Astrophysics of Galaxies
The Computed Microwave Spectrum of the Protonated Fullerene C60H+
Laszlo Nemes, Jos Oomens, Vincent J. Esposito et al. (+2 more)
The largest known molecule in space, C60 , has been detected in its neutral and cationic form through its vibrational, UV-driven fluorescence emission spectrum and its electronic absorption spectrum, respectively. The detection of several polycyclic aromatic hydrocarbon molecules through their pure rotation spectrum in cold, dense, molecular cloud cores suggests that C60 might be present in these environments as well. The low flux of UV pumping
photons in molecular cloud cores and the absence of suitably bright background
stars, make detection of C60 and its cation through the commonly used methods impractical. As C60 has no permanent dipole moment, its pure rotational transitions are forbidden and its presence must be inferred from the rotational transitions of C60 derivatives with permanent dipole moments. Here, we present a study of the predicted rotational spectrum of protonated C60 that has a sizeable permanent dipole moment. Protonation of C60 reduces the icosahedral
symmetry to Cs and results in a dipole moment of about 3.8 Debye. The resulting C60H+ is a closed shell system
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All authors Laszlo Nemes, Jos Oomens, Vincent J. Esposito, Vincent Boudon, Alexander G. G. M. Tielens
Instrumentation and Methods for Astrophysics
PySME v1.0: improved modelling of stellar spectra for survey-scale applications
Mingjie Jian, Nikolai Piskunov, Jeff Valenti et al. (+4 more)
Stellar abundance analysis relies on flexible, high-performance spectral synthesis. To meet these needs, we present PySME v1.0, an updated Python implementation of Spectroscopy Made Easy (SME) designed for precise and survey-scale modelling of
stellar spectra.A central challenge in SME based synthesis is the efficient treatment of very large line lists, including both the preselection of negligible lines and the subsequent formal synthesis. PySME v1.0 introduces a revised line-selection framework based on opacity ratio and line depth, together with dynamic line list construction and control of the effective wavelength span over which each line contributes to the synthetic spectrum. These workflows support parallel preprocessing of weak-line selection and reduce the line list passed to the synthesis core, thereby improving scalability while preserving synthetic accuracy. PySME v1.0 also incorporates an updated equation-of-state treatment that improves the modelling of hydrogen lines, particularly Balmer features, while maintaining close agreement with previous SME results for metal lines. The Python interface has further been extended to support parameter-dependent derived quantities updated during optimisation, and PySME provides non-local thermodynamic
equilibrium (NLTE) departure-coefficient grids for 17 elements. Together, these developments establish PySME v1.0 as a robust and efficient framework for high-precision
stellar abundance analyses in large spectroscopic surveys.
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All authors Mingjie Jian, Nikolai Piskunov, Jeff Valenti, Ella Xi Wang, Brian Thorsbro, Henrik Jönsson, Ansgar Wehrhahn
Earth and Planetary Astrophysics
Synergistic Effects of Ocean Salinity and Planetary Obliquity Enhance Habitability of Cold Exo-Earths
Kyle Batra, Stephanie Olson and Edward Schwieterman
Past work has shown that ocean salinity and planetary obliquity both influence the climates of Earth-like
exoplanets throughout the habitable zone of Sun-like
stars. The effects of salinity and obliquity can be profound, with low vs. high salinity or obliquity resulting in distinct
climate states in some scenarios. However, past work has considered salinity or obliquity in isolation and has not explored how each may modulate the effects of the other. We investigate how ocean salinity and planetary obliquity jointly impact
climate and habitability using the ROCKE-3D coupled ocean-atmosphere general circulation model. We find that salinity and obliquity have a greater combined impact on planetary
climate than the sum of their effects in isolation. This synergy between salinity and obliquity arises due to the ice-albedo feedback, producing distinct
climate states that range from ice-free to globally glaciated while having same initial atmospheric conditions and receiving the same instellation. Consequently, ocean salinity and planetary obliquity can together lead to divergent habitability outcomes for otherwise identical planetary scenarios and initial conditions. Salinity and obliquity can jointly increase the planetary fractional habitability across oceans and continents, especially for cold
exoplanets. Although neither ocean salinity nor planetary obliquity can be reliably predicted or observationally constrained, their synergistic effects must be considered in future studies of planetary
climate and
exoplanet observations, especially when characterizing planetary habitability.
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High Energy Astrophysical Phenomena
The jet-shaped pipe morphology in planetary nebulae and core-collapse supernova remnants
Jessica Braudo and Noam Soker
We compare images of core-collapse
supernova (CCSN) remnants (CCSNRs) and jet-shaped planetary nebulae (PNe) that have a narrow, faint zone extending from side to side, termed a pipe, with a hydrodynamical numerical simulation exploding a massive
star with three pairs of jets in the framework of the jittering jets explosion mechanism (JJEM), and conclude that jets shaped the pipes in these CCSNRs and PNe. We present two jet-shaped PNe with a pipe and three PNe with two opposite narrow jet-shaped lobes, and argue that in some cases the two opposite narrow lobes might merge to form one long, faint zone extending from side to side of the PN, namely, a pipe. From the qualitative similarity between the pipe morphology of the two CCSNRs we analyze and the pipe of the PNe, we suggest that jets also shaped the pipe of these CCSNRs. We strengthen this conclusion with a three-dimensional hydrodynamic simulation that reproduces two opposite narrow lobes, similar to those observed in PNe with lobes. These lobes can merge later to form a pipe. This paper is another in a series that strengthens the case for the JJEM as the primary explosion mechanism of CCSNe by comparing CCSNR morphologies with those of jet-shaped PNe.
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High Energy Astrophysical Phenomena
Effects of magnetically driven shocks on nucleosynthesis and kilonovae from neutron star mergers
Yuan Feng, Oleg Korobkin, Elias R. Most et al. (+2 more)
Neutron-
star mergers can launch mildly relativistic to moderately relativistic
outflows whose interaction with the ejecta can reshape kilonova emission. We parametrically study magnetically powered outbursts from long-lived merger remnants, such as
flare-like eruptions and collapse-driven shocks, and quantify their impact on ejecta dynamics, composition, and observables. Using two-dimensional special-relativistic magnetohydrodynamic simulations, we follow magnetized blast waves injected into expanding merger ejecta for early- and late-launch scenarios across a range of shock strengths. We then post-process Lagrangian tracer histories with the
nuclear reaction network WinNet and the radiative-transfer code SuperNu with realistic opacities, to connect shock heating directly to nucleosynthesis and kilonova light curves. We find that sufficiently strong shocks can reheat portions of the ejecta to
nuclear statistical
equilibrium, increase the electron fraction in the shocked material, and deposit
entropy, leading to systematic changes in $r$-process yields. These thermodynamic and compositional changes can leave observable imprints on kilonova emission – especially in color
evolution and late-time light-curve behavior – indicating that magnetically driven remnant variability can potentially contribute to kilonova diversity.
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All authors Yuan Feng, Oleg Korobkin, Elias R. Most, Ananda F. Smith, Christopher J. Fontes
Earth and Planetary Astrophysics
The Range of Cumulative XUV Flux on GJ 1132 b
Rory Barnes, Laura N. R. do Amaral, Jessica Birky et al. (+4 more)
We investigate the plausible history of the XUV luminosity
evolution of the
planet-hosting M4
star GJ 1132 (~0.2
solar masses) to infer the cumulative incident XUV flux intercepted by the short-period (~1.6 d) Earth-sized transiting
planet GJ 1132 b. We include the dominant observational uncertainties, compare two quiescent XUV luminosity
evolution models, and simulate the XUV luminosity
evolution from
flares based on TESS data and a re-analysis of Kepler
stars. We find only 4
flares in GJ 1132's TESS 123 day lightcurve, which is relatively few for M
dwarfs and, in conjunction with the ~125 day period, suggests that this
star is many Gyr old. We find that all model permutations predict that the
planet has at least a 95% chance of receiving more than 50 times as much XUV flux as modern Earth, confirming that this
planet is a good candidate for permanent atmospheric loss. We also find that an empirical XUV model for M
dwarfs predicts 2-3 times more total XUV flux than a commonly used
solar twin model and that the empirical model's distribution is 2-3 times narrower.
Flares contribute about 20% of the cumulative XUV flux on
planet b, which, while modest, ensures the
planet lies firmly on the atmosphere-free side of the "
cosmic shoreline."
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All authors Rory Barnes, Laura N. R. do Amaral, Jessica Birky, James R. A. Davenport, Scott Engle, Megan Gialluca, Evgenya L. Shkolnik
Astrophysics of Galaxies
The slope of the power spectrum of the density field in isothermal supersonic compressible turbulence
Pierre Dumond, Jérémy Fensch, Gilles Chabrier et al. (+1 more)
The power spectrum (PS) of the density field in supersonic
turbulence is a fundamental quantity that characterizes the statistical properties of the structures formed in compressible flows. It is also widely used to estimate the Mach number in the interstellar medium from simulation-derived relations. In this paper, we provide a first quantitative explanation for the
evolution of the slope of the PS of the density field with the Mach number in homogeneous isotropic isothermal
turbulence using a time-invariant quantity derived by Chandrasekhar (1951). For simulated turbulent flows, the model reproduces the measured slopes for different widths of the inertial range and density variances very well. Our model also provides a comprehensive interpretation of the characteristic slopes of the PS of the density field measured in the interstellar medium. Based on these results, we stress that the Mach number cannot be reliably deduced from the slope of the PS of the density field. In closing, we discuss a resolution criterion that must be fulfilled to correctly simulate a turbulent flow with a given density PS slope.
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All authors Pierre Dumond, Jérémy Fensch, Gilles Chabrier, Noé Brucy
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Minimum lifetime of a black hole
Eugenio Bianchi, Matthew Brandsema, Kenneth Czuprynski et al. (+1 more)
We derive bounds on the lifetime of an evaporating black hole. The minimum lifetime bound follows from energy conservation and purification, within the framework of `asymptotically semiclassical spacetimes'. The recently derived expression for the Bondi flux of Hawking radiation, together with the expression for the
entanglement entropy of Hawking radiation at null infinity, is used to investigate the purification phase after the last semiclassical ray. We discuss the energy-cost of
entanglement purification and find a lower bound on the purification time of the black hole, which scales as $M_0^4/\hbar^{3/2}$, where $M_0$ is the initial black hole mass. Additionally, motivated by the Planck luminosity bound in
quantum gravity, we include the additional assumption that a Planck mass black hole is metastable. With this assumption, the purification time is in fact exponential in the square of the initial black hole mass, $\tau\sim\sqrt{\hbar}\,\exp(\gamma M_0^2/\hbar)$ with $\gamma>0$, i.e., exponential in its initial area. We find that the
redshift exponent is negative in this purification phase, which indicates the existence of a white-hole remnant that releases information slowly. We comment on phenomenological implications for
primordial black hole remnants.
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All authors Eugenio Bianchi, Matthew Brandsema, Kenneth Czuprynski, Daniel E. Paraizo
Astrophysics of Galaxies
Microlensing time-scales and flux magnification probabilities of a sample of 204 lensed quasars
F. Ávila-Vera, V. Motta and E. Mediavilla
Quasar microlensing is both a very useful tool in cosmology and astrophysics, and a source of uncertainty in some studies like the determination of the Hubble constant from lensed
quasars. Microlensing probability and time-scales have been statistically studied using as a reference scale the Einstein ring crossing time of an isolated mass. Our goal is to extend the statistical analysis of microlensing to all currently known lensed
quasars with available data, considering realistic optical depths and the gravitational effect of the lens
galaxy. We take into account new observational results about
quasar sizes and peculiar velocities of lens
galaxies. We apply automatic lens modeling to the 204 systems available. For each image, we compute microlensing magnification maps and histograms. Using thin disk source sizes scaled to take into account recent measurements of
accretion disk sizes, we find a mean source crossing time of $2.59\pm 0.07$ years. The mean Einstein radius crossing time is $ 11.29 \pm 0.05$ years. When a fraction of mass in microlenses $\alpha=0.2$ is adopted, we find a good matching between the modeled histogram of mean microlensing magnifications for the images in our sample and the experimental histogram of microlensing magnifications. From the modeling of microlensing magnification histograms, we estimate the average half-light radius of the
quasar source, $R_{1/2}=5.4\pm 2.7$ light-days, and a lower limit to the mass fraction in microlenses, $\alpha\ge 0.15$. From the microlensing magnification maps, we find that a lensed
quasar image has a mean probability of approximately 9% of being involved in a high-magnification event ($\Delta m \le -0.32$). We select a group of images with the largest probabilities and the smallest crossing times.
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Astrophysics of Galaxies
The Keplerian disk, envelope, and streamers surrounding an early O-type protostar in the Sagittarius C cloud of the Central Molecular Zone
Jixiang Weng, Xing Lu, Yu Cheng et al. (+22 more)
Disk-mediated
accretion is central to theories of massive
star formation, setting the initial conditions for their
evolution. Yet observations of Keplerian disks around early O-type protostars remain scarce, as they are often blended into complex surrounding structures. We report ALMA Band 6 observations (300 au resolution) of an
accretion disk surrounding a high-mass protostar in the Sagittarius C (Sgr C) cloud in the Central Molecular Zone (CMZ) around the
Galactic Center. We identify spectral lines and analyze the spatial distribution of the emission of the complex organic molecules. We use a dynamical model with an inner Keplerian disk and an outer free-fall envelope to fit the three-dimensional position-position-velocity data of the stacked CH$_3$OCHO molecular lines and constrain the mass of the central protostar to be $\sim40^{+2}_{-3} M_{\odot}$. The fitting results additionally show that the disk has a centrifugal radius at about 1300 au. Considering the infall velocity, radius, and mass of the envelope, we estimate the
accretion rate from the envelope onto the disk to be $\sim7\times 10^{-3}\ M_{\odot}\,\mathrm{yr^{-1}}$. We also identify spiral-like structures in the disk that can be described by free-falling streamers. Our results highlight the critical role of
accretion disks and streamers in the mass accumulation of early O-type
stars in the CMZ.
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All authors Jixiang Weng, Xing Lu, Yu Cheng, Hongping Deng, Xiaofeng Mai, Suinan Zhang, Cara Battersby, Adam Ginsburg, Elisabeth A.C. Mills, Yichen Zhang, Tie Liu, Thushara Pillai, Xindi Tang, Fernando Olguin, Hauyu Baobab Liu, Qizhou Zhang, Shanghuo Li, Guang-Xing Li, Patricio Sanhueza, Yunfan Jiao, Qilao Gu, Kai Smith, YanKun Zhang, Tianning Lyu, Zhiqiang Shen
Instrumentation and Methods for Astrophysics
Multipole Functions for Image Analysis II: Equal Area Weighting and Application to Supernova Remnant Images
D.A. Leahy, S. Ranasinghe, M. D. Filipovic et al. (+1 more)
New basis functions for 2 dimensional (2D) image analysis with a circular boundary (referred to as multipole analysis) are derived which are equal-area weighted. We present open access Python code hosted by GitHub, with which users can apply the multipole analysis to images. The new multipole analysis is applied to a set of 28
supernova remnants (SNRs) which are selected to have both
radio and X-ray images, and have been identified as Type Ia or Type CC. Each pair of SNR images (
radio and X-ray) was convolved to the same spatial resolution prior to analysis. The resulting multipole radial powers and angular powers, from order 0 to 5, for a given SNR are different for different multipoles and for a given multipole are different between X-ray and
radio images. The X-ray radial powers (for orders >0) are larger on average than the
radio radial powers (more radial structure in X-rays than
radio). The angular powers are smaller than the radial powers on average (more radial structure than angular structure). Comparing Type Ia and Type CC populations, the radial powers (for orders >0) are on average larger for Type CC than Type Ia for X-ray and
radio images, with larger difference for X-ray images. The angular powers (for orders >0) are similar between Type Ia and Type CC for both
radio and X-ray images.
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All authors D.A. Leahy, S. Ranasinghe, M. D. Filipovic, Z. J. Smeaton
Solar and Stellar Astrophysics
IRIS NUV diagnostics for Ellerman bombs: spectral properties, thermodynamics, and formation height
I. J. Soler Poquet, C. J. Díaz Baso, A. Sainz Dalda et al. (+3 more)
Context. Ellerman bombs (EBs) are observational signatures of small-scale
magnetic reconnection, key to understanding the lower
solar atmosphere. While their role in active regions has been widely studied using the H$\alpha$ line, near-ultraviolet (NUV) spectra routinely observed by the Interface Region Imaging Spectrograph (IRIS) offer a promising alternative for EB identification, enabling large-scale studies. Aims. We aim to identify the most important spectral signatures of EBs in the IRIS NUV spectra. With this, we seek to develop a robust criterion for their detection solely using the IRIS NUV spectra. In parallel, we determine the typical atmospheric stratification associated with EBs. Methods. We used four coordinated observations between the Swedish 1-m
Solar Telescope (SST) and IRIS. Using the H$\alpha$ line as a reference, we detected 18 different EBs and studied their associated IRIS NUV spectra. In addition, we used the IRIS$^{2+}$ inversion tool to infer the temperature, line-of-sight velocity, and non-thermal broadening from the EB spectra. Results. The defining feature of EBs in the IRIS NUV is the enhancement of the wings of the subordinated Mg II triplet in between the Mg II h&k lines. Inversions reveal that these signatures are produced by localized temperature increase of $\Delta$ T~1650 K around log$\tau$=-3.8. Using only the Mg II triplet signatures, we found a detection criterion that successfully recovered 14 of 18 H$\alpha$-detected EBs. In addition, the shape of the Mg II h&k lines in relation to the Mg II triplet can serve as a proxy for the EB formation height. Conclusions. The NUV spectrum observed by IRIS is a good candidate for detecting EBs, opening the doors to large-scale studies across the extensive IRIS database, removing the dependence on H$\alpha$ observations.
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All authors I. J. Soler Poquet, C. J. Díaz Baso, A. Sainz Dalda, L. H. M. Rouppe van der Voort, D. Nóbrega-Siverio, R. Joshi
Solar and Stellar Astrophysics
Unifying Transport Models of Thermohaline Convection in Stars
Valentin A. Skoutnev
Thermohaline convection is a standard chemical mixing process in
stellar interiors, yet its mixing efficiency is not fully settled. Competing theories predict turbulent
diffusion coefficients, $D_\mu$, that can differ by orders of magnitude, leading to uncertainties in
stellar models and interpretations of observations. This paper explores a potential resolution to existing discrepancies. We first complete the linear stability theory and identify two types of unstable modes: slow growing modes at large length scales and fast growing modes at small length scales. We then reevaluate $D_\mu$ considering the full spectrum of unstable modes and find that it can self-consistently interpolate between previously proposed theoretical scalings across the instability parameter space. The question of thermohaline mixing efficiency in
stars may be settled by future simulations that quantify the scale-dependent contributions of fast and slow modes to $D_\mu$ and determine how the modes dominating the transport change across parameter space.
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Cosmology and Nongalactic Astrophysics
New constraints on primordial non-Gaussianity from large-scale cross-correlations of CMB lensing and the cosmic infrared background
Joseph Thornton, Fiona McCarthy, Carmen Embil Villagra et al. (+1 more)
We present new constraints on the local-type
primordial non-Gaussianity parameter, $f_\mathrm{NL}^\mathrm{local}$, through analysis of the scale-dependent bias effect on the
cosmic infrared background (CIB). To avoid biases from
galactic dust contamination on large scales, we use cross-correlations between the CIB and Planck
cosmic microwave background (CMB)
lensing maps to constrain non-Gaussianity. Our measurement employs new
dust-cleaned CIB maps that have been designed to be unbiased on large scales, which allows us to improve our constraining power on $f_\mathrm{NL}^\mathrm{local}$ by a factor of $\sim 2$ over previous CIB analyses. We derive a constraint of $f_\mathrm{NL}^\mathrm{local}=43 \pm 23$, matching the precision of the tightest existing constraints from cross-correlation methods. Consistency- and null-tests demonstrate that our results are robust to modeling assumptions and residual
dust contamination.
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All authors Joseph Thornton, Fiona McCarthy, Carmen Embil Villagra, Blake D. Sherwin
Cosmology and Nongalactic Astrophysics
VERSUS: An excursion-set-inspired void-finder for the Stage-IV era
Nathan Findlay and Seshadri Nadathur
We present VERSUS, a publicly available, fast void-finding
algorithm designed to identify spherical underdensities in the density field that can be accurately described by excursion set predictions of the void size function. We validate the
algorithm against both a synthetic distribution of particles designed to trace a known input void population, and mock
galaxy sample built from a $(2\ h^{-1}\text{Gpc})^3$ AbacusSummit simulation populated with a realistic
galaxy-
halo connection, including systematic effects designed to mimic real survey data. In all cases, VERSUS demonstrates excellent performance, achieving strong agreement with theoretical predictions for the void size function across the range $25 < R \,[\ h^{-1}\text{Mpc}] < 61$ without requiring any post-processing of the void catalogue. The code is user-friendly, modular, and readily applicable to observational survey data. Its computational efficiency further enables the use of simulation-based modelling approaches, facilitating robust and consistent
cosmic void analyses with Stage-IV surveys.
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Cosmology and Nongalactic Astrophysics
Thermal activation rate of dilute axion stars close to the maximum mass
Pierre-Henri Chavanis
We compute the thermal activation rate of metastable self-gravitating Bose-Einstein condensates with attractive self-interaction (e.g., dilute
axion stars) by using the instanton theory. Explicit analytical results are given close to the maximum mass $M_{\rm max}$ [P.H. Chavanis, Phys. Rev. D 84, 043531 (2011)] by using the normal form of the saddle-node bifurcation close to that point. We show that the lifetime of metastable states is extremely long, scaling as $t_{\rm life}\sim e^N\, t_D$, where $N$ is the number of
bosons in the system and $t_D$ is the dynamical time ($N\sim 10^{57}$ and $t_D\sim 10\, {\rm hrs}$ for typical QCD
axion stars; $N\sim 10^{96}$ and $t_D\sim 100\, {\rm Myrs}$ for the
quantum core of a dark matter
halo made of ultralight
axions). Therefore, metastable
equilibrium states can be considered as stable
equilibrium states in practice. We compare our results with similar results obtained for Bose-Einstein condensates in laboratory, globular clusters and self-gravitating Brownian particles in astrophysics, the Brownian mean field model (BMF) in statistical mechanics, and bacterial populations in biology. Our presentation parallels the calculation of the
quantum tunneling rate of dilute
axion stars given in a previous paper [P.H. Chavanis, Phys. Rev. D 102, 083531 (2020)]. These calculations can find application in various domains of physics and astrophysics.
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Astrophysics of Galaxies
What is the Strouhal number of turbulence driven by supernovae?
James R. Beattie, Isabelle Connor and Enrico Ramirez-Ruiz
The Strouhal number, ${\rm{St}}=t_{\rm cor}/t_{\rm out}$, measures the temporal coherence of turbulent driving relative to the outer-scale eddy turnover time. In
turbulence-box models one commonly sets ${\rm{St}}=1$, although recent work by \citet{Grete2025_density_distribution} and \citet{Scannapieco2025_density_distribution} has shown that
turbulence statistics, especially the mass-density distribution in compressively driven
turbulence, are sensitive to this choice. In this Letter, we compute ${\rm{St}}$ directly from the measured two-time correlation tensor and outer-scale eddy time in stratified multiphase ISM simulations of Milky Way-like and starburst disks. We find isotropic median values ${\rm{St}}=0.26^{+0.30}_{-0.16}$ for the Milky Way-like model and ${\rm{St}}=0.25^{+0.11}_{-0.12}$ for the starburst model. These values are consistent with the picture that
supernova remnants (SNRs) drive
turbulence locally near $R_{\rm cool}$, where the unstable contact discontinuity in the expanding SNR sets comparable forcing and eddy times, ${\rm{St}}(R_{\rm cool})\approx 1$. The reconstructed scale-dependent curves reach ${\rm{St}}=1$ at a nearly universal outer-scale fraction, $\ell_\ast/\ell_{\rm out}\approx0.12\text{--}0.13$ ($\ell_\ast\approx25\text{--}32\,\rm{pc}$), so the standard ${\rm{St}}=1$ prescription is not an outer-scale model of SN-driven ISM
turbulence, but a local-scale approximation tied to injection near the cooling radius of the SNR.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Resonances as signatures of scalar clouds in eccentric extreme-mass-ratio inspirals
Qi-Xuan Xu, Richard Brito, Riccardo Della Monica et al. (+2 more)
Ultralight scalars arise naturally in many extensions to the Standard Model and are compelling dark matter candidates. Around spinning black holes, dense scalar clouds could form through the conversion of rotational energy into particles via black hole superradiance. Extreme-mass-ratio inspirals (EMRIs) targeted by future space-based detectors will give us unparalleled access to the environments of massive black holes, allowing us to probe the presence of scalar clouds. We consider EMRIs around a Schwarzschild black hole and show that eccentricity induces a dense sequence of resonances in the scalar fluxes near the last stable orbit. These resonances arise only in a fully relativistic treatment, as they are intrinsically tied to the splitting between the azimuthal and radial orbital frequencies in the strong-field regime. By evolving the orbits adiabatically, we show that the resulting resonant transitions substantially enhance the exchange of energy and angular momentum between the EMRI and the scalar cloud, significantly amplifying the accumulated dephasing in the gravitational waveform relative to circular motion. Our results highlight the importance of eccentricity in shaping the observational signatures of EMRIs embedded in scalar clouds.
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All authors Qi-Xuan Xu, Richard Brito, Riccardo Della Monica, Rodrigo Vicente, Chen Yuan
Earth and Planetary Astrophysics
PALEOS: Multiphase equations of state and mass-radius relations for exoplanet interiors
Mara Attia, Tim Lichtenberg, Ema Jungová et al. (+1 more)
Modeling the interior of a rocky or water-rich
exoplanet is a thermodynamic closure problem: every layer's density, temperature gradient, and phase must follow from an equation of state (EoS) that remains self-consistent across the pressure-temperature range from surface to core. Existing EoS span disciplines, use different formalisms, and rarely supply the full thermodynamic quantities needed by evolutionary models of interior phase transitions. We present PALEOS (Planetary Assemblage Layers: Equations of State), an open-source toolkit consolidating EoS for iron, magnesium silicate (MgSiO$_3$), and water (H$_2$O) into a unified, phase-aware, thermally responsive framework spanning 17 phases. PALEOS derives density, energy,
entropy, heat capacities, thermal expansion, and the adiabatic gradient analytically via Maxwell relations, and is released as lookup tables on regular P-T grids. We validate it against the Preliminary Reference Earth Model, recovering Earth's radius to 0.3% and lower-mantle densities to 3%, and compute 17,900 mass-radius relations from 0.1 to 100 $M_\oplus$ for rocky (Fe + MgSiO$_3$) and water-rich (Earth-like core + H$_2$O envelope) compositions at 300-4000 K. Continuous solid-to-melt EoS let thermal expansion span the fully-solid to magma-ocean regime: the radius offset exceeds 1% above 1500 K and reaches 16% at 4000 K for low-mass silicate
planets, comparable to composition degeneracy and transit-radius uncertainties. We demonstrate this on two ultrashort-period super-Earths, WASP-47 e and TOI-1807 b: each admits two purely rocky solutions indistinguishable in mass and radius but in radically different states, one fully solid with no dynamo, the other hosting a deep magma ocean and a
liquid iron core capable of sustaining a
magnetic field. Phase-aware, thermally resolved EoS are essential for translating astronomical observations into exoplanetary geophysics.
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All authors Mara Attia, Tim Lichtenberg, Ema Jungová, Mariana Sastre
Astrophysics of Galaxies
Modeling the UV-photon irradiation of CS$_2$-bearing ices in the laboratory with the pyRate gas-grain astrochemical code. New insights into the missing sulfur problem
O. Sipilä, R. Martín-Doménech, W. Riedel et al. (+4 more)
Observations indicate that the total abundance of S-bearing species in dense clouds is orders of magnitude lower than the
cosmic sulfur abundance. Addressing this "missing sulfur problem" requires a combination of astronomical observations, laboratory experiments, and theoretical models. In this work, we use the pyRate astrochemical model to simulate the VUV
photon irradiation of a CO$_2$:CS$_2$ ice mixture at 10 K in the laboratory, with the goal of supporting the interpretation of the experimental results and testing our current understanding of the sulfur
evolution in interstellar ices. For this purpose, the astrochemical model was adapted to the experimental conditions, and the chemical network was compiled from several sources to ensure that all known reactions involving sulfur species were included. The results indicate that nondiffusive chemistry is necessary to reproduce the formation of S-bearing species observed in the experiment. However, some discrepancies were found in the major S-bearing ice chemistry products predicted by the model and the experiment. The compounds OCS, CS, and SO are overpredicted by the model, while it falls short in accounting for $\rm SO_2$ and sulfur allotropes. These discrepancies are likely due to a combination of an incomplete knowledge of the chemical reactions at play (either because of missing reactions and/or because of unconstrained reaction barriers), and uncertainties in the experimental analysis. This work represents the first effort to model the chemistry of a multicomponent ice analog with a rate-equation based code, and highlights the complementary nature of theoretical and experimental astrochemistry to disentangle the chemical
evolution of sulfur in the interstellar medium.
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All authors O. Sipilä, R. Martín-Doménech, W. Riedel, D. Navarro-Almaida, A. Fuente, A. Taillard, G.M. Muñoz Caro
Instrumentation and Methods for Astrophysics
The First Look of Gaia: Daily data quality and instrument health assessment with automated early warnings
M. Altmann, Z. Balog, W. Löffler et al. (+15 more)
The ESA
Gaia mission is a 10+ year astrometric whole-sky scan, demanding consistent data quality over the whole timespan of operations Aims. The
Gaia First Look (FL) is a system whose aim is monitoring the data quality to identify problems, which includes early warning capabilities for potential upcoming issues. Methods. In order to achieve its goals, the
Gaia FL implemented its own limited astrometric solution, and used the daily calibrations from other segments of the Data Processing and Analysis Consortium (DPAC), as well as the diagnostic data from the satellite itself, in order to obtain a complete picture of the situation of the
Gaia satellite on a daily basis. This led to a short-term health and data quality check, but also to a broader overview of the longer-term trends and evolutions within the payload. Potential issues that were encountered were reported to other groups within DPAC for further analysis purposes. When required, ways to mitigate the problems were discussed, and implemented. Results. We show a number of findings by the
Gaia FL concerning longer-term
evolution, individual but common effects, as well as detrimental impacts, all of which occurred over the operational phase of the
Gaia mission
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All authors M. Altmann, Z. Balog, W. Löffler, U. Bastian, M. Biermann, A. Sagrista Selles, M. Davidson, N. Rowell, E. Serpell, A. Abreu Aramburu, T. Brüsemeister, C. Crowley, M. Hauser, S. Jordan, J. Martín-Fleitas, A. Mora, E. Fernandez del Peloso, U. Stampa
Earth and Planetary Astrophysics
A public dataset of Ariel simulated observations for developing exoplanetary atmosphere data reduction pipelines
Lorenzo V. Mugnai, Kai Hou Yip, Andrea Bocchieri et al. (+7 more)
Detecting and characterising
exoplanet atmospheres remains challenging because atmospheric signals can be comparable to residual noise and instrumental/astrophysical systematics. Spectral features span from a few ppm for small
planets up to $\sim 10^3$ ppm for warm/hot
giants, while high-quality JWST time-series spectroscopy typically reaches $\sim 10$–$50$ ppm (occasionally $\sim 100$–$200$ ppm in the presence of
stellar variability or stronger systematics), making correlated noise across temporal and spectral dimensions a key limitation. With JWST delivering an increasing volume of high-precision transmission spectra, and Ariel set to extend this to a homogeneous survey of $\sim 10^3$
exoplanet atmospheres, robust benchmarking resources with known ground truth are essential to develop and validate data-driven (including ML-based) detrending approaches. As a major step towards this goal, we use ExoSim2 and TauREx to generate one of the most comprehensive public
datasets based on the current payload design of the ESA Ariel mission, specifically intended to
benchmark detrending
algorithms. We also provide a deep neural network baseline for time-series reduction, and use it to highlight the limitations of ML based detrendng methods, i.e. the risks posed by
dataset shift when observed distributions diverge from those of the training set, a scenario likely to arise in real observations. This
dataset is featured in the Ariel Data Challenge 2024 on Kaggle and has been field-tested for robustness and simulation fidelity. By making these resources publicly available, we aim to support the community in developing, comparing, and stress-testing scalable and reliable methods for
exoplanet transmission spectroscopy.
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All authors Lorenzo V. Mugnai, Kai Hou Yip, Andrea Bocchieri, Andreas Papageorgiou, Virginie Batista, Orphée Faucoz, Angèle Syty, Tara Tahseen, Enzo Pascale, Ingo Waldmann
Astrophysics of Galaxies
Not So Isolated: Green Pea Galaxies in Overdense Environments revealed by VLT/MUSE
A. Arroyo-Polonio, J.M. Vílchez, J. Iglesias-Páramo et al. (+9 more)
Context. Green Pea
galaxies (GPs) are local starburst
galaxies serving as analogues for high-
redshift star-forming
galaxies, particularly Lyman continuum leakers. It remains debated whether their starbursts are driven by internal secular processes or external triggers. Aims. We aim to constrain the role of environment in this triggering, testing whether external influence comes from close interactions or diffuse processes like gas
accretion. Methods. We analyse VLT/MUSE observations of 24 GPs at $z \sim 0.2$ to identify companions via spectral line features. We derive key physical properties (extinction, SFR,
stellar mass, age,
metallicity) for GPs and companions, and estimate group dynamical masses. Results. We identify 22 emission-line
galaxies, 11 being companions ($|\Delta v| \leq 500$ km s$^{-1}$). We find a high companion fraction ($33^{+11}_{-8}$%) and a $\sim$1 dex number density excess compared to the field, confirming GPs reside in overdense environments. Companions typically lie at projected separations of $\sim$100 kpc with no evidence of ongoing interactions. Physically, GPs form a homogeneous class of young (mass-weighted age $\sim$230 Myr), metal-poor, high-sSFR starbursts with elevated velocity dispersions. In contrast, companions are more evolved ($\sim$1.6 Gyr) and heterogeneous in
stellar mass,
metallicity, and
dust attenuation. Inferred group dynamical masses are $\sim$3 dex higher than total
stellar masses, suggesting significant dark matter and neutral gas. Conclusions. GPs do not appear triggered by ongoing major mergers with close (10-30 kpc) companions. Results favor a scenario where GPs are transient starbursts in overdense regions, plausibly sustained by gas
accretion. Limited spatial resolution prevents ruling out very close mergers ($\lesssim 10$ kpc). High dynamical-to-
stellar mass ratios imply substantial non-
stellar mass in these systems.
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All authors A. Arroyo-Polonio, J.M. Vílchez, J. Iglesias-Páramo, C. Kehrig, E. Pérez-Montero, R. Amorín, B. Pérez-Díaz, M. Hayes, I. Breda, J. Sánchez Almeida, A. Giménez Alcazar, M. González-Otero
Cosmology and Nongalactic Astrophysics
The JWST early galaxy crisis resolved by a reionization degeneracy
Zihan Wang and Huanyuan Shan
JWST's discovery of unexpectedly bright $z>10$
galaxies has triggered claims that standard $\Lambda$CDM cannot reproduce their abundances, while estimates of the ionizing escape fraction $f_{\rm esc}$ at $z>6$ have spanned a factor of four for over a decade. Here we show that both tensions arise from a structural degeneracy in reionization equations: global observables constrain only the product $f_{\rm esc}\times f_{\star,0}$ (peak
star formation efficiency), not individual parameters. We demonstrate that this degeneracy, previously considered a limitation, provides a precise diagnostic framework. By leveraging JWST UV luminosity function shapes to independently constrain $f_{\star,0}$, we derive robust bounds on $f_{\rm esc}$. Joint profile-likelihood analysis across Gaussian, log-normal, and duty-cycle burst scatter models excludes the proposed crisis threshold ($\varepsilon > 3.5\%$) at $4.5\sigma$ confidence, with
stochastic star formation histories strengthening rather than weakening the result. Combining these constraints with constant and evolving $f_{\star,0}$ measurements yields the first empirical reconstruction of $f_{\rm esc}(z)$ across $z=7$–$12$. A constant-efficiency scenario ($f_{\rm esc}\approx 10$–$16\%$) connects smoothly to low-
redshift direct detections, whereas an evolving scenario ($f_{\rm esc} \approx 6\%$ at $z=12$) conflicts with low-
metallicity ISM porosity expectations. JWST Cycle 3–4 will distinguish these pathways at $>2\sigma$, transforming a long-standing fundamental inference barrier into a powerful quantitative probe of early-universe physics.
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High Energy Astrophysical Phenomena
Nicolas Grimbaum Yamamoto
Among the few ways to probe the early Universe,
neutrinos offer a particular window on high energy phenomena occurring before recombination. We discuss the opportunities of observing
primordial high energy
neutrinos (Phenus):
neutrinos produced before or around recombination from the decay or annihilation of long-lived relics, arriving at detectors today with energies in the GeV-PeV range. We summarise the results of a general study of this scenario, covering the sharp spectral features such fluxes would display, the theoretical (BBN and CMB) and experimental constraints on the source particle parameter space, and the regions that could realistically be probed by current and future
neutrino telescopes. We also present a dedicated Monte Carlo code for computing the distortion of the Phenu spectrum by final state radiation and interactions with the
cosmic neutrino background during propagation, and apply it to assess the
primordial origin hypothesis for the KM3-230213A ultrahigh energy
neutrino event.
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Astrophysics of Galaxies
Reddening maps of the Magellanic Clouds using spectral energy distribution fitting of red giants
H. Netzel, G. Pietrzyński, M. Górski et al. (+9 more)
Robust reddening maps of the Large and Small Magellanic Clouds (LMC/SMC) are crucial for a wide range of astrophysical studies, including the calibration of the
cosmic distance ladder, investigations of
stellar populations in low-
metallicity environments, and the characterization of interstellar
dust properties. We aim to construct reddening maps of the Magellanic Clouds using spectral energy distribution (SED) fitting, and to investigate the impact of different
stellar atmosphere models on the resulting maps. We combined optical ($ugriz$) photometry from the SMASH survey with near-infrared ($YJK_{\rm s}$) photometry from the VMC survey for red
giant branch (RGB)
stars. Observed SEDs were matched to synthetic photometry derived from three atmosphere model grids. Our maps cover 34.5 deg$^2$ of the LMC and 24.5 deg$^2$ of the SMC at 4 arcmin resolution. We find mean reddening values of $E(B-V)=0.076 \pm 0.022$ mag for the LMC and $0.058 \pm 0.024$ mag for the SMC. We found that employing different atmospheric models results in differences up to 0.03 mag in the mean reddening. Canonical $R_V$ values for the Magellanic Clouds (3.41 for LMC and 2.74 for SMC, Gordon et al. 2003) provide results consistent with previous studies. We confirm higher and more structured reddening in the LMC compared to the SMC, with 30 Doradus standing out as the dominant high-reddening region. Our results show that the absolute reddening scale depends on the choice of
stellar atmosphere models, while the relative spatial structure of the reddening maps remains stable.
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All authors H. Netzel, G. Pietrzyński, M. Górski, P. Kervella, G. Hajdu, R. Kudritzki, R. Chini, W. Kiviaho, B. Zgirski, P. Wielgórski, D. Graczyk, W. Gieren
Astrophysics of Galaxies
Optical Variability Structure Function of Low-Luminosity AGN using ATLAS Lightcurves
Ashley Hai Tung Tan, Christian Wolf, Neelesh Amrutha et al. (+3 more)
The origin of the optical flux variability in active
galactic nuclei (AGN) is largely unknown. Previous studies have correlated features of the variability structure function (SF) with AGN properties, though they mostly involved high-luminosity AGN to avoid biases from host
galaxy flux. In this work, we characterise optical variability in a sample of 246 low-luminosity AGN at $z < 0.1$ from the Six-degree Field
Galaxy Survey (6dFGS) through the ensemble variability SF. We use lightcurves from the Asteroid Terrestrial-impact Last Alert System (ATLAS) with a cadence of $\sim$2 days over eight years, and perform host-AGN decomposition on recent spectra to obtain the host fraction. We find that the slope of the SF depends on black hole mass, increasing from $\sim 0.1$ at $\log M_{\mathrm{BH}}/M_\odot \sim 6.5$ to $\sim 0.3$ at $\log M_{\mathrm{BH}}/M_\odot \sim 8$. Contrary to some earlier work, we do not find breaks in the SF, and two-epoch spectra taken 20 years apart suggest that the SF keeps rising into decadal timescales. In addition, we measure an anticorrelation of the amplitude with the luminosity and a positive correlation with the black hole mass. The variability behaviour also suggests that extinction is not the main driver of the variety in Seyfert subtypes.
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All authors Ashley Hai Tung Tan, Christian Wolf, Neelesh Amrutha, Christopher A. Onken, John L. Tonry, Rachel Webster
Astrophysics of Galaxies
The Significant Role of Hydrogen in the Formation of Silicon Carbide in Evolved Stars
Guillermo Tajuelo-Castilla, Gonzalo Santoro, Lidia Martínez et al. (+13 more)
Cosmic dust is mainly formed in the atmospheres of evolved
stars. In carbon rich
stars, amorphous carbon along with silicon carbide are the main constituents of
dust grains yet the mechanisms involved in the formation of these grains are still poorly understood. Several molecular precursors have been proposed to form silicon carbide grains. Here, we have simulated in the laboratory the formation of silicon carbide
dust starting from atomic C, atomic Si and H$_2$ and we have clearly identified SiC$_2$ as a key molecular precursor of nanodust analogues. We show that the interaction of molecular hydrogen with atomic carbon initiates the formation of hydrocarbons, which then react with atomic silicon to produce gas-phase SiC$_2$. In our experiments, the silicon carbide nanodust analogues are partially hydrogenated. Chemical routes for the formation of SiC$_2$ and organosilicon species are discussed on the basis of thermochemical calculations and chemical kinetics modelling. Our findings reveal the central role of molecular hydrogen in the formation of SiC$_2$ and contribute to a deeper understanding of silicon carbide
dust formation processes in evolved
stars, from atoms to molecules, clusters, and ultimately
dust grains.
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All authors Guillermo Tajuelo-Castilla, Gonzalo Santoro, Lidia Martínez, Pablo Merino, José Ignacio Martínez, Pedro L. de Andres, Gary J. Ellis, Álvaro Mayoral, Ramón J. Peláez, Isabel Tanarro, Marcelino Agúndez, Sandra Wiersma, Hassan Sabbah, José Cernicharo, Christine Joblin, José Ángel Martín-Gago
Instrumentation and Methods for Astrophysics
Iterative Poisson Solvers for Self-gravity with the GPU Code Astaroth
Ruben Krasnopolsky, Touko Puro, Wei-Wen Li et al. (+5 more)
We present the development and benchmarking of Poisson solvers for graphics processing units (GPUs). Implemented in the Astaroth platform, the solvers feature high computational efficiency. We present novel combinations of discretizations and smoothers and document practical and performance-focused implementations aimed at reducing time-to-solution for self-gravitating systems. We describe the solver architectures and validate their accuracy against known analytic solutions. We measure convergence and timing per iteration for various solver
algorithms, including conjugate gradient, successive overrelaxation, and multigrid in Cartesian coordinates, along with biconjugate gradient stabilized in spherical coordinates. We also couple the solvers to the Astaroth hydrodynamics to simulate a classic time-dependent problem in
star formation, measuring accuracy and time-to-solution, for self-
gravity on three-dimensional structured grids. Our results demonstrate that the solvers achieve performance similar to other
algorithms implemented in Astaroth, and provide a solid foundation for integration into production-scale astrophysical simulations.
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All authors Ruben Krasnopolsky, Touko Puro, Wei-Wen Li, Hsien Shang, Miikka S. Väisälä, Mordecai-Mark Mac Low, Matthias Rheinhardt, Maarit Korpi-Lagg
High Energy Astrophysical Phenomena
The Cocoon from a Massive Star's Death: VLA Radio Polarization Study of Possible Historical Supernova Remnant G7.7$-$3.7
Tian-Xian Luo, Ping Zhou, C.-Y. Ng et al. (+3 more)
G7.7$-$3.7 is a possible historical SNR, with the origin of its cocoon-like morphology and its
supernova type remaining unclear. We performed L-band
radio polarization observations of G7.7$-$3.7 using the Very Large Array in C and B-configurations. The high-resolution 1.4 GHz continuum image reveals a cocoon-like morphology with multiple shells and faint blowout structures. The total flux density is 9.6$\pm$0.5 Jy and the spectral index map shows predominantly nonthermal emission, with an integrated spectral index of $-$0.38$\pm$0.04. Polarization images of G7.7$-$3.7 show high linear polarization fraction (30%-40%) in the northwestern filaments and moderate polarization (10%-20%) in the northeast and south. The
magnetic fields aligned with the filamentary structures, consistent with shock compression. Large rotation measure (RM) variations across the SNR likely originate from magnetized massive progenitor winds. We suggest that the cocoon-like morphology results from the interaction between the SNR and pre-existing circumstellar shells, demonstrating that the
radio polarization provides useful constraints on the environments and even the progenitor mass-loss.
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All authors Tian-Xian Luo, Ping Zhou, C.-Y. Ng, Zhi-Yu Zhang, Shumeng Zhang, Hai-Chen Lin