Earth and Planetary Astrophysics
Modelling Palomar Transients: Constraints from Reflection Geometry and Orbital Altitude
Beatriz Villarroel, Alina Streblyanska, Hichem Guergouri et al. (+3 more)
Recent searches of digitised photographic plates from the Palomar Observatory have uncovered tens of thousands of short-lived transients, each visible in only a single exposure. Their morphologies indicate sub-second flashes, consistent with specular reflections from highly reflective objects in near-Earth orbits. In this paper, we present a modelling study using
geometric shadow modelling, Monte Carlo simulations, and photometric constraints to infer their physical properties. We examine the observed groupings and
alignments, which appear to be consistent with sudden changes in attitude. Assuming a spherical-shell model, the angular profile of the measured transient deficit around the antisolar point is consistent with a population at characteristic altitudes of $\sim 20,000$–25,000 km. A complementary estimate, based on the altitude dependence of the global Earth-shadow deficit, yields a broader characteristic range of $\sim$ 20,000–35,000 km above Earth's surface, extending into the geosynchronous orbital (GSO) region. Under simplified
geometric and photometric assumptions and assuming $\sim20{,}000$ to $35{,}786$ km above the Earth's surface, the inferred sizes of the specularly reflecting facets range from centimetre scales up to $\sim3$ m, with characteristic flash durations of $\sim320$ ms and slow rotation rates. We explore both natural and non-natural toy models consistent with the data, and provide constraints to guide future observational searches.
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All authors Beatriz Villarroel, Alina Streblyanska, Hichem Guergouri, Brian Doherty, Matthew Shultz, Stephen Bruehl
Earth and Planetary Astrophysics
Gravitational instability in planet-forming discs
Cristiano Longarini and Giuseppe Lodato
During the earliest phases of
star and
planet formation, a young
star is surrounded by a disc that can become gravitationally unstable. Indeed, if the protoplanetary disc is sufficiently massive, its self-
gravity triggers the formation of large scale spiral arms, transporting angular momentum, trapping solid particles and, potentially, collapsing to form sub-stellar companions. In this paper, we review the theoretical and observational advances in the study of gravitational instability in protoplanetary discs over the last 10 years, since the advent of ALMA. These developments have transformed our understanding of gravitational instability, moving beyond its historical role as a theoretical mechanism for giant
planet formation toward a physically rich framework that can be directly tested against high-resolution observations.
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Cosmology and Nongalactic Astrophysics
Supernovae Unite: Combining Pantheon+ and DES-SN5YR
Ryan Camilleri, Jaemyoung Lee, Tamara Davis et al. (+21 more)
We present the Hubble diagram and cosmological constraints resulting from the combination of the Pantheon+ and DES-SN5YR
supernova (SN) samples, which we refer to as Unite. Unite updates Pantheon+, including methodology improvements that the DES sample enabled, and adds the new SN from the DES survey. This represents the most comprehensive and internally consistent SN Ia
dataset available, consisting of 2884 likely type Ia
supernovae. This work features consistent SN Ia modelling, sample selection, and bias corrections. We also redetermine host-
galaxy stellar masses for over 98% of the sample using a consistent framework. Using Unite alone, for a flat universe with a cosmological constant (Flat-$\Lambda$CDM), we find $\Omega_{\rm m} = 0.310^{+0.012}_{-0.011}$. We further present constraints using the Unite sample combined with
Cosmic Microwave Background and both DES and DESI Baryon Acoustic Oscillation data. We find strong evidence of tension between CMB measurements and the combined BAO and
supernova datasets when fitting a model with constant dark energy equation of state ($w$), which is alleviated when allowing $w$ to vary with time. For a flat universe with dark energy that has a time-evolving equation of state parametrized by $w_0$ and $w_a$ we find $(\Omega_{\rm m},w_0,w_a) = (0.305\pm0.004,-0.861^{+0.044}_{-0.042},-0.60^{+0.17}_{-0.19})$ with a dark energy Figure of Merit of 315. This corresponds to a $\sim30\%$ reduction in the area of the $w_0-w_a$ confidence region relative to previous constraints from the combination of DES Y6, DESI-DR2, and CMB data (arXiv:2605.27221). The
Bayesian evidence indicates only weak preference for time evolving dark energy, whereas frequentist analyses yield a preference over Flat-$\Lambda$CDM at a significance of $3.3\sigma$ ($3.1\sigma$) when using the maximum $\textit{a posteriori}$ probability (maximum likelihood).
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All authors Ryan Camilleri, Jaemyoung Lee, Tamara Davis, David Rubin, Paul Shah, Dan Scolnic, Chris Lidman, Brodie Popovic, Koby Grech, Maria Vincenzi, Dillon Brout, Maria Acevedo, Patrick Armstrong, Bruce Bassett, Keith Bechtol, Rebecca Chen, Herman Diehl, Josh Frieman, Lluís Galbany, Anais Möller, Masao Sako, Bruno Sánchez, Mark Sullivan, Brad Tucker
High Energy Astrophysical Phenomena
Nonstationary Stochastic Timing Signatures in the Prompt Gamma-Ray Light Curve of GRB 170817A
Lin Xie and Dahai Yan
We investigate time-dependent
stochastic structure in the weak
prompt gamma-ray emission of GRB 170817A using change-point and deep-kernel Gaussian-process (GP) models. The analysis is based on the 10-300 keV Fermi/GBM light curve with 0.10 s time resolution. Two change-point configurations identify similar covariance transitions at 0.269 and 0.237 s after the gravitational-wave merger, with 10-90% transition widths of 0.441 and 0.393 s, respectively. At the representative gate-defined boundary of t_tr = 0.27 s, all four fixed-split assignments yield positive evidence gains over the full-exposure stationary Matern-3/2 reference. The largest gain is Delta ln Z_split = 5.72 +/- 0.16 for the Matern-3/2 to Matern-3/2 assignment, while the gate-matched damped random walk (DRW) to Matern-3/2 assignment gives Delta ln Z_split = 5.50 +/- 0.16. The fixed-split comparison therefore supports segment-specific covariance
evolution without requiring a change of covariance family. The deep-kernel models recover localized time-deformation features peaking at 1.65 and 1.75 s after the merger for DRW and Matern-3/2 base kernels, respectively. Their offsets from the adopted gamma-ray onset at 1.74 s are -0.09 and +0.01 s, both within the 0.10 s sampling resolution. The full-band timing features remain stable when the bin width is changed from 0.10 to 0.12 s, whereas energy subdivision produces larger shifts in gate locations than in warp peaks. Residual diagnostics show that the models reproduce the dominant temporal structure, although localized residual dependence remains. We interpret the gate-defined covariance transition and the localized time-deformation feature as model-dependent phenomenological timing diagnostics. Further simulation calibration and count-level modelling are needed to assess the statistical robustness and physical origin of the recovered nonstationary structure.
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Astrophysics of Galaxies
Corona Australis 151: an extremely young protostar
E. Redaelli, S. Spezzano, P. Caselli et al. (+9 more)
Context. Prestellar cores are the birthplace of
stars and planetary systems, but they are short-lived objects, since the initial stages of dense core
evolution, collapse, and the formation of a protostellar seed are fast. In an effort to build a catalogue of bona-fide prestellar cores in the Solar neighbourhood, we used APEX observations to identify dynamically evolved cores among dense cores observed with Herschel. One of them, Corona Australis 151, stood out because of its centrally peaked structure, with densities above 1e7cm-3 in the central 500-1000 au, and high deuteration levels (N2D+/N2H+~0.5), suggestive of an evolved, prestellar stage. Aims. Corona Australis 151 appears to be an evolved prestellar core, but the presence of broad wings in some of the detected lines and a tentative 70micron detection with Herschel partially challenges its prestellar stage. We intend to assess its evolutionary stage. Methods. We analyse new ALMA data of the continuum emission and of several line tracers (including typical outflow tracers) at a resolution of~150-200au, tracing the envelope. Results. We unveil the presence of a compact and young outflow (projected dynamical age:~500yr), traced by SiO, CO, and H2CO emission. The continuum emission traces an envelope structure of size~1000 au and mass 0.33M_sun(assuming Tdust=20 K). Conclusions. Corona Australis 151 is an extremely young protostar, possibly one of the youngest known in the Solar neighbourhood, and hence a new laboratory to study the chemical and dynamical
evolution at the dawn of
star formation.
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All authors E. Redaelli, S. Spezzano, P. Caselli, J. Harju, D. Arzoumanian, O. Sipilä, A. Belloche, F. Wyrowski, J. E. Pineda, S. Jensen, Y. Misugi, G. Majerczyk
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Probing Dark Matter with Strongly Lensed Binary Black Hole Mergers: Prospects in the Near Future
Koustav N. Maity, Souvik Jana, Ankur Barsode et al. (+2 more)
Gravitational-wave~(GW) transients, strongly lensed by intervening
galaxies and clusters, are expected to constitute a small fraction ($\sim 0.1$-$0.5\%$) of the events detectable by ground-based detectors. A strongly lensed binary black hole (BBH) merger will produce multiple copies of the GW signal arriving at different times at the detector. The abundance and time-delay distribution of these lensed events are sensitive to the mass, density profile, and
redshift distribution of the lens population, and in turn, to the underlying nature of dark matter. Jana et al. (Phys.Rev.Lett. 135 (2025) 11, 111402) recently proposed a method to constrain the masses of warm dark matter (WDM) particles making use of the strongly lensed events detectable by next-generation GW detectors. In this work, we investigate the prospects of constraining the mass of the WDM particle using upcoming observations of the upgraded LIGO-Virgo-KAGRA network. This requires a careful modeling of the detector selection effects. The upcoming fifth observing run (O5) is expected to yield only a modest bound, since only a few lensed pairs are expected at that early stage. By the sixth observing run (O6), we forecast a bound on the WDM particle mass, $m_{\rm wdm}^{-1} \lesssim 0.1$-$0.2\text{keV}^{-1}$ ($m_{\rm wdm} \gtrsim 5$-$10\text{keV}$), which is comparable to the tightest existing astrophysical constraints. Runs beyond O6 will tighten the constraint by roughly an order of magnitude. Strongly lensed GWs therefore offer a complementary, competitive, and independent probe of dark matter.
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All authors Koustav N. Maity, Souvik Jana, Ankur Barsode, Tejaswi Venumadhav, Parameswaran Ajith
High Energy Astrophysical Phenomena
The October 2022 flare in OJ 287 and the mass of its primary black hole
Mauri J. Valtonen, Staszek Zola, Manpreet Singh et al. (+21 more)
The bright blazar OJ~287 has demonstrated a sequence of
flares, which are well explained by a quasi-Keplerian orbit model. The
flares are associated with the impact of the secondary on the
accretion disk of the primary. The orbit must precess in order to produce the correct sequence of
flares, and from the precession rate we calculate the mass of the primary. This precession rate gives the mass of the primary $M_{BH} = (18.35\pm0.05) \times 10^9 M_{\odot}$. Two kinds of
flares have been identified: direct
flares from the impacts, and tidal
flares arising from an increased
accretion flow into the jet. The precession rate and the primary black hole mass may be independently determined from both sets of
flares; the tidal
flare of October 2022 was recommended for an intense campaign for this reason. This paper describes these observations over a wide spectral range. We show that the October 2022
flare fits the expectations for a tidal
flare and thus supports the earlier determination of the mass of the binary black hole system in OJ 287. The mass of the primary may also be deduced from secondary indicators such as the correlation with the hydrogen line strength and the black hole mass. These studies require that the mass is above $M_{BH} \sim 10^{10} M_{\odot}$, but do not specify the value more exactly.
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All authors Mauri J. Valtonen, Staszek Zola, Manpreet Singh, Andrei V. Berdyugin, Kari Nilsson, A. Gopakumar, Alok C. Gupta, Tapio Pursimo, Alexandr E. Volvach, Marek Drozdz, Waldemar Ogloza, Rene Hudec, Martin Jelínek, Jan Štrobl, Michal Zejmo, Stefano Ciprini, Daniel E. Reichart, Vladimir V. Kouprianov, Alberto Sadun, Markus Mugrauer, Katsura Matsumoto, Ryo Imazawa, Makoto Uemura, Lankeswar Dey
Cosmology and Nongalactic Astrophysics
Expanding the scope of dark siren cosmology: Inferring the population properties of gravitational wave-hosting galaxies
Rachel Gray, Daniel Williams and Alexander Papadopoulos
The field of gravitational wave "dark siren" cosmology is facing a number of challenges surrounding the way in which
galaxy catalogue data is incorporated into the analysis. The three biggest challenges are adequately compensating for
galaxy catalogue incompleteness, robust treatment of
galaxy redshift and source properties, and the as-yet unknown host
galaxy weighting model. We present an updated methodology for inferring cosmological parameters using dark sirens and incomplete
galaxy catalogues. By switching to a sampled
redshift prior, rather than one which is pre-computed on a grid, we can jointly infer parameters which describe the population of gravitational-wave hosting
galaxies, alongside the gravitational wave population and cosmological model. Using the cosmological inference software gwcosmo, we reproduce a subset of GWTC-5.0 cosmology results, then extend the analysis to jointly infer the host
galaxy weighting model - the first measurement of its kind to do so - leading to an updated measurement of the Hubble constant with $H_0 = {71.9}_{-7.5}^{+9.1}$ km s$^{-1}$ Mpc$^{-1}$ (median and 68% symmetric credible interval). This innovative new method opens the door to solving several of the biggest challenges currently facing the field of dark siren cosmology.
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Cosmology and Nongalactic Astrophysics
Late-Time Emergence of Dark Energy and Its Interaction with Dark Matter
Sibo Zhang, Weiqiang Yang, Supriya Pan et al. (+3 more)
We present an interacting scenario between dark energy (DE) and dark matter (DM), where DE has an emergent nature, that means, DE was absent in the early universe but it becomes effective only at late times. We consider two specific emergent DE models, one with no free parameters and the other featuring two parameters describing the speed and epoch of the transition. We constrain both scenarios using the
cosmic microwave background (CMB) measurements from the Planck 2018 release, baryon acoustic oscillations from DESI DR2, and three different compilations of Type Ia
supernovae (PantheonPlus, DES-Dovekie, and Union3). Our analysis indicates that current cosmological probes are not able to tightly constrain the speed of the transition. For both scenarios, the posterior distribution of the interaction parameter is shifted away from zero at more than 95% CL whenever the CMB data are combined with any of these additional probes, with the preferred direction corresponding to a transfer of energy from DE to DM. While CMB alone yields a high value of $H_0$, in agreement with local determinations, this effect is reduced when DESI is added and disappears once
supernova data are included. In contrast, the clustering parameter $S_8$ is consistently shifted toward lower values in the combined
datasets, and it is correlated with the preference for a negative interaction. However, according to the $\Delta \chi^2_{\rm min}$ and
Bayesian evidence, none of the interacting models is favored over $\Lambda$CDM or $w_0w_a$CDM, indicating that the interaction does not rescue these emergent DE models. Our results therefore highlight the limitations of these scenarios in addressing current cosmological tensions, while pointing to the crucial role of future data in further assessing their viability.
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All authors Sibo Zhang, Weiqiang Yang, Supriya Pan, Olga Mena, Eleonora Di Valentino, Subenoy Chakraborty
Earth and Planetary Astrophysics
Updated in-flight calibration of the Hayabusa2/NIRS3 spectrometer: new global near-infrared photometric properties of asteroid (162173) Ryugu
Antonin Wargnier, Eri Tatsumi, Koki Yumoto et al. (+10 more)
The Near InfraRed Spectrometer (NIRS3) onboard Hayabusa2 observed asteroid (162173) Ryugu, searching especially for signatures of water-bearing minerals. However, during the mission, absolute reflectance measured by the Telescopic Optical Navigation Camera (ONC-T) and NIRS3 showed a systematic offset. Additionally, touchdown operations have modified the instrumental response, which has made post-second-touchdown data less reliable. Correction of these issues is crucial to interpret the subtle spectroscopic differences across the surface, better understand the origin and
evolution of carbonaceous asteroids, and support the Hayabusa2$\sharp$ mission's future observations of the asteroids (98943) Torifune and 1998 KY26. We used Ryugu observations at different mission phases for relative calibrations and lunar observations for the absolute calibration. Moon spectra acquired during the first Earth swing-by were compared to simulated ones from photometric models based on lunar orbiter and ground-based data. We then applied the updated calibration to the full Hayabusa2 proximity phase
dataset, enabling disk-resolved global and regional photometric analyses. We showed that the data obtained following the first and second touchdowns required downscaled corrections of $5.4 \pm 1.8 $% and $10.3 \pm 0.4 $% at 2 $\mu m$, respectively, while the absolute calibration revealed that NIRS3 reflectance was underestimated by about 8% compared with the original calibration. Our new photometric parameters are consistent with previous studies and indicate a weak east-west dichotomy in phase ratio and phase reddening, pointing to higher surface roughness and higher abundance of fine-grained regolith in Ryugu eastern hemisphere.
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All authors Antonin Wargnier, Eri Tatsumi, Koki Yumoto, Mayumi Ichikawa, Shin-ya Murakami, Yuichiro Nagai, Kazuhiro Honda, Yasuhiro Yokota, Toru Kouyama, Takahiro Iwata, Moe Matsuoka, Satoshi Tanaka, Kohei Kitazato
Astrophysics of Galaxies
Rubin J122659.4+090236: An Extremely Low Surface Brightness Galaxy Candidate Discovered in the Rubin LSST Early Data Preview 2
Dipanjan Mitra, Kanak Saha, Sugata Kaviraj et al. (+28 more)
We report the serendipitous discovery of an exceptionally low surface brightness
galaxy (LSBG) candidate, Rubin J122659.4+090236, in Rubin Observatory imaging of the interacting NGC 4410 system, identified in the
Cosmic Treasure Chest public release. 2D Sérsic modelling of the Rubin g, r, and i images reveals a nearly round system with a shallow profile (n ~ 0.4), an effective radius of R_e ~ 6”, and central surface brightnesses of $\mu_{0,g}=27.52\pm0.04$, $\mu_{0,r}=27.62\pm0.07$, and $\mu_{0,i}=27.04\pm0.08$ mag arcsec$^{-2}$. EAZY photo-z fitting favours an intermediate-z solution at z~0.3, while a low-
redshift solution at z~0.028, consistent with the NGC 4410 system, is also permitted by a restricted EAZY fit over 0<z<0.1 without imposing a
redshift prior. These alternatives imply substantially different physical interpretations, ranging from a diffuse dwarf-like system to an exceptionally extended background LSBG. This discovery demonstrates Rubin's sensitivity to extremely diffuse
galaxies and highlights the potential of the LSST survey to uncover large samples of such elusive systems across wide areas, enabling systematic studies of the LSBG population and its role in
galaxy evolution.
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All authors Dipanjan Mitra, Kanak Saha, Sugata Kaviraj, Alister W. Graham, Sandro Tacchella, Ricardo Demarco, Dieu D. Nguyen, Elham Saremi, hernandez toledo, hector., Jose Benavides, Natanael M. Cardoso, Samuel Boissier, Dan S. Taranu, Bililign Dullo, Patricia B. Tissera, Matias Blana, Hao Fu, Priyanka Chakraborty, Kevin A. Pimbblet, Tayyaba Zafar, Anirban Dutta, Aidan P Cotter, Darko Donevski, Katarzyna Malek, Rossella Ragusa, Agnieszka Pollo, Unnikrishnan Sureshkumar, Aritra Ghosh, Antonio Vanzanella, Hareesh Thuruthipilly
Earth and Planetary Astrophysics
Mapping the WISPIT2 Planet-Hosting Cavity at Sub-Hill-Radius scales
Myriam Benisty, Stefano Facchini, Richard Teague et al. (+6 more)
We present new deep, very high angular resolution observations of the sub-mm continuum (19x13 mas) and 12CO (67x52 mas) emission from the disk surrounding the
planet host WISPIT2. Our analysis reveals a clear gas gap carved by WISPIT 2b and an empty cavity within the orbit of WISPIT 2c. We also find a gaseous and optically thin dusty ring located between the orbits of the two
planets. Channel maps show a pronounced change in the emission surface height of the disk, which transitions from flat within the cavity to strongly flared beyond the orbit of
planet b, producing clear breaks in the velocity channels. A pronounced thunderbolt-shaped feature, identified as a kinematic planetary signature (KPS), is detected at the location of WISPIT 2b, in agreement with predictions from
planet-disk interaction simulations. This constitutes the first system with a confirmed kinematic signature associated with a directly imaged
planet. By mirroring opposite velocity-channel maps about the systemic velocity, we further investigate the KPS and identify spatially resolved excess emission in the vicinity of WISPIT 2b. We find that this emission is resolved across the full Hill sphere of the
planet, significantly exceeding the expected extent of a circumplanetary disk. We therefore suggest that the observed emission arises from a combination of processes, including prominent
planet-driven spiral wakes, localized heating induced by the
planet and a circumplanetary disk. Although higher spectral resolution is required to disentangle these contributions, our observations demonstrate the potential to directly characterize the birth environment of forming massive
planets at scales down to sub-Hill radius.
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All authors Myriam Benisty, Stefano Facchini, Richard Teague, Francesco Zagaria, Pietro Curone, Viviana Pezzotta, Jaehan Bae, Gabriele Cugno, Daniel J. Price
Earth and Planetary Astrophysics
The metallicity of giant exoplanets around low-mass stars and how Ariel can help
Ravit Helled, Sho Shibata, Shubham Kanodia et al. (+1 more)
Giant
planets orbiting low-mass
stars represent a unique population of giant
planets that can be studied to constrain
planet formation theory. Surveys of transiting giant
exoplanets around M-dwarfs (GEMS) allow for measurement of their masses and radii, which in turn can be used to estimate their bulk densities. Coupling these observations to interior structure and
evolution models can yield the bulk
metallicity of these
planets, however there are degeneracies to this that are improved by measurements of atmospheric
metallicity. Estimates of bulk
metallicity can be crucial to our understanding of
planet formation timescales and mass budgets, particularly in these extreme (
planet-to-
star) mass ratio systems. Here we show that GEMS are expected to have a low bulk
metallicity as a natural result of the
planet formation process, and the low efficiency of planetesimal capture post-formation. To test this empirically, we need a larger sample of GEMS with atmospheric measurements, which can reduce some of the degeneracies with the interior modelling of
planets. Measuring the atmospheric composition of GEMS with JWST and Ariel will be crucial for better understanding this unique planetary type, which sits at the tail of standard
planet formation conditions.
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All authors Ravit Helled, Sho Shibata, Shubham Kanodia, Billy Edwards
Earth and Planetary Astrophysics
Multi-Wavelength Post-Perihelion Polarimetry of Interstellar Comet 3I/ATLAS
Zuri Gray, Galin Borisov, Ludmilla Kolokolova et al. (+15 more)
We present new post-perihelion polarimetric observations of the third discovered interstellar object, 3I/ATLAS (C/2025 N1; hereafter 3I), obtained using FORS2 at the Very Large
Telescope, ALFOSC at the Nordic Optical
Telescope, and FoReRo2 at the 2 m Ritchey-Chrétien-Coudé
telescope. The observations span phase angles 1-30$^{\circ}$, providing the most extensive polarimetric phase angle coverage obtained for an interstellar object to date. The post-perihelion measurements reveal that the unusual polarimetric properties of 3I persist across perihelion and match recent independent post-perihelion observations, indicating no significant
evolution in the polarimetric properties. The increased phase angle coverage allowed us to further constrain the minimum polarisation to $-2.9\%$ at phase angle $5.5^{\circ}$. Multi-band BVRI observations reveal a wavelength dependence of polarisation, with the negative polarisation branch becoming deeper and shifted toward smaller phase angles at longer wavelengths. The polarimetric colour is predominantly red and increases with phase angle, consistent with behaviour observed in other comets. Imaging and polarimetric maps show a substantially more extended coma after perihelion, while the polarisation distribution itself remains smooth and spatially homogeneous. Numerical modelling suggests that the unusually deep polarisation phase curve originates from moderately porous dust aggregates consisting of weakly absorbing sub-micron monomers, resulting in much brighter dust than that in typical solar system comets.
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All authors Zuri Gray, Galin Borisov, Ludmilla Kolokolova, Johannes Markkanen, Yuna G. Kwon, Stefano Bagnulo, Alberto Cellino, Rosemary C. Dorsey, Grigori Fedorets, Mikael Granvik, Eric MacLennan, Antti Penttilä, Karri Muinonen, Olga Muñoz, Philippe Bendjoya, Maxime Devogèle, Simone Ieva, Francisco J. García-Izquierdo
Earth and Planetary Astrophysics
Disk dispersal freezes overstable resonant librations
Linghong Lin and Beibei Liu
Context. Convergent migration in a gaseous protoplanetary disk can capture a
planet pair into mean-motion resonance. Eccentricity damping can subsequently make the resonant libration overstable and drive the pair out of resonance. Most studies of this process, however, assume a static disk. Aims. We examine how the decay of disk torques during dispersal changes this outcome and whether it can freeze an overstable libration before the pair escapes. Methods. We describe disk dispersal by allowing the migration and eccentricity-damping timescales to increase exponentially on a local timescale $\tau_{\rm d}$. Integrating the time-dependent growth rate predicts $\tau_{\rm d,crit}\propto\tau_{e,0}$. We test this scaling with direct $N$-body integrations and relate $\tau_{\rm d}$ to the time taken by a photoevaporative cavity edge to cross the local torque-producing region. Results. The simulations recover a linear boundary, $\tau_{\rm d,crit}\simeq S\tau_{e,0}$, with $S\simeq3$ over the explored parameter range. In a fiducial minimum-mass solar nebula, faster propagation of the cavity edge shortens the local dispersal time. The ratio $\tau_{\rm d}/\tau_{\rm d,crit}$ also decreases with orbital radius, so both effects favour resonant survival. Conclusions. When local disk dispersal is sufficiently rapid, the libration amplitude can freeze and the
planet pair can remain in resonance instead of escaping through overstability. Late disk
evolution can therefore alter the outcome of resonant overstability.
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Astrophysics of Galaxies
Quantifying collision-driven mass loss in supermassive star formation: the role of stellar structure and accretion
P. A. Solar, B. Reinoso, D. R. G. Schleicher et al. (+1 more)
Observations of high-
redshift galaxies with JWST have renewed interest in scenarios where supermassive
stars form via runaway stellar collisions in dense clusters, yet the impact of collision-driven mass loss on their growth remains uncertain. In this work, we perform a post-processing analysis of 3D hydrodynamical simulations of the formation of a supermassive
star, applying an analytic mass-loss prescription to stellar collisions while exploring different assumptions for the internal stellar structure. We consider a polytropic main-sequence model, a semi-analytic accreting protostar model, and structures derived from stellar
evolution calculations. We find that the cumulative mass-loss fraction depends sensitively on the adopted stellar structure, ranging from $\lesssim 10-25\%$ for more compact configurations to $\gtrsim 30-40\%$ for more extended protostellar models. The importance of mass loss further depends on the dynamical state of the system, including the ratio of stellar velocity dispersion to the stellar surface escape velocity. We find significant uncertainty depending on the prescription used. As a result, collision-driven mass loss could significantly limit the growth of the central object, at least in some cases. Overall, our results indicate that uncertainties in the internal structure of rapidly accreting protostars represent a major source of systematic uncertainty and must be better constrained to robustly assess the viability of runaway-collision pathways for forming massive black hole seeds.
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All authors P. A. Solar, B. Reinoso, D. R. G. Schleicher, R. Banerjee
Earth and Planetary Astrophysics
Habitable-zone Earths at the detection frontier: Measured completeness and false-alarm rate of a transit pipeline for the PLATO M-dwarf sample
Yohann Tschudi
The PLATO mission will observe its first long-pointing field, LOPS2 (Long-duration Observation Phase, South field), for at least two years, bringing the habitable zones (HZ) of its M-dwarf sample within reach of a transit search. The completeness and false-alarm rate of a pipeline validated on TESS M dwarfs are measured on simulated PLATO photometry and converted into a candidate-level forecast for the LOPS2 M dwarfs. Simulated PLATO light curves (717 d baseline; three stellar
cells of the faint half of the sample) were processed end to end in two arms, without and with a pre-launch model of the instrument systematics: 930 in the first (465 realisations, 525 injected
planets, 465 noise-only twins) and 790 in the second. Injected
planets measure completeness against the expected signal-to-noise ratio (S/N), separately for the long-period regime of the HZ; noise-only twins measure the false-alarm rate against the floor on the red-noise-aware statistic S/N_pink. Completeness reaches 50% at S/N = 7.7 +/- 0.15 over all periods and 8.6 +/- 0.3 in the long-period regime. The false-alarm rate falls from 79 +/- 2% to 0.6% as the S/N_pink floor rises from 6 to 8, and 6 +/- 1% at the adopted floor 7.5 (completeness 54 +/- 2%). In the field, the 50 known transiting objects of interest (19 confirmed
planets, 31 candidates) would all be recovered; a transiting HZ
planet of 1.0 (1.5) Earth radii would be recovered as a candidate with ~40% (65%) probability, giving about 4 HZ Earths and 7 super-Earths over 16 929 field M dwarfs. The systematics arm shifts the 50% point by +0.54 (+0.27/-0.22) in S/N, a penalty localised on the transition, leaving the floor robust and negligible on the long-period injections that feed the HZ. Habitable-zone Earths around the PLATO M dwarfs sit at the measured detection frontier, where completeness and reliability, both measurable before launch, decide the yield.
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Astrophysics of Galaxies
Membership Determination of 45 Open Clusters Beyond 3 kpc
Qian Cui, Zhihong He, Yangping Luo et al. (+1 more)
Context. Open clusters (OCs) are fundamental tracers for studying the structure and chemical
evolution of the Galactic disc. Reliable identification of cluster members, particularly at the faint end of the main sequence, remains challenging owing to severe field-
star contamination and the declining photometric completeness for distant, obscured systems. Aims. We aim to identify and characterise distant OC candidates at heliocentric distances $d \gtrsim 3$ kpc using Gaia DR3 astrometry, with emphasis on improving the recovery of faint candidate members in highly contaminated stellar fields. Methods. We apply a probabilistic membership method based on Gaia DR3 proper motions and parallaxes. Candidate members are selected through combined astrometric criteria and refined via spatial filtering using radial density profiles, with photometric data serving as a consistency check. For clusters affected by significant extinction, near-infrared photometry from 2MASS is incorporated to compensate for the limitations of optical data. Results. We analyse a sample of 45 targets, comprising 30 previously reported OCs and 15 newly identified candidates, all located at $d \gtrsim 3$ kpc. The method yields more compact astrometric distributions and improves the recovery of faint candidate members in several systems. However, residual field contamination remains non-negligible for the most obscured clusters projected against the Galactic plane. Conclusions. Gaia DR3 astrometry provides an effective basis for the exploratory identification and first-order characterisation of distant OC candidates. Dedicated near-infrared follow-up observations will be essential for robust membership assessment in high extincted regions.
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All authors Qian Cui, Zhihong He, Yangping Luo, Yan Jiang
Cosmology and Nongalactic Astrophysics
A guide to choosing data compression methods for cosmological inference
Susan Pyne, Benjamin Joachimi, Calum Gordon et al. (+1 more)
We provide a pedagogical guide to help researchers choose an appropriate compression method for cosmological inference and numerical covariance estimation, trading off the balance between information loss and complexity. We describe methods used in the literature, categorising them by the form of the loss function – Fisher information, mutual information, or mean squared error – and by whether they are linear or non-linear. We consider in detail the linear compression methods: massively optimised parameter estimation and data compression (MOPED), canonical correlation analysis (CCA), principal component analysis, and linear neural networks. We also investigate simple non-linear methods based on neural networks with similar architectures but different loss functions. We use tomographic weak
lensing power spectra as example data vectors, deriving constraints on the cosmological parameters $\Omega_\mathrm{m}$, $\sigma_8$, $w_0$ and $w_a$ from compressed data. For our figure of merit (FoM) we use the log determinant of the Fisher
matrix, which approximates the covariance of the full posterior well. MOPED and a Fisher information-based linear neural network both achieve lossless compression. Neural networks with loss functions which optimise mutual information achieve at most 84 per cent of the uncompressed FoM and those which minimise mean squared errors achieve at most 72 per cent. We show how to determine whether MOPED will retain information even if the fiducial cosmology is not known with certainty, and demonstrate a strategy for CCA which results in an FoM close to that of MOPED while requiring only an approximate idea of where the bulk of the posterior mass is located.
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All authors Susan Pyne, Benjamin Joachimi, Calum Gordon, Kiyam Lin
Earth and Planetary Astrophysics
Signatures of rocky debris accretion in AF-Type planet hosts
J. Maldonado, I. Mendigutía, S. Barceló Forteza et al. (+3 more)
The gas-giant
planet-
metallicity correlation plays a fundamental role in our understanding of
planet formation. We determine in a homogeneous way the
metallicity and individual abundances of a sample of A and early-F
stars, with and without known planetary companions, and discuss their abundance distribution and trends. We find that
stars with
planets generally exhibit higher abundances of both iron-peak and volatile elements compared to
stars without known
planets although in most cases this tendency is not statistically significant. The $\rm {C/O}$ ratio remains similar between both samples, while the $\rm {Mg/Si}$ ratio is shifted towards higher values in the general
planet host sample. When the sample is limited to fully radiative
stars (spectral type earlier than F5), the statistical significance of carbon overabundances vanishes. In contrast, elements such as O and Ni remain significantly overabundant. The $\rm {C/O}$ and $\rm {Mg/Si}$ ratios in this radiative subsample are statistically indistinguishable from that of the comparison sample. The persistent overabundance of O and Ni, combined with $\rm {C/O}$ and $\rm {Mg/Si}$ ratios similar to those of
stars without
planets in fully radiative hosts, points to the ongoing surface pollution by volatile-poor, silicate-rich rocky debris, rather than the
accretion of gas giants. These findings might position early-type main-sequence
stars as a crucial dynamical missing link in the chemical life-cycle of planetary systems: bridging the initial dust-trapping phase in pre-main sequence transition discs, the dilution of this superficial pollution during the fully convective red giant phase, and the eventual dynamically-driven
accretion of asteroid material observed in polluted white dwarfs
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All authors J. Maldonado, I. Mendigutía, S. Barceló Forteza, G. M. Mirouh, B. Montesinos, E. Villaver
High Energy Astrophysical Phenomena
The angular structure of the GW170817 jet from prompt emission alone
R. Moradi and R. Ruffini
We determine the angular structure of the GW170817 jet by the
prompt emission alone, without afterglow fitting, circumburst density or microphysical parameters. We assume that GRB 090510 and GW170817 have outflows of the same kind, observed respectively on-axis and at the interferometric viewing angle of $20^\circ$. We support this assumption with independent gravitational-wave data showing compatible binary masses and radiated energies. We show that for an observer whose beaming cone is filled with outflow, the point-source Doppler scalings do not apply: $E_{\rm iso}=4\pi\epsilon(\theta_v)$, with $\epsilon$ the energy radiated per unit solid angle along the line of sight, while the peak energy follows $E_{\rm p,i}\propto\Gamma(\theta_v)$. We obtain $n={\rm d}\ln\epsilon/{\rm d}\ln\Gamma = 3.76\pm0.29$ from the ratio of the two bursts, with no free parameter and no assumed angle. This excludes four structures in common use at $4.7\sigma$ to $13\sigma$; three remain above $4\sigma$ across the full reported range of the peak energy of the GW170817 jet. Two
prompt spectra fix no angular scale; supplying it with the core Lorentz factor of GRB 090510 and the viewing angle gives $\epsilon\propto\theta^{-7.4}$ outside a core of $2^\circ$–$5^\circ$, in agreement with the width inferred from $367$ short bursts, the outflow remaining relativistic at $\Gamma=33$ on the line of sight. The exponent exceeds what the Lorentz boost of a uniform comoving flow can produce, so the structure is intrinsic to the outflow and not a consequence of the boost. The same structure fixes the emission radius, which contributes $0.41$~s of the $1.74$~s delay between the gravitational-wave signal and the gamma-rays, the remainder being the launch and breakout of the jet, with no free parameters. We conclude that the faintness lies in the structure of the GW170817 jet, not in the de-beaming of a bright core.
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High Energy Astrophysical Phenomena
Through a glass, darkly: a combined framework for estimating fast radio burst host galaxy and population properties in an era of uncertain host identification
C.W. James, B.C. Andersen, L. Marnoch et al. (+5 more)
The identification of fast
radio burst (FRB) host
galaxies, and subsequently their
redshifts ($z$), has allowed the FRB dispersion measure (DM) to be used to probe the cosmological distribution of ionised gas, and study the properties of the FRB population itself. However, current methods cannot account for FRBs with uncertain host
galaxy associations, leading to underutilisation of data, and potential biases towards nearby, bright hosts. In this work, we develop a methodology which can. We do so by combining three ingredients - the zDM code, for modelling the Macquart relation; PATH, for statistical host
galaxy identification; and a set of models able to describe the intrinsic FRB host
galaxy distribution - into a single formalism. We prove the fidelity of our formalism by using a synthetic set of FRB observations, with simulated hosts sampled from
galaxy catalogues, and show that it reproduces intrinsic host
galaxy properties even for FRB localisation uncertainties of 30", where a traditional PATH analysis produces no confidant host associations. When applied to a sample of FRBs localised by the Australian Square Kilometre Array Pathfinder, we confirm previous results showing that FRBs prefer host
galaxies fainter than that predicted by
star-formation, consistent with an exponential surface density scaling as $0.41^{+0.13}_{-0.09}$ times the half-light radius. We encourage the application of this formalism to data-sets from other FRB-hunting instruments.
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All authors C.W. James, B.C. Andersen, L. Marnoch, J.L. Hoffmann, N. Loudas, J.X. Prochaska, S.D. Ryder, M. Woodland
Cosmology and Nongalactic Astrophysics
Studies on the dark sector interaction from joint analysis of cosmological probes
Jianfeng Meng, Xiaofeng Yang, Yunliang Ren et al. (+4 more)
We test whether constraints on the nonlinear interaction $\xi$IDE are stable under different treatments of the Type Ia
supernovae absolute calibration. Fermi GRBs measurements and the Amati-relation parameters are fitted jointly with PantheonPlus SNe Ia, DESI DR2 BAO, and an updated
cosmic-chronometer compilation. We compare the PantheonPlus-SH0ES route, which retains the SN absolute calibration, with the PantheonPlus-only route, in which the SN absolute magnitude is analytically marginalized. The GOLD GRB sample is adopted for the main analysis, while the FULL GRB sample is used to assess sample dependence. For the interaction parameter $\gamma\equiv\xi+3w$, where $\gamma=0$ denotes the non-interacting limit, the GOLD sample gives $\gamma=1.453^{+1.297}_{-1.597}$ for the PantheonPlus-SH0ES and $\gamma=-0.634^{+1.668}_{-2.486}$ for the PantheonPlus-only. Although the posterior medians correspond to opposite directions of energy transfer, neither route excludes $\gamma=0$ at 68% credibility, and the reconstructed interaction rate remains consistent with zero over the
redshift range considered. Replacing the GOLD sample with the FULL sample produces negligible changes in the interaction constraints. Moreover, $w$CDM and CPL achieve likelihood improvements comparable to that of $\xi$IDE, while the information criteria do not consistently favor the interacting model. A
redshift-bin diagnostic finds no significant
redshift evolution of the Amati relation. We find no compelling evidence for a dark sector interaction that is robust to the choice of SN calibration or specifically favored over noninteracting dark energy extensions.
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All authors Jianfeng Meng, Xiaofeng Yang, Yunliang Ren, Bohao Wang, Jingze Li, Kang Jiao, Xiongwei Liu
High Energy Astrophysical Phenomena
Evidence of Orbital Evolution of Gigahertz-Peaked Spectra in Binary Millisecond Pulsar
Rahul Sharan and Bhaswati Bhattacharyya
We present the first systematic investigation of the continuous orbital
evolution of the Gigahertz-Peaked Spectum turnover frequency ($\nu_{peak}$) in the binary millisecond
pulsar, PSR J2144$-$5237. Using approximately 50 hours of densely sampled observations spanning the $\sim10$-day orbit with the Parkes Ultra-Wideband Low frequency receiver, we obtained continuous frequency coverage from 704 MHz to 4 GHz, enabling robust measurements of the spectral
evolution throughout the binary orbit. We detect a clear and systematic modulation of the turnover frequency with orbital phase for both the $1^{st}$ pulse and $2^{nd}$ pulse components, with both emission components exhibiting remarkably similar evolutionary trends despite originating from distinct emission regions within the
pulsar magnetosphere. The correlated
evolution of the two pulse components strongly suggests that the observed spectral variability is governed by propagation through the intra-binary environment. The large orbital modulation of turnover frequency can be explained by cyclotron resonance absorption in magnetized
plasma associated with the companion, while alternative absorption mechanisms are unable to reproduce the observed behaviour. Modelling the orbital
evolution of the turnover frequency within the cyclotron absorption framework, can constrain the electron density distribution in the
pulsar wind, estimate the
magnetic field strength of the companion, and place limits on the geometry of the absorbing
plasma and the binary system. This study establish orbital
evolution of the Gigahertz Peaked Spectum as a powerful new diagnostic of the magnetized intra-binary medium and provide a hitherto unexplored probe of
pulsar wind-companion interactions in eclipsing millisecond
pulsar binaries.
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Instrumentation and Methods for Astrophysics
Validating the SCALES DRP: A Performance Study of the Medium-Resolution IFS Mode
Athira Unni, Steph Sallum, Max Brodheim et al. (+11 more)
We present a performance verification of the medium-resolution integral field spectrograph (IFS) mode of the SCALES Data Reduction Pipeline (SCALES-DRP) using data obtained during recent cryogenic cooldown testing. SCALES (Slicer Combined with Array of Lenslets for
Exoplanet Spectroscopy), scheduled for deployment on the Keck II
Telescope in late 2026, will be the first facility-class high-contrast thermal-infrared IFS, operating over the 2-5 micrometer wavelength range. The SCALES-DRP, developed within the Keck Data Reduction Pipeline Framework and implemented in Python, converts raw detector reads into calibrated three-dimensional datacubes using rectification
matrices derived from position-dependent monochromatic lenslet point-spread functions, and supports both optimal and chi-sqaure-based spectral extraction to maximize signal-to-noise and extraction fidelity. We present laboratory verification results for the medium-resolution IFS mode, which combines a 0.34x0.36 arcsec lenslet subarray with an image slicer to achieve spectral resolutions of R ~ 2,000 - 5,000, focusing on the performance of the rectification
matrices and the robustness of the extraction
algorithms. These results demonstrate the readiness of the SCALES-DRP for instrument commissioning and early science operations. The pipeline is publicly available on GitHub.
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All authors Athira Unni, Steph Sallum, Max Brodheim, Rosalie McGurk, Andy Skemer, Matthew Brown, Peyton Benac, Michael P. Fitzgerald, Deno Stelter, Dusty Reichwein, Aaron Hunter, William T. S. Deich, Isabel Kain, Mackenzie Lach
High Energy Astrophysical Phenomena
A Differentiable Neural Surrogate for Photon Propagation in Neutrino Telescopes
Felix J. Yu, Berthy T. Feng, Nicholas Kamp et al. (+1 more)
Large-volume
neutrino telescopes infer
neutrino properties from Cherenkov light, but simulating the transport of billions of
photons through highly scattering ice or water is computationally costly. We introduce candela, a differentiable SIREN neural field that learns the
photon Green's function of the IceCube
Neutrino Observatory, a cubic-kilometer detector embedded in Antarctic glacial ice. Given a point-like energy deposit and sensor, it predicts the expected
photon yield and full arrival-time distribution at the sensor. Complete events are simulated by decomposing charged-particle energy deposits into point-like sources and superposing their predicted sensor responses. Trained on Monte-Carlo simulations, candela generates events $50$–$100\times$ faster than existing methods, with cost scaling only weakly with
neutrino energy. It keeps median yields within $2\%$ of the MC expectation and timing distributions at the MC statistical floor across six
photon-count decades. The model also provides end-to-end gradients with respect to event parameters and opens a path toward optimizing scattering-medium properties, which often dominate systematic uncertainties in
neutrino telescopes.
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All authors Felix J. Yu, Berthy T. Feng, Nicholas Kamp, Carlos A. Argüelles
Earth and Planetary Astrophysics
Retrieving Ocean Glint Reflectance Signatures from Directly Imaged Earth-like Exoplanets
Eleanor Cornish and Tyler D. Robinson
Future space
telescopes searching for extraterrestrial life require methods to detect environments that can potentially support life.
Liquid water is considered essential for life as we know it and its presence is therefore an important observable when characterizing potentially Earth-like
exoplanets. Remotely inferring the presence of surface
liquid water on a world from spatially unresolved observations is an outstanding challenge where the detection of ocean glint could provide supporting evidence. This study assesses the feasibility of detecting ocean glint from Earth-like
exoplanets using simulated data from NASA's Habitable World Observatory (HWO). We conducted
retrievals on these simulated observations using a model that included a glint contribution and performed model selection against
retrievals that did not include glint. We find that over a range of spectral signal-to-noise ratios from 5 to 25, a phase angle of at least 120 deg is necessary for glint detection. Our results offer the opportunity to shape mission development by providing constraints on key
telescope observing requirements.
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