy emission evolves is therefore essential for understanding the evolution of stellar magnetic dynamos and planetary atmospheres and habitability. In this work, we investigate the evolution of X-ray activity and XUV irradiation for a sample of F-M dwarf stars based on Chandra and XMM-Newton observations. We find that F- and G-type stars broadly follow the traditional evolutionary picture of an early saturated (or weakly declining) phase followed by a modest decline, whereas K- and M-type stars exhibit a clear three-phase evolution of a saturated phase, an intermediate phase of rapid decay, and a final modest decline phase. By combining X-ray, ultraviolet, and Ca II H&K bands, we show that coronal emission becomes increasingly dominant toward lower-mass stars. Based on the cumulative XUV emission calculated from our fitted relation, planets around F- and G-type stars experience relatively moderate XUV environments, while those around K- and M-type stars may exceed the empirical cosmic shoreline shortly after reaching the main sequence, though this conclusion depends on the adopted shoreline value.
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All authors Xue Li, Song Wang, Henggeng Han, Jun Ma, Yang Huang, Jifeng Liu

Earth and Planetary Astrophysics

Dynamical Mass Demography of Single S-type Planets Shaped by Stellar Companions

Xiumin Huang and Jianghui Ji

More than 700 S-type planets have been identified from Gaia and TESS observations, including over 150 transiting targets, enabling the precise dynamical orbits and planetary mass characterization in binary environments. Here we present the first systematic N-body dynamical mass determination for 40 single S-type (Satellite-type orbit) planets in close binaries using an improved Markov Chain Monte Carlo (MCMC) framework with Gaussian priors to model stellar companion perturbations. {For binary systems with $a_\mathrm{B}<100$ au, companion-induced perturbations can bias the RV semi-amplitude and consequently the inferred planetary masses. The impact is strongest for short-period sub-Jovian planets, whose masses decrease by up to 20% when transitioning from Keplerian to N-body modeling, while massive Jovian planets with $M_{\mathrm{Jup}} < M_{\mathrm{p}} < 5$ $M_{\mathrm{Jup}}$ show only a 7.2% reduction.} Applying the NAFF stability criterion to TOI-4633, $i_{\mathrm{mut}} = 70^{\circ}$ is the upper limit for the fast rejection of unstable orbital solutions. Our results reveal that intermediate-mass planets exhibit both positive or negative biases in the inferred masses and influence the observed population of the sub-Jovian desert.
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Friday 28 August

Earth and Planetary Astrophysics

Magnitude of stable iron isotope fractionation limited by multiple stages of terrestrial core formation

Gabriel Nathan and Seth A. Jacobson

One proposed mechanism for generating iron isotopic differences between planetary mantles and chondrites is metal-silicate equilibration during terrestrial core formation. Prior studies of this isotopic fractionation effect employ single-stage core formation models that are inconsistent with reproducing the siderophile element budget of the Earth's mantle. Here, we model iron isotopic evolution of the Earth's mantle in a multistage core formation scenario that is consistent with dynamic models of planet formation and reproduces the geochemistry of the bulk silicate Earth, specifically the refractory moderately siderophile elements. We find that multiple stages of core formation rebalance the fractionating effect of metal-silicate equilibration for the iron isotopic system, comparable to or smaller than typical analytical uncertainties in mantle rocks. Ultimately, this rebalancing effect - coupled with stochastic accretion and differentiation histories which further complicate planetary formation processes - makes it unlikely that isotopic fractionation during metal-silicate equilibration is the primary mechanism responsible for the iron isotopic composition of the Earth's mantle.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Pre-shipment optical characterization of the SCALES instrument

Isabel J. Kain, Reni Kupke, Daren Dillon et al. (+31 more)

The Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument is a 1-5 micron imager and 2-5 micron integral field spectrograph, currently being commissioned on the Keck II Telescope. SCALES is optimized for exoplanet high-contrast imaging and spectroscopic characterization, and will be sensitive to older, colder exoplanets than existing instrumentation. The 12.3" x 12.3" imaging channel is designed to replicate the capabilities of NIRC2, and the low (R~35-200, 2.2" x 2.2" FOV) and medium (R~2500-5000, 0.36" x 0.34" FOV) spectral resolution modes offer new capabilities compared to existing Keck instrumentation. We present preliminary optical performance results from laboratory testing and commissioning of SCALES.
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All authors Isabel J. Kain, Reni Kupke, Daren Dillon, R. Deno Stelter, Rosalie McGurk, Gwendolin Weber-Stover, Athira Unni, Marc Kassis, Scott Lilley, Peyton Benac, Mackenzie Lach, Arun Surya, Amirul Hasan, Ravinder Banyal, Raquel Martinez, Nicholas MacDonald, Will Deich, Aaron Hunter, Emily Plume, Michael Gonzales, Cristian Rodriguez, Arjun Kumar, Cyril Bourgenot, Paul Whiteg, Juergen Schmollg, James Wells, Spencer Davies, David Bramall, Dimitri Mawet, Olivier Absil, Michael Fitzgerald, Eric Wang, Steph Sallum, Andrew Skemer

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

A Terrestrial Gamma-ray Flash with an Asymmetric Footprint Observed at the Pierre Auger Observatory

The Pierre Auger Collaboration, John Ortberg, David M. Smith et al. (+1 more)

The Pierre Auger Observatory, a $3000km^2$ detector array that sits 1400m above sea level in Argentina, has the ability to map the entire footprint of Terrestrial Gamma-ray Flashes (TGFs), which are short, intense bursts of gamma rays associated with lightning. This is in contrast to the vast majority of TGF detections that only occur in a single detector in space. In this paper we leverage this capability to perform two important analyses on an event from 2007, chosen for its large footprint and high signal quality. First, we triangulate the source of the TGF to $2.3\pm0.5$km height above ground level using the arrival time of the gamma rays themselves at the detector array, independently of any information regarding the lightning channel. With the source position established, we can analyze the spatial distribution of the TGF on the ground with respect to that source. Not only do we find that one side of the TGF footprint shows an order of magnitude higher flux than the other, but we also find an asymmetric azimuthal structure consisting of two clear peaks in intensity. These peaks are offset by about $120^o$ from each other. This azimuthal structure is not possible under the traditional uniform electric-field model of a TGF. Using Geant4 simulations of collimated beams of the relativistic runaway electron-avalanche spectrum, we attempt to reconstruct the source geometry of the TGF and find that it likely had significant components in the $\theta > 75^o$ range, where $\theta$ is the off-nadir angle.
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All authors The Pierre Auger Collaboration, John Ortberg, David M. Smith, Joseph Dwyer

Earth and Planetary Astrophysics · Cross-listed from q-bio.OT

Geochemical Hazard Assessment of Martian Regolith for Future Human Exploration

Mavia Anjum and Gwendolyn D. Bart

As human missions to Mars move from concept to planning to reality, a systematic quantitative health risk assessment of martian regolith exposure has become critically important. This study presents a comprehensive multi-element, multi-pathway health hazard analysis of martian regolith for a 70 kg adult astronaut on an 18-month surface mission, using bulk silicate Mars geochemical data and Earth Upper Continental Crust reference values as baseline comparators. We computed Average Daily Dose, Hazard Quotient, Hazard Index, Enrichment Factor, Ecological Risk Factor, and Incremental Lifetime Cancer Risk across all three exposure pathways (oral ingestion, inhalation, and dermal contact) for toxic and heavy metals, under four filtration scenarios (0%, 25%, 50%, 95%). Results demonstrate that Cr and Co represent the most critical non-carcinogenic hazards, exceeding the regulatory threshold (HI > 1) even at 50% filtration, while Cr also poses the most significant carcinogenic risk, near the $10^{-4}$ regulatory threshold level. At least 92% regolith filtration efficiency is required to reduce Cr to acceptable non-cancer hazard levels. Nickel exceeds the acceptable cancer risk threshold of $10^{-6}$ at all filtration levels below 95%. No element other than Cr and Co exceeds HI = 1 in the unfiltered scenario, although Fe, Ni and Mn approach concerning levels. These results establish that a minimum 95% High-Efficiency Particulate Air (HEPA)-grade filtration efficiency combined with active chemical sorption is required for acceptable Cr and Co short term exposure and Cr, Ni long term exposure management. This study provides a pathway-specific quantitative risk framework applicable to habitat air quality standards and EVA suit specifications for Mars surface operations
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Earth and Planetary Astrophysics

Probing the Taxonomic Diversity of the Small Near-Earth Object Population

Andy J. López-Oquendo, David E. Trilling, Michael Mommert et al. (+1 more)

Small near-Earth objects (NEOs) represent the immediate source population of meteors and meteorites and provide a direct window into the compositional and dynamical evolution of the inner Solar System. However, their small sizes, rapid rotation rates, and short observability windows have historically limited systematic compositional characterization. We present results from a multi-year rapid-response near-infrared spectrophotometric survey of recently discovered NEOs conducted with the UKIRT-WFCAM instrument between 2016 and 2024. Our campaign obtained 371 observation sequences, yielding reliable color measurements and probabilistic taxonomic classifications for 122 NEOs, with diameters ranging from 5 m to 150 m and a median size of 60 m. We employed lightcurve-corrected Z, J, H, and K photometry and a machine-learning-based classification framework to derive both observed and debiased taxonomic distributions as a function of object size. The observed taxonomic fractions show a population of small NEOs dominated by S-complex and CX-complex objects in nearly equal proportions. After accounting for observational selection biases, however, the inferred intrinsic population is instead dominated by dark, carbonaceous (CX-complex) bodies, with important implications for the intrinsic composition of the small NEO population. We further explore the relationship between small NEOs, meteorite fall statistics, and atmospheric filtering effects, finding that a substantial fraction of carbonaceous material likely does not survive atmospheric entry. These results highlight the importance of debiased surveys of small NEOs for interpreting the meteorite record, refining delivery models from the main belt, and informing the selection of future mission targets and planetary defense strategies.
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All authors Andy J. López-Oquendo, David E. Trilling, Michael Mommert, Michaël Marsset

Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn

Internal heating in rapidly rotating convection is not a shortcut to geostrophic turbulence

Justin A. Nicoski, Tobias G. Oliver, Stefano Maffei et al. (+1 more)

Convective turbulence in planets and stars is often driven by internal heating. This forcing mechanism has also been proposed as a means of accessing the diffusion-free scalings of the geostrophic turbulence (GT) regime at modest forcing. We test this with the asymptotically reduced quasi-geostrophic model, which is formally valid in the limit of vanishing Ekman number, $Ek \rightarrow 0$, and retains the Prandtl number as an independent parameter. We find no such shortcut: the Nusselt and Reynolds numbers are no closer to their diffusion-free predictions than in the boundary-heated case, and at $Pr = 7$ they are further from them; the predicted $Pr^{-1/2}$ collapse fails; and the prefactor depends on the form of the heating. Our no-slip/stress-free cases track the radiatively driven simulations of Hadjerci et al. (2024) case by case, yet a $25\%$ variation in $Nu$ persists between sweeps that share the same reduced Rayleigh and Prandtl numbers but differ in Ekman number. Those data span only the narrow range of forcing over which the compensated Nusselt number is stationary; across the wider range accessible to the reduced model it rises to a maximum and then falls. We argue that bulk transport scalings are incomplete diagnostics of GT, whereas the saturation of the interior mean temperature gradient and of the vertical velocity kurtosis remain reliable indicators.
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All authors Justin A. Nicoski, Tobias G. Oliver, Stefano Maffei, Michael A. Calkins

Earth and Planetary Astrophysics

Impacts of Correlated Noise on Retrievals of Exo-Earth Atmospheres

Nicole Wolff, Bruce Macintosh, Tyler D. Robinson et al. (+6 more)

The Habitable Worlds Observatory (HWO) aims to accomplish high-contrast imaging and spectroscopy of true Earth analogs for the first time. However, high-contrast spectroscopy with HWO may be limited by residual speckles which persist after deformable mirror correction and post-processing, hindering atmospheric characterization. Previous studies of self-luminous giant planets showed that neglecting spectrally correlated errors due to speckles results in biased inferences of planetary parameters. Currently, HWO retrieval studies generate spectra without noise spectral correlations. We present a Gaussian Process model of correlated noise of known properties in simulated HWO exo-Earth spectra, and the integration of this noise source into the forward and inverse modeling tool rfast. We quantify the impact of correlated noise on inferred molecular abundances and planetary properties across the ultraviolet/visible/near-infrared bandpass, for varying spectral resolutions (R), signal-to-noise ratios (SNR), and noise correlation length-scales (L). We find that, at the fiducial UV/Vis/NIR R=7/140/70 and SNR=10, including spectrally correlated noise at L=200 nm and L=10 nm yields a 57% and 161% higher average uncertainty on log oxygen abundance, compared to uncorrelated noise. Consequently, it is critical for both instrument design and post-processing algorithms to minimize short length-scale chromaticity. Additionally, we find that a moderate resolution can constrain carbon dioxide (R$\geq 280$) and weakly detect methane (R$\geq2800$) abundances, demonstrating the benefit of a moderate resolution near-infrared spectrograph. These findings can aid the interpretation of future HWO reflectance spectra and set requirements on optical quality, instrument stability, and observing configurations.
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All authors Nicole Wolff, Bruce Macintosh, Tyler D. Robinson, Sarah Blunt, Jean-Baptiste Ruffio, Beck Dacus, Alex Madurowicz, Marshall Perrin, Laurent Pueyo

Earth and Planetary Astrophysics

On the Impact of Correlated Noise and Spectral Resolution on the Retrieval Analysis of the Habitable World Observatory

Ji Wang, Philipp A. Huber and Sascha P. Quanz

Finding signs of life elsewhere in the universe is the holy grail of the field of exoplanets. Future space missions such as the Habitable World Observatory (HWO) are under development to search for biosignatures in exoplanets. We investigate the impact of correlated noise and spectral resolution on the retrieved biosignature chemical abundances. At the nominal spectral resolving power R=140 for HWO, we show that in 40% of the simulated runs the retrieved biosignature (H$_2$O and O$_2$) abundances are at least 1-$\sigma$ off the input ground truth. At R=1000, the 1-$\sigma$ inaccuracy rate drops to 10%. We provide an empirical relationship between the retrieved biosignature abundance uncertainty and the amplitude of the correlated noise. As part of the mitigation plan to reduce the impact of correlated noise on retrieval accuracy at low spectral resolution, we investigate the synergy between the HWO and LIFE space missions that cover ultraviolet, optical, and thermal-infrared wavelengths. After considering clouds and their effect on planet albedo, we find that the two missions are complementary in that (1) more biosignatures (H$_2$O, CO$_2$, O$_2$, and O$_3$) are detectable with a broader wavelength coverage; (2) retrieval uncertainty improves with the joint HWO+LIFE data set; and (3) LIFE is more sensitive to the atmospheric temperature profile, surface pressure, and planet radius. This work provides evidence to support the choice of a medium resolution at R=1000 instead of R=140 for HWO and a quantitative relationship between the retrieved abundance uncertainty and the level of correlated noise at different spectral resolutions.
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Earth and Planetary Astrophysics

ExoMOD II. A Statistical Model of Transit Timing Variations in Kepler Multi-Planet Systems

David Nesvorny, Daniel A. Yahalomi, David Kipping et al. (+2 more)

In Paper I (Nesvorný et al. 2026), we forward modeled transit observations of the Kepler telescope to characterize the orbital properties of close-in planetary systems. The new population model, ExoMOD, was calibrated on Kepler's DR25 data. Here we use ExoMOD to statistically predict Transit Timing Variations (TTVs) from gravitationally interacting planets in the close-in systems, and compare these predictions with TTVs actually detected in the Kepler data. We find that planet-planet interactions are not expected to produce significant short-period TTVs, $P_{\rm TTV}/P_{\rm orb}<10$, where $P_{\rm TTV}$ and $P_{\rm orb}$ are the TTV and orbital periods, often enough to explain the short-period TTV signals inferred from the Kepler data. Most measured short-period signals must therefore have a different origin. The statistics of long-period TTVs – likely arising from the gravitational interaction between planets – indicates that single transiting planets have TTV-inducing companions nearly as often as doubles, thus ruling out multiplicity distributions with a prevalence of intrinsic singles. The fraction of planets with measured long-period TTVs increases to $\simeq 15$-18% for observed multiplicities $m \geq 3$, suggesting a change in the orbital architecture. High-multiplicity planetary systems have low gap complexities and probably retained a memory of their formation conditions. Ultimately, our work aims at developing a more informative feedback between observations and planet formation theories.
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All authors David Nesvorny, Daniel A. Yahalomi, David Kipping, Cristian Beauge, Sarah C. Millholland