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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 31 July

Earth and Planetary Astrophysics

Towards Autodifferentiable Point Spread Function Modelling for the VLT/ERIS Vortex Coronagraph

P. Van de Walle Suarez, G. Orban De Xivry, O. Absil et al. (+3 more)

High-contrast imaging of exoplanets is limited by the presence of quasi-static speckles and existing post-processing methods remain above the theoretical noise limit. We investigate a novel framework that incorporates adaptive optics (AO) wavefront sensor telemetry into post-processing using a differentiable optical model of the ERIS vortex coronagraph. As a first proof of concept, we inject AO telemetry into an ERIS forward model and assess its ability to reproduce the on-sky point spread function (PSF). We find that jitter discrepancies between the science camera and the AO telemetry hinder accurate PSF reconstruction. We proposed a plan to characterise this jitter and find its mechanical origin.
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All authors P. Van de Walle Suarez, G. Orban De Xivry, O. Absil, M. J. Bonse, R. J. De Rosa, V. Christiaens

Astrophysics of Galaxies

The TOP-SCOPE Survey of Planck Galactic Cold Clumps: Molecular gas properties

Yuebin Yang, Jarken Esimbek, Tie Liu et al. (+11 more)

We surveyed 2008 Planck Galactic Cold Clumps (PGCCs) in $^{12}\mathrm{CO}$ and $^{13}\mathrm{CO}$ $J=1$–0 lines using the Taeduk Radio Astronomy Observatory (TRAO) 14 m telescope's multi-beam receiver. We detected 2784 ($^{12}\mathrm{CO}$) and 2291 ($^{13}\mathrm{CO}$) velocity components, their closely correlated centroid velocities suggest that $^{12}$CO and $^{13}$CO generally trace kinematically associated gas. PGCCs have low excitation temperatures (mean $\sim$10 K), mean $^{13}\mathrm{CO}$ optical depth $\sim$0.5, and mean $^{13}\mathrm{CO}$-derived H$_2$ column density $4.3\times10^{21}$~cm$^{-2}$. Gas–dust correlations are moderate, with $N_{^{13}\mathrm{CO}}$ more tightly correlated with the dust-derived H$_2$ column density from the PGCC catalog than $I_{^{12}\mathrm{CO}}$. Colder PGCCs tend to have higher CO-to-H$_2$ conversion factor ($X_{\mathrm{CO}}$) and $[\mathrm{H_{2}}]/[^{13}\mathrm{CO}]$ ratio. $X_{\mathrm{CO}}$ increases clearly with the dust-derived H$_2$ column density, consistent with enhanced CO freeze-out in high-column-density gas. Supersonic non-thermal motions are widespread: the Mach number derived from $^{13}\mathrm{CO}$ has a mean of 4.3 and a median of 3.6, increasing slightly with dust-derived H$_2$ column density. Overall, PGCCs are cold but dynamically active, serving as a valuable laboratory for studying the initial conditions of star formation.
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All authors Yuebin Yang, Jarken Esimbek, Tie Liu, Willem Baan, Xunchuan Liu, Kee-Tae Kim, Gang Wu, Xindi Tang, Jianjun Zhou, Dalei Li, Yuxin He, Sung-ju Kang, Yingxiu Ma, Dongdong Zhou

Astrophysics of Galaxies

ROLLIN': Rotating globular cluster simulations II. The complex morphology of globular clusters driven by multi-scale dynamics

Arn Marklund, Paolo Bianchini, Anna Lisa Varri et al. (+2 more)

Globular clusters (GCs) are inherently non-spherical systems that in many cases show internal rotation. Typically, rotation is considered the main driver of GC morphology; however, the relationship between ellipticity and rotational support is not a simple one-to-one mapping, and other multi-scale dynamical processes may contribute. We investigate how morphology evolves in realistic models of rotating GCs, and how it correlates with key physical ingredients, including mass loss, stellar evolution, external tidal fields, and two-body relaxation. Using the ROLLIN' suite of direct N-body simulations, we measure the intrinsic ellipticity and triaxiality of our models using the second-moment tensor method, and explore their evolution and the physical mechanisms driving them. We find that early GC evolution can be dominated by dynamical instabilities driven by internal rotation and velocity anisotropy, leading to bar-like structures that rapidly erode due to collisional effects around the time of the first core collapse. These bars are stronger and longer-lived ($\lesssim 800,\mathrm{Myr}$) in strongly rotating clusters with longer relaxation times and subject to stellar evolution. In the long term, clusters evolve toward less flattened and gradually triaxial configurations, particularly when they experience stronger mass loss, are more tidally filling and isotropic, and have lower rotational support. Our models provide a physical explanation for the observational $V/\sigma$–ellipticity relation and demonstrate that morphology can serve as a reliable tracer of the dynamical state of GCs. Initially retrograde, dense, and inclined rotating models deviate from this relation, providing a physical explanation for observational outliers. This framework will aid the interpretation of GC evolution in upcoming large-scale photometric surveys.
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All authors Arn Marklund, Paolo Bianchini, Anna Lisa Varri, Katarina Kraljic, Giulia Pagnini

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

The price for monopole dark matter

Felix Brümmer, Giacomo Ferrante, Théodore Fischer et al. (+1 more)

We construct an explicit model where dark matter consists of 't Hooft-Polyakov monopoles. The dark sector is in thermal contact with the Standard Model, and dark monopoles are created by a thermal phase transition in the early Universe. Generically, the abundance of monopoles is negligible with respect to that of stable dark elementary particles. We show how to avoid this by taking the lightest stable particle, a dark fermion, sufficiently light for its abundance to be suppressed, yet heavy enough to satisfy constraints on dark radiation. In this specific window of parameters, dark matter is composed of monopoles with a mass of about $10^8$ GeV or larger, depending on the nature of the phase transition. This candidate lies beyond the reach of present, conventional dark-matter detection experiments. However, the model necessarily predicts dark radiation, with $\Delta N_{\rm eff}$ close to present-day bounds. In addition, if the dark phase transition is strongly first order, we find that the corresponding gravitational wave spectrum lies close to the region probed by future interferometers.
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All authors Felix Brümmer, Giacomo Ferrante, Théodore Fischer, Michele Frigerio

Solar and Stellar Astrophysics

Spectroscopic Analysis of the 2025 Eclipse of the Symbiotic Binary V1413 Aquilae

David Boyd, James Foster, Forrest Sims et al. (+12 more)

We report on a coordinated campaign by amateur astronomers using a combination of high and low resolution spectroscopy to observe the 2025 eclipse of the symbiotic binary V1413 Aql shortly after a probable Z And-type symbiotic outburst. We measured the eclipse time of minimum and computed an updated eclipse ephemeris. Our spectra were calibrated in absolute flux and multi-Gaussian fits were used to resolve and quantify components of the H{\alpha} emission line. We measured the radial velocity curve of the white dwarf and determined the semi-amplitude as 25.7 km/s and the systemic radial velocity as 95.1 km/s. We found the spectral continuum was consistent with that of a late F or early G type giant star.
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All authors David Boyd, James Foster, Forrest Sims, David Cejudo, Robin Leadbeater, Pavol Dubovsky, Xavier Dupont, Keith Shank, David Trowbridge, Jerry Hinnefeld, Colin Eldridge, Joan Guarro Flo, Kevin Gurney, Gary Walker, Josch Hambsch

High Energy Astrophysical Phenomena

Gamma-ray emission from particle illumination and shock-cloud interaction in the W51 Complex

Alan Sunny and Martina Cardillo

In the current era of very-high-energy (VHE) and ultra-high-energy (UHE) $\gamma$-ray astronomy, understanding Galactic PeVatrons and their acceleration mechanisms remains a primary objective. Recent LHAASO observations of the W51 Complex make it an ideal laboratory for investigating the origin of UHE emission, particularly due to the presence of massive and dense molecular environment surrounding multiple potential particle accelerators. In this work, we study two hadronic scenarios for the W51 Complex. First, we model the direct interaction between the SNR W51C and the nearby clouds in W51B, incorporating fresh particle acceleration, shock-driven adiabatic compression, and reacceleration of permeating Galactic cosmic rays. Second, we explore an accelerator-independent illumination scenario in which the W51B cloud acts as a long-term confinement region for high-energy particles injected during an earlier epoch. We find that the direct shock-cloud interaction scenario successfully reproduces the GeV emission observed by Fermi-LAT, but fails to account for the UHE emission detected by LHAASO. In contrast, the illumination scenario naturally explains the UHE spectrum, indicating that dense molecular clouds can efficiently confine and sustain energetic hadronic populations over long timescales. Although the inferred injection history is compatible with a young SNR origin, the source-independent nature of the illumination framework also permits other accelerators within the W51 Complex. Our results therefore identify dense molecular environments as the key structures sustaining historical PeVatron activity and shaping the observed UHE $\gamma$-ray emission.
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Earth and Planetary Astrophysics

Twin Impact Lunar Telescope network: Lunar Impact Flash observations of the 2025 Geminids

Daniel Sheward, Marco Delbo, Chrysa Avdellidou et al. (+23 more)

Meteoroid impacts on the Moon, observed from Earth as flashes typically lasting a few tens of milliseconds, have been monitored for three decades for determining meteoroids' size and mass frequency distribution in the cm to dm range. Studies link these observed impact events to fresh craters advancing our understanding of energy partitioning during an impact. Currently we are transitioning to a new era where lunar impact flashes (LIFs) can be used to supplement upcoming lunar seismology to study the internal lunar structure. Here we present results from the first station of a telescope network under development for continuous LIF monitoring. Observations were carried out during the Geminids 2025 campaign, initiated by the LUMIO Science Team in the framework of their public engagement activities. We detected 53 potential impact flashes and confirmed 11 of them through multiframe observations, and independent detections by other observers. We present evidence suggesting that some of the yet unconfirmed events may be real. Our confirmed events range between magnitude +7.5 and +10.4, primarily in the V and R band. We obtained a high rate of observations per hour, highlighting the importance of high ZHR meteoroid streams for observing LIFs. We also discuss the scientific value of potential LIFs that remain unconfirmed in optical data alone. Even without multi station confirmation, these events can correlate to seismic signals in future lunar seismic networks, thereby providing useful physical constraints on impact processes. This approach would also allow stations equipped with a single telescope/camera to meaningfully contribute to the network.
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All authors Daniel Sheward, Marco Delbo, Chrysa Avdellidou, Philippe Lognonné, Jeremie Vaubaillon, Pierre-Yves Froissart, Christelle Saliby, Paul Girard, Nicolas Mauclert, Bruno Mongellaz, Laurent Herrier, Nicolas Anfosso, Thierry Parra, Fausto Giacometti, Andrea Ferrero, Jean-Pierre Rivet, Elisa Maria Alessi, Anthony Cook, Detlef Koschny, James Dawson, Chris Hooker, Alex Pratt, Michael O'Connell, Aldo Tonon, Vincenzo della Vecchia, Luigi Zanatta

Solar and Stellar Astrophysics

The Fe I 4377 Å Line as a Solar Faculae Indicator: Insights from Spectral Ratio Analysis

Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes et al. (+21 more)

Faculae are a dominant source of stellar activity noise in radial velocity measurements, yet their low contrast and broad surface distribution make them difficult to track in disc-integrated observations. We apply Spectral Ratio Analysis (SRA) to HARPS-N Sun-as-a-star observations to isolate and characterize the spectral imprint of facular regions over rotational timescales. The resulting SRA spectra show coherent, line-dependent variability sensitive to surface magnetic activity, with the Fe I 4377 Angstrom line exhibiting a particularly strong diagnostic response to facular coverage. We interpret the observed signatures using two complementary synthetic frameworks: composite PHOENIX spectra, from which we derive best-fit facular temperature contrasts in the range 200-400 K, and MPS-ATLAS spectra synthesized using MURaM simulations of the quiet Sun including a small-scale dynamo and magnetically-enhanced facular analogues with initial mean vertical magnetic fields of 100G, 200G, and 300G. Both approaches are benchmarked against facular filling factors measured from Solar Dynamics Observatory (SDO) disc-resolved images. We find good agreement between SDO-measured and SRA-inferred filling factors using the Fe I 4377 Angstrom line, with Pearson R coefficients of 0.587-0.927 across models and timescales. The estimated filling factors track the solar activity cycle, rising from ~1.5% at lower activity to ~5.5% at higher activity, consistent with SDO-measured filling factors. These results demonstrate that SRA offers a means to reliably track surface magnetic activity in disc-resolved spectra, which is necessary for mitigating the effects of activity on RV characterization of exoplanet masses and atmospheres at modern precision.
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All authors Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes, Yvonne Unruh, Dana Clarice Yaptangco, Krishnamurthy Sowmya, Mitchell E. Young, Ernst J. W. de Mooij, Alexander G. M. Pietrow, Pál Váradi Nagy, Alexander I. Shapiro, Veronika Witzke, Federica Rescigno, Ryan A. Rubenzahl, Megan Bedell, Andrew Collier Cameron, Xavier Dumusque, Sean M. O'Brien, Benjamin M. J. Cadell, Baptiste Klein, Niamh Mallaghan, Niamh K. O'Sullivan, Toby Rodel, Sara Tavella

High Energy Astrophysical Phenomena

Rates of tidal disruption events from constrained cosmological simulations of the local Universe: population properties and implications for transient surveys

Julian S. Sommer, Ildar Khabibullin, Klaus Dolag et al. (+4 more)

(abridged) Motivated by upcoming surveys like LSST, we estimate tidal disruption event (TDE) rates using the constrained cosmological Simulation of the LOcal Web (SLOW) to test the limitations of traditional 2D analytical extrapolations within a fully 3D framework. We aim to provide reliable TDE budgets extracted from the simulated zoom-in volumes of the digital counterparts of the Coma, Hercules, Shapley, Virgo, and Perseus supercluster environments, and the Fornax galaxy cluster. From the zoom-in boundary volumes of the six environments, reaching radial extents of $55-92\,$Mpc, we extracted black hole demographics (including spin) and their host galaxy properties to establish a filter scheme that strictly preserves dynamically stable "main-sequence" black holes. We further classified host galaxies as cuspy or cored based on the slope of their 3D stellar density profile measured within $1\,$kpc as a proxy for unresolved nuclear structure and applied the relativistic Kesden efficiency correction to the filtered sample. We find an average volumetric and per black hole TDE rate of $\approx 600\,$Gpc$^{-3}\,$yr$^{-1}$ and $\approx 4.5\times 10^{-5}\,$yr$^{-1}$ across all six environments, respectively. Although our absolute TDE rates match early literature estimates, the underlying spatial distribution fundamentally differs. Central core rates are heavily reduced by dynamical depletion and direct capture constraints, meaning the total TDE budget is overwhelmingly dominated by cuspy satellite galaxies in the extended cluster halos. TDE yields are driven by black hole demographics and spatial concentration rather than total cluster mass. Actively assembling superclusters (e.g., Hercules) reduce per-black-hole TDE efficiencies via merger-driven black hole mass growth, whereas low-mass environments (e.g., Fornax) are highly efficient due to unmerged, low-mass black holes.
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All authors Julian S. Sommer, Ildar Khabibullin, Klaus Dolag, Luca Sala, Benjamin Seidel, Jenny G. Sorce, Alice Damiano

Instrumentation and Methods for Astrophysics

Charge migration characterization in the METIS H2RG detectors

Danny Gasman, Benoît Serra, Roy van Boekel et al. (+4 more)

The Mid-infrared ELT Imager and Spectrograph (METIS) is one of the first-light instruments of the Extremely Large Telescope (ELT). For the L and M band, the instrument makes use of Teledyne's H2RG detectors, known to be affected by charge migration, also known as the brighter-fatter effect (BFE). In the H2RG detectors this manifests as photo-electrons moving from a central bright pixel to neighboring pixels as the depletion region of the central pixel shrinks with accumulated charge. Due to its effect of `blurring' information, it especially affects direct imaging, transit, and high-resolution spectroscopy applications. We aim to characterize its effect in the METIS H2RG detectors, such that we can remove it without losing information.
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All authors Danny Gasman, Benoît Serra, Roy van Boekel, Ioannis Argyriou, Daniel Dicken, Vianak Naranjo, Peter Bizenberger

Astrophysics of Galaxies

CatBoost versus Spectral Energy Distribution-Fitting: Estimating Galaxy Properties under Controlled Photometric Incompleteness

Vahid Asadi, Hosein Haghi and Akram Hasani Zonoozi

Estimating galaxy physical parameters from photometric data is fundamentally challenged by missing measurements that are endemic to astronomical surveys. Using a mock catalog from the Horizon-AGN hydrodynamical simulation that provides the true physical parameters, we evaluate CatBoost, a gradient-boosting algorithm that natively handles missing data, under a deliberately adversarial scenario: we train it on 12 photometric bands with increasing levels of injected missingness (10%, 20%, 30% missing per band) and compare its performance against an idealised parametric spectral energy distribution (SED)-fitting reference that uses complete 26-band photometry (no missing data, all bands available). This asymmetric design represents an upper-bound, best-case baseline for traditional methods. Despite this intentional disadvantage, CatBoost's performance degradation is limited: moving from complete data to 30% missing, mass RMSE increases from 0.08 to 0.18 dex, SFR RMSE from 0.41 to 0.53 dex, and redshift RMSE from 0.20 to 0.28, while bias remains near zero. Against the ideal SED-fitting reference, CatBoost trained on only 12 bands with 30% missing values achieves lower errors for mass (0.18 vs. 0.28 dex) and SFR (0.53 vs. 0.57 dex) and removes the systematic biases present in the SED-fitting results. For redshift, the SED-fitting reference has lower NMAD (0.030 vs. 0.093 at extreme missingness) while CatBoost maintains smaller bias. These results suggest that CatBoost's native handling of missing values can offer practical advantages for extracting galaxy properties from imperfect photometric surveys, at least under the conditions explored here.
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Instrumentation and Methods for Astrophysics

Persistence characteristics of H4RG-15 detectors for ESO instruments

Elizabeth M. George, Domingo Alvarez Mendez, Nagaraja Naidu Bezawada et al. (+3 more)

As a part of the ESO Instrumentation Program, we already ordered 23 H4RG-15 (2.5 um cut-off) detectors for the instruments MOONS, MICADO, and HARMONI, with more of these detectors planned for future instruments on the ELT as well as possibly other ESO telescopes. As part of our comprehensive detector testing program, we characterize detector persistence at different temperatures between 40 and 85 K, allowing the best-informed choice of operating temperature for the science focal planes. We report the characteristics of persistence as a function of temperature for the 5 MOONS detectors and 10 MICADO detectors that have already been tested between 2019 and 2025. These detectors show a rich variety of persistence behaviour that can be fit with a single persistence model with varying parameters. We produce persistence trap maps and a model for persistence decay for each device, allowing automatic pipeline correction of persistence and also simulation of persistence behaviour of individual detectors using the Pyxel detector simulator. Each detector was unique and had different optimal operation temperatures for reduced persistence. We therefore recommend implementing a flexible thermal interface in the instrument design phase allowing for the detector operating temperature to be optimized after the science detectors have been fully characterized.
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All authors Elizabeth M. George, Domingo Alvarez Mendez, Nagaraja Naidu Bezawada, Derek J. Ives, Mark Neeser, Benoit Serra

Instrumentation and Methods for Astrophysics

Visual analytics for cosmological simulation results

Paul Vauterin and Maarten Baes

Context: Modern cosmological simulations rely on sophisticated assumptions and generate rich, highly complex datasets. Interpreting their results in order to extract new scientific insights remains challenging. Existing visualisation tools offer powerful capabilities but often come with a relatively high barrier for entry, and are not designed with a focus on knowledge discovery through real-time, intuitive visual analytics. This stands in contrast to other research domains, such as bioinformatics, where visual analytics tools have become deeply embedded in scientific discovery workflows. Aim: Our goal is to complement the existing ecosystem of cosmological visualisation tools with a lightweight, user-friendly application that supports visual analytics and frictionless dissemination of results to the scientific community. Methods: We developed ARGOS, an open-source, web-based environment for real-time visual analytics, tailored to cosmological simulation outputs and designed with an emphasis on user experience. ARGOS combines GPU-accelerated browser rendering for interactive exploration of large datasets with a template-driven approach that enables rapid adaptation to other types of data and analysis workflows. Importantly, ARGOS combines catalogue-level and object-level exploration, allowing users to move seamlessly from large ensembles of objects to snapshots of individual objects. Results: We demonstrate how ARGOS can support intuitive visual data exploration through example dashboards for multiple cosmological particle datasets, and illustrate broader applicability with dashboards for SKIRT synthetic multi-band imaging data products. Source code is freely available at https://github.com/pvaut/skirt-argos under the MIT licence. A reference deployment, including sample data, is available at https://skirt-argos.ugent.be.
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Cosmology and Nongalactic Astrophysics

Planck Constraints on Turbulence in the Coma Cluster

Baptiste Sigal, Etienne Pointecouteau, Nicolas Clerc et al. (+6 more)

Turbulence within the intracluster medium (ICM) influences galaxy cluster thermodynamics and virialisation, contributing to non-thermal pressure support and impacting hydrostatic mass estimates. Characterising this turbulence through thermodynamic fluctuations remains observationally challenging due to the non-linear relationships between observables such as density and pressure, and the underlying velocity field. This study aims to constrain the properties of ICM turbulence by performing a comprehensive reanalysis of the Sunyaev-Zel'dovich (SZ) surface brightness fluctuations based on Planck survey observations of the Coma cluster. We analyse the 2D power spectrum of SZ fluctuations, modelling the underlying 3D pressure fluctuation power spectrum assuming Kolmogorov-type turbulence. We infer key parameters from a simulation-based inference framework relying on normalizing flows to accurately recover posterior distributions. By constraining the pressure fluctuation power spectrum, we are able to infer the properties of turbulence in the Coma cluster, finding a large injection scale of $l_{\text{inj}} = 540^{+450}_{-200}$ kpc, a slope of $\alpha = 3.50_{-0.46}^{+0.50}$ (under Gaussian prior), and a substantial 3D Mach number of $\mathcal{M}_{3D} = 0.60^{+0.13}_{-0.09}$. These values correspond to turbulent velocities in the range $\sigma_{v,\text{ }3D} = 357-1095$ km/s and a non thermal pressure fraction of $P_{\text{turb}}/P_{\text{tot}} = 0.17_{-0.04}^{+0.06}$. Our results are consistent with recent direct velocity measurements from XRISM, supporting a scenario of significant turbulence in the Coma cluster and highlighting the complex interplay of dynamical processes within its ICM. Our simulation-based inference approach applied to SZ fluctuations paves the way for systematic multi-probe studies combining SZ and X-ray data, as well as direct and indirect observations.
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All authors Baptiste Sigal, Etienne Pointecouteau, Nicolas Clerc, Simon Dupourqué, Alexeï Molin, François Mernier, Rémi Adam, Tanguy Dusserre, François Pajot

Astrophysics of Galaxies

Recovering pattern speeds of simulated face-on barred galaxies via Schwarzschild modelling

Iliya S. Tikhonenko, Jens Thomas and Roberto P. Saglia

Stellar bars are a major driving force in the secular evolution of their host galaxies. To better understand the connections between the 3D bar density structure, its orbital composition, stellar populations, and underlying dark matter distribution, it is desirable to construct detailed dynamical models of barred galaxies. However, only a few external barred galaxies have been studied in this way so far. We present a new Schwarzschild orbit superposition code for triaxial potentials with figure rotation and test it extensively using mock data from an N-body simulation of a strongly barred galaxy. We investigate the recovery of model parameters in the nearly face-on case which was not previously considered. In particular, we demonstrate a 10% accuracy of both the pattern speed and mass-to-light ratio and a 20% accuracy for the dark matter halo mass scaling at the inclination 20{\deg}. Surprisingly, we obtain a similarly accurate result for the pattern speed in an exact face-on limit, where conventional methods such as Tremaine-Weinberg are no longer applicable. This result suggests that varying the pattern speed at fixed bar length, corresponding to the transition between slow and fast bars, alters the distribution function in a way that produces a systematic change in the vertical velocity distribution, which can not be compensated by the in-plane velocity components.
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Instrumentation and Methods for Astrophysics · Cross-listed from hep-ph

Halbach Magnetic Weber Bars

Valerie Domcke and Itay M. Bloch

Magnetic Weber Bars have been proposed to search for gravitational waves in the kHz to GHz regime by exploiting the mechanical deformation of a large magnet induced by a gravitational wave. Here we propose to increase the effectiveness of such devices by considering magnetic field configurations with strong gradients, albeit lower field strengths, such as Halbach arrays. We focus on one of the most challenging but most realistic signals, with short duration and low coherence, exploiting the ring-down period of the mechanical resonator. We show that with demonstrated technology this setup can reach sensitivities of $S_h^{1/2} \simeq 10^{-21}/\sqrt{\text{Hz}}$ at a broad set of frequencies around several resonance peaks at $\sim 10$ kHz, and $S_h^{1/2} \simeq 5 \cdot 10^{-20}/\sqrt{\text{Hz}}$ in a broadband search at higher frequencies. We discuss plausible upgrades to reach $S_h^{1/2} \simeq (10^{-23} - 10^{-21})/\sqrt{\text{Hz}}$ in a broadband search covering 10 kHz - MHz.
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Earth and Planetary Astrophysics

Gas Phase Ion Species Released During Grain Collisions: Implications For Protoplanetary Disks

Patrick Hock and Gerhard Wurm

Grain charging and gas ionization are important processes in protoplanetary disks. Both occur in mutual collisions between grains, as charge is exchanged between grain surfaces but also released into the surrounding gas as ions. The charge carrier for tribocharging, the origin of the gaseous ions, and their composition are currently unknown. However, it is important to know to validate the significance of these processes under disk conditions. In this work, we approach these questions by detecting molecules ejected during grain collisions by mass spectrometry. As tribocharging works well under normal atmospheric conditions, we use untreated "dirty" particles here. Without collisions, our measurements show a background mix of molecules. Among these are organics, but especially water-related molecules. During collisions, the abundances of not all but quite a few molecules change. Water-related molecules account for one of the largest changing fractions. These results suggest that particle collisions release adsorbates even at very low pressure, which is relevant for protoplanetary disks. As monolayers of water and organics are present on all surfaces in cool to moderately tempered parts of protoplanetary disks, this supports the importance of triboionization in disks.
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Earth and Planetary Astrophysics · Cross-listed from gr-qc

Deviation of trajectories in nonrelativistic and relativistic cases and Shirokov effect

Yu. V. Pavlov and V. P. Vandeev

We compare the deviations of circular orbits in the nonrelativistic and relativistic cases. General solutions of the deviation equations are obtained. We find the potentials for the nonrelativistic case and the metric components in general relativity for which trajectories close to circular ones are closed curves. Explicit expressions for the pericenter shift of an orbit close to a circular one in a static spherically symmetric spacetime are obtained. Estimates of the cosmological constant effect on the orbit pericenter shift are given. Finally, we find the spherically symmetric metric in which the Shirokov effect is absent.
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Instrumentation and Methods for Astrophysics

Information limits of photonic lantern wavefront sensing: a Fisher- and quantum-Fisher-information framework and its relation to Fourier-filtering sensitivity limits

Kalaga Madhav

The photonic lantern is an all-photonic wavefront sensor native to single-mode-fibre-fed instruments, but its performance is almost always quoted through a specific reconstruction algorithm, obscuring how much wavefront information the device itself encodes. We develop, from first principles, the Fisher-information and Cramer-Rao theory of the photonic-lantern wavefront sensor, benchmark it against the quantum Cramer-Rao bound via an explicit multi-parameter quantum-Fisher-information calculation, and relate it to two established frameworks: the Fourier-filtering noise-propagation model of Chambouleyron et al (2023) and the classical/quantum sensitivity limit of Haffert et al (2023). Treating the lantern as a deterministic map from aberration coefficients to N output intensities, we derive the Poisson and read-noise Fisher information matrices (FIM), the per-mode CRLB, the per- photon Fisher-Rao geometry on the intensity simplex, and a flux- and estimator-independent sensitivity metric beta with quantum ceiling beta = 2. The lantern CRLB scales as N_ph^(-1/2) and is bounded, mode by mode, by the quantum limit of 1/2 rad rms per photon. That multi-parameter bound is jointly saturable: the phase generators are real and commuting, so the mean Uhlmann curvature vanishes and wavefront sensing carries no quantum incompatibility between simultaneously estimated modes, extending Haffert et al's single-mode ceiling to all low-order modes at once. We further show that the photon-noise sensitivity s_gamma of Chambouleyron et al is exactly the diagonal of our per- photon FIM, whereas the CRLB uses the diagonal of its inverse; the two coincide only for a diagonal FIM, so s_gamma is optimistic for a mode-mixing lantern. The framework is device-agnostic: it returns estimator-independent sensitivities comparable on a common beta <= 2 scale with pyramid, Zernike and PIAA-ZWFS sensors.
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Instrumentation and Methods for Astrophysics

Maximising the mid-infrared high-contrast performance of ELT/METIS despite water vapour seeing

Olivier Absil, Gilles Orban de Xivry, Prashant Pathak et al. (+7 more)

The Mid-infrared ELT Imager and Spectrograph (METIS) will be equipped with a SCAO system delivering Strehl ratios above 90% at L band (3.5 - 4.1 um) and close to 99% at N band (8 - 13 um) on bright stars. Yet, the actual wavefront quality seen by the METIS coronagraphic modules used for high-contrast imaging will be significantly affected by water vapour seeing, which add a strong chromatic component to dry air seeing in the mid-infrared. We analysed two years of VLTI/GRAVITY fringe tracker archives to assess the variability of differential water vapour column density at millisecond timescales on ELT scales. Our analysis suggests that water vapour seeing will add a median wavefront error of about 175 nm rms at N band, consisting mostly of low-order aberrations, with around 150 nm rms of tip-tilt errors. If not corrected, this effect would degrade the achievable sensitivity limits in terms of contrast by more than two magnitudes. To mitigate this effect, we plan to deploy a focal-plane wavefront sensing and control algorithm based on an asymmetric pupil using a deep learning approach. After briefly discussing the practical impacts of focal-plane wavefront control in METIS, we compare the expected high-contrast imaging performance with and without focal-plane wavefront control.
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All authors Olivier Absil, Gilles Orban de Xivry, Prashant Pathak, Abhirami S. Raghu, Benjamin Courtney-Barrer, Roy van Boekel, Thomas Bertram, Markus Feldt, Matthew Kenworthy, Bernhard Brandl

Solar and Stellar Astrophysics

Spectroscopy of flares on AU Mic

P. Odert, M. Leitzinger, P. Kabáth et al. (+6 more)

Photometric space missions like Kepler and TESS have revealed unprecedented statistics of stellar flares, including the frequent detection of highly energetic superflares. Spectroscopic characterization of flares and especially superflares, however, is still not as commonly available. In contrast to broad-band photometry, spectroscopic data can give more insights into the physical parameters of flares, as well as allowing to identify possibly accompanying CMEs. In this context, we monitored the young planet-hosting flare star AU Mic for about 60 partial nights (>160 hours) between 2022 and 2023 spectroscopically with the ESO 1.52m telescope hosted by the PLATOSpec consortium. Here, we report on the search for signatures of flares and CMEs in these data, including the partial observation of a possible extreme superflare.
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All authors P. Odert, M. Leitzinger, P. Kabáth, R. Greimel, J. Lipták, R. Karjalainen, P. Heinzel, J. Wollmann, E.W. Guenther

Solar and Stellar Astrophysics

Spectroscopic investigation of the southern late-K/early-M dwarf binary CC Eri

M. Leitzinger, P. Odert, R. Greimel et al. (+6 more)

In the recent past investigations of stellar Coronal Mass Ejections (CMEs) and flares/superflares gained special attention because of their relevance for planetary habitability and stellar evolution. With respect to that, we present an observing campaign at the ESO152 telescope on LaSilla operated by the PLATOSpec consortium of the late-K/early-M dwarf binary CC Eri. The ESO152 telescope is currently equipped with an Echelle spectrograph which enables the investigation of a broad spectral range, allowing the investigation of CMEs and flares/superflares in various spectral lines. Within the observing campaign CC Eri was not observed by TESS, but we have coordinated g'-band photometry to cross-check for white light flares. Preliminary results of the observing campaign are presented.
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All authors M. Leitzinger, P. Odert, R. Greimel, P. Kabáth, J. Lipták, R. Karjalainen, P. Heinzel, J. Wollmann, E.W. Guenther

Astrophysics of Galaxies

The Radial Acceleration Relation in Galaxies and Clusters from a Two-Component, Virial-Motivated Framework

Christine C. Dantas, Andre L. B. Ribeiro and Hugo V. Capelato

We present a comparative analysis of acceleration data for gravitational systems drawn from multiple observational sources, including: (i) early-type galaxies (ETGs) (Lelli et al. 2017); (ii) Brightest Cluster Galaxies (BCGs) and galaxy clusters (Tian et al. 2020, 2024); and (iii) weak gravitational lensing of isolated galaxies (Brouwer et al. 2021; Mistele et al. 2024). These data are interpreted within a framework motivated by the Two-component Virial Theorem (2VT), which defines a global baryon-dark matter (DM) coupling and sets a characteristic acceleration scale. This baseline is complemented by two models that account for the main empirical features of the Radial Acceleration Relation (RAR) over a broad range of masses and accelerations. The Constant-Interaction Approximation Model (CIA) reproduces the observed RAR trends for ETGs, BCGs, and galaxy clusters. It extends earlier results (Dantas et al. 2000, 2018), and accounts for both the small intrinsic scatter and the emergence of a characteristic acceleration scale. At the very low accelerations probed by weak-lensing data (below accelerations of order $10^{-14}~\mathrm{m\,s^{-2}}$), however, this model breaks down. In this regime, the Virial-Motivated Interaction Model (VIM) incorporates the radial structure of the baryon-DM interaction through a local, radius-dependent contribution to the acceleration. Taken together, the 2VT (global scale), the CIA and the VIM provide a physically motivated framework that captures the main empirical features of the RAR.
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Instrumentation and Methods for Astrophysics

Liquid nitrogen pre-cooling system for ELT instruments utilizing additively manufactured heat exchangers, integrated temperature and liquid level control

Anastasios Aretos, Younes Chahid, Lee Chapman et al. (+5 more)

Using liquid Nitrogen as the cryogenic fluid for pre-cooling purposes is almost ubiquitous across modern observatories. That method tends to be inefficient since it relies on the evaporation of the fluid afforded by the available surface area within the exchanger without capturing any of its latent heat. An additively manufactured heat exchanger could address that inefficiency by providing an increased evaporation area as well as internal structures that can interact with Nitrogen in its gaseous phase. A miniature pre-cooling system utilizing an existing cryostat was developed so the performance of conventionally and additively manufactured heat exchangers would be compared by recording the time required to cool an instrumented mass. Our findings indicate that there is a clear cost and performance advantage of additively manufactured heat exchangers when compared to conventional units, that could lead to reducing the operating costs of observatories hosting large size instruments such as HARMONI.
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All authors Anastasios Aretos, Younes Chahid, Lee Chapman, Mark Cliffe, Maia Jones, Scott McPhee, Chris Miller, Graham Wilks

Solar and Stellar Astrophysics

Turbulent Convection: Modal Equations and Energy Pathways

S. Sridhar and Nishant K. Singh

We present a framework for studying high Rayleigh number turbulent convection to better understand stellar and planetary convection zones. Utilizing the statistical symmetries of the fully developed turbulent state of Boussinesq convection, we identify relevant mean and fluctuating quantities. After validating these symmetry assumptions through numerical simulations, we formulate the governing equations. Vertical profiles of key physical quantities in the saturated turbulent state are explored in the simulations. To develop a modal theory, we use Fourier expansions, review linear theory, and use the Craya-Herring velocity decomposition. The modal equations we derive describe high Rayleigh-number turbulent convection dynamics self-consistently in terms of nonlinear interactions between three mode types: growing gravity modes, decaying gravity modes, and horizontal modes. Energy extracted by the growing modes from the superadiabatic background subsequently follows multiple pathways toward dissipation, enabled by the mode couplings. Among these, the traditionally dominant pathway is the turbulent cascade of the growing modes themselves. Reduced modal equations capture this pathway, precisely describing (i) mutual interactions between growing modes, and (ii) the excitation of decaying and horizontal modes, which are subordinate to the growing modes. Determining the relative efficiency of the pathways requires investigating their modal spectra using numerical simulations and kinetic models.
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High Energy Astrophysical Phenomena

Spectral densification and macroscopic phase delay of gravitational echoes from exotic compact objects

Corentin Guigot

Gravitational-wave echoes from Exotic Compact Objects (ECOs) provide an observable probe for horizon-scale physics. Standard phenomenological models for these signals typically assume a constant Free Spectral Range, relying on the geometric optics approximation. In this work, we demonstrate that wave dispersion at the photon sphere induces a systematic deviation from this assumption, manifesting instead as a hyperbolic spectral densification. By employing an analytical framework based on the Riccati equation and macroscopic impedance mapping, we extract the spectrum of these high-finesse resonances without semi-classical approximations. We characterize the structural transition from the eikonal geometric asymptote ($\ell \gg 1$) down to the wave-tunneling dominated quadrupolar mode ($\ell=2$). In this wave-dominated regime ($\ell \in [2, 10]$), the macroscopic deviation from the semi-classical limit is governed by a phenomenological $\mathcal{L}^{-3/2}$ inverse power law. Finally, we show that this macroscopic densification isolates the structural dispersion of the external spacetime, decoupled from the boundary microphysics, provided the membrane phase shift is frequency-independent.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Rare processes in ultrahigh-energy tau-lepton transport

Guo-yuan Huang

In cosmic neutrino observatories, charged-lepton transport is a key input for interpreting observables and reconstructing neutrino events. Charged leptons propagating through matter undergo several energy loss processes, such as electron pair production and photonuclear interaction. In this work, we investigate several rare processes in tau-lepton transport, focusing primarily on muon pair production, $\tau N \to \tau \mu^+\mu^- N$, and Primakoff neutral-pion production, $\tau N \to \tau \pi^0 N$. At EeV energies, we find that the energy loss contributions from muon pair and Primakoff pion production are only $0.6\%$ and $0.2\%$, respectively, of that from electron pair production. Nevertheless, dimuon production may be relevant to tau neutrino searches in underwater and under-ice Cherenkov telescopes. The interaction length for dimuon emission by an EeV tau is only $6~{\rm km}$ in standard rock. Such events may be identified through the lateral separation of dimuon tracks or through a kebab topology if tau decays in the detector.
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Instrumentation and Methods for Astrophysics

The CUSP CubeSat mission for space weather multi-physics analysis, design, and testing

Giovanni Lombardi, Riccardo Di Spirito, Sergio Fabiani et al. (+48 more)

The CUbesat Solar Polarimeter (CUSP) mission aims to measure the linear polarization of solar flares in the hard X-ray band by means of a Compton scattering polarimeter. CUSP is a project in the framework of the Alcor Program of the Italian Space Agency aimed at developing new CubeSat missions. We present the outcomes of the CUSP's Phase B study, which is ended on 2 July 2026. The design solutions adopted for the mission's most critical multi-physics design drivers will be discussed, these solutions have been formulated and applied to demonstrate compliance with system requirements at both the spacecraft and platform levels. Moreover, we will discuss the validation of the Payload model based on the environmental testing campaign (e.g., vibration) carried out on a demonstrator.
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All authors Giovanni Lombardi, Riccardo Di Spirito, Sergio Fabiani, Daniele Censi, Giovanni De Cesare, Ettore Del Monte, Riccardo Campana, Enrico Costa, Mauro Centrone, Nicolas De Angelis, Sergio Di Cosimo, Giuseppe Di Persio, Abhay Kumar, Pasqualino Loffredo, Gabriele Minervini, Fabio Muleri, Paolo Romano, Alda Rubini, Emanuele Scalise, Paolo Soffitta, Andrea Alimenti, Enrico Silva, Bruna Bertucci, Giovanni Ambrosi, Giovanni Cucinella, Vito Di Bari, Simone Di Filippo, Andrea Negri, Massimo Perelli, Dario Modenini, Andrea Curatolo, Nicolas Gagliardi, Daniele Pecorella, Alice Ponti, Paolo Tortora, Andrea Del Re, Davide Albanesi, Valerio Campamaggiore, Giulia De Iulis, Adam Ebrahim, Marco Schepis, Alessandro Zambardi, Ilaria Baffo, Pierluigi Fanelli, Costantino Zazza, Valerio Vagelli, Daniele Brienza, Immacolata Donnarumma, Matteo Mergè, Emanuele Zaccagnino, Alessandro Turchi

Solar and Stellar Astrophysics

Pulsations along the Asymptotic Giant Branch (AGB): a global view

Pierre Darriulat, Pham Thi Tuyet Nhung and Do Thi Hoai

In three preceding articles, we studied the relation between the light curves of Mira variables and their stellar properties. The analysis was restricted to a sample of stars offering high density and quality of observations in the visible, allowing for the definition of simple parameterizations of the light curves. Clear relations were revealed between the evolution of the stars along the AGB and parameters such as the width of the light pulse or the deviation of its ascending branch from a sine wave. However, the restriction to Mira variables was found to be a major drawback preventing a complete picture to be drawn. The present article overcomes this deficiency by reviewing a large sample of semi-regular and irregular variables. It gives evidence for two families of stars having different progenies. The first family enters the AGB already pulsating with amplitudes at the scale of one unit of magnitude. It keeps cooling down and expanding, while pulsating with increasing amplitudes and periods and decreasing width of the light pulse; its progeny is dominated by some of the Mira variables studied in the three preceding articles. The second family enters the AGB before displaying significant pulsations; some of its progeny may leave the AGB without entering the Thermally Pulsing Branch and experiencing strong TDU events; others may instead become Mira variables studied in the three preceding articles and pulsating with a broader light pulse. The possible transition of both families from oxygen-rich to carbon-rich is studied and described. Comments on the interpretation of these results in the context of current state-of-the-art knowledge are presented. While the stars of the first family tend to have larger initial masses than the stars of the second family, details of the properties of the convective envelope seem also to play a role in defining which families a star belongs to.
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Cosmology and Nongalactic Astrophysics

A Quantitative Framework for Testing the Hubble Tension in a Bianchi Type I Cosmological Background

Luigi Tedesco

The Hubble tension is usually formulated as a disagreement between two determinations of a single scalar parameter, $H_0$, within an isotropic FLRW model. We develop a quantitative framework treating the tension as a consistency test of the scalar FLRW compression of cosmological data in a homogeneous, anisotropically expanding Bianchi type I background. Beyond synthesizing established results on Bianchi I kinematics, null geodesics, and optical propagation, our original contribution is a worked weak-shear, axisymmetric calculation mapping a specified shear history into a low-redshift luminosity-distance quadrupole. The calculation explicitly separates the direction-dependent redshift–affine-parameter mapping from the Jacobi-focusing contribution, propagating the resulting distance quadrupole through an analytic polar-cap toy window. For freely decaying shear, we obtain $A_D(z) = -B_{H0} + (2q_0-1)B_{H0}z/2 + (5-q_0-18q_0^2+6j_0)B_{H0}z^2/12 + O(z^3, B_{H0}^2)$, where $B_{H0}=(H_{\parallel 0}-H_{\perp 0})/H_0$ and $j_0$ is the mean jerk parameter. A representative BBN limit, $\Omega_{\sigma 0} \le 10^{-23}$, implies $\vert{}B_{H0}\vert{} \le 9.5 \times 10^{-12}$ and a distance-modulus quadrupole below $2.4 \times 10^{-11}$ mag at $z=0.15$. The early-Universe bound used is adopted from prior work; the novelty lies in propagating it through the derived Sachs–Jacobi mapping into limits on the luminosity-distance quadrupole and catalogue-window bias. By contrast, a 1% directional shift requires $\Omega_{\sigma 0} \approx 2.5 \times 10^{-5}$, while matching the Planck 2018–SH0ES 2022 separation requires $\Omega_{\sigma 0} \approx 1.8 \times 10^{-3}$. Thus, the minimal shear-only model cannot resolve the tension, though the framework supplies a falsifiable programme for testing late-time anisotropy with SNe, BAO, and standard sirens.
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