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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Friday 25 September

Earth and Planetary Astrophysics · Cross-listed from cond-mat.soft

A Bonded-Particle Discrete-Element Model with Self-Gravity for the Collision and Reaccumulation of Rubble-Pile Asteroids: Formulation and Numerical Protocol

Yohann Trivino

I present a discrete-element approach developed to study the collisional and gravitational evolution of small self-gravitating granular aggregates. Each body is represented as a composite of cohesively bonded spherical grains, so that fragmentation and reaccumulation emerge from the microscopic competition between short-range dissipative contact forces, an irreversible bond-breaking criterion, and pairwise Newtonian self-gravity summed over every particle pair, including those internal to a single body. A numerical experiment is described: a random-sequential packing procedure that generates two bonded spherical aggregates, a controlled two-body encounter with tunable approach speed and impact parameter, and a systematic parameter sweep designed to map the conditions under which two bodies launched from rest under their mutual gravity alone either merge into a single remnant or fail to settle after a low-speed encounter. Of the 125 simulated collisions, 56.8% result in the formation of a single residue. The cohesive network remains intact for $\Pi_\sigma\lesssim0.036$, is partially damaged with dispersion determined by the contact damping ratio, and breaks completely for $\Pi_\sigma\approx3.59$
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Earth and Planetary Astrophysics

On the Compositions of Interstellar Objects

Matthew J. Hopkins, Michele T. Bannister, Bertram Bitsch et al. (+2 more)

As physical samples of distant planetary systems, the compositions of interstellar objects (ISOs) should correlate with the properties of their diverse parent stars. We combine a chemical partition model with a sample of stellar elemental abundances from APOGEE DR17 to predict the abundances of commonly-observed cometary volatiles in ISOs. We find that the compositions of ISOs vary significantly between different stars. In particular, we predict a strong correlation between an ISO's ammonia abundance and its parent star's metallicity: high-metallicity stars will create ISOs rich in ammonia. This suggests the production rates of NH$_3$'s photolytic daughter products are an ideal observational tracer for the origins of ISOs. We infer that 2I/Borisov formed around a star of near-solar metallicity ($-0.4\lesssim[\mathrm{Fe}/\mathrm{H}]\lesssim0.3$), and corroborate the velocity- and isotope-based inferences that 3I/ATLAS formed around a lower-metallicity star ($-0.8\lesssim[\mathrm{Fe}/\mathrm{H}]\lesssim0.0$). The production rates of 2I and 3I imply both only contain hypervolatiles such as CO and N$_2$ that are trapped in other less-volatile ices, similar to typical Solar System comets. Despite this, we argue that true hypervolatile-ice-rich ISOs may exist; they would exhibit high CO and N$_2$ production rate ratios, possibly similar to those of C/2016 R2 (PanSTARRS). Our predictions provide context for future ISO discoveries, opening a path to link the properties of their origin systems to observable production rates.
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All authors Matthew J. Hopkins, Michele T. Bannister, Bertram Bitsch, Chris Lintott, John C. Forbes

Earth and Planetary Astrophysics

Pulsed Accretion onto Eccentric Binaries in Highly Misaligned Circumbinary Disks

Ruiqi Yang, Jeremy L. Smallwood, Shang-Fei Liu et al. (+1 more)

We present three-dimensional smoothed particle hydrodynamics simulations of highly misaligned circumbinary disks (CBDs) around moderately eccentric equal-mass binaries ($e_\mathrm{b}=0.5$). We show that the binary accretion is modulated on the binary orbital period and exhibits two pulses near periastron. The dominant pulse peaks before periastron for an initial binary-disk misalignment of $60^\circ$, shifts to after periastron at $90^\circ$, and occurs at an even later post-periastron phase at $120^\circ$. We further show that the two pulses are accompanied by a time-dependent response of the circumstellar disks (CSDs) and by different distributions of accreting material within the cavity and around the CSDs. The qualitative pre- versus post-periastron distinction is also present in individual binary orbits despite variations in pulse amplitude. Our results motivate future tests of whether pulse timing is related to binary-disk orientation.
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All authors Ruiqi Yang, Jeremy L. Smallwood, Shang-Fei Liu, Alessia Franchini

Thursday 24 September

Earth and Planetary Astrophysics

Hot Rocks Survey VI: An anomalously hot dayside for the rocky planet GJ 357 b

Merlin Zgraggen, Brice-Olivier Demory, Hannah Diamond-Lowe et al. (+15 more)

As part of the JWST Hot Rocks Survey, we analyzed a JWST/MIRI F1500W secondary-eclipse observation of GJ 357 b, a rocky exoplanet orbiting a nearby M dwarf. We also performed a new global analysis of the GJ 357 system, combining TESS photometry, a JWST/NIRSpec transit observation, the MIRI secondary eclipse, radial velocities, and Gaia parallax measurements to obtain a self-consistent set of stellar and planetary parameters. We measure an occultation depth of $200.5 \pm 12.7,\mathrm{ppm}$, corresponding to a dayside brightness temperature at $15,\mu\mathrm{m}$ of $T_{\mathrm{b},15,\mu\mathrm{m}}=923^{+39}_{-38},\mathrm{K}$. The inferred brightness temperature substantially exceeds the zero-Bond-albedo, no-redistribution, disk-integrated bolometric dayside reference temperature of $686 \pm 14,\mathrm{K}$. The measured eclipse depth differs from the tested zero-albedo, grey airless-surface model by $5.2\sigma$ and is also inconsistent with the high-mean-molecular-weight atmospheric models considered here, including pure CO$_2$, pure H$_2$O, and N$_2$ with 100 ppm CO$_2$. Possible explanations for the excess emission in the MIRI/F1500W band include wavelength-dependent surface emissivity, localized hot regions, or atmospheric temperature structures and opacity sources not included in the tested models. Follow-up mid-infrared eclipse spectroscopy would constrain the shape of the dayside emission spectrum and help test the proposed surface and atmospheric explanations.
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All authors Merlin Zgraggen, Brice-Olivier Demory, Hannah Diamond-Lowe, João M. Mendonça, Erik Meier Valdés, Mark Fortune, Kathryn D. Jones, Daniel Kitzmann, Millie Smith, Natalie H. Allen, Prune C. August, Amélie Gressier, Måns Holmberg, Jegug Ih, Lars A. Buchhave, Néstor Espinoza, Neale P. Gibson, Kevin Heng

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

Non-linear dynamo waves in magnetized shear flows: a candidate mechanism for the solar cycle

Uddipan Banik

Large-scale magnetic reversals in planets, stars, and accretion disks require a non-linear theory coupling the magnetic field to its sustaining flow. We derive exact non-linear solutions to incompressible magnetohydrodynamics in background rotational shear, with large-scale velocity and magnetic fields linear in position (affine form). They reveal a cyclic feedback between meridional circulation, shear, magnetic tension, induction, and the Coriolis force. The steady-circulation reversal orbit, or dynamo wave, periodically reverses all magnetic components and supports slower modulations. In the solar near-surface shear layer (NSSL), moderate shear permits stable 11-year reversals with poleward speeds of 8-12 m/s and poloidal and toroidal amplitudes of 4-11 G and 2.2-3.8 kG near 1 Mm depth, in reasonable agreement with regional observations. At stronger shear, an 88-year reversal exhibits a 203-207-year modulation, reproducing the Gleissberg and Suess-de Vries activity timescales but requiring weaker poloidal fields. Such reversals, however, remain observationally unestablished. At tachocline density, an 11-year reversal and the inferred return flow require toroidal fields of hundreds of kilogauss over a broad shear range, exceeding large-scale-field reconstructions but partly permitted by seismic upper limits. This favors a shallow NSSL origin for a local cycle, while leaving open the issue of a global dynamo. Toroidal dominance prolongs the cycle because shear acting on a weak poloidal field changes only a small fraction of the stronger toroidal field per rotation. Balancing the weak magnetic torque against advection and the Coriolis force also requires slow circulation, which gradually turns the poloidal field and reverses toroidal induction. Efficient poloidal regeneration would shorten this delay. A long solar cycle therefore favors a primarily shear-driven dynamo.
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Earth and Planetary Astrophysics

Tails and Trails: Comets and NEOs Survive Co-addition in Rubin Early Data Preview 2

Colin Orion Chandler, Joseph Murtagh, Ian Chow et al. (+11 more)

We identify effectively single-visit imaging hidden within the deep co-added images of the NSF-DOE Vera C. Rubin Observatory Early Data Preview 2 (EDP2). These shallow regions contain only one or two contributing visits, providing access to single-visit-depth imaging ahead of the full Data Preview 2 (DP2) release in late 2026. We develop a workflow to locate known small Solar System bodies in these data, using our Ponder orchestrator with the Sorcha survey simulator to predict their positions and the Rubin Science Platform (RSP) to identify shallow coadds and extract image cutouts. Because cometary activity and near-Earth-object (NEO) trails produce extended morphologies, both remain identifiable in these shallow coadds. From approximately 700 comet and active-object cutouts, we identify 59 activity detections spanning 32 objects. We discover activity in 2025 NC6, previously unknown to be active; identify the first reported pre-perihelion activity of 2008 QZ44; and independently rediscover known comets 243P/NEAT and 510P/Boattini through their activity. We also recover 336 NEO cutouts, including 29 with predicted trails longer than 25 pixels. We provide accompanying galleries and tabular data, and highlight 99P/Kowal 1, 510P, and 303P/NEAT as targets for immediate follow-up. Shallow coadds are a relatively unexplored facet of Rubin data with applications beyond the Solar System examples presented here: regions with varying numbers of contributing visits will persist throughout the Legacy Survey of Space and Time (LSST).
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All authors Colin Orion Chandler, Joseph Murtagh, Ian Chow, Maxine West, A. Fraser Gillan, Peter S. Ferguson, Michael S. P. Kelley, Jacob A. Kurlander, Henry H. Hsieh, Pedro H. Bernardinelli, Wilson Beebe, Jeremy Kubica, Andrew Connolly, James R. A. Davenport

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

The geometric origin of the thermal eccentricity law

Václav Pavlík

The distribution $f(e)=2e$ is commonly referred to as the `thermal eccentricity distribution' of Keplerian binaries. However, the result does not require thermal equilibrium, and its usual derivations obscure why the distribution is linear in eccentricity. We seek a simple geometrical interpretation of this result and its relation to more general eccentricity distributions. We consider bound Kepler orbits in a Euclidean space of dimension $D\geq2$, with a phase-space distribution depending only on energy, and derive the eccentricity distribution from the Liouville measure. We obtain $f_D(e)=(D-1) e (1-e^2)^{(D-3)/2}$, so that, within this family, $D=3$ is the only case for which the distribution function is linear in $e$. This follows from the $D-1$ transverse momentum dimensions and the Kepler period degeneracy. We further show that two known generalisations – namely a power-law weighting of the normalised angular momentum and a constant velocity anisotropy – are, in fact, two representations of the same one-parameter family of eccentricity distributions.
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Earth and Planetary Astrophysics

Simulating the thermodynamics of gas, radiation, and multispecies dust: Method and applications to protoplanetary disks

Dhruv Muley, David Melon Fuksman, Prakruti Sudarshan et al. (+2 more)

The thermodynamics of protoplanetary disks, governed by a complex interplay between gas, dust, and radiation, exerts a strong influence on their morphology and dynamics at both large and small scales. Historically, hydrodynamical simulations have treated thermodynamics with approximate prescriptions, such as local isothermality, parametrized $\beta$-cooling, and radiation hydrodynamics with gas-dust thermal equilibrium. However, a more comprehensive and self-consistent approach would more accurately reproduce the wealth of features found in observations, which in modern times have reached unprecedented spectral, angular, and vertical resolution. With this motivation, we have devised a radiation-hydrodynamics scheme for the PLUTO code with energy exchange (via absorption, emission, and collisions) for gas, radiation, and multiple species of dust. Dust-gas dynamics are handled by treating each dust species as a pressureless, diffusive fluid, ensuring that our scheme can represent changes in disk illumination caused by grain settling and trapping. We demonstrate the effectiveness of our scheme in several test problems, and conclude by discussing its relevance to open questions in protoplanetary disk studies.
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All authors Dhruv Muley, David Melon Fuksman, Prakruti Sudarshan, Alexandros Ziampras, Mario Flock

Earth and Planetary Astrophysics

Deep HST/STIS Coronagraphic Imaging of the $\beta$ Pictoris Debris Disk: On the Scattered Light Component of the Cat's Tail

Arin M. Avsar, Kevin Wagner, Daniel Apai et al. (+6 more)

The $\beta$ Pictoris debris disk is a unique system where mid-infrared coronagraphic imaging with JWST/MIRI revealed a new spatially resolved substructure known as the Cat's Tail. We present deep HST/STIS coronagraphic imaging of $\beta$ Pic in scattered light, combining six epochs of observations between 2012 and 2025, in search of the scattered light component of the Cat's Tail. We detect the disk out to a projected separation of 500 au for the first time with HST/STIS, achieving SNR > 100 across much of the midplane between 50 and 200 au. We report the detection of the visible/near-infrared scattered light component of the Cat's Tail substructure. We find through injection-recovery analysis that the scattered light component of the Cat's Tail has a total flux of $0.1-0.4\%$ of the MIRI F1550C flux. Using the measured STIS-to-MIRI flux ratio, we model the Cat's Tail grain properties and find that the grains are highly porous and almost entirely composed of organic refractory material, which is in agreement with findings with JWST/MIRI. We use the organics content of Solar System dwarf planets and dust in the local ISM as a proxy to estimate the size of the colliding progenitors that can produce enough organic refractory material seen in the Cat's Tail. We find that each colliding progenitor must have a mass of at least $1-3\times 10^{21}$ kg, comparable to Charon and Makemake in our Kuiper Belt. Additionally, we find a prominent warped morphology and surface brightness asymmetry in the outer dust halo of $\beta$ Pic. We compare the observed halo morphology and asymmetry to predicted vertical structures, which may arise from planet–disk interactions.
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All authors Arin M. Avsar, Kevin Wagner, Daniel Apai, Isabel Rebollido, Antranik A. Sefilian, Marshall D. Perrin, Christopher C. Stark, Gabriel Weible, Andras Gaspar

Earth and Planetary Astrophysics

The GAPS programme at TNG LXXIX. New mass constraints for the infant planets in the V1298 Tau system through a long-term radial velocity monitoring with HARPS-N

M. Damasso, P. Leonardi, L. Borsato et al. (+26 more)

We aim to constrain the dynamical masses of the four confirmed transiting planets orbiting the infant ($20\pm10$ Myr) star V1298,Tau (orbital periods $P_b\sim$24.1 d, $P_c\sim$8.2 d, $P_d\sim$12.4 d, and $P_e\sim$48.7 d), through a new analysis of a homogeneous radial velocity dataset. This system is a key benchmark for testing formation and early-stage evolutionary models of planets. We analysed more than 380 high-resolution spectra collected with the HARPS-N spectrograph over a time span of 4.5,yr. To account for dominant stellar activity and transit-timing-derived planet-planet interactions, we analysed radial velocities extracted using two different approaches, and combined N-body simulations with multi-dimensional Gaussian process regression. We tested a set of spectroscopic and photometric activity diagnostics to mitigate the variability due to the stellar magnetic activity in the radial velocity time series. The mass determinations are sensitive to the choice of the radial velocity extraction method and activity diagnostics. For some specific models, we measured masses with a significance of 3.5–4$\sigma$ for planets b ($0.52^{+0.12}{-0.14}$, $0.65^{+0.21}{-0.18}$, $0.67\pm0.16$, and $0.78^{+0.19}{-0.20}$ $M_{\rm Jup}$) and e (0.40$^{+0.14}{-0.13}$, 0.66$^{+0.17}{-0.18}$, and $0.71\pm0.20$ $M_{\rm Jup}$). These values are compatible with masses of giant planets, and are notably higher than those recently derived from transit timing variations alone, which indicate that these are low-density “super-puffy” planets. Injection-and-recovery simulations moderately support this conclusion for planet b. For planets c and d, we primarily provide updated mass upper limits. Our analysis represents an exploratory study to address the complex issue of mass measurement in a multi-planetary system characterised by high levels of stellar activity.
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All authors M. Damasso, P. Leonardi, L. Borsato, S. Benatti, A. Suárez Mascareño, A. Bonfanti, C. Di Maio, M. Mallorquín, L. Fossati, F. Marzari, D. Nardiello, S. Desidera, L. Naponiello, A. Sozzetti, G. Andreuzzi, M. Basilicata, A. Bignamini, A. S. Bonomo, M. Brogi, P. Giacobbe, G. Guilluy, A. F. Lanza, M. Lodi, L. Malavolta, L. Mancini, S. Messina, G. Micela, V. Nascimbeni, T. Zingales

Earth and Planetary Astrophysics

Extracting Asteroid Physical Properties from Vera C. Rubin Observatory Science Validation Survey Data: Rotational Periods, Colors, and Taxonomies

V. Carruba, S. Greenstreet, M. Mastropietro et al. (+7 more)

The Vera C. Rubin Observatory will enable large-scale characterization of minor bodies through high-cadence, multi-band photometry. Early Science Validation (SV) observations from 2025-2026 provide one of the first extensive datasets for Solar System studies, but typically with sparser and more heterogeneous coverage than the Rubin First Look data, where hundreds of observations were available for well-characterized objects. In this work, we build on the methodology developed for the Rubin First Look data to extract asteroid rotation periods, amplitudes, colors, and taxonomic classifications from early Rubin SV data using multi-band (griz) photometry. Rotation periods are determined through a combination of high-order Fourier light-curve fitting and multi-band Lomb-Scargle analysis. A unified light-curve model is then used to derive rotation-corrected colors, which are converted into taxonomic classes using calibrated color indices and spectral slopes. We validate the method on objects with sufficient observational coverage and show that preliminary physical properties can be estimated from sparse and irregular datasets, while robust determinations require improved temporal coverage. By simulating sparsely observed data, we identify the observational conditions required for period determinations. The inclusion of z-band photometry extends traditional color-based taxonomy and improves compositional discrimination relative to gri-only analyses.
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All authors V. Carruba, S. Greenstreet, M. Mastropietro, S. Aljbaae, G. Caritá, R. C. Domingos, M. Huaman, M. M. Bala, R. D. Z. Pedroso, E. M. D. S. Delfino

Earth and Planetary Astrophysics

VLTI/MATISSE observations of the hot dust around $\beta$ Pictoris: Observing faint objects with MATISSE

P. Priolet, J.-C. Augereau, J. Milli et al. (+32 more)

Context: Hot exozodiacal dust has been detected around approximately 20% of nearby main-sequence stars, indicating that it is a common feature of extrasolar planetary systems. However, its spatial distribution and grain properties remain poorly understood. Aims: We aim to show that the spatial distribution of hot dust around beta Pictoris, an iconic planetary system with two known planets and a population of exocomets, can be constrained through a detailed analysis of optical long-baseline interferometry data. Methods: We obtained L-band observations at approximately 3.5 microns of beta Pictoris with MATISSE at the VLTI. We developed a method to assess correlations in the visibility measurements by estimating the full data covariance matrix, and modeled the circumstellar emission with geometric brightness distributions. Results: We detect circumstellar emission around beta Pictoris consistent with hot exozodiacal dust. Modeling the emission with and without accounting for data correlations demonstrates their significant impact on the inferred dust properties. The best-fit model reveals a compact (approximately 0.05 au), highly inclined dust structure near the sublimation radius, misaligned by approximately 60 degrees on the sky with respect to the extended edge-on outer disk. It contributes approximately 4%-7.5% of the total flux at 3.4 microns and is composed of submicron-sized grains. The data are also compatible with an additional dust component near 1 au. Conclusions: For beta Pictoris, the two-decade-old paradigm placing hot exozodiacal dust near the sublimation radius and consisting of submicron-sized grains finds observational support in the detailed analysis of MATISSE data. The misalignment with the known debris disk further supports a link to exocometary activity.
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All authors P. Priolet, J.-C. Augereau, J. Milli, A. Matter, B. Lopez, H. Beust, J. Varga, P. Boley, W.-C. Danchi, L. Foteini, T. Henning, M. Houllé, M. Letessier, F. Millour, J. Scigliuto, G. Weigelt, S. Wolf, O. Absil, J.-P. Berger, Y.-I. Bouarour, G. Bourdarot, D. Defrère, C. Desgrange, J.-B. Le Bouquin, D. Iglesias, T. A. Stuber, P. Berio, F. Bettonvil, P. Cruzalèbes, M. Heininger, J. W. Isbell, S. Lagarde, A. Meilland, R. Petrov, S. Robbe-Dubois

Earth and Planetary Astrophysics

Exoplanet Detection Techniques: Radial Velocity

Rafael Luque and Matthew R. Standing

The radial velocity (RV) technique enabled the discovery of the first exoplanets orbiting Sun-like stars. Since then, improvements in precision and sensitivity have enabled the detection of smaller planets, bringing us closer to the goal of discovering Earth analogs in the coming years. In this chapter, we provide an overview of the radial velocity method. We begin with a detailed description of the technique, including how precise radial velocities are measured and what limitations must be addressed to achieve reliable detection of small signals. We examine the unique challenges associated with the detection of circumbinary planets and outline the developments that have, for the first time, made their detection feasible using the radial velocity method. With over 2,000 planets detected to date, the radial velocity method remains one of the most reliable techniques, offering valuable insights into the demographics of exoplanets, especially at long orbital distances. As an example of its applications, we provide an analysis and interpretation of three publicly available radial velocity datasets: one from a single star, one for a circumbinary planet system, and another from a single star with transiting planets. Furthermore, we compile information on the spectrographs currently and soon-to-be available worldwide for radial velocity observations and a list of open-source tools designed for their analysis. In the Supplementary Material, we include a sample telescope proposal for obtaining radial velocity data, along with practical tips on writing a competitive proposal to aid early-career researchers entering the field. This chapter serves as a comprehensive guide for understanding the capabilities and applications of the radial velocity method, equipping readers with the knowledge and resources to address their own scientific questions using this technique.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

JWST Observations of the Metal-poor T Dwarf WISEA J155349.96+693355.2: The First Brown Dwarf Associated with the Gaia-Enceladus Milky Way Substructure

Aaron M. Meisner, Adam J. Burgasser, Chih-Chun Hsu et al. (+15 more)

We present JWST NIRSpec and MIRI observations of the metal-poor T dwarf WISEA J155349.96+693355.2. The combined NIRSpec/prism plus MIRI/LRS spectrum (R ~ 100) provides 0.6-12 $\mu$m spectroscopic coverage that reveals the presence of H$_2$O, CH$_4$, and NH$_3$ absorption features, enhanced collision-induced H$_2$ absorption, and weak or absent CO and CO$_2$ absorption, all indicators of a metal-poor low-temperature atmosphere. Comparison of the spectral data to a suite of atmosphere models yields an effective temperature $T_{\rm eff}$ = 960$^{+28}_{-32}$ K and a solar-scaled metallicity of [M/H] = -1.16$^{+0.28}_{-0.25}$ dex. We find indications that the uncertain trigonometric parallax, likely subject to Lutz-Kelker bias, may be overestimated. Adopting the photometric distance yields a bolometric luminosity log$_{10}L_{bol}/L_{\odot}$ = -5.29 $\pm$ 0.10, from which we infer $T_{\rm eff}$ = 974 $\pm$ 56 K, consistent with the temperature derived via our atmospheric model fits. From the moderate-resolution (R ~ 3,000) NIRSpec/G395H spectrum, we measure a radial velocity of -163 $\pm$ 5 km/s, which combined with the source's measured proper motion and estimated distance indicates a highly eccentric (e $\geq$ 0.9) Galactic orbit consistent with an accreted halo object. The UVW kinematics of WISEA J155349.96+693355.2, its bulk metallicity, and its modest alpha enrichment ([$\alpha$/Fe] = +0.15$^{+0.04}_{-0.06}$ dex) are all equivalent to stars identified in the Gaia-Enceladus Milky Way substructure, making it the first brown dwarf with kinematic and chemical evidence of association.
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All authors Aaron M. Meisner, Adam J. Burgasser, Chih-Chun Hsu, Sherelyn Alejandro Merchan, Jacqueline K. Faherty, Genaro Suárez, ZengHua Zhang, Roman Gerasimov, Christian Aganze, Nicolas Lodieu, Eileen C. Gonzales, Adam C. Schneider, Stanimir A. Metchev, Dan Caselden, Michael C. Cushing, Christopher A. Theissen, Jason J. Wang, Harshil Kothari

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

Metal-Poor Stars as Metal-Rich Impostors via Planet Engulfment

Zongheng Li, Shi Jia, Jie Su et al. (+2 more)

Planet engulfment leads to planetary mass accretion and angular momentum deposition into the stellar envelope. This study uses MESA models to investigate the long-term impact of engulfment on stellar metallicity and rotational velocity, as well as the effect of rotational mixing on metal enrichment. Our models show that engulfment occurring during the late main-sequence (MS) stage yields significantly higher surface enrichment than at the ZAMS. Rotational mixing generally suppresses enrichment; however, metal-poor stars can sustain super-solar abundances for several Gyr, whereas high-metallicity stars remain largely unaffected. Although engulfment causes an instantaneous spin-up, this angular momentum injection is transient, and the star quickly re-converges to its standard rotational evolution. Thus, MS spin-up cannot serve as a long-term observational indicator. Because convective envelope thickness and MS lifetime dictate the magnitude and duration of enrichment, identifying engulfment signatures requires balancing the long-lived but diluted signals in 0.7 M_sun stars against the strong yet short-lived enrichment in 1.2 M_sun stars. Consequently, 1.0 M_sun stars offering both substantial enrichment and a relatively long MS lifetime represent optimal targets for observational searches.
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All authors Zongheng Li, Shi Jia, Jie Su, Shang-Fei Liu, Jianheng Guo

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

Binary-pulsar Timing: A 3D Solar-System Accelerometer and Unknown-Source Probe

Zheng-Long Wang, Zi-Qing Xia, Bo Zhang et al. (+1 more)

The acceleration of the Solar System barycenter (SSB) offers a unique precision probe of the local gravitational environment, enabling searches for otherwise invisible gravitating sources such as Planet Nine and nearby (primordial) black holes. Using the binary-pulsar timing measurements, we develop an analysis framework that combines the line-of-sight differential accelerations of 26 binary pulsars to jointly reconstruct the three-dimensional acceleration of the SSB and place directional upper limits. Across three smooth Galactic-potential baselines, the residual acceleration is consistent with zero. We obtain directional 95% upper limits of $0.198$, $0.262$, and $0.693~\mu\mathrm{as}\,\mathrm{yr}^{-1}$ over 50%, 75%, and all sampled directions, respectively. These limits are tighter by factors of 3.5, 3.6, and 1.6 than a matched Gaia EDR3 benchmark and improve previous pulsar constraints by more than an order of magnitude. We further extend the framework to the full SSB–pulsar two-endpoint response, enabling direct position-dependent mass constraints on unknown gravitational sources. A $10\,M_\odot$ object is excluded within 0.39, 0.34, and 0.21 pc over the same sky fractions. Our unknown-mass limits surpass the tidal-equivalent INPOP19a reference beyond 0.2 pc by about an order of magnitude over most of the sky at 1 pc.
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All authors Zheng-Long Wang, Zi-Qing Xia, Bo Zhang, Yi-Zhong Fan

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

On the altitude profile of lower ionospheric D-region response time delay during solar flares

Sayak Chakraborty, Rakhi Paul and Tamal Basak

The D-region ionosphere is sluggish in nature while responding to the incoming solar radiation. We study the altitude (h) profile of mid-latitude D-region response time delay (Delta t) during three chosen solar flares, namely, C5.2, M5.2, and X2.2 classes. We solve "electron continuity equation" numerically at each and every h to obtain Delta t-h profile. We investigate the 1) latitudinal variation (over both Northern and Southern hemispheres) and 2) seasonal variation (throughout the year) of Delta t-h profiles of each of these solar flares separately. We go over noteworthy variations of Delta t-h profile for both 1) and 2) with reasonably different results over different hemispheres. Also, we study some contrasting behaviours of Delta t-h profile of X2.2 class for both 1) and 2) in comparison to C5.2 or M5.2 classes. We conclude the outcome with possible explanations.
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Earth and Planetary Astrophysics

A Possible Complication of Using the 4.14 {\mu}m band to Assess D/H Ratios on Icy Bodies

Mark J. Loeffler, Rebecca A. Carmack and Stephen C. Tegler

Determining isotopic ratios on the surfaces of extraterrestrial objects can provide insight into their formation conditions and evolution. Recently, remote-sensing detections of the 4.14 {\mu}m HDO absorption band have enabled astronomers to estimate the D/H ratio on several icy objects in the outer solar system. Here, we quantify how ice phase and radiation processing affect the 4.14 {\mu}m absorption band. While the band is visible in H2O-ice samples with a crystalline component, we cannot detect it in amorphous H2O-ice. Furthermore, we find that radiation processing, using 10 keV electrons as a proxy, quickly makes this absorption feature undetectable at a rate consistent with the amorphization of an initially crystalline sample. Interestingly, we also find that recrystallizing the irradiated sample causes this band to reappear nearly to its original band depth. For the Saturnian satellite Mimas, we estimate that the HDO feature will decrease by a factor of two within ~1 x 10^4 yrs at typical depths probed by remote sensing spectroscopy. While we suspect that existing methods could still determine the D/H ratio from a surface composed entirely of crystalline H2O-ice, deriving it for surfaces with a significant amorphous fraction may lead to severe underestimation of the true D/H ratio. However, given the direct correlation between the amorphous fraction of the sample and the HDO band depth, we propose that one could still estimate the D/H ratio of a surface with mixed phases by determining the crystalline fraction of the surface H2O-ice using other absorption features.
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Earth and Planetary Astrophysics

A Collisional Origin for Ice-rich Iapetus and Titan's Anomalous Eccentricity

Ignacio Mosqueira

We test whether collisions involving Titan can eject enough water-rich material onto sufficiently distant Saturn-bound orbits to form Iapetus, while also accounting for Titan's orbital eccentricity. Three-dimensional impact calculations and post-impact trajectories examine initially Saturn-unbound and bound impactors. In the oblique unbound case with a differentiated impactor roughly a tenth the mass of Titan at a speed of 10 km s\(^{-1}\), outgoing predominantly icy material from a selected population totaling about 3.5 times Iapetus's mass remains Saturn-bound for days after impact. We track an icy sample whose orbital apoapsis extends beyond Iapetus's distance. After impact, Titan's eccentricity increases to near 0.13, while the impactor's rocky core escapes Saturn. In another case, a bound companion one quarter Titan's mass collides at \(45^\circ\) and about 3.7 km s\(^{-1}\), ejecting 0.60 Iapetus masses of ice. The rocky impactor core initially skips past Titan; an orbital continuation reaches return contact after 6.9 yr. This run also retains 0.48 Iapetus masses of ice. Titan's eccentricity evolves due to the initial impact and debris scattering. The merger results in a Titan with an eccentricity of about 0.10. These results establish the collisional production of an icy debris reservoir, with some material on orbits of large semimajor axis; raising Iapetus's periapse would require gas drag or dynamical friction.
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Wednesday 23 September

Earth and Planetary Astrophysics

On the Long-Term Orbital Behaviour of Hilda Asteroids - I. Global Stability Patterns and Catalogue

Cristian F. Chavez, Jonathan Horner, Patryk Sofia Lykawka et al. (+2 more)

The Hildas are objects trapped in 3:2 mean-motion resonance (MMR) with Jupiter, and are a fascinating window into the Solar system's formation and evolution. We present the results of detailed dynamical integrations of 2,699 numbered asteroids in the Hilda region, following 243 clones of each Hilda for 1 Gyr under the influence of the giant planets and the Sun; 54.7% of our sample exhibit extreme dynamical stability, with all clones of 1,475 Hildas remaining trapped in the 3:2 MMR for the full 1 Gyr of our integrations. A further 408 Hildas (15.1% of the sample) see more than 50% of their clones surviving within the MMR at the end of the simulations. Of the remaining 30.2% of the population, 327 objects (12.1%) lose 50% of their clones at some point between the 100 Myr and 1 Gyr point, leading to dynamical half-lives measured in hundreds of millions of years – a result compatible with those objects being members of a once larger population of Hildas trapped since the Solar system's youth. The final 489 objects (18.12%) prove highly unstable – and may well be interlopers, captured to the Hilda population in the relatively recent past. Overall, our results suggest that the Hilda population was larger in the past, while its remarkably high stability over Gyr timescales is consistent with a primordial origin.
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All authors Cristian F. Chavez, Jonathan Horner, Patryk Sofia Lykawka, Timothy R. Holt, Brad Carter

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

Metal-poor Brown Dwarf Kinematics from JWST NIRSpec Spectroscopy

Chih-Chun Hsu, Christopher A. Theissen, Adam J. Burgasser et al. (+14 more)

Galactic archaeology relies on stellar kinematics and chemical abundances to identify various stellar populations and associations. With JWST, Galactic archaeology of ancient metal-poor brown dwarfs is now possible through high-sensitivity, medium-resolution spectroscopy. We present the first metal-poor brown dwarf radial velocity (RV) survey using JWST/NIRSpec G395H spectra ($\lambda/\Delta\lambda \sim$ 3,000) for a sample of 23 LTY dwarfs across a wide range of temperatures and metallicities. We introduce a forward-modeling framework to measure robust RVs for brown dwarfs by focusing on the CO fundamental band at $\sim$4.5 $\mu$m. By comparing to sources with existing high-resolution RV measurements, we demonstrate that G395H RVs can achieve a systematic uncertainty of 5 km s$^{-1}$, sufficient to examine their Galactic space motions. We identify kinematic members of the Milky Way's thin disk, thick disk, and halo populations in this sample. We also confirm WISE J155349.98$+$693355.2 as likely associated with the Gaia-Enceladus merger remnant, and 2MASS J05325346$+$8246465 is likely associated with the Thamnos stream. Our study systematically demonstrates that JWST G395H spectroscopy can provide robust RVs in addition to detailed chemical abundances, necessary for Galactic archaeology studies. Future discoveries and characterization of brown dwarfs associated with Galactic halo substructures and streams will enable a stringent test of stellar/substellar formation and evolutionary models for diverse metallicities.
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All authors Chih-Chun Hsu, Christopher A. Theissen, Adam J. Burgasser, Adam C. Schneider, Christian Aganze, Aaron M. Meisner, Jonathan Gagné, Nicolas Lodieu, Zenghua Zhang, Genaro Suárez, Eileen C. Gonzales, Jacqueline K. Faherty, Jason J. Wang, Stanimir Metchev, Dan Caselden, Michael C. Cushing, Roman Gerasimov

Earth and Planetary Astrophysics

Triggering star formation by free-floating planets

Yu. N. Eroshenko

Recently, a population of free-floating planets has been discovered in the Galaxy. This paper examines the influence of the planets trapped within a protostellar hydrogen clouds on the processes of gravitational instability in the gas. A sufficiently massive planet can become an alternative dynamic center for the contracting cloud. This occurs due to rapid mass growth from accretion onto the planet within the cloud. Owing to residual velocity and density gradients in the cloud, the planet that triggers star formation is likely to end up in a distant orbit around the newborn star. Some second- and subsequent-generation stars in the Galaxy may have formed via this mechanism.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

External photoevaporation in the center of Tr14

Katia Gkimisi, Da Eun Kang, Dominika Itrich et al. (+11 more)

Most stars form in massive stellar clusters, where intense far-ultraviolet (FUV) radiation from OB stars can accelerate the dispersal of protoplanetary disks through external photoevaporation. Quantifying the impact of this process on disk evolution remains challenging, particularly in distant and crowded star-forming regions. We investigate the low-mass stellar population in the highly irradiated center of Trumpler 14 and examine how the local FUV radiation field influences circumstellar disk evolution. We extracted stellar spectra from VLT/MUSE observations using an enhanced background-optimized extraction method, carefully corrected for instrumental response as a function of wavelength and finally derived the stellar parameters with the SAPSAL deep-learning framework. We combined these results with a probabilistic estimate of the local FUV field and near-infrared photometry to identify disk-bearing stars. We identify 310 bona fide cluster members with an age of $0.66^{+0.73}_{-0.35}$ Myr and local radiation fields spanning $\log(FUV)\simeq4.2-6.0\ G_{\mathrm{0}}$. The fraction of stars exhibiting near-infrared excess decreases from 30% at the lowest FUV fluxes to under 5% at $\log(FUV)\gtrsim5.6 \ G_{\mathrm{0}}$, while no significant correlation is found between our simplified estimate of the optical veiling and the local FUV field. The pronounced decline in the disk fraction with ambient FUV flux provides strong evidence for external photoevaporation rapidly dispersing circumstellar disks in the core of Trumpler 14. Our results confirm previous disk dispersal estimates and extend to higher values of the FUV field strength.
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All authors Katia Gkimisi, Da Eun Kang, Dominika Itrich, Rossella Anania, Eleonora Fiorellino, Sacha Gavino, Ralf S. Klessen, Victor F. Ksoll, Giuseppe Milazzo, Anna McLeod, Thomas Preibisch, Veronica Roccatagliata, Leonardo Testi, Claudia Toci

Earth and Planetary Astrophysics

Just a Phase? Weakening Vertical Shear Instability Explains Class II Disk Morphologies: Simulations with dust coagulation, sedimentation, thermal relaxation, and backreaction

Thomas Pfeil, Alexandros Ziampras, Shangjia Zhang et al. (+2 more)

The Vertical Shear Instability (VSI) is known to create turbulence and strong vertical mixing in protoplanetary disks if thermal relaxation is sufficiently fast. In simulations where this condition is met, VSI can loft dust particles to large altitudes, creating a vertically extended appearance in mock millimeter-wavelength observations, which is inconsistent with the morphology of the majority of observed class II disks. We present simulations of protoplanetary disks with VSI that are consistent with the observed thin-disk geometries, while maintaining the commonly observed bowl-shaped morphology in scattered light images at micrometer wavelength. We show that this outcome arises naturally when the effects of dust coagulation, sedimentation, and dust-gas thermal accommodation are taken into account. Sedimentation-driven coagulation removes large amounts of dust from the disk atmosphere, in the process slowing down the dust-driven cooling of the gas. At the same time, a dense midplane layer of millimeter-sized grains forms, which exerts aerodynamic drag on the gas. This results in the termination of the VSI's corrugation mode. Only weak VSI activity remains in the upper and lower hemispheres. These processes occur on the typical dust growth timescale and suppress strong VSI-induced turbulence within a few hundred thousand years. VSI could thus generally be restricted to the class I evolutionary stages of protoplanetary disks.
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All authors Thomas Pfeil, Alexandros Ziampras, Shangjia Zhang, Philip J. Armitage, Yan-Fei Jiang

Earth and Planetary Astrophysics

The dust in Sauron's eye - Observational and experimental results on the debris disk around HR 4796

M. Bonduelle, J. Milli, O. Poch et al. (+14 more)

The optical properties (scattering phase function SPF; degree of linear polarization DoLP; reflectance) of the dust particles orbiting in debris disks can be retrieved through scattered light imaging and are linked to the physicochemical properties of the dust (size, shape, composition...). Among debris disks, the bright, narrow disk surrounding HR 4796A presents several peculiarities, in particular unusually high DoLP values at small scattering angles. We aim at improving the constraints on the properties of the dust particles orbiting in HR 4796. We use new observational data (SPHERE/ZIMPOL and IRDIS) in scattered light of HR 4796, for lambda = 0.63 um; 0.79 um and 1.25 um. We modeled the disk at each of these wavelengths and found geometric parameters consistent with previous results. We obtained the parametrized SPF and DoLP over the whole range of scattering angles (13 degrees to 167 degrees) and extracted the DoLP and spectral reflectance at 90 degrees (without any parametrization) from the visible to the NIR wavelength range. We compared the reflectance and polarimetric properties of HR 4796 to those measured on a laboratory dust sample and find that the sample providing the best match appears to be large iron sulfides particles. We confirm that the DoLP of HR 4796 peaks at high values (> 45 percent) and for small scattering angles (< 55 degrees). At a 90 degrees scattering angle, we observe a red spectral slope in the visible and NIR wavelength range, as well as a blue polarimetric slope. These results are compatible with large (a few um to 100 um) absorbents being the main scatterers in the disk. We show that the DoLP of HR 4796 is notably different from that of Solar System comets and seems closer to that of some more processed near-Earth orbit asteroids, possibly indicating devolatilization and/or melting induced by space weathering on the dust particles of HR 4796.
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All authors M. Bonduelle, J. Milli, O. Poch, N. Engler, M. Rigouleau, R. Tazaki, J. Ma, J. Olofsson, J-B. Renard, J. Lasue, R. Sultana, G. Duchêne, L. Martinien, M. Roumesy, C.H. Chen, C. Lisse, J-C. Augereau

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

Stellar flares with Ariel: detection prospects and impacts on exoplanet spectroscopy

K. Vida, B. Seli and B. Edwards

Stellar flares are important tracers of magnetic activity and can significantly influence the characterization of exoplanet host stars by introducing time-dependent astrophysical variability. ESA's Ariel mission, designed for atmospheric characterization of exoplanets, will include the VISPhot instrument, providing high-cadence optical photometry offering an opportunity to study stellar flares while identifying and mitigating their impact on transit spectroscopy. We discuss Ariel's potential for flare studies, emphasizing the importance of short-cadence observations for resolving flare morphology and estimating flare energies. We identify potential flaring targets within the Ariel Mission Candidate Sample by cross-matching it with a TESS-based flare catalog, identifying 44 stars in the sample of 3321 host stars with flare rates spanning 0.0012-1.05 flares per day yielding a lower limit. The majority of these active stars are expected to flare infrequently during typical Ariel observations, but for a few of the most active targets there is a significant chance of flaring during a typical Ariel observing window. We further investigate the detectability of stellar flares in Ariel's wavelength range using synthetic spectra based on time-dependent RADYN flare models propagated through the Ariel radiometric simulator. Our simulations indicate that strong flares on cool dwarfs can produce measurable infrared signatures, with flux variations reaching several percent, substantially exceeding the amplitudes of typical exoplanet atmospheric features. These results demonstrate stellar flares represent both a valuable ancillary science case and a potential source of contamination for Ariel observations, highlighting the need for improved flare models and mitigation strategies to maximize the mission's scientific return.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.SR

ALMA's sharpest view of IRAS 08544-4431: Unveiling the dust distribution asymmetries in the circumbinary disk

Maksym Mohorian, Devika Kamath, Elizabeth Cappellazzo et al. (+10 more)

The interactions between post-asymptotic giant branch (post-AGB) binaries and their circumbinary disks play a central role in shaping the evolution of these systems. Circumbinary disks around post-AGB binaries are stable, though relatively short-lived structures ($10^4-10^5$ years) and their physical properties and evolution remain poorly understood. In this study, we target IRAS 08544-4431, one of the best-studied post-AGB binaries. This system has well-constrained stellar and orbital parameters, exhibits well-defined characteristic refractory-depleted photospheric chemistry, and hosts a stable, sub-Keplerian circumbinary disk extending from a well-resolved sublimation rim at approximately 8 au to outer radii of approximately 1 000 au. We probe the disk layers close to the midplane using ALMA Band 7 continuum and $^{12}$CO $J=3-2$ observations of IRAS 08544-4431 obtained with baselines up to 16.2 km. These data provide the finest angular resolution yet achieved with ALMA for dust-continuum observations of post-AGB binaries with a (almost) face-on disk (15 au; 10 mas). The resulting map of dust continuum enabled resolving disk inner rim, a largely smooth radial profile, and a prominent azimuthal asymmetry at a radius of $\sim$45 mas. Notably, the location of this dust asymmetry coincides with the forward-scattering peak reported in SPHERE/VLT observations of IRAS 08544-4431. The $^{12}$CO emission is more extended than the dust continuum and confirms the disk rotation in this system. However, the global $^{12}$CO map shows indications of a spatial offset from the dust asymmetry, suggesting some degree of gas-dust decoupling. Together, these observations establish IRAS 08544-4431 as a key laboratory for studying disk and dust evolution in a parameter space distinct from that of young stars with protoplanetary disks.
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All authors Maksym Mohorian, Devika Kamath, Elizabeth Cappellazzo, Kateryna Andrych, Jacques Kluska, Hans van Winckel, Daniel Price, Toon De Prins, Arancha Castro-Carrizo, Javier Alcolea, Nicolas Cuello, Matthias Fabry, Valentin Bujarrabal

Earth and Planetary Astrophysics

Nordic-based observations of binary asteroid (163693) Atira reveal a hydrated CM chondrite composition

Eric M. MacLennan, Grigori Fedorets, Zuri Gray et al. (+5 more)

We present photometric, spectroscopic, and polarimetric observations of (163693) Atira collected on the night of 05 March 2024. A dual-band lightcurve acquired in the V and R_C filters using the Metsähovi Observatory (L08) in Kirkkonummi, Finland spans nearly 8~hours. From these measurements we estimate a V-R_C = 0.43 +/- 0.07 mag. A visible spectrum and linear polarisation measurement were obtained with the Nordic Optical Telescope in La Palma, Spain. We employ a semi-empirical model to recover the spectral flux that was lost due to a mis-aligned spectroscopic slit. The corrected model reflectance spectrum indicates a primitive Cgh taxonomic type with a distinct absorption feature from 0.60 to 0.85 um with a depth of ~7.4 %. Direct comparison with laboratory spectra of meteorites indicates close matches with CM carbonaceous chondrites. We detect a large degree of linear polarisation at a phase angle of 83 degrees which is consistent with (3200) Phaethon and (155140) 2005 UD, but lower than (162173) Ryugu and (152679) 1998 KU2. We use a CM carbonaceous chondrite density to estimate its bulk porosity of 51 +/- 31 % from previously estimated bulk density. The uncertainty in bulk density and bulk porosity is dominated by the volume of the primary. Future near-infrared spectroscopic and thermal infrared observations can be used to refine the composition and bulk density. Finally, we discuss implications for ground-based physical characterisation studies of the Atira population.
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All authors Eric M. MacLennan, Grigori Fedorets, Zuri Gray, Teemu Willamo, Tuomas Salo, Anne Virkki, Mikael Granvik, Karri Muinonen

Earth and Planetary Astrophysics

Probing Exoplanetary Chemistry with Ariel: Scientific Priorities and Observational Strategies

Olivia Venot, Yamila Miguel, Robin Baeyens et al. (+30 more)

Over the past two decades, increasingly precise observations have revealed that exoplanet atmospheres are chemically diverse and often far from equilibrium, with processes such as vertical mixing, photochemistry, and atmospheric circulation producing significant departures from thermochemical expectations. As large surveys across a wide range of planets begin to uncover population-level chemical trends, a coherent interpretation of these patterns remains elusive, particularly for gas giants and Neptune-like planets where disequilibrium processes likely dominate. The ESA Ariel mission will provide the first homogeneous, statistically significant atmospheric dataset for nearly a thousand exoplanets, offering an unprecedented opportunity to investigate the origins of chemical diversity across planetary populations. This white paper highlights central scientific questions for understanding atmospheric chemistry and recognized as priorities for the community. These questions span the mechanisms driving disequilibrium chemistry, the role of sulfur- and phosphorus-bearing species, the influence of stellar activity, the formation of haze precursors, and the chemical evolution of atmospheres around stars of different ages and types. Because these topics connect chemistry, physics, and planetary evolution, they form the core focus of the Ariel Chemistry Working Group, which synthesizes current knowledge and identifies the diagnostics best addressed by Ariel's spectral capabilities. For each theme, we outline observational strategies and representative targets already included in the Mission Candidate Sample, illustrating Ariel's ability to address these questions. By linking large-scale observations to predictive atmospheric models, this work supports refinement of Ariel's target selection and enables population-level studies that will transform our understanding of planetary atmospheres.
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All authors Olivia Venot, Yamila Miguel, Robin Baeyens, Stefano Bellotti, Giuseppe Cassone, Quentin Changeat, Ryan Cloutier, Athena Coustenis, Dwaipayan Dubey, Billy Edwards, Kaustubh Hakim, Eric Hébrard, Christiane Helling, Helgi Rafn Hrodmarsson, Leoni Janssen, Adam Yassin Jaziri, Gaia Lacedelli, Panayotis Lavvas, Jorge Lillo-Box, Amy Louca, Adrien Masson, Zita Martins, Karan Molaverdikhani, Benjamín Montesinos, Harrison Nicholls, Enric Palle, Paul Rimmer, Donna Rodgers-Lee, Jonathan Tennyson, Shang-Min Tsai, Roméo Veillet, Sergey N. Yurchenko, Maria Zamyatina

Earth and Planetary Astrophysics

Juice-SWI during the Lunar-Earth-Gravity-Assist (LEGA) - Part 2: Instrument operations

T. Cavalié, R. Moreno, L. Rezac et al. (+17 more)

The Jupiter Icy Moons Explorer (Juice) embarked in 2023 on a 8-year interplanetary journey to Jupiter and its icy moons. The Submillimetre Wave Instrument (SWI) is one of the ten science instruments aboard the spacecraft. SWI is a sophisticated and first-of-its-kind payload visiting the outer solar system, featuring dual-band tunable receivers, two independent pointing mechanisms, and spectrometers capable of high resolution (up to a resolving power of 10^{7}). It is designed to support the diverse science objectives of the Juice mission targeting Jupiter's middle atmosphere, icy-moon's exospheres as well as near sub-surface thermophysical properties. For this purpose the Juice mission adopts a complex trajectory tour within the Jovian system, which further necessitates a sophisticated, mission-driven operations concept for SWI. This presents significant planning, operations and commanding challenges which are described in this paper in the context of the Lunar and Earth Gravity Assist (LEGA). After the development and ground calibration of the instrument, the SWI Team has designed a comprehensive calibration strategy applicable during the Cruise Phase of Juice. Among the various opportunities for calibration, including the Near-Earth Commissioning Phase and more than ten Payload Checkout Windows, the LEGA offers the means not only to improve the calibration of the instrument, but also to validate the operational strategy of future icy moon flybys.
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All authors T. Cavalié, R. Moreno, L. Rezac, F. Herpin, C. Jarchow, P. Hartogh, A. Carrasco-Gallardo, S. Goodyear, P. Mancini, A. Schulz-Ravanbakhsh, B. Dabrowski, Y. Kasai, E. Lellouch, A. Murk, D. Murtagh, M. Olberg, M. Rengel, H. Sagawa, S. Szutowicz, E. Wirström