ALT Rings are ubiquitous among the giant planets in the Solar System, yet their presence around exoplanets remains observationally unconstrained. As direct imaging missions such as the Nancy Grace Roman Space Telescope approach first light, understanding the influence of circumplanetary rings on reflected light photometry is critical for the accurate interpretation and follow-up of direct imaging observations. We present a hybrid forward model for reflected light phase curves of ringed exoplanets, coupling a ray casting framework for computing mutual planet-ring shadowing with empirical reflectance spectra from Cassini observations of Saturn's rings. We model Jupiter-like planets with opaque, icy rings spanning 1 - 10x the radial extent of Saturn's A, B, and C rings across a grid of inclinations and ring obliquities. Our simulations show that rings enhance the flux ratios at favorable ring geometries. Saturn-equivalent rings increase peak flux by a factor of 3.1 in the visible, while more

ALT The Nancy Grace Roman Space Telescope's Coronagraph Instrument (CGI) will provide the first opportunity to directly detect mature giant exoplanets in reflected light. However, most known radial-velocity planets lie near CGI's sensitivity limit. In contrast, Saturn-like rings around these planets may be much more accessible: our models show that rings can outshine their host planets by one to two orders of magnitude or more, making them easier to detect than the planets themselves. However, because the planet and rings would be unresolved in reflected light, unrecognized rings could lead to misinterpretation of the planet's intrinsic brightness and physical properties. To disentangle these blended signals, we model reflected-light phase curves of ringed and ringless planets. Ring systems can produce a distinctive phase-curve morphology, often with four extrema rather than the two expected for unringed planets, enabling robust confirmation with multi-epoch CGI observations. We develop an

ALT Impact cratering of celestial bodies produces an ejecta plume containing underground material, which helps us understand the properties of subsurface grains and the surface evolution. In most cases, the ejecta plume forms an inverted conical structure so-called ejecta curtain. In-situ measurements of light scattering of ejecta curtain, such as the images taken at the Hayabusa2's impact experiment help to constrain the size and composition of these less-processed grains using Monte-Carlo radiative transfer models. Here, we analyse the variation in the predicted scattered intensities of an ejecta curtain set up after that of Hayabusa2's case and test its sensitivity to different compositions, sizes, and phase function of grains. Initially, the optical depth of the ejecta curtain is assumed to be constant. The intensities are seen to deviate from single scattering expectations, which we attribute to the effect of varying scattering angles and optical depths of the photons. Further, we sho

ALT The Student-led Threatening Asteroid Reconnaissance of Tsinghua (START) marks the inaugural mission of the Tianxing Program, a deep-space exploration initiative led by students at Tsinghua University. Conceived as a low-cost, rapid-response small-satellite mission, START will investigate the near-Earth asteroid (99942) Apophis during its close approach to Earth in April 2029, when significant terrestrial tidal forces will offer a rare opportunity to observe the physical and dynamical response of a rubble-pile asteroid in real time. The 300 kg spacecraft is scheduled for rideshare launch into low Earth orbit in early 2028 and will then use solar electric propulsion to transfer to a circular mission orbit with a semimajor axis of approximately 38,000 km and an inclination of 55 degrees. START will execute a high-speed flyby of Apophis from a closest distance of 7 km at the asteroid's closest approach to Earth, to capture its tidal response. The payload suite consists of a high-resolution

ALT We present the first determination of the occurrence of transiting circumbinary planets (CBPs) in TESS data. Since tight binaries represent a constrained environment relative to single stars, CBPs contribute to our understanding of planet formation and evolution. We applied our custom single-transit detection algorithm to the recently-published sample of TESS eclipsing binaries containing two M-dwarfs (M&Ms), finding only one signal attributable to a new candidate planet-sized object. We further performed sensitivity analysis and applied corrections to account for the TESS window function to arrive at our survey completeness. We find a 95% confidence level (CL) upper limit on the occurrence rate of coplanar CBPs with sizes in the range 2-16 R⊕ and with orbital periods up to 600 days of 33.0%. If the mutual inclinations of CBPs are isotropically distributed with respect to the binaries, the occurrence rate upper limit increases to 40.2%. Our occurrence rate estimates are limited in part

ALT Water and methanol are the fundamental constituents of interstellar and cometary ices: understanding their abundances in disks is therefore of high importance to reveal how this ice reservoir evolves across the timeline of star and planet formation. We present ALMA band 5 line emission observations of water and methanol in the warm Herbig disks of HD 100546 and IRS 48. While the IRS 48 disk is methanol-rich, water vapor is not detected, implying a high methanol-to-water column density ratio >0.2, possibly reflecting a distinct ice composition. Methanol and water are both detected in the HD 100546 disk, leading to a CH3OH/H2O ratio of 0.02, consistent with the median of the cometary distribution and with the lower edge of the distribution of Young Stellar Objects. We suggest that the gas-phase methanol-to-water ratio in the HD 100546 disk directly reveals the ice reservoir subsequently sublimated in the warm disk stage. Moreover, we report a methyl formate-to-methanol ratio in the IRS 4

ALT Phenomena requiring close proximity between two bodies, from black-hole mergers to hot Jupiters, may originate in hierarchical triples, in which secular torques from a distant companion drive the inner binary's eccentricity nearly to unity. Population syntheses of these channels commonly integrate the double-averaged (DA) secular equations truncated at octupole order. We show that, for a fixed outer orbit, this truncation fails for the slow evolution on librating Kozai-Lidov cycles, in which the argument of pericenter librates. On these cycles the leading octupole kicks to jz, the component of the inner angular momentum along the outer one, cancel pairwise, and the hexadecapole enters at the order of the surviving octupole torque, with the opposite sign. Strikingly, as the inner mass ratio vanishes the two nearly cancel, and their sum changes sign within the librating window, so octupole-truncated integrations omit part of the leading slow torque on this class. For |jz|≪1, the slow dyn

ALT We characterize comet P/2026 N2, whose outer Main Belt orbit has a=3.07 au, e=0.21, and i=2.25°, using optical observations, archival imaging, and dynamical integrations. Observations from the Legacy Survey of Space and Time (LSST) at NSF-DOE Vera C. Rubin Observatory in 2026 June-July and Keck/LRIS imaging on October 7 show active morphology across perihelion over 102 days. Within a projected aperture radius of approximately 1,000 km, Keck colors of g-r=0.50±0.05 and r-i=0.06±0.06 mag are consistent with nearly neutral B/C-complex reflectance. Phase-corrected a(0°)fρ=3.66±0.12 cm in derived r and 3.46±0.17 cm in i are comparable to LSST measurements. The geometry-corrected i-band aperture brightness changes by 0.07±0.07 mag between July 9 and October 7; the 2,000 km r-band aperture measurements are also consistent between epochs. These results support sustained observable activity, consistent with prolonged or recurrent dust production. Archival DECam images recover N2 on 2021 July 4,

ALT NASA's Kepler mission found more systems with one transiting planet (“singles”) than expected from those with several (“multis”). This excess was first taken as evidence for a Kepler dichotomy – a second population of intrinsically single or highly inclined systems – but later work argued that selection effects acting on a single population can reproduce it. Singles also show a puzzling excess of low signal-to-noise ratio (SNR) detections relative to multis. The question arises whether this excess reflects false positives, a selection effect, or an inherent population difference. Here we show, using the ExoMOD population synthesis model and the Kepler DR25 catalog, that multis drawn from the same parent population as singles have shorter mean orbital periods, and thus higher-SNR detections on average. Detecting several planets in one system favors compact architectures, so long-period, low-SNR detections are preferentially cataloged as singles, most of them intrinsically multi-planet s

ALT The shape of an exoplanet encodes fundamental information about its internal structure. For close-in giant planets, strong stellar tidal forces induce measurable deformations that can be probed through high-precision photometry. These deformations are quantified by the fluid Love numbers, which characterise a planet's response to external perturbations and are directly linked to its internal density distribution. In this work, we assess the potential of JWST and the future Ariel mission to constrain the Love numbers of hot Jupiters through full-orbit phase curve observations. To identify the most promising targets for this science case, we introduce a new detection metric, the deformation metric (D), which combines the expected deformation amplitude with the anticipated photometric signal-to-noise ratio. We apply this metric to the Ariel target list and identify WASP-33 b, WASP-76 b, and HAT-P-32 b as the three most favourable targets that currently lack Love number measurements. Using

ALT A growing number of transiting exoplanets exhibit spectroscopic evidence that their leading and trailing limbs differ. Interpreting these observations is now the limiting step. The standard approach of fitting limb-resolved transit depths results in highly anti-correlated transit depths, and treating them as independent measurements can result in strongly biased (3σ) retrieved molecular abundances. We present an inference framework that avoids these correlations by using the temporal signature of limb asymmetry instead. This wavelength-dependent shift in mid-transit time, or `time-shift spectrum', carries the limb-asymmetry information, is measurable from existing light curves with a spherically symmetric transit model, and is uncorrelated with the spherically-averaged transit depth. Simultaneously fitting the resulting transmission and time-shift spectrum with an independent atmospheric column for each limb enables the retrieval of limb-resolved properties from two independent measure

ALT We present a homogeneous analysis of 268 confirmed and candidate transiting hot-Jupiter host stars with 4800K < Teff < 6200K. We combine high-resolution TRES spectra, Gaia, 2MASS and WISE photometry, and Gaia astrometry to determine these stars' Teff, log g, Rstar, [alpha/Fe] and [Fe/H]. Based on their [alpha/Fe] and [Fe/H], we classify the stars as members of the Milky Way's low-[alpha/Fe] thin disk, high-[alpha/Fe] thick disk or an ambiguous intermediate population. We identify two confirmed hot Jupiters (WASP-81 b and TOI-5322 b) and three candidate hot Jupiters (TOI-3118.01, TOI-2728.01, and TOI-5781.01) as orbiting previously-unrecognized members of the high-alpha thick disk. We compare the properties of the confirmed planets in the three populations and note two indications of a potential difference between the populations: both high-[alpha/Fe] confirmed planets and eight out of the eleven ambiguous-disk confirmed planets are less massive than the median low-[alpha/Fe] planet, an

ALT Simulating chaotic planetary system evolution requires resolving small time-scales due to close encounters, scattering, collisions, and more. Simulations typically assign fixed timesteps to all particles, however, which is inefficient and wastes compute resources in a chaotically evolving system; moreover, it may under-resolve the simulation. Hybrid methods are a blunt tool for resolving small time-scales as they do not allow for fine-grained adaptation. Assigning individual timesteps, which vary in time, to planetary bodies usually violates desirable properties such as symplecticity and reversibility. In this work, we develop an "almost" exactly time-reversible direct N-body integrator, MTR, in which each pair of planets gets its own timestep, which itself can vary as the system evolves. In contrast to our previous work, we achieve this adaptation on the fly, independent of a global timestep. We provide a C version of the code and test it on several problems, demonstrating no energy e

ALT Understanding the origin and evolution of planetary atmospheres, and the connection between their lower and upper atmospheric layers, remains a fundamental challenge in exoplanet science. Addressing these questions requires observations spanning a broad wavelength range, from the ultraviolet to the near-infrared, together with the ability to simultaneously characterise planetary and stellar variability. The Wide-band Atmospheric Laboratory for Transiting Exoplanet Research (WALTzER) is an ESA F3 mission candidate designed to address this need through simultaneous low-resolution spectroscopy and high-precision photometry of transiting exoplanets. WALTzER covers simultaneously the near-ultraviolet (NUV: 240–325 nm) and visible (VIS: 450–820 nm) bands with two medium resolution spectrographs and the near-infrared (NIR: 900–1700 nm) range with a broadband photometer. We outline the main science drivers and present the mission concept and instrument design. WALTzER's broad, simultaneous wav

ALT Confirmed observations of young protoplanets actively undergoing the process of formation have remained rare to date. In this Letter, we present new insights into the nature of the recently identified protoplanet WISPIT 2 b (age ∼ 5 Myr) from VLTI/GRAVITY+ observations. Through the analysis of the spectral energy distribution (SED) and astrometry of WISPIT 2 b, with the inclusion of new GRAVITY+ data, we investigate the nature of the protoplanet's thermal emission and orbital properties. We performed an orbit fit with the inclusion of new high-precision GRAVITY+ astrometry to provide an updated orbital solution. We also analyzed the medium resolution GRAVITY+ K band spectrum in combination with new VLT/SPHERE and literature photometry, exploring both the atmospheric properties and the constraints on the circumplanetary environment. Finally, we checked for any signal from a resolved circumplanetary disk in the GRAVITY+ data. We detected the protoplanet WISPIT 2 b at ∼322 mas separation

ALT Circumplanetary disks (CPDs) play an important role in the formation of gas giants and their satellites, yet remain poorly understood owing to the lack of observables and comprehensive theoretical models. Incorporating α-viscosity, a free-fall prescription of mass infall and boundary layer accretion, we develop an axisymmetric viscous radiation hydrodynamic (RHD) model. We evolve this model for different physical parameters using the RHD code Guangqi, which solves RHD equations under the flux-limited diffusion approximation. In eight out of nine simulations, we obtain quasi-steady-state solutions and verify self-consistent energy conversion and transport. Overall, disk thickness increases with accretion rate and decreases with planet mass, consistent with the expected trend in conventional α-disk models. On the other hand, we highlight that the boundary layer plays a significant role in setting angular momentum transport and thermodynamics of the inner CPD, yielding “hot” (s_real>11 k_

ALT We analyze the post-perihelion coma of the Great Comet of 2024, C/2023 A3 (Tsuchinshan–ATLAS) to characterize dust activity and assess the contribution of sublimating icy grains to a candidate near-nucleus halo. Using archival Zwicky Transient Facility images from 15 February to 26 May 2025, we performed aperture photometry within a fixed projected radius of 40,000 km and derived azimuthally averaged surface-brightness profiles. The comet faded from 12.86 to 14.77 mag as heliocentric distance increased from 2.64 to 3.90 au, with two short-lived brightenings. The effective dust cross section decreased by a factor of 2.4, following Cₑ∝ rₕ⁻³.¹, while the dust mass production rate scaled as Ṁd∝ rₕ⁻³.⁴¹, consistent with a contribution from water-ice-driven activity. Extrapolating the fitted relation to perihelion implies a model-dependent cumulative dust mass loss of 3.0×10¹¹ kg, equivalent to a globally averaged erosion depth of ∼1.4 m for an assumed nucleus radius of 5.9 km. Coma profiles

ALT We present Zwicky Transient Facility observations of the interstellar comet 3I/ATLAS to characterize its dust-activity evolution before and after perihelion. Before perihelion, the effective scattering cross section Cₑ brightened across the inner 2×10⁴ km as Cₑ∝ r_H⁻ᵞ, with γ increasing from 1.63±0.14 to 1.88±0.34 with aperture size. After perihelion, the heliocentric index decreased from 2.44±0.09 in the 5×10³ km aperture to 1.54±0.09 in the 8×10⁴ km aperture, indicating faster fading of the inner coma. Under adopted grain-size and residence-time assumptions, the implied dust mass-loss rates are ∼123–203 kg s⁻¹ before perihelion and ∼596–1412 kg s⁻¹ after perihelion. The morphology yields a sunward ejection-speed scale of vₑⱼ∼(190±3)aμₘ⁻¹/² m s⁻¹ and an effective perpendicular velocity of v⊥=(79±6)aμₘ⁻¹/² m s⁻¹. Post-perihelion surface-brightness profiles transiently steepened to k∼-2.7 in late November and early December, then became shallower and approached k=-1.5 by January. Matche

ALT The dynamical stability of compact planetary systems is known to depend strongly on orbital eccentricities, but the physical role of apsidal alignment remains poorly understood. We investigate this problem using direct N-body simulations by separating planetary eccentricities into a systematic component shared by all planets and a random component that determines the degree of apsidal alignment. We find that these two components play fundamentally different dynamical roles. Random eccentricity destabilizes planetary systems by driving neighboring planet pairs into the regime of mean-motion resonance overlap, leading to chaotic evolution. In contrast, systematic eccentricity has little effect on the instability timescale over a wide range of values because the planetary orbits remain in apsidal alignment, preserving nearly fixed relative orbital orientations despite finite eccentricities. As a result, systems that start in apsidal alignment are nearly as stable as initially circular sys

ALT Observations of debris disks provide a valuable window to investigate the formation and evolution of planetary systems. We present high-contrast JWST/NIRCam observations of CPD-72 2713, a 24 Myr-old star that belongs to the β Pic moving group. We obtained the first scattered-light images of the disk in both F210M and F444W filters, revealing a nearly face-on orientation. Forward modeling yields disk radii of 55.4⁺³.⁰₋₃.₂ AU (F210M) and 39.1⁺⁴.⁶_ -2.6 AU (F444W), both significantly smaller than the thermal emission radii measured with ALMA and Herschel/PACS. This discrepancy suggests that scattered light traces the inner region of the disk while thermal emission probes the outer regions. Combining the stellar rotation period (4.47±0.67 days) from TESS light curves and spectroscopic vsin i_*, we constrained the stellar inclination to 47°.2⁺¹¹.¹₋₇.₇ (1σ). The minimum star-disk mutual inclinations are 27°.6 ₋₈.₂ ⁺¹¹.⁵ (1σ) from F210M data and 27°.3 ₋₁₀.₉⁺¹².⁵ (1σ) in F444W data. We find th