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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Tuesday 13 October · still arriving

Earth and Planetary Astrophysics

Elastic Properties of Titan Tholins Revealed by Brillouin Spectroscopy

Mark A. Johnson, Jose R. Montes-Bojorquez, Adis Husic et al. (+7 more)

Titan tholins, complex organic solids synthesized by simulating photochemical processes in Titan's atmosphere, are widely regarded as analogs to organic surface materials on the Saturnian moon. Their mechanical properties are critical for understanding the evolution of Titan's geomorphology and crustal layering. Here, we report the first direct experimental determination of the complete set of aggregate elastic moduli of tholins using Brillouin spectroscopy. Measurements conducted on tholin powder samples yielded a bulk modulus of 11 (2) GPa and a shear modulus of 3.9 (5) GPa, from which we derive a Young's modulus of 11 (1) GPa and a Poisson's ratio of 0.34 (3). Thin-film samples synthesized under slightly different conditions yield similar results. Compared with other Titan-relevant organic compounds, tholins exhibit the highest elastic stiffness measured to date, exceeding even H2O ice in both bulk and shear moduli. These results support the interpretation that complex organics contribute significantly to the mechanical stability and transport behavior of Titan's equatorial dune sediments. Measurements following prolonged atmospheric exposure reveal persistent stiffening of tholins that remains after vacuum treatment, likely associated with minor chemical modification and physical reorganization, highlighting the importance of controlled sample handling for future laboratory investigations. This study also demonstrates the effectiveness of Brillouin spectroscopy as a non-destructive technique for characterizing planetary organic materials and provides new constraints relevant to future seismic and geophysical investigations by the Dragonfly mission.
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All authors Mark A. Johnson, Jose R. Montes-Bojorquez, Adis Husic, Xinting Yu, Wenhao Su, Jia-Sen Hu, Ryan Blase, Edward Patrick, Alan Whittington, Jin S. Zhang

Monday 12 October

Earth and Planetary Astrophysics

Ultraviolet Reflected-Light Spectroscopy of Modern Earth Analogs with Starshade Observations

Zahra Ahmed, Stuart Shaklan, Mario Damiano et al. (+3 more)

Characterizing rocky, habitable zone planets in reflected light is a key science objective for future direct imaging missions, and the ultraviolet (UV) is uniquely suited for supporting the characterization of Earth-like atmospheres. The Hartley-Huggins ozone band at $0.25 ~\mu\mathrm{m}$ remains detectable at low spectral resolution down to $0.1\%$ PAL $\mathrm{O}_2$, providing a sensitive proxy for oxygen-bearing chemistry even for Proterozoic-like atmospheres where the visible and near-infrared $\mathrm{O}_2$ features become inaccessible. This work uses an end-to-end framework for UV starshade spectroscopy of modern Earth analogs that integrates high-fidelity observation simulation, conservative post-processing, and Bayesian spectral retrieval to quantify ozone detection significance. The framework is applied across 108 simulated scenes spanning a range of planet phase angles, system inclinations, and exozodiacal dust densities. The results establish that robust ozone detection with UV-only, $R=7$ reflected light spectroscopy requires a photometric $\mathrm{SNR} \sim 30$. UV starshade observations with the Habitable Worlds Observatory achieve this threshold within 3-day integrations for solar-type systems at 10 parsecs with inclinations up to $60^\circ$ at favorable phases ($\leq 90^\circ$). Above this SNR threshold, ozone detections are robust to systematic bias from imperfect exozodi calibration within $\sim30\%$, and the median retrieved ozone abundance remains accurate to within one order of magnitude of the true value.
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All authors Zahra Ahmed, Stuart Shaklan, Mario Damiano, Armen Tokadjian, Edward W. Schwieterman, Simone D'Amico

Earth and Planetary Astrophysics

DEMOS. II. What the full Lupus demographics truly tell us about protoplanetary disc evolution

Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato et al. (+7 more)

Assessing whether disc evolution is driven by viscosity or MHD winds is crucial to determine the conditions in which planets form. The rich statistical information encoded in nearby star-forming regions provides an excellent opportunity to probe disc evolution. In this paper, we apply the Bayesian inference tool DEMOS, designed to exploit the statistical properties of disc populations and infer initial conditions and model parameters, to the Lupus disc population. We consider the observed distributions of stellar mass $M_\star$, disc mass $M$ (from continuum flux), mass accretion rate $\dot{M}$ and CO disc size $R_{90%, CO}$. We constrain all parameters for both the viscous model, with internal photoevaporation, and the MHD winds model, with unprecedented precision. The inferred initial conditions suggest that positive correlations between initial disc properties and $M_\star$ must be present. Both models yield a typical $R_0$ of $3-5$ au for a disc around a $0.3\ \text{M}_\odot$ star, with positive stellar-mass dependence. We infer $\alpha$ (or $\alpha_\text{DW}$) of $3-4 \times 10^{-4}$ for discs around $0.3\ \text{M}_\odot$ stars, with an approximately quadratic dependence on $M_\star$. For the viscous-photoevaporative model, the typical wind mass-loss rate is $\dot{M}_\text{w} \sim 10^{-9}$ M$_\odot$ yr$^{-1}$, scaling with $M_\star$ with an exponent of $\sim 2.5$. The inferred mean age is 1.6 Myr for the MHD winds model and 0.9 Myr for the viscous-photoevaporative model. Despite a slight preference for the latter, Bayesian evidence shows that both models reproduce the data comparably well, and neither can be ruled out. However, their best-fit synthetic populations predict substantially different evolutionary pathways. Applying DEMOS to multiple populations, especially evolved ones like Upper Scorpius, will allow to place stronger constraints on disc evolution mechanisms.
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All authors Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato, Alice Somigliana, Benoît Tabone, Rossella Anania, Carlo F. Manara, Leonardo Testi, Claudia Toci, Francesco Zagaria

Earth and Planetary Astrophysics

DEMOS I. A Bayesian inference framework to constrain disc evolution from observed demographics

Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato et al. (+3 more)

The mechanism driving the evolution and dispersal of protoplanetary discs has a substantial impact on the theories of planet formation. To date, neither the viscous paradigm nor the MHD wind-driven framework have been ruled out by the observations. The statistical richness of the observed samples provides a unique opportunity to test evolutionary models through population synthesis. However, comparisons between models and observations are normally carried out by eye, and a more statistically rigorous approach has not yet been implemented. We present DEMOS, a Bayesian inference tool that aims to infer the model parameters and initial conditions that best reproduce the full distribution of global properties of disc populations. This framework relies on a comparison between observations and synthetic populations generated with the 1D disc population-synthesis code Diskpop. We tested the tool with both the MHD wind model and the viscous framework with internal photoevaporation. Applying DEMOS to synthetic populations, we find that, for both models, it accurately recovers the model parameters of disc populations and their associated uncertainties, including cases in which initial conditions are correlated with the stellar mass. In the optimal scenario in which disc masses, accretion rates and disc sizes are available, the tool can also constrain the angular-momentum transport parameter. We show that, although parameter estimates are the most precise with samples of about 100 discs, the tool also yields meaningful constraints for smaller populations of 10-30 discs. We further find that the predictions obtained with DEMOS closely align with those found by previous works. We anticipate that DEMOS will be a valuable tool to infer the initial conditions of observed disc populations, to design observational programmes, and to assess which evolutionary model best reproduces the data.
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All authors Lorenzo A. Malanga, Giovanni P. Rosotti, Giuseppe Lodato, Benoît Tabone, Alice Somigliana, Leonardo Testi

Earth and Planetary Astrophysics

High-resolution transmission spectroscopy of KELT-18b Metastable helium detection at 1083 nm

M. Chella, M. Monticelli, F. Biassoni et al. (+5 more)

We present the first high-resolution transmission spectroscopy of the ultrahot Jupiter KELT-18b, probing its escaping atmosphere by analyzing a single transit obtained with the CARMENES spectrograph. Transmission spectroscopy and Doppler tomography were utilized to isolate the planetary signal. To mitigate contamination from the strong telluric OH lines overlapping the region of interest, two distinct data analysis procedures were applied: a standard Molecfit and OH-masking approach as well as a PCA-based method. By combining the two complementary approaches, we successfully detect a He\,I triplet absorption feature of $1.10 \pm 0.22\%$ ($5.1\sigma$). The signal exhibits a velocity shift consistent with zero and is attributed to the exoplanetary atmosphere. An injection test reveals that the PCA-based method significantly suppresses the retrieved signal. Additionally, using the ATES and TPM codes, we modeled the atmospheric photoevaporation and the helium triplet profile for different He/H ratios and stellar XUV fluxes, accounting for instrument and planetary rotational broadening. From our simulations we derive a mass-loss rate and an evaporation efficiency for KELT-18b of $10.47 \leq \log_{10}(\dot{M}) \leq 11.68$ and $0.153 \leq \eta \leq 0.321$, demonstrating that the atmosphere of KELT-18b is undergoing photoevaporation. Furthermore, our simulations show good agreement with the observed transmission spectrum, allowing us to exclude very low He/H ratios at a $3\sigma$ confidence level for XUV fluxes up to approximately twice the nominal reconstructed value. Our result expands the known parameter space of exoplanets with confirmed helium absorption, establishing KELT-18b as the most massive planet orbiting the hottest host star with such a detection.
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All authors M. Chella, M. Monticelli, F. Biassoni, F. Borsa, M. Rainer, G. Guilluy, M. Basilicata, L. Cabona

Earth and Planetary Astrophysics

JWST Imaging of Edge-on Protoplanetary Disks. V. Flux Ratio Reversal and Disk-edge Structure in the Flying Saucer

Jie Ma, Karl R. Stapelfeldt, Marion Villenave et al. (+8 more)

We present near- and mid-infrared broadband imaging observations of the edge-on protoplanetary disk 2MASS J16281370-2431391, a.k.a. the 'Flying Saucer', obtained with NIRCam and MIRI on board JWST. These data are combined with archival optical and near-IR broadband imaging from HST, millimeter dust continuum emission from ALMA, and optical lightcurves from the K2 and TESS for a comprehensive multi-wavelength study. The JWST observations reveal a reversal of the flux ratio between the two reflection nebulae at near-infrared wavelengths (2-3 $\mu m$), which can be explained by a misaligned inner disk. For the first time, JWST reveals the bright lining along the disk edge at 2 and 3 $\mu m$, arising from forward scattering of background photons by dust grains near the $\tau\approx 1$ layer. By combining the dust lane thickness measured with HST and JWST, we find the dust grains up to at least $\sim$3$\mu$m are vertically mixed throughout the disk and have undergone significant growth. In addition, comparison of earlier HST/NICMOS J and K band images with those from JWST/NIRCam reveals variability in the scattered-light morphology, as well as measurable proper motion of the system with respect to the background stars, confirming that the Flying Saucer is co-moving with the young star population of $\rho$ Ophiuchi.
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All authors Jie Ma, Karl R. Stapelfeldt, Marion Villenave, Gaspard Duchêne, François Ménard, Ryo Tazaki, Youcef I. Bouarour, Greta Guidi, Laurine Martinien, Maxime Roumesy, Christophe Pinte

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

Extinction by non-spherical particles with the Nanoparticle Transition Matrix Code: perspectives for interstellar medium and exoplanetary atmospheres

G. La Mura, G. Mulas, M. A. Iatì et al. (+4 more)

The Transition Matrix formalism (T-matrix) offers an optimal solution to the problem of radiation scattering and absorption by particles characterized by a high degree of chemical and structural complexity. However, its application to particle models composed by large numbers of constituents has been classically limited by the substantial computational burden of the method. As a consequence, the investigation of light scattering and absorption processes, in cases where particle asymmetry and non-homogeneity play an important role, typically need to rely on simplifying assumptions which affect the correct interpretation of transmission spectra and extinction curves. This problem has a huge impact on many fields of scientific application. In particular, it has a critical role in astrophysics, because the ability to model highly non homogeneous particles is a fundamental requirement to understand the role of extinction in different phases of the interstellar medium (ISM), as well as to probe the physics of light transmission in planetary atmospheres within the Solar System and beyond. In this work we describe the application of a new implementation of the T-matrix formalism, based on the framework originally developed by Borghese, Denti & Saija and named Nano-particle Transition Matrix code, which leverages the power of modern hardware architectures to reduce the computational costs related to the solution of relevant particle models for the investigation of dust in the ISM and of hot-Jupyter class planets atmospheric aerosols. This new implementation of the T-matrix formalism can handle calculations of increasing complexity with a direct impact in the interpretation of the transmission spectra of transiting exoplanets produced by the James Webb Space Telescope (JWST) and of those expected from the Atmospheric Remote-sensing Infrared Exoplanet Large survey (ARIEL).
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All authors G. La Mura, G. Mulas, M. A. Iatì, C. Cecchi-Pestellini, G. Aresu, S. Rezaei, R. Saija

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

An Intermediate-orbit Brown Dwarf Confirmed with Astrometry+Radial Velocity Joint Analysis, and the Eccentricity Distribution of Brown Dwarfs Across Different Locations

Lei Ren, Tianjun Gan, Yifan Xuan et al. (+5 more)

Intermediate-orbit ($\sim 1$ AU) brown dwarfs with absolute mass measurements are essential for understanding the evolution of substellar objects. Although such systems remain rare, their number is now being enlarged thanks to astrometry. Here, we present the absolute mass measurements for HD 203771B, a massive brown dwarf orbiting a K dwarf ($M_\ast=0.79\pm0.08\ M_\odot$) with a period of 1140 days on an eccentric ($e\approx0.5$) and inclined ($i\approx 130^{\circ}$) orbit. Through joint analysis of (1) radial velocities and Gaia two-body solution, as well as (2) radial velocities, Hipparcos Intermediate Astrometric Data and two-epoch Gaia astrometry, we obtain true companion masses of $74.20^{+3.46}_{-3.64} M_{\mathrm{J}}$ and $69.03^{+4.99}_{-4.95} M_{\mathrm{J}}$, respectively, agreeing with each other within $1\sigma$. Taking a sample of 159 brown dwarfs with absolute mass measurements from different detection techniques, we investigate their eccentricity distributions across different semi-major axis ranges by fitting a Beta distribution. We find that the peak of eccentricity distribution tends to gradually shift toward lower values from wide orbits ($a>20$ AU) to intermediate ($1<a<20$ AU) and inner ($0.1<a<1$ AU) regions. Such trend is plausibly due to disk friction during orbital evolution. Together with obliquity studies showing that brown dwarfs are mostly aligned, our result suggests that brown dwarfs may migrate inward through quiescent coplanar disk-driven processes.
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All authors Lei Ren, Tianjun Gan, Yifan Xuan, Shude Mao, Shigeru Ida, Guang-yao Xiao, Fabo Feng, Enric Pallé

Earth and Planetary Astrophysics

An updated view of Jupiter's UV main auroral emission: large-scale analysis of UV and particle data from Juno's first 60 orbits

Linus Head, Denis Grodent, Bertrand Bonfond et al. (+9 more)

The properties and origins of Jupiter's UV main auroral emission are, at present, not yet fully understood, particularly the extent to which its two distinct zones, the Zone-I and Zone-II aurora, originate from a common source. In this work, remote-sensing and in-situ data from the Juno spacecraft are used to investigate and produce maps of the average properties of the main emission over Juno's first 60 orbits. It is found that the peak in mean energy of electrons precipitating in the main emission is consistently poleward of the energy-flux (or brightness) peak, in both hemispheres and at all local times, and is co-located with the statistical location of the Zone-II aurora. Evidence is presented that the flux-energy relationship of the main emission is adequately characterised by theoretical power laws describing electron acceleration from quasi-static potentials or Alfvénic turbulence and that it shows a modulation with ionospheric electron density consistent with theoretical predictions. Finally, the average energy spectra of precipitating electrons in the Zone-I aurora remain power-law-like between an energy flux of 1 and 100 mW m$^{-2}$, whereas the average Zone-II spectra develop a distinct “plateau” or “flattop” shape beyond an energy flux of $\sim$5 mW m$^{-2}$. Our results provide some evidence that the Zone-I and Zone-II aurorae are phenomenologically distinct, and the consequences of this interpretation for future investigation of the main emission are discussed.
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All authors Linus Head, Denis Grodent, Bertrand Bonfond, Nicholas Kruegler, Ali Sulaiman, George Clark, Bilal Benmahi, Guillaume Sicorello, Julie Vinesse, Thomas Greathouse, Rohini Giles, Barry Mauk

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

From the QBO to Rieger-type periods: Explaining extreme solar events by tidally triggered magneto-Rossby waves

F. Stefani, G.M. Horstmann, G. Mamatsashvili et al. (+1 more)

It has recently been demonstrated that the occurrence of extreme solar events is governed by a phase-stable period close to 1.723 years (629.29 days). According to our previously developed tidally-synchronized solar dynamo model, this is one of the periods resulting from two-planet spring tides exerted by the tidally dominant planets Venus, Earth and Jupiter, which trigger magneto-Rossby waves in the solar tachocline. Overall, the squared sum of these three waves incorporates nine periods ranging from 59 to 629 days. Using a standard Rayleigh test, we demonstrate that all nine of these periods can be identified in the data on extreme solar events. For the latter, we use a combination of 72 ground-level enhancement (GLE) events with various X-flare data, the number of which increases when the threshold is successively lowered from X10 to X1. To identify the spectral peaks, it is necessary to analyze the sidebands that emerge due to the modulation with the longer-term periods such as the 11-year Schwabe cycle and the third harmonics of the Hale cycle. In this framework, the seminal Rieger period of 154 days is re-interpreted as the lower sideband of 146 days which is the quarter of the synodic period of Venus and Earth.
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All authors F. Stefani, G.M. Horstmann, G. Mamatsashvili, T. Weier

Earth and Planetary Astrophysics

Interaction of eccentricity tide and convection

Jiachen Zheng and Xing Wei

Aim. We try to understand the interaction of eccentricity tide and convection in icy satellites. Method. We use the numerical calculation of rotating convection with eccentricity tide in a spherical shell. Results. We have the following results. (1) Energy scaling exponent about buoyancy force (or tidal force) decreases with increasing tidal force (or buoyancy force). (2) The combined tide-convection flow is not identical to superposition of two pure flows in respect of energy spectrum. (3) Tide controls large-scale of fluid motion but convection is important for small scale, and the mode-mode transition occurs at intermediate scales. (4) Tide suppresses heat transport efficiency. (5) Dissipation of kinetic energy scales as square of tidal force with a very weak dependence on buoyancy force, which has little impact on dissipation but suppresses the tidal influence on dissipation.
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Earth and Planetary Astrophysics

Capture of Interstellar Planetesimals in Protoplanetary Discs in Binary Star Systems

Alia Pollard and Evgeni Grishin

Planet formation requires growth over 12 orders of magnitude in size, from micron-sized dust grains to fully formed planets. The formation of km sized planetesimals is the most challenging stage, where radial drift and fragmentation rapidly remove meter- sized solids from the protoplanetary disc. Overcoming this barrier requires favourable conditions for streaming instability to concentrate solids. These problems are exacerbated in binary star systems, where gravitational perturbations and disc truncation reduce the efficiency of planetesimal formation pathways. Planetesimal capture provides an alternative mechanism where unbound planetesimals are captured by the protoplanetary disc through gas-drag, potentially bypassing the most restrictive growth stages. We investigate this process in circumstellar and circumbinary discs using over 30 million numerical experiments across a range of binary separations. For circumstellar discs, capture of large planetesimals is suppressed below 50 au, with the strongest reduction at around 10 au, broadly consistent with the observed decrease in planet occurrence in binaries. Tight binaries can still capture O(1) km-sized planetesimals, increasing to O(10) km-sized in wider systems during the birth cluster's lifetime. Circumbinary discs are much less efficient, with capture rates dropping to around 1 percent of the single-star case for binaries above 1 au and becoming negligible for large planetesimals at wider separations. Overall, planetesimal capture provides a supplementary channel for delivering solids to binary systems and mitigating inefficiencies in in-situ planetesimal formation.
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Sunday 11 October

Earth and Planetary Astrophysics

Scaled three-dimensional simulations of giant-planet accretion and disk clearing

Ignacio Mosqueira

We develop accelerated three-dimensional simulations of growing planet pairs that draw on a finite gas reservoir. An annulus compression (Scaling A) shortens the predicted clearing time and shrinks the computational domain at equal grid resolution while preserving key physical parameters. Planetary seeds start with Hill radii equal to the disk scale height, retaining three-dimensional accretion. We demonstrate the method in scaled PDS 70 and Solar-System configurations, assuming perfect Hill capture by growing planets on circular orbits. We compare Scaling A at radius-compression factor \(\Gamma=1.75\) with the unscaled PDS system at matched resolution, through a 1% reduction of the interplanetary gas inventory. The scaled run is nearly an order of magnitude faster, with similar accreted mass and a comparable partition of gas between the planets. For the Solar-System configuration at \(\Gamma=3\), the scaling forecasts a speedup of nearly two orders of magnitude at equal local resolution. The scaling is complementary to orbital advection. On eight CPU cores of a desktop computer, the scaled PDS 70 and Solar-System runs reduce the gas inventory between the orbiting planets by roughly half in less than a day. Accretion-driven orbital convergence narrows the shared feeding zone and, together with gas clearing, limits the planetary growth budget. In our scaled PDS 70 and Solar-System runs, the angular momentum carried by meridional inflow directly constrains delivery theory. These results establish a practical route to testing accretion theory against simulations at matched scaled parameters, before applying it to unscaled planetary systems.
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Earth and Planetary Astrophysics

Photometric and Spectroscopic Observations of Comet 2P/Encke's Nucleus in the Mid-Infrared Wavelength Region

Takafumi Ootsubo, Hideyo Kawakita, Jun-ichi Watanabe et al. (+2 more)

We observed comet 2P/Encke with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the Subaru telescope on UT 2003 November 12.3, when the comet was at heliocentric and geocentric distances of 1.09 and 0.27 au, respectively. Imaging observations of the comet with narrow-band filters centered at 8.8, 10.5, 11.7, 12.4, 18.8, and 24.5 $\mu$m and low-resolution spectroscopic observations in the N-band (8-13 $\mu$m, $R\sim250$) of the comet were performed. The observed spatial profiles of the comet were consistent with those of a standard star (FWHM $\sim$ 0.3” at 10.5 $\mu$m, close to the diffraction-limited image size), indicating that the observed spectrum was dominated by thermal emission from the cometary nucleus. The semi-axial ratio ($a$/$b$) of the nucleus of 2P/Encke is estimated as 2.26$^{+0.33}_{-0.21}$ based on the isothermal, prolate ellipsoid model. The photometric data with the correction for rotational phases, can be explained by a blackbody temperature of $328\pm7$ K, consistent with the nucleus surface temperature empirically estimated at 1.09 au from the Sun (327 K). This blackbody approximation for the nucleus leads to $a = 3.6^{+0.5}_{-0.3}$ km and $b = 1.6^{+0.2}_{-0.2}$ km by assuming an emissivity of unity. The observed low-resolution N-band spectrum showed an overall smooth continuum with no prominent excess emission feature at $\sim$10 $\mu$m due to fine silicate grains in the cometary coma. The relative emissivity spectrum of the nucleus showed a negative feature at $\sim$9.5 $\mu$m, as seen in the mid-infrared nucleus spectrum of 460P/PanSTARRS [T. Ootsubo, et al. (2021), Icarus, 363, 114425].
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All authors Takafumi Ootsubo, Hideyo Kawakita, Jun-ichi Watanabe, Hitomi Kobayashi, Yoshiharu Shinnaka

Saturday 10 October

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

Mid-IR Water-Vapor Seeing: Implications for ELT/METIS High-Contrast Imaging from VLTI Data

Abhirami S Raghu, Prashant Pathak, Olivier Absil et al. (+7 more)

Direct imaging and characterization of rocky exoplanets remains one of the central challenges in exoplanetary science. The mid-infrared (mid-IR) offers a favorable high-contrast imaging (HCI) regime, as the planet-star contrast is more moderate than at shorter wavelengths. However, mid-IR observations with extremely large ground-based telescopes (ELTs) are strongly affected by spatio-temporal fluctuations in atmospheric water vapor (WV), which introduce chromatic wavefront errors that are largely invisible to adaptive optics systems operating at shorter wavelengths. This poses a significant challenge for mid-IR HCI instruments such as METIS, which aims to detect thermal emission from rocky exoplanets in the $N$-band (8–13 $\mu$ m). To quantify WV-induced wavefront errors, we analyze $K$-band fringe-tracker data from the GRAVITY instrument at the VLTI and derive the optical path difference between group-delay and phase-delay measurements. This difference provides a direct measure of the differential WV column density ($\Sigma$) above the telescopes. We examine the dependence of the RMS differential WV column density ($\sigma_{\Sigma}$) on precipitable water vapor (PWV), airmass, seeing, and wind speed across multiple VLTI configurations. Among these parameters, PWV shows the strongest correlation with $\sigma_{\Sigma}$. We further explore the influence of the vertical PWV distribution on this relationship. Next, we use power-spectral-density analysis to quantify how increasing PWV modulates $\Sigma$ variability. The wavefront error associated with this phenomenon on ELT scale is approximately 15~nm RMS in the $L$-band and 175~nm RMS in the $N$-band, relative to the $K$-band. These results provide a quantitative framework for assessing and mitigating atmospheric WV effects in next-generation mid-IR HCI instruments.
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All authors Abhirami S Raghu, Prashant Pathak, Olivier Absil, Benjamin Courtney-Barrer, Gilles Orban de Xivry, Julien Woillez, Alexis Matter, Philippe Bério, Roy van Boekel, Bernhard Brandl

Earth and Planetary Astrophysics

Milani and Juventas Optical Navigation Images in Support of the Hera Radio Science Experiment

Edoardo Gramigna, Ozgur Karatekin, Birgit Ritter et al. (+7 more)

The European Space Agency's Hera mission aims to advance planetary defense by investigating the Didymos binary asteroid system following NASA's DART impact on Dimorphos. Incorporating simulated CubeSat images into Hera's orbit determination framework significantly improves positional accuracy, reducing uncertainties by up to three orders of magnitude for Milani and one for Juventas. This data enable more precise estimation of key parameters such as asteroid masses, rotational states, and moments of inertia, with up to 90% uncertainty reduction in Dimorphos' dynamical state under chaotic scenarios. Sensitivity analysis reveals the influence of pointing accuracy, image noise, and imaging frequency. Additionally, dedicated scientific investigations using Dimorphos-focused CubeSat images further advance understanding of the system. These findings underscore the critical role of CubeSat images in refining navigation and advancing science, offering valuable insights for future small-body missions.
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All authors Edoardo Gramigna, Ozgur Karatekin, Birgit Ritter, Iosto Fodde, Fabio Ferrari, Felice Piccolo, Paolo Tortora, Riccardo Lasagni Manghi, Marco Zannoni, Ryan S. Park

Earth and Planetary Astrophysics

Hera Orbit Determination Covariance Analysis of Didymos Binary Asteroid with the Full Two-Body Problem

Edoardo Gramigna, Riccardo Lasagni Manghi, Marco Zannoni et al. (+7 more)

Standard planetary radio science analyses may be inadequate for accurately interpreting data from the Hera mission at the Didymos system due to the anticipated challenge posed by the coupling between the translational and rotational motions of the asteroids. A more precise dynamical model, the full two-body problem model, which includes a mutual gravitational potential, may be required to fit the Hera data properly. This work presents a covariance analysis of the Hera radio science experiment using this advanced model. The tested dynamical scenarios are based on recent lightcurve observations indicating that Dimorphos is in an excited non-principal axis spin state that is, on average, tidally locked. Three non-principal axis scenarios are analyzed using a multi-arc local estimation approach instead of the global one adopted in previous investigations involving non-chaotic states. The results show that tumbling or chaotic cases significantly improve the recovery of the bodies' moments of inertia due to the enhanced observability of the system's dynamics from the excited spin state. However, the local estimation approach slightly degrades the accuracy of the mass estimation by a factor of 1.3-3 and Dimorphos' relative orbit by about one order of magnitude. Developing a dedicated constrained multi-arc filter is thus required to improve the estimation accuracy of the Didymos system's dynamical state further. Nevertheless, these results still meet the Hera radio science requirements.
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All authors Edoardo Gramigna, Riccardo Lasagni Manghi, Marco Zannoni, Paolo Tortora, Michalis Gaitanas, Ioannis Gkolias, Kleomenis Tsiganis, Ryan S. Park, Alex Meyer, Petr Pravec

Friday 9 October

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

TESS Pulsation Timing Reveals the JWST Calibration Star HD 158485 as a Double-pulsator Binary

Chenglong Lv, Ali Esamdin, Shuguo Ma et al. (+5 more)

HD~158485 is an A-type $\delta$~Scuti star in the CALSPEC network and the JWST absolute-flux calibration program. Gaia DR3 assigns it a binary classification probability close to unity but provides no orbital solution. Using TESS observations from Sectors 14–26, 40–41, 47–60, and 73–86, we measure the pulsation phases of six $\delta$~Scuti modes. The frequencies form two groups with opposite light-travel-time delays, revealing two pulsating components. A direct light-curve forward model yields an orbital period of $P_{\rm orb}=382.80^{+0.80}_{-0.76}$~d, eccentricity $e=0.242^{+0.045}_{-0.046}$, projected light-time amplitudes of $195.8^{+9.2}_{-8.9}$ and $239.7^{+6.8}_{-6.8}$~s, and a dynamical mass ratio of $q=M_B/M_A=0.818^{+0.046}_{-0.045}$. A blind prediction based only on the first two long TESS campaigns reproduces the third campaign without updating the orbital parameters, with a Pearson correlation coefficient of $r=0.983$. Its held-out rms is 83.8~s, compared with 289.9~s when the period is fixed at 365.25~d. A 5.15-$\sigma$ Hipparcos–Gaia EDR3 proper-motion anomaly independently indicates unresolved astrometric motion. The unresolved companion can also affect spectrophotometric predictions: a conditional PB2-constrained two-atmosphere model differs from the corresponding single-star atmosphere prediction by 1.6% over 1–5~$\mu$m and 2.5% over 5–28~$\mu$m. HD~158485 therefore shows that a calibration-relevant binary can lack a catalogued orbital solution while two independent pulsation clocks reveal and measure its orbit.
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All authors Chenglong Lv, Ali Esamdin, Shuguo Ma, Shahidin Yaqup, Haozhi Wang, Ayzada Jmahali, Jianwei Yao, Kedieryemu Kamili

Earth and Planetary Astrophysics

OGLE-2016-BLG-0523: A Low-mass Brown Dwarf or super-Jupiter in a $>100$ au Orbit

Hongjing Yang, Weicheng Zang, Yoon-Hyun Ryu et al. (+37 more)

To search for very wide-orbit binary-lens events, we cross-match microlensing events detected by OGLE-IV and KMTNet between 2011 and 2024. After removing contaminants from variable stars, we identify OGLE-2016-BLG-0523 as a microlensing event showing two short-lived bumps in its light curve, with the two separated by 8.36 yr. We investigate three scenarios to explain the two bumps, including a binary-lens single-source (2L1S), a single-lens binary-source (1L2S), and two unrelated single-lens single-source events (2$\times$1L1S). The 1L2S interpretation is excluded due to its poorer fit to the data, while the 2$\times$1L1S scenario is disfavored by the low event rate, unphysical total source flux, and unphysical color for one of the two putative sources. For the surviving 2L1S interpretation, the Einstein timescales of the two bumps are $8.343 \pm 0.076$ days and $3.231 \pm 0.047$ days, respectively, implying a binary mass ratio of $q = 0.15$. A Bayesian analysis indicates that the primary lens is most likely a low-mass M dwarf, while the companion is probably a low-mass brown dwarf or super-Jupiter. The inferred projected separation is about 450 au, making the companion the widest low-mass object discovered via microlensing to date. Our discovery highlights both the promise and challenges of identifying very wide, low-mass companions through microlensing. Although upcoming facilities such as Roman and Earth 2.0 space telescopes will improve sensitivity to such events, overcoming degeneracies and distinguishing them from variable phenomena will remain essential for building a robust statistical sample.
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All authors Hongjing Yang, Weicheng Zang, Yoon-Hyun Ryu, Andrzej Udalski, Yuchen Tang, Michael D. Albrow, Sun-Ju Chung, Andrew Gould, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, In-Gu Shin, Yossi Shvartzvald, Jennifer C. Yee, Sang-Mok Cha, Dong-Jin Kim, Hyoun-Woo Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radoslaw Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof A. Rybicki, Patryk Iwanek, Krzysztof Ulaczyk, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz, Jiyuan Zhang, Shude Mao, Hongyu Li, Qiyue Qian

Earth and Planetary Astrophysics

The origin of the large heavy element contents of warm Jupiters

Bertram Bitsch

Planet interior models have revealed that warm Jupiters should harbor large heavy element masses (up to 30-40% of the planetary mass). Within the pebble drift and evaporation scenario, inward drifting pebbles can evaporate and enrich the inner disc with vapor to super-stellar values, accreteable by giant planets. As H$_2$O ice evaporates in the inner disc, while CO$_2$, CH$_4$ and CO evaporate in the outer disc, the enrichment of the disc with vapor decreases with increasing orbital distance. We use the chemcomp code to model the migration and growth of planets via pebble and gas accretion in discs around stars with different masses and discs with different sizes. We show (i) that pebble drift and evaporation can explain the wide range of derived heavy element contents of giant planets. (ii) Giant planets forming around stars with larger disc sizes can accrete larger quantities of heavy elements, because these discs can maintain a high pebble flux for a longer time. (iii) Planets forming or migrating interior to the water ice line can accrete larger amounts of heavy elements via the accretion of vapor enriched gas compared to planets forming in the outer disc regions. (iv) Metal rich stars can allow the formation of planets that are more enriched in heavy elements, if they form in the inner disc regions. Planets forming in the outer disc regions will be - independently of the disc metallicity - much less enriched compared. (v) Planets forming in discs with the same size and total mass, but around stars with higher mass, are only marginally more enriched compared to their counterparts forming around lower mass star. Our study suggests that the trend of increasing total heavy element mass with increasing planetary mass is caused by the accretion of vapor enriched gas in discs with different sizes in the combination with different origins of warm giant planets from the inner and outer disc.
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Earth and Planetary Astrophysics

Assessing PLATO's Discovery Potential across Different Observing Strategies

Yoshi Nike Emilia Eschen, Michelle Kunimoto, Juan Cabrera et al. (+11 more)

The PLATO mission, planned to launch in spring 2027, will observe a fixed Southern field, LOPS2, for at least 2 years with the goal of discovering and deriving precise parameters for planets as small as Earth around FGK dwarfs and sub-giants. Afterwards, PLATO could continue to monitor the same field or move to a Northern field, LOPN1, overlapping with the Kepler field. We assess these two observing strategies in terms of sensitivity of detecting small and long period planets, and subsequently we estimate yields for both observing strategies. Within this we account for including the Kepler data in the LOPN1 field, monitoring of up to 8 years of the LOPS2 field, and the sensitivity improvement from combining TESS and PLATO data since both fields have been and will be continued to be observed with TESS. We find that by monitoring both fields, and hence more stars, the total number of newly discovered planets is maximised. However, to optimise the number of discovered small and long periods planets, long-term monitoring of one field produces the best results. The combination of Kepler and PLATO data improves detection sensitivities; however, as this only covers a fraction of the LOPN1 field and stellar sample, it improves the yields of small and long period planets only marginally. Hence, to detect and characterise small and long period planets in this sparsely explored exoplanet parameter space, a longer continuous observation of the LOPS2 field is best.
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All authors Yoshi Nike Emilia Eschen, Michelle Kunimoto, Juan Cabrera, Adrien Leleu, Thomas G. Wilson, Heike Rauer, Alex Romanec, François Bouchy, Magali Deleuil, Nicholas Jannsen, Don Pollacco, Toby Rodel, Sophia Sulis, Stéphane Udry

Earth and Planetary Astrophysics

How long could volcanic plumes persist in the Venus atmosphere?

Maureen Cohen, James Holmes, Joanna Egan et al. (+2 more)

Resolving the ambiguity surrounding current Venusian volcanism is a primary objective for upcoming missions like EnVision and VERITAS. This study uses the Venus Planetary Climate Model to simulate the dispersal and detectability of volcanic plumes containing water vapour (H2O), hydrogen chloride (HCl), carbon monoxide (CO), and carbonyl sulphide (OCS) within a three-dimensional atmospheric environment. We model localised gas enhancements at altitudes probed by nightside spectral windows (8.62, 20.91, and 35.45 km above surface). Results indicate that plumes persist longest in the deep atmosphere (8.62 km) at equatorial latitudes, where H2O enhancements remain distinguishable from low background variability for up to 100 hours, forming distinct downstream streaks. In contrast, at 35 km, high intrinsic variability in chemically active species (CO and OCS) driven by atmospheric dynamics obscures plume signatures and chemically inert species disperse within 0.5-2 Earth days. Plumes at high latitudes disperse more rapidly than at low latitudes at all altitudes. We perform sensitivity tests with trace gas increases of 50%, 40%, 30%, 20%, 10%, and 3% above baseline and plume injection times of 6, 12, 28, 38, and 126 hours at all three altitudes and two latitudes. We conclude that observing inert gases, in particular H2O, at low altitudes and latitudes offers the best opportunity for successful plume detection.
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All authors Maureen Cohen, James Holmes, Joanna Egan, Stephen Lewis, Manish R. Patel

Earth and Planetary Astrophysics

The Hydrological Cycle and Circulation of Tidally-Locked Planets with a Finite Moisture Inventory

Daniel A. Williams, Geoffrey K. Vallis, Stephen I. Thomson et al. (+1 more)

Tidally-locked planets express a range of climate regimes distinct from those found in our solar system. Their atmospheres are often dominated by planetary-wide overturning circulations and super- rotating jets. In this paper we explore the hydrological cycle of such planets and how it might depend on the total inventory of condensate. To this end we use a set of idealised GCM simulations to probe the response of the hydrological cycle to the surface moisture budget in their atmospheres. We find that for low moisture inventories the climate quickly develops a barren day side and a moist night side where the moisture is trapped, as might be expected. For higher moisture inventories the drying of the day side is significantly delayed by the development of a substellar lake just east of the substellar point, which is sustained by the presence of a local thunderstorm-like convective system that persists even after the lake disappears. The timescales for the lake to disappear are millennia, suggesting that even a weak transfer of moisture through surface processes could maintain a moist day side. We also find that adjusting the threshold at which the evaporative rate becomes constrained by the remaining surface liquid depth modifies the longevity of the lake and surrounding day side conditions. These findings have implications for understanding a diverse range of planetary climates and habitability, given the distribution of moisture and presence of a substellar lake.
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All authors Daniel A. Williams, Geoffrey K. Vallis, Stephen I. Thomson, William J. M. Seviour

Earth and Planetary Astrophysics

Fermentation heterotrophy can reproduce Enceladus's plume H2 and CH4 under limited serpentinization

Sam Nasreldine, Antonin Affholder, Laura Molares Moncayo et al. (+2 more)

Saturn's icy moon Enceladus is a prime target in the search for life beyond Earth. Abundant H2 and CH4 in Enceladus's south-polar plume have been shown to be consistent with hydrogenotrophic methanogens feeding on products of long-lived serpentinization. However, thermo-permeability models make sustained core-wide H2 production by serpentinization uncertain. We therefore explore whether an alternative metabolism based on fermentation-driven heterotrophy could reproduce Cassini H2 and CH4 escape fluxes under limited serpentinization. We develop a coupled ecosystem model of fermentation and methanogenesis in a hydrothermal-ocean-plume framework, using glycine as a proxy for amino-acid-like fermentable organics. With effectively no abiotic H2 and CH4 input, purely heterotrophic communities with fermenters and methanogens can reproduce both Cassini-derived flux intervals given sufficient hydrothermal glycine-equivalent supply, while the estimated organic stock could sustain the required H2 production on gigayear timescales if fully available. We then test a scenario with input ranges for fermentable organic matter, H2, and CH4 informed by asteroid-sample measurements and geochemical estimates of limited serpentinization. Simulations within both Cassini-derived flux intervals are concentrated in communities with acetoclastic methanogens; Bayesian model comparison favors the same communities. This holds even allowing for greater abiotic H2 and CH4 inputs that reduce the fermentable-organic supply required to reproduce the plume. We therefore identify fermentation heterotrophy as a testable alternative to purely hydrogenotrophic, serpentinization-dominated biotic interpretations and motivate future plume searches for co-exported fermentation products, including acetate and ammonium, together with measurements of methane carbon isotopes.
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All authors Sam Nasreldine, Antonin Affholder, Laura Molares Moncayo, Régis Ferrière, François Guyot

Earth and Planetary Astrophysics

Towards a coupled activity-fallback model for comets I) 67P/Churyumov-Gerasimenko's water activity from a microphysics model with dynamic dust-depth

Nicholas Attree, Yuri Skorov, Pedro Gutiérrez et al. (+4 more)

We apply a two-layer thermophysical model, with water sublimating from below a dust-crust with dynamically varying depth, to simulate the water outgassing rate, dust-ejections, and non-gravitational forces and torques of comet 67P/Churyumov-Gerasimenko. The dust-depth is determined at each time-step by the balance of dehydration and subsurface pressure, leading to alternating ejections and crust build-up. This model is the first stage of implementing a fully coupled activity-fallback model that self-consistently incorporates dust-fallback into the ejection depth calculation, but already a number of conclusions can be drawn from these results. The two-layer model with only dehydration and ejections is able to reproduce much of the Rosetta outgassing, dust-ejection data and non-gravitational dynamics, particularly in the comet's more primitive southern terrain. Best agreement is found for nucleus material made up of small aggregates ($d_{agg}\sim1$ mm) with not-too-high dust-to-ice ratios ($\delta\sim2-8$) and low average strengths ($\lesssim1$ Pa) that decreases with depth. Disagreements between the observations and model are greatest for the northern-facing and dust-covered terrains, suggesting the importance of surface modification by fallback and material processing here, which will be the subject of investigation in the next paper.
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All authors Nicholas Attree, Yuri Skorov, Pedro Gutiérrez, Olivier Groussin, Abhinav Jindal, Raphael Marschall, Samuel P.D. Birch

Earth and Planetary Astrophysics

Combination of multi-observatory photometry to determine asteroid rotation periods

Kristers Nagainis and Ilgmars Eglitis

This study aims to determine asteroid rotation periods from sparse, unevenly sampled, multi-observatory photometry using the Lomb-Scargle (L-S) method. The photometric measurements of the asteroids are taken from the circulars of the Minor Planet Center (MPC). Twelve asteroids, four of them with known rotation periods, were analyzed with two complementary methods. In the separate dataset analysis (S-method), each observatory dataset was analyzed separately, and the final period was obtained as a weighted average of the consistent candidate periods, with weights based on the peak power of the power spectrum, the number of measurements, and the quality of the corresponding light curve fit. In the combined dataset analysis (C-method), all measurements were corrected for the biases of the photometric band, the star catalog and the observatory, reduced to a common scale and merged into a single dataset, after which the period was derived directly from the L-S analysis of the combined time series. Both methods produced consistent results, and they reproduced the known periods of the four test asteroids within 0.05%. The results show that the L-S method is well suited for finding rotation periods in sparse observations with uneven sampling over long time intervals. New rotation periods were found for asteroids 2968, 2971, 3081, 3473, 3716, and 4303. The period of 2968 remains ambiguous because of daily aliasing. For 3716, the most likely period is 10.474 hours, but its daily alias at 13.405 hours cannot be excluded completely. For 3173, the strongest peaks at 22.99 and 45.98 hours are probably daily aliases of a slower brightness variation. For asteroid 2607, the period agrees with a recently published value and is more precise. The approach is therefore promising for automated searches for unknown asteroid rotation periods.
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Earth and Planetary Astrophysics

Detailed study of HD 219134: a benchmark K-dwarf with a compact planetary system

Jérôme Bétrisey, Camilla Pezzotti, Gaël Buldgen et al. (+4 more)

Space missions such as CoRoT, Kepler, and TESS have transformed asteroseismology and its synergies with exoplanet science. We revisit the nearby K-dwarf HD 219134 to investigate the tension between asteroseismic and interferometric radii, update its fundamental parameters, and reconstruct the rotational, magnetic, and atmospheric evolution of the system. We combine forward asteroseismic modeling with seismic inversions to assess systematics from non-seismic constraints, radius measurements, and surface modeling. The revised stellar properties are then used for rotational evolution, stellar-wind, and high-energy irradiation calculations. Seismic inversions rule out the most recent interferometric radius, while the asteroseismic and spectroscopic results are compatible with the 2019 interferometric measurement. We obtain $M=0.779\pm0.015_\mathrm{(stat)}\pm0.006_\mathrm{(sys)}\ M_\odot$, $R=0.753\pm0.005_\mathrm{(stat)}\pm0.002_\mathrm{(sys)}\ R_\odot$, and an age of $8.92\pm0.89_\mathrm{(stat)}\pm0.19_\mathrm{(sys)}$ Gyr. These systematics include only non-seismic constraints; literature combined uncertainties from physical inputs and surface effects are $0.007M_\odot$, $0.002R_\odot$, and $0.81$ Gyr. Rotational and wind modelling shows that standard magnetic braking is broadly compatible with the present-day rotation and angular-momentum loss. Weakened braking gives a closer match but challenges standard wind-loss scalings. The inferred X-ray history suggests early stripping of the innermost planets, while the outer planets likely retained part of their primordial envelopes; HD 219134d experienced only moderate erosion. The apparent radius discrepancy likely reflects underestimated uncertainties in previous interferometric analyses rather than an astrophysical inconsistency. We advocate adopting the asteroseismic radius, which is robust to modeling assumptions and optimisation strategies.
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All authors Jérôme Bétrisey, Camilla Pezzotti, Gaël Buldgen, Aline A. Vidotto, Colin P. Folsom, Michaël De Becker, Michaël Gillon

Earth and Planetary Astrophysics

Star Cluster Ecology VIII. – Dynamically Forming S-Type and $\alpha$Centauri-like Systems

Erwan Hochart and Simon Portegies Zwart

Aims: To analyse the impact of dynamically formed binaries emerging naturally from various star cluster environments on already established planetary systems. Methods: Numerical simulations replicating the star-forming region NGC 1333 are conducted. We consider three models, each using identical cluster realisations and simulation parameters. The cluster itself is initially sub-virial and fractally distributed. Model~A assumes planetary systems are initially in mean motion resonance. In Model~B, the same planetary systems are moved out of resonance, but remain intrinsically stable. Finally, Model~C removes all planets from the simulation. Ten independent realisations are integrated per model until 30 Myr. Results: Dynamically formed binaries emerge at similar rates across models, indicating planets play little role in their formation. We also find a higher production rate of wide binaries compared to previous numerical studies which we attribute to the sub-virial and sub-clustered initial conditions. S-type and binary S-type planetary systems naturally emerge in our simulations, while P-type systems are rare. For Model~A, the fraction of S-type or binary S-type systems is f_S=0.02 and $f_Bin,\, S=0.05, respectively. Rogue planets originating from a binary system are ejected with a substantially larger velocity than those around singletons. Planet-star collisions and planet capture events occur disproportionately within binary systems. Finally, several \alphaCentauri-like systems emerge in our simulations, suggesting that the nearest stellar system to the Sun may have a dynamical origin.
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Earth and Planetary Astrophysics

The Neptunian Final Parsec Problem: How Inertial Waves Enable Neptunes and Gas Giants to Survive Tidal Migration

Tim Hallatt, Adrian J. Barker and Sarah C. Millholland

Observations indicate that some hot Neptunes and Jupiters underwent high eccentricity migration (HEM). A longstanding issue facing HEM theory remains, however: in order to shrink their orbits by ${\sim}1{-}2$ orders of magnitude, planets must dissipate ${\gtrsim}10{\times}$ more orbital energy than is contained in their structural binding energy. Previous work suggests that excitation of planets' fundamental modes (”$f$-modes”) at very high eccentricities, $e{\sim}$0.99, can shrink semi-major axes by ${\sim}$an order of magnitude (${\sim}5{\rightarrow}0.5$ au) while safely bleeding tidal energy to space. We examine how planets traverse the remaining order of magnitude in orbital shrinkage, $a{\sim}$0.5${\rightarrow}$0.05 au, which still poses a danger for Neptunian planets due to their lower binding energies (their ”final parsec” problem). To assess whether tidally-migrating Neptunes balance their energy budgets, we perform coupled orbit/structure calculations tracking their frequency-dependent tidal response under inertial waves (IWs). We show that tidal radius inflation at moderate eccentricities sweeps Neptunes' fundamental modes back into resonance with tidal forcing; only a small amount of tidal heat relative to a Neptune's binding energy is needed to drive this $f$-mode excitation. This excitation of Neptunes' $f$-modes may offer a route to safe circularization, provided the $f$-mode dissipates without harming the planet. In contrast, eccentric gas giants ($e{\sim}0.9$) circularize without drama over ${\sim}$Gyr. Our theory predicts that warm Neptunes on a HEM track ($a{\gtrsim}0.1 \ \mathrm{au}, \ e{\gtrsim}0.8$) should be rare, in opposition to warm gas giants and lower eccentricity Neptunes. Observational confirmation of our predictions would constrain the interior structures of Neptunian planets via tidal theory.
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Thursday 8 October

Earth and Planetary Astrophysics

The GAPS programme at TNG LXXXII. The first atmospheric investigation of the gas giant WASP-13b at high resolution with GIARPS

D. Sicilia, M. Basilicata, G. Guilluy et al. (+17 more)

Low-density transiting gas giant exoplanets are key benchmarks for atmospheric studies. Despite their large-scale heights, many of them remain poorly characterised. We present the first atmospheric investigation at high-resolution of the inflated (R$_\mathrm{p}$$\sim$1.4 R$_{\mathrm{J}}$), hot Jupiter (T$\sim$1500$ \mathrm{K}$) WASP-13 b aiming at constraining its atmospheric composition and refine its orbital geometry. We analysed four transits observed with GIARPS at the TNG. Updated stellar and planetary parameters were re-derived from the most precise literature values, and a new Rossiter-McLaughlin analysis was performed to measure the projected spin-orbit angle ($\lambda$) and stellar rotational velocity ($v\sin{i_\star}$). Atmospheric signals were searched using high-resolution spectroscopy, both with cross-correlation and single-line analyses, targeting key atomic and molecular species (e.g. \ion{He}{I}, H$\alpha$, \ion{Na}{I}, H$_2$O, CO). We find a well-aligned orbit ($\lambda$ = 2.7$\pm$1.1$^\circ$) and $v\sin{i_\star}$ = 4.5$\pm$0.1 km s$^{-1}$, improving upon previous constraints. No significant atmospheric absorption is detected in either VIS or NIR data. Injection-and-recovery tests exclude an isothermal atmosphere with metallicity [M/H]$\lesssim$10$\times$[M/H]$_\odot$ and simultaneously a grey cloud top pressure P$_{\rm cloud}\gtrsim10$ mbar, under the assumption of chemical equilibrium. WASP-13 b appears to belong to the class of low-density hot Jupiters with weak or featureless transmission spectra, most likely shaped by the presence of high-altitude clouds. Although a highly metal-enriched atmosphere cannot be fully excluded, current evidence disfavours this scenario. Further observations with next-generation facilities will be essential to characterise the atmospheric properties of this challenging target.
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All authors D. Sicilia, M. Basilicata, G. Guilluy, G. Scandariato, F. Borsa, C. Di Maio, M. Brogi, A. Chiavassa, L. Fossati, F. Amadori, P. Giacobbe, A. S. Bonomo, A. Sozzetti, L. Mancini, G. Andreuzzi, S. Colombo, V. Fardella, A. Ghedina, G. Mantovan, G. Piccinini