Cosmology and Nongalactic Astrophysics
Cosmology in the Einstein Telescope era: comparing traditional and simulation-based methods for population inference
Giovanni Antinozzi, Guillermo Franco Abellán, Davide Sciotti et al. (+1 more)
The next generation of gravitational wave detectors, such as the Einstein
Telescope (ET), will observe orders of magnitude more binary black hole mergers than current facilities. Most of these events will lack an electromagnetic counterpart, also known as dark siren events, yet will still enable percent-level cosmological constraints. However, the likelihood traditionally used in Hierarchical
Bayesian Inference (HBI) for population-level analyses becomes computationally prohibitive as the size of dark siren catalogues and population parameters grow. In this work we compare HBI against simulation-based inference (SBI) as a scalable alternative for cosmological population inference in the ET era. Studying a proof-of-concept example of a mock ET inference, we build a catalogue of $O(10^4)$ binary black hole events, then perform inference on the Hubble constant $H_0$ and matter density $\Omega_m$ in a flat $\Lambda$CDM cosmology, using both a hierarchical analytical likelihood and Marginal Neural Ratio Estimation (MNRE). We find excellent agreement between the two approaches, with SBI reproducing the HBI posteriors to high accuracy, while requiring orders of magnitude less computation once the simulation and training cost is amortized. We further demonstrate that SBI extends straightforwardly to a joint cosmology-plus-astrophysics analysis, simultaneously constraining $(H_0,\Omega_m)$ together with the parameters of the
star formation rate density, at negligible additional cost compared to the significant increase in complexity such an extension would require within the HBI framework. Our results indicate that SBI is a promising and scalable tool for population inference with third-generation GW detectors.
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All authors Giovanni Antinozzi, Guillermo Franco Abellán, Davide Sciotti, Matteo Martinelli
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A Tale of Two Couplings: Bayesian Selection in the Interacting Dark Sector
Miguel Barroso Varela and Álvaro de la Cruz-Dombriz
$\Lambda$CDM provides a remarkably successful description of the Universe, yet it suffers from persistent discrepancies, with one of the most prominent being the $\sigma_8$ tension between early-Universe
Cosmic Microwave Background (CMB) measurements and late-time structure growth probes. To address this mismatch, we investigate generalized interacting dark sector models governed by a quintessence field coupled to dark matter via conformal and disformal transformations. By generically engineering a quintessence potential that ensures the combined
evolution of dark matter and dark energy exactly mimics $\Lambda$CDM, our models satisfy all background constraints while signaling modified
gravity effects within the linear perturbation sector. We perform a statistical analysis using late-time structure growth data anchored to Planck 2018 constraints. Furthermore, we address the initial conditions problem inherent to purely disformal models, demonstrating the necessity of a non-zero initial kinetic energy to initiate dynamical
evolution. Our results indicate that purely conformal couplings efficiently transfer energy from dark matter to the quintessence field, suppressing late-time structure formation and successfully accommodating CMB data within late-time modified structure growth. This purely conformal limit yields a strong statistical preference over the $\Lambda$CDM baseline according to both the Akaike and
Bayesian Information Criteria. Conversely, while non-zero disformal couplings introduce a kinetic friction that dampens the dark sector energy exchange, their expanded parameter space incurs heavy statistical penalties without providing a decisive improvement over the purely conformal scenario.
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Earth and Planetary Astrophysics
Helium-poor winds do not require helium-poor planets
Leonardos Gkouvelis and Francisco J. Pozuelos
Observations of the metastable He,i,10830,Å\ triplet have revealed escaping
exoplanet atmospheres whose inferred helium abundances range from nearly nebular compositions to strongly helium-depleted winds. Such depletion is commonly interpreted as evidence for atmospheric
evolution, preferential escape, or departures from
primordial composition. We present a closed-form analytic transport-retention theory for the atmospheric transition region between the homopause and the base of the planetary wind. The theory quantifies the competition between upward transport and molecular separation, demonstrating that transport physics alone can substantially deplete the helium abundance supplied to the escaping flow. Our solution yields a retention factor, $\chi_{\rm He}$, that measures the fraction of helium supplied to the base of the hydrodynamic wind relative to the deep atmospheric abundance. Combining the analytic framework with numerical forward models of the He,i,10830,Å\ absorption and a sample of twelve helium-observed sub-Neptunes and mini-Neptunes, we find that observed systems span the full range of predicted retention states, from nearly complete retention to strong helium depletion. These forward models use the helium abundance supplied by the analytic framework as the lower-boundary condition to predict the corresponding He,i,10830,Å\ absorption. We further show that increasing helium retention systematically strengthens the expected absorption signal by increasing the helium reservoir available to the upper atmosphere. These results suggest that helium depletion does not necessarily imply intrinsically helium-poor atmospheres or evolutionary transitions toward secondary compositions, but may instead be a natural consequence of transport physics in escaping atmospheres.
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Astrophysics of Galaxies
Profile Analysis of the Multiwavelength 2.1-year Oscillations of PG 1553+113
P. Peñil, N. Torres-Albà, A. Rico et al. (+5 more)
We investigate the morphology of the oscillation profiles of the blazar PG~1553+113 in relation to its well-known $\sim$2.1 yr periodicity. We identify individual cycles in the $\gamma$-ray, X-ray, UV, and optical light curves and characterize their temporal profiles using analytical models for single- and multi-peaked events. We find that the oscillations are generally described by a broad activity envelope with shorter-timescale substructure, showing that the $\sim$2.1 yr signal is not a strictly sinusoidal or self-similar modulation. The internal morphology varies across cycles and energy bands. This is particularly evident in X-rays, where all analyzed cycles show a strong formal preference for multi-component profiles, unlike the $\gamma$-ray band, where several cycles admit statistically comparable empirical descriptions. The contemporaneous MWL oscillations show broadly aligned activity episodes, but the timing and relative amplitudes of secondary components are not systematically repeated. This suggests that a common long-term modulation affects the broadband emission, while additional local or energy-dependent processes shape individual cycles. Such a picture is compatible with a
geometric, jet-related contribution to the broad recurrent envelope, with intrinsic variability superimposed on it. We also identify new cycles with a dominant peak accompanied by weaker twin-peak-like features, similar to structures previously discussed in a supermassive black hole binary scenario for PG~1553+113. Although our results do not provide definitive evidence for this interpretation, the recurrence of comparable morphologies in newly analyzed cycles keeps this scenario viable.
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All authors P. Peñil, N. Torres-Albà, A. Rico, L. Marcotulli, A. Domínguez, M. Ajello, S. Buson, S. Adhikari
High Energy Astrophysical Phenomena
First fast radio burst search campaign at the Argentine Institute of Radio Astronomy
Carlos O. Lousto, Harsh Prajapati, Ezequiel Zubieta et al. (+7 more)
Fast
radio bursts (FRBs) are intense millisecond-duration
radio transients of extragalactic origin whose physical nature remains under active investigation, and which also serve as probes of the intergalactic medium. We report on the first FRB search campaign carried out at the Argentine Institute of
Radio Astronomy (IAR) between December 2024 and March 2026, targeting nearby
galaxy superclusters in the southern sky. We observed fields in the Ophiuchus, Shapley, and Sculptor/Phoenix supercluster regions with one of the two 30~m
antennas of the IAR, using a ROACH-based backend with 400~MHz of bandwidth centred at 1400~MHz and a time resolution of 41–82~$\mu$s, for a total net observing time of 212~h. The data were searched for dispersed single pulses with PRESTO in the dispersion measure range $100 \leq \mathrm{DM} \leq 500$, and candidates were classified with the FETCH machine learning classifier. The pipeline was validated on archival Parkes data containing known FRBs and on synthetic bursts injected into IAR observations. One FRB candidate, FRB~20251018, was identified on 18 October 2025 in an observation pointed towards the
galaxy cluster A2870, in the Phoenix supercluster, with a dispersion measure of $243$, a signal-to-noise ratio of 8.2, and a FETCH probability of $p=0.99$. To the best of our knowledge, this would be the first FRB detected from South America. A set of more marginal candidates is also presented. These results demonstrate the capability of the IAR
antennas to detect FRBs and support the continuation and extension of the monitoring campaign, including coincident dual-
antenna observations and cross-matches with gravitational-wave events and electromagnetic transients.
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All authors Carlos O. Lousto, Harsh Prajapati, Ezequiel Zubieta, Susana B. Araujo Furlan, Guillermo Gancio, Joaquín Pelle, Gustavo E. Romero, Federico García, Santiago del Palacio, Nathan Cahill
Cosmology and Nongalactic Astrophysics
Fisher Forecasting for the DESC with $\texttt{Augur}$
Paul Rogozenski, Sankarshana Srinivasan, Javier Sánchez et al. (+15 more)
The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) has begun its ten-year survey of the entire visible southern hemisphere. To ensure robust cosmological measurements, computationally inexpensive investigations of modeling choices must be made to gauge the performance of proposed cosmological analyses. In this paper, we introduce the $\texttt{Augur}$ tool of the Dark Energy Science Collaboration (DESC), which provides Fisher forecasts for cosmological inference for the LSST using software frameworks designed for DESC science. We test the pipeline by comparing it to forecasts produced by external code and direct sampling of the posterior via nested sampling methods, finding good agreement between all methods. We additionally investigate a range of modeling and hyperparameter choices for a 3$\times$2pt investigation in harmonic space, providing users with diagnostics to obtain reliable forecasts. $\texttt{Augur}$ will be continually updated to be compatible with the other tools in the DESC software ecosystem as additional probes and functionality become available.
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All authors Paul Rogozenski, Sankarshana Srinivasan, Javier Sánchez, Nora Elisa Chisari, Arthur Loureiro, Marc Paterno, Rebekah Polen, Heather Prince, Biancamaria Sersante, Anže Slosar, Sandro Vitenti, Carlos García-García, Eric Gawiser, Christos Georgiou, C. Danielle Leonard, Ayan Mitra, Jeremy Neveu, The LSST Dark Energy Science Collaboration
High Energy Astrophysical Phenomena
Probing Axion Like Particle-Proton Interactions through the Interplay of Dark Matter and Cosmic Rays in Large-Scale Structure
Wen-Qing Guo
Axion-like particles (ALPs) provide a well-motivated dark matter candidate whose interactions with Standard Model particles may generate observable cosmological signatures. We investigate the diffuse $\gamma$-ray emission produced by the scattering process between ALP dark matter and
cosmic-ray (CR)
protons inside dark matter
halos, and explore its detectability through the cross-correlation between the unresolved $\gamma$-ray background (UGRB) measured by
Fermi Large Area
Telescope (LAT) and the Two Micron All Sky Survey
Redshift Survey (2MRS)
galaxy catalog in the local Universe ($z\leq0.1$). To model the cosmological $\mathrm{GeV}$-$\mathrm{PeV}$ CR
proton population, we develop a phenomenological bottom-up prescription that links CR injection to the
star formation rate through the
supernova rate, while the steady-state CR density is determined by diffusive escape. Our forecasts indicate that UGRB-
galaxy cross-correlation measurements can probe previously unexplored regions of the ALP parameter space over a broad range of ALP masses. More generally, this work presents a general framework for cosmological observables generated by interactions between dark matter and an additional astrophysical field, opening a new avenue for indirect dark matter searches using large-scale structure observations.
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Earth and Planetary Astrophysics
A broad exploration of climate and observability of close-in rocky exoplanets: applications to Ross 128 b
Mathilde Houelle, Emeline Bolmont, Christophe Lovis et al. (+4 more)
VLT/RISTRETTO, ELT/ANDES and ELT/PCS will soon enable atmospheric characterization of non-transiting, small rocky
exoplanets orbiting closer than the inner edge of the Habitable Zone around M
dwarfs, combining high-contrast imaging with high-resolution spectroscopy in reflected light. A key parameter for reflected-light observability is wavelength-dependent reflectivity, shaped by
climate, surface and atmospheric properties. This work refines spectral reflectivity predictions for this population. Using Ross 128 b as a prototype, we provide physically consistent
geometric albedo estimates within the RISTRETTO and ANDES spectral ranges across diverse atmospheric scenarios. We run 3D global
climate model simulations of Ross 128 b for varying atmospheric compositions, surface pressures, water inventories and
spin-orbit resonances to explore its possible
climate regimes. We then compute synthetic reflectance spectra with Pytmosph3R to assess spectral signatures per scenario and discuss detectability and instrument capacity for constraining
climate. Results show hazeless rocky
planets receiving irradiation similar to Ross 128 b exhibit low reflectivity, with
geometric albedos of 0.07-0.2 in the RISTRETTO bandpass and 0-0.14 in the ANDES bandpass across all scenarios. This low reflectivity can stem from the lack of clouds or surface ice deposits on the dayside, or from strong atmospheric absorption due to high water vapor concentrations, depending on the parameter configurations. These features are characteristic of the
climate moist bistability found in close-in, low-water-reservoir
planets in previous studies. Our results suggest arbitrary albedo assumptions, such as the common 0.3 Earth-like value, can overestimate reflectivity for this population, highlighting the need for accurate
climate models to improve reflectivity predictions and optimize preparation for next-generation spectrographs.
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All authors Mathilde Houelle, Emeline Bolmont, Christophe Lovis, Martin Turbet, Guillaume Chaverot, Alexandre Mechineau, Jérémy Leconte
Earth and Planetary Astrophysics
Formation of nitriles and isonitriles by the heavy-ion irradiation of propionitrile in N2-rich astrophysical ices
Ana L.F. de Barros, David Dubois, Sreeja Raghunandanan et al. (+4 more)
Context. Nitriles are key nitrogen-bearing organic molecules in dense clouds,
star-forming regions, and nitrogen-rich icy environments. Understanding their stability and chemical
evolution under energetic processing is essential for understanding the formation of complex organic species in astrophysical ices. Aims. We investigate the radiolytic processing of propionitrile (CH3CH2CN, hereafter referred to as PCN) in a nitrogen-rich ice
matrix and evaluate the formation of nitriles, isonitriles, hydrocarbons, and other nitrogen-bearing products induced by swift heavy ions. Methods. A PCN:N2 ice mixture with an approximate molecular ratio of 1:10 was deposited at 10 K and irradiated with 40 MeV 40Ar9+ ions up to a fluence of 1 x 1013 ions cm-2. The chemical
evolution was monitored in situ by
Fourier-transform infrared spectroscopy. Destruction and formation cross sections, as well as radiation chemical yields, were derived from the fluence dependence of selected infrared bands. Results. Ion irradiation efficiently destroys PCN and produces a rich inventory of daughter species. The products include: nitriles and isonitriles such as HCN, HCNN, HC3N, CH3CN, CH3C3N, CH3CHCNH, CH2CHCN, NCCN/C2N2, CN, and C2N; nitrogen-bearing species such as CH2NH, CH3NH2, CH3N3, and N3- ; and hydrocarbons, including CH4, C2H2, C2H4, C2H6, and C4H4. The derived cross sections indicate that CN-bearing fragments and hydrocarbons are among the most efficiently formed products, demonstrating that the CN group is efficiently preserved and that extensive carbon-chain reorganization also occurs. Conclusions. The results demonstrate that the energetic processing of PCN in N2-rich ices provides an efficient pathway to molecular complexity under conditions relevant to dense interstellar clouds, protostellar environments, and nitrogen-rich outer
Solar System surfaces.
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All authors Ana L.F. de Barros, David Dubois, Sreeja Raghunandanan, Thibault Nguyen Trung, Tarek Sbera, Hermann Rothard, Alicja Domaracka
Solar and Stellar Astrophysics
Expanding magnetic canopy structure and parasitic polarities in a quiet-Sun network element observed by Sunrise III/SCIP
Ryan J. Campbell, Carlos Quintero Noda, Mihalis Mathioudakis et al. (+35 more)
We present high-resolution multi-line spectropolarimetric observations of a quiet-Sun network element obtained with the Sunrise~iii Chromospheric Infrared SpectroPolarimeter. The observations combine photospheric, upper-photospheric, and chromospheric diagnostics at a spatial resolution and polarimetric sensitivity that allow the transverse
magnetic structure of the network boundary to be examined directly. We find that the strongest linear polarisation is concentrated in a narrow ridge around the edge of the
magnetic element, co-spatial with enhanced transverse
magnetic field inferred from multiline inversions. The
magnetic azimuth exhibits a coherent, predominantly radial organisation around a more vertical core, consistent with an expanding
magnetic canopy. An azimuth proxy derived directly from the observed Fe~i and K~i linear polarisation reproduces the same large-scale organisation, showing that this structure is encoded in the Stokes profiles rather than imposed by the inversion. Response functions and a MURaM-based forward-synthesis test indicate that the Fe~i~8468~Å\ linear polarisation is sensitive to
magnetic azimuth in the upper photosphere, with the closest proxy agreement occurring near $\log\tau\approx-3$. We find no evidence for strong azimuthal shear between the Fe- and K-sensitive diagnostics. At the network boundary, we also identify localised parasitic-polarity patches associated with complex, multi-lobed Stokes $V$ profiles, and one case in which the Stokes $V$ polarity reverses between photospheric Fe~i and chromospheric Ca~ii lines. These results demonstrate that quiet-Sun network boundaries contain organised upper-photospheric canopy fields together with small-scale mixed-polarity structure, providing new constraints on the three-dimensional
magnetic structure of network elements.
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All authors Ryan J. Campbell, Carlos Quintero Noda, Mihalis Mathioudakis, Manuel Collados, Jack McFall, David B. Jess, Sami K. Solanki, Andreas Lagg, Achim Gandorfer, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmüller, Alberto Álvarez-Herrero, Masahito Kubo, H. N. Smitha, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Francisco A. Iglesias, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović, Hirohisa Hara, Toshifumi Shimizu
High Energy Astrophysical Phenomena
Iron K$\alpha$ signatures from accretion disks around fermionic dark matter cores
V. Crespi, F. L. Vieyro, C. R. Argüelles et al. (+1 more)
The fluorescent iron line and its broadening due to relativistic effects are excellent probes to study the inner part of an
accretion disk and the space-time geometry near the compact object. We investigate the iron K$\alpha$ line profile within the extended RAR model, which describes a fermionic dark matter distribution on
galaxy scales. The most general solutions are characterized by a compact and highly degenerate core able to mimic the central black hole, transitioning into an extended
halo composed of the same particles. We aim to contrast the resulting line morphologies in this scenario with those predicted by the standard Kerr black hole paradigm. Special
attention will be given to MCG-06-30-15
galaxy. We compute the line profile using the numerical ray-tracing code, Skylight. We consider two distinct configurations for the emissivity of the cold
accretion disk: an irradiation profile based on the lamp-post corona prescription, and a phenomenological power-law profile. The resulting profiles exhibit a diverse phenomenology. In particular, the most compact
fermion cores produce a line broadening comparable to that observed in rapidly rotating black holes. The presence of emitting matter at radii smaller than a gravitational radius yields distinctive spectral features that are entirely absent in the black hole scenario. For MCG-06-30-15
galaxy, we find a good agreement with the observed broad features of the iron line profile, provided the compactness of the
fermion core is close to critical. These results reinforce the need for independent black hole
spin measurements. Combined with such constraints, iron-line spectroscopy may provide a powerful observational tool to distinguish black holes from alternative compact solutions, in particular compact fermionic dark-matter cores.
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All authors V. Crespi, F. L. Vieyro, C. R. Argüelles, J. A. Rueda
Instrumentation and Methods for Astrophysics
Data reduction pipeline for the SuMAC millimeter-wave spectrometer at the LMT
A. M. Lapuente, P. S. Barry, M. Becerril-Tapia et al. (+22 more)
We present the data reduction and analysis pipeline for the SuperSpec-MUSCAT Collaboration (SuMAC) along with several key science data products. In Summer 2025, SuperSpec on-chip spectrometers operating from $190-300$ GHz at $R\sim200$ were deployed in the MUSCAT cryostat at the Large Millimeter
Telescope, obtaining several days of on-sky data. Analysis of these data has been used to characterize noise performance and study spectra of various astrophysical sources, establishing the viability of deploying SuperSpec detectors in future instruments. These proceedings discuss the modular data reduction pipeline which uses timestreams of the kinetic inductance detectors (KIDs) and auxiliary instrument data to generate a variety of data products. We present an on-sky calibration method for converting the KID fractional frequency shift to on-sky brightness temperature. The mapmaking module generates 3D data cubes of extended sources, while the spectrum module produces a millimeter-wave spectrum of an object. The observations all incorporate measurements of the atmosphere to model and correct for absorption. We also discuss data processing choices including detector weighting, despiking, and notch filtering. Finally, we present preliminary data products including detection of carbon monoxide in NGC 253 and spectral maps of the central region of the Orion KL nebula.
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All authors A. M. Lapuente, P. S. Barry, M. Becerril-Tapia, C. Benson, C. M. Bradford, T. Brien, S. C. Chapman, S. Doyle, V. Gómez-Rivera, S. Hailey-Dunsheath, J. Hernández-Aguilar, J. L. Hernández-Rebollar, D. Hughes, E. Kane, K. S. Karkare, R. McGeehan, R. Naranjo-Romero, A. Papageorgiou, J. G. Redford, I. Rodríguez-Montoya, S. Rowe, D. O. Sánchez-Argüelles, S. Savorgnano, A. Tan, J. Vega-Méndez
Instrumentation and Methods for Astrophysics
SuMAC: On-sky demonstration of multi-pixel on-chip millimeter-wave spectroscopy at the Large Millimeter Telescope
Marcial Becerril-Tapia, Peter S. Barry, Christopher S. Benson et al. (+22 more)
The SuperSpec-MUSCAT Collaboration (SuMAC) is an effort to operate SuperSpec spectrometers in the MUSCAT instrument at the Large Millimeter
Telescope (LMT). SuperSpec is an on-chip filterbank spectrometer using kinetic inductance detectors (KIDs), with moderate $R\sim 200$ spectral resolution for observing in the 1 mm atmospheric window (190-300 GHz). While nominally a continuum camera operating a 1.1 mm, MUSCAT was also designed to operate as a testbed for pioneering detection technologies. In July 2025, three SuperSpec devices were installed and commissioned in the MUSCAT cryostat with minimal modifications to the system. This work presents an overview of SuperSpec's deployment and performance in MUSCAT along with the main results from the Summer 2025 observation campaign. Highlights include the detection of CO emission line in the
galaxy NGC253, mapping the Orion KL region, and preliminary line intensity mapping scans.
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All authors Marcial Becerril-Tapia, Peter S. Barry, Christopher S. Benson, Charles M. Bradford, Thomas L. R. Brien, Scott C. Chapman, Simon Doyle, Víctor Gómez-Rivera, Steven Hailey-Dunsheath, Jesús Hernández-Aguilar, José Luis Hernández-Rebollar, David H. Hughes, Elijah Kane, Kirit S. Karkare, Alex M. Lapuente, Ryan McGeehan, Raúl Naranjo-Romero, Andreas Papageorgiou, Joseph Redford, Iván Rodríguez-Montoya, Sam Rowe, David O. Sánchez-Argüelles, Sofia Savorgnano, Annie Tan, Jair Vega-Méndez
Earth and Planetary Astrophysics · Cross-listed from physics.space-ph
Simultaneous Mars-orbit observations reveal Kelvin-Helmholtz instability-driven bulk atmospheric ion escape
Chi Zhang, Chuanfei Dong, Gangkai Poh et al. (+11 more)
Atmospheric ion escape driven by the
solar wind is a key process controlling the long-term loss of the Martian atmosphere. Localized
plasma clouds can carry substantial fluxes of planetary ions away from Mars, representing episodes of bulk escape. However, their origin has remained unclear due to the absence of simultaneous upstream measurements. Using joint observations from the MAVEN and Tianwen-1 missions, which provide real-time upstream monitoring, we present direct evidence that these
plasma clouds are nonlinear wave packets generated by the Kelvin-Helmholtz instability (KHI). The spatial scale of KH waves is constrained for the first time via two-point measurements. Ion fluxes within
plasma clouds are one to two orders of magnitude higher than those in typical steady-state escape channels. Our results indicate that KHI is an important process for
solar wind coupling to planetary upper atmospheres and plays a crucial role in shaping atmospheric ion escape for unmagnetized
planets.
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All authors Chi Zhang, Chuanfei Dong, Gangkai Poh, Jasper Halekas, Xuanye Ma, Ruhunusiri Suranga, Kathleen G. Hanley, Han-Wen Shen, Hongyang Zhou, Xinmin Li, Liang Wang, Jiawei Gao, Shannon Curry, Christian Mazelle
Solar and Stellar Astrophysics
Horizontal Magnetic Fields Dominate the Quiet Sun Internetwork in Sunrise III Observations. Evidence from Traditional and Transformer-Based Inversions
Ryan J. Campbell, Carlos Quintero Noda, Manuel Collados et al. (+32 more)
The relative prevalence of horizontal and vertical
magnetic fields in the quiet-Sun internetwork remains debated, owing to the weak linear polarisation signals that make the inferred
magnetic inclination distributions sensitive to observational quality and inversion methodology. We investigate the
magnetic topology of the quiet-Sun internetwork in Sunrise~iii observations by independently applying
transformer-based and traditional inversion techniques to the same spectropolarimetric
dataset. We analyse observations obtained with the Sunrise Chromospheric Infrared spectroPolarimeter (SCIP).
Transformer-based inversions (SINN), trained exclusively on synthetic Stokes profiles generated from a large radiative magnetohydrodynamic simulation, are compared with independent inversions performed using the DeSIRe code. Both inversion methods recover a quiet-Sun
magnetic topology in which internetwork fields are strongly dominated by the horizontal component, whereas network fields exhibit a substantially more balanced
topology. At $\log\tau=-1.2$, the median horizontal and unsigned line-of-sight field components in the internetwork are 64 and 7G with DeSIRe, and 71 and 8G with SINN, respectively, corresponding to a horizontal-to-line-of-sight ratio of approximately nine for both methods. The agreement between the two fundamentally different inversion methodologies indicates that the quiet-Sun internetwork is characterised by a substantially stronger horizontal than vertical
magnetic field component. These results demonstrate that
transformer-based inversions can be successfully transferred from synthetic training data to real spectropolarimetric observations, while providing inference orders of magnitude faster than traditional inversion techniques.
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All authors Ryan J. Campbell, Carlos Quintero Noda, Manuel Collados, Mihalis Mathioudakis, Andreas Lagg, Achim Gandorfer, Jose Carlos del Toro Iniesta, Yukio Katsukawa, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmüller, Alberto Álvarez-Herrero, Masahito Kubo, H. N. Smitha, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Francisco A. Iglesias, Ryohtaroh T. Ishikawa, Yusuke Kawabata, Takuma Matsumoto, Takayoshi Oba, Azaymi L. Siu-Tapia, Hanna Strecker, Dušan Vukadinović, Hirohisa Hara, Toshifumi Shimizu
Cosmology and Nongalactic Astrophysics
Integrated cosmological memory: A dark-siren method to probe dark energy
Indranil Chakraborty, Sayantan Ghosh, Susmita Jana et al. (+2 more)
Gravitational-wave (GW) cosmology is currently bottlenecked by the scarcity of electromagnetic counterparts for bright sirens and the systematic uncertainties of
galaxy catalogs for dark sirens. We propose a purely gravitational resolution using the Integrated Cosmological
Memory (ICM)-the cumulative GW strain encoded in the spacetime geometry of an expanding Universe. While the GW transient emitted by the source provides the luminosity distance, the ICM accumulates a mathematically distinct integral of the
cosmic expansion history. We demonstrate that extracting both observables from a single binary merger completely breaks the distance-
redshift degeneracy within the gravitational sector. This establishes a novel, catalog-free dark siren framework for third-generation GW detector networks. Crucially, the resulting constraints on late-time dark energy are only weakly sensitive to the local expansion rate, providing a robust cosmological probe that can potentially mitigate the impact of the H0 tension.
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All authors Indranil Chakraborty, Sayantan Ghosh, Susmita Jana, Archana Pai, S. Shankaranarayanan
High Energy Astrophysical Phenomena
Thermal evolution of neo-neutron stars. II. Temperature-dependent crusts
Sagnik Chatterjee, Mikhail V. Beznogov, Dany Page et al. (+1 more)
The neo-
neutron star phase is an intermediate stage in the
evolution from a hot,
lepton-rich compact object, which is formed in the aftermath of a core-collapse
supernova or an
accretion-induced collapse of a white
dwarf, to a cold deleptonized
neutron star (NS). Alternatively, this phase can occur after a binary NS merger if the final compact object does not collapse immediately into a black hole. Radial temperature profiles provided by numerical simulations of proto-NS
evolution suggest that the composition and mechanical structure of the
star's core at the beginning of the neo-NS phase are approximately identical to those of a cold NS. In contrast, the composition and mechanical structure of the outer layers (i.e., the crust) are expected to change as the
star cools. The thermal
evolution of neo-NSs with temperature-dependent (inner) envelopes was considered by Beznogov et al. (2020). Here, we investigated what happens if the equation of state (EoS) of the entire crust, including its composition, depends on temperature. We analyzed the thermal, mechanical, and chemical
evolution of neo-NSs by further developing and employing neo-NSCool, our NS thermal
evolution code. First, we show that thermally dripped
neutrons slightly slow down the cooling during the early thermal relaxation stage. Then, we demonstrate that the EoSs featuring exotic light species in the deepest layers of the crust result in significantly slower cooling in the
photon-cooling era compared to the EoSs that favor massive
nuclei. The crust's composition also impacts the crystallization process as well as the contraction of the crust during cooling. The EoSs with light
nuclei cause the innermost layers to remain
liquid for a longer time than the EoSs with heavy
nuclei.
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All authors Sagnik Chatterjee, Mikhail V. Beznogov, Dany Page, Adriana R. Raduta
Solar and Stellar Astrophysics
Statistical Study of Solar Prominence Plumes Based on NVST H$\alpha$ Observations
Yangrui Chen, Yijun Hou, Jincheng Wang et al. (+9 more)
Plumes are one of the most representative dynamic features observed in prominences and play a key role in mass and
magnetic transport within them. However, their physical nature and triggering processes remain actively debated. Based on limb H$\alpha$ observations from the New
Vacuum Solar Telescope (NVST) during 2013–2025, we statistically investigated 34 plumes with clear and complete evolutions by developing an automated image-processing pipeline. It is revealed that plume lifetimes mainly range from 300 s to 700 s, with vertical displacements between 3–7 Mm. The mean widths and velocities are concentrated in the range of 0.5–1.5 Mm and 10–20 km s$^{-1}$, respectively. Besides wide distribution ranges, plume parameters exhibit irregular
evolution fluctuations, indicating that the formation and
evolution of various plumes may exhibit different physical patterns. Correlation analysis among the parameters further reveals that: (1) Positive correlations were found among lifetime, vertical displacement, and mean width, indicating an intrinsic coupling between the temporal and spatial scales of plumes. (2) Trajectory
curvature is negatively correlated with lifetime, vertical displacement, and velocity. Accelerating and width-contracting plumes typically have lower
curvature, suggesting that
curvature may reflect environmental influences and the stability of plumes. (3) Plumes with higher initial velocities were more likely to be accompanied by precursor brightening, suggesting that these plumes may be triggered by
magnetic reconnection. Furthermore, we infer that some plumes in non-bubble regions may be inherently driven by mini-filament eruptions. These results establish a statistical framework for prominence plumes and reveal diversity in their dynamical
evolution and triggering mechanisms.
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All authors Yangrui Chen, Yijun Hou, Jincheng Wang, Ting Li, Shuo Yang, Yilin Guo, Junyi Zhang, Haitang Li, Feiyang Sha, Qing Zhou, Yu Liu, Xiaoli Yan
Cosmology and Nongalactic Astrophysics
How Dilatation Invariance Suppresses Loop Corrections to Curvature Perturbations on CMB Scales
Danilo Artigas, Shi Pi, Takahiro Tanaka et al. (+1 more)
Departures from standard slow-roll (SR) inflation have attracted increasing interest in recent years. In particular, scenarios that strongly enhance the power spectrum of the
curvature perturbation are often proposed as a mechanism for producing
primordial black holes, which could account for part or the totality of dark matter. An ongoing debate in these models is whether non-linear interactions of cosmological perturbations on small scales, namely loop corrections, can become sufficiently large to backreact on CMB scales. In this work, we adopt a non-linear framework, dropping spatial-gradient terms, to study loop corrections at super-Hubble scales. Our focus is to clarify the role of spatial-diffeomorphism invariance, especially dilatation invariance, which is the
symmetry under overall rescaling of spatial coordinates, in demonstrating the suppression of loop corrections to the CMB power spectrum. This analysis is valid for any inflaton potential, both with smooth and sharp transitions, and at any loop order, as long as the CMB scales cross the horizon during an SR phase. We compare this result with the different explanations proposed in the literature using various gauge choices, and show our analysis is consistent both in the comoving and in the spatially-flat gauges. In particular, we show that in the spatially-flat gauge, the cubic interaction contains a term that diverges in the sharp transition limit. However, this contribution is exactly cancelled by the quartic interaction.
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All authors Danilo Artigas, Shi Pi, Takahiro Tanaka, Yuko Urakawa
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Gravitational Enstrophy: Local Geometric Origin and Energy-Cascade Constraints
Luis Lehner
Two-dimensional incompressible fluids conserve energy and enstrophy in the inviscid limit. Fjørtoft's argument uses this pair to constrain nonlinear energy transfer. We examine the corresponding question in General Relativity using the
magnetic Weyl functional $\mathcal Z=\int B_{ab}B^{ab}\sqrt{\gamma}\,d^3x$. Its transverse radiativ e part carries an additional frequency-squared weight relative to gravitational-wave energy: $\delta\mathcal Z_k\simeq\omega_k^2W_k$ in the radiation zone, with $W=8\pi G E_{\rm GW}$. We derive its balance law from the Bianchi identities, obtaining the algebraic cancellations, bulk sources and boundary fluxes. Conservation of positive e nergy and
curvature norm through nonlinear transfer gives a Fjørtoft constraint when their weights are ordered. Resonant weak-wave interactions generally change the c urvature norm; $2\leftrightarrow2$ dynamics instead conserves energy and wave action. We examine the competition between transfer and linear losses in Kerr and AdS backg rounds, where long-lived or confined modes provide time for nonlinear
evolution. In the hydrodynamic regime of AdS$_4$, a fluid-weighted
magnetic Weyl functional inherit s fluid enstrophy conservation in the inviscid limit. We compute its proportionality coefficient to boundary enstrophy in closed form at leading gradient order, giving a bulk diagnostic for
holographic turbulence.
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Astrophysics of Galaxies
Circumgalactic medium depletion drives satellite quenching in IllustrisTNG
Natan de Isídio, Paola Popesso, Sandro Tacchella et al. (+5 more)
Satellite
galaxies dominate the quenched population at low
stellar masses ($M_\star \lesssim 10^{10}~\rm M_\odot$), yet identifying which processes shut down their
star formation, their relative importance, and on what timescales, remains a central problem in
galaxy evolution. We use MaNGA-like mock
galaxies from IllustrisTNG to dissect different satellite quenching pathways, paying special
attention to the role of the circumgalactic medium (CGM) during quenching phase. We reconstruct the baryonic, dark matter, structural, and chemical histories of $\sim$7 300
galaxies (2 800 satellites), using time since infall as the physical axis along which quenching unfolds. Satellites retain rotation-supported
stellar kinematics throughout quenching, with disturbed velocity fields confined to systems with $M_\star \lesssim 10^{10.5}~\rm M_\odot$. For the first time, we present the coupled time
evolution of the depletion of both the hot and cool gas reservoirs after infall: satellites lose $\sim$90% of their hot CGM within $\sim$$4.2^{+0.6}_{-0.6}$ Gyr, increasing with residence time and independent of
stellar mass. The hot gas mass correlates strongly with SFR, establishing the CGM as the long-term fuel reservoir, unlike quenched centrals, which retain massive hot
halos likely maintained by AGN feedback. Present-day quenched satellites were accreted earlier than
star-forming ones (6.5$^{+0.3}_{-0.3}$ vs. 4.3$^{+0.3}_{-0.3}$ Gyr ago), forming
stars for at least $\sim$3 Gyr after infall before declining sharply, consistent with a delayed-then-rapid quenching scenario. Losing little
stellar mass, yet with their gas depleted and their dark matter and metal-poor
stellar outskirts tidally stripped, satellites emerge more compact and metal-rich than centrals at fixed mass. Our results suggest the gradual erosion of the hot CGM as the key link connecting infall to the slow shutdown of
star formation.
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All authors Natan de Isídio, Paola Popesso, Sandro Tacchella, Anna Pasquali, Ilaria Marini, Daudi Mazengo, Victoria Toptun, Sean McGee
High Energy Astrophysical Phenomena
Revisiting the XMM-Newton Observations of the Galactic Microquasar SS 433: Implications for the Origin of the Ultrahigh-Energy Emission Detected by LHAASO
Chao-Nan Tong, Hong-Bin Tan and Ruo-Yu Liu
Recently, the Large High Altitude Air Shower Observatory (LHAASO) detected ultrahigh-energy (UHE;
photon energy E>100TeV) $\gamma$-ray emission toward SS 433, the microquasar embedded in the W50 nebula, making it a promising
Galactic PeVatron candidate. We reanalyze the archival XMM-Newton observations covering the bipolar jets and the thermal X-ray shell north of SS 433, and derive spatially resolved profiles of the nonthermal X-ray intensity and
photon index along both jets. The jet emission softens with distance from the source, implying a correspondingly evolving electron population. In particular, a hard electron component appears close to the jet bases, which can account for the UHE emission from SS 433 via inverse Compton radiation if the
magnetic field remains approximately uniform along the jets. The result, however, is highly sensitive to the
magnetic field profile. For flux-conserving configurations in which the field decreases as the jet expands, the stronger field required in the inner regions may reduce the number of X-ray-emitting electrons and suppress their inverse Compton emission. Furthermore, electron transport calculations show that injection only at the jet bases cannot reproduce the observed intensity and spectral
evolution, particularly the downstream re-brightening features, indicating additional particle injection and/or re-acceleration within the jets.
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High Energy Astrophysical Phenomena
General-relativistic structure of two-component quantum dark fermion stars
Ilídio Lopes
We develop a general-relativistic framework for two-component
quantum dark
fermion stars:
equilibrium configurations of two degenerate
fermion species governed by
gravity, a Yukawa-mediated dark fifth force and a globally relevant Bohm
quantum-pressure correction. The treatment retains the full covariant form of the nonlinear Klein–Gordon equation in the Schwarzschild interior, with closure relations valid at arbitrary compactness, from the ultralight baseline up to densities of order $0.16\,\mathrm{fm}^{-3}$ at which relativistic scalar densities and self-consistent effective
fermion masses become unavoidable. Two Lagrangian parameters, the dark-
fermion mass and the dimensionless ratio between the Yukawa channel and
gravity, together fix the
equilibrium structure; a joint measurement of mass and radius therefore constrains the dark-sector microphysics directly from gravitational-wave observables. For particle masses in the band $10^{-11}$–$10^{-10}$ eV, the configurations exhibit radii of $3$-$24\,\mathrm{km}$ and compactness in the range $0.14$-$0.34$, behaving as dual mimickers: at moderate compactness they overlap with
neutron stars in mass, radius, and inspiral frequency; at the most compact end ($\kappa\sim 0.34$, $R_T/R_S\simeq 1.5$) they cross the
photon sphere and could masquerade as low-mass black holes in the mass-gap region.
Tidal-deformability measurements discriminate against both populations: the dimensionless
tidal deformability is measurably smaller than the
neutron-
star value yet remains non-zero, unlike that of a genuine black hole. These objects populate the sensitivity bands of LISA, the Einstein
Telescope, and
Cosmic Explorer, producing astrometric microlensing signatures individually resolvable by
Gaia. The framework thus provides a reproducible and falsifiable template for constraining dark-sector properties through multi-messenger observations.
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High Energy Astrophysical Phenomena
A JWST redshift for the host galaxy of EP250207b of z=3.2: a collapsar origin is viable
Agnes P. C. van Hoof, Peter G. Jonker, Andrew J. Levan et al. (+24 more)
We present James Webb Space
Telescope (JWST) and Hubble Space
Telescope (HST) observations of the field of the fast X-ray transient (FXT) detected by Einstein Probe, EP250207b, to resolve any ambiguity about the host
galaxy and
redshift of the FXT. EP250207b was originally associated with a nearby
galaxy at z=0.082, based on its low chance
alignment probability, and a binary
neutron star merger origin was proposed. However, we report the detection of a background
galaxy at z=3.2 at the location of EP250207b. Assuming this
galaxy is the actual host
galaxy, the rest-frame energetics and timescales of the event change. Furthermore, the available data are not able to rule out the presence of a
supernova associated with EP250207b if at this
redshift. We model the X-ray, optical, near-infrared and
radio light curves using a tophat jet model implemented in Redback and find that they are consistent with an on-axis gamma ray burst afterglow. The energetics and host
galaxy properties do not allow us to distinguish between a collapsar and a merger driven event.
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All authors Agnes P. C. van Hoof, Peter G. Jonker, Andrew J. Levan, Nial R. Tanvir, Franz E. Bauer, Joe Bright, Francesco Carotenuto, Ting-Wan Chen, Ashley Chrimes, Gregory Corcoran, Laura Cotter, Joyce N. D. van Dalen, Rob A.J. Eyles-Ferris, Morgan Fraser, Daniele B. Malesani, Daniel Mata Sánchez, Antonio Martin-Carrillo, Paul O'Brien, Francesca Onori, Jonathan Quirola-Vásquez, Maria E. Ravasio, Andrea Rossi, Javi Sánchez-Sierras, Nikhil Sarin, Steve Schulze, Hui Sun, Manuel A.P. Torres
Astrophysics of Galaxies
MIGHTEE-HI / LADUMA: Investigating the link between baryons and dynamics with 130 resolved HI-selected galaxies
Andreea A Vărăşteanu, Matt J. Jarvis, Harry Desmond et al. (+15 more)
The baryonic Tully-Fisher relation (bTFR) and the radial acceleration relation (RAR) link the observed dynamics in
galaxies to that expected from their baryonic mass distributions. The relations' small intrinsic scatters place strong constraints on
galaxy formation models, dark matter properties and theories of modified dynamics, yet detailed measurements beyond the very local Universe remain limited. We use 130 purely HI-selected
galaxies with resolved HI kinematics and baryonic mass profiles to measure the bTFR and RAR up to $z\approx0.09$. We measure a tight RAR with an acceleration scale $a_0=(1.50\pm0.05)\times10^{-10},{\rm m,s^{-2}}$ and an intrinsic scatter of $0.096\pm0.006$ dex, consistent with local results. We fit the bTFR in the `inverse' direction, conditioning on $M_{\rm bar}$ to mitigate HI flux-related selection effects, measuring a logarithmic slope of $0.27\pm0.01$ (corresponding to a forward slope of $3.72\pm0.16$), with vertical intrinsic scatter $\sigma_\perp\approx0.05$ dex. Fitting the general $\delta$-family of MOND interpolating functions to the RAR, we infer $\delta=4.10^{+1.4}_{-0.68}$, consistent with the value required by
Solar System gravitational constraints and a null Wide Binary Test. We find no significant
redshift evolution in the RAR acceleration scale for our pure HI-selected sample. However, the bTFR zero-point shows an apparent evolutionary trend that is strongly dependent on the fit direction: the traditional forward fit yields an $8.7\sigma$ preference for $z$
evolution, while for our fiducial inverse fit, this reduces to $3.4\sigma$, within $\approx2\sigma$ of the RAR
evolution constraint. This suggests selection effects bias the forward fit; a careful consideration of such effects will be required in future endeavours to robustly measure the
redshift evolution of dynamical scaling relations.
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All authors Andreea A Vărăşteanu, Matt J. Jarvis, Harry Desmond, Anastasia A. Ponomareva, Tariq Yasin, Michalina Maksymowicz-Maciata, Ian Heywood, Natasha Maddox, Andrew J. Baker, Laurent Chemin, Martin Meyer, Danail Obreschkow, Kristine Spekkens, Natalia Stylianou, Rohan G. Varadaraj, Marcin Glowacki, Maarten Baes, Abhisek Mohapatra
Cosmology and Nongalactic Astrophysics
Cosmic Velocity Flows: from Theory to Observations
Saee Dhawalikar
The Large-Scale Structure (LSS) of the Universe forms a complex network of nodes, filaments, sheets, and voids known as the
Cosmic Web. As current and upcoming
galaxy surveys increasingly probe the quasi-linear and non-linear regimes of structure formation, understanding its geometry and dynamics is essential for precision cosmology. In particular,
cosmic filaments, which channel matter across the web, are central to these dynamical processes. This thesis develops numerical tools to study the non-linear
cosmic web. First, the Sahyadri suite of high-resolution cosmological $N$-body simulations is introduced, providing a framework for precision studies of LSS and its cosmological dependence. A calibration framework for filament reconstruction is then developed using controlled filament realizations, enabling systematic investigation of reconstruction biases. The effects of filament
curvature and reconstruction noise on inferred filament properties are quantified, and a novel
Fourier-space smoothing approach is introduced to improve profile recovery. The thesis further presents Skeletor, a Voronoi-based filament finder that identifies filamentary structures directly from discrete tracers while explicitly incorporating the hierarchical nature of the
cosmic web. A novel framework for classifying sub-filamentary structure is developed. Applying these tools to cosmological simulations reveals distinct properties of filament substructure and provides a detailed view of filament phase space, including coherent inflows, multistreaming, and caustic-like features. Together, these developments provide a framework for studying the geometry, hierarchy, and dynamics of the non-linear
cosmic web. More broadly, they contribute to the ongoing effort to build a physically motivated understanding of the non-linear
cosmic web beyond traditional measures of clustering.
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Solar and Stellar Astrophysics
Hot water emission during an outburst in a classical T Tauri star
Zhen Guo, Javier Osses, Vitor Fermiano et al. (+34 more)
In this paper, we present observations of an eruptive young
star in the Rosette Nebula, identified by the
Gaia Science Alerts system using
Gaia time series data. We aim to investigate the
evolution of the brightness and mass
accretion rate of V557 Mon throughout its outburst and subsequent decline. In addition, we trace the
evolution of the inner
accretion disk during the outburst by monitoring molecular emission features. We compiled multi-band photometric time series from
Gaia, ZTF, and several 1 m-class ground-based
telescopes and obtained optical and near-infrared spectra at multiple epochs covering the outburst and fading phases.
Stellar parameters were derived from quiescent colour/spectra and spectral energy distribution (SED) fitting. We also measured the mass
accretion rate and fit models to molecular emission bands. Since late 2024, V557 Mon has undergone a year-long outburst consistent with EXor variability. Based on quiescent photometry, V557 Mon has a spectral type of M1 with an extinction of AV = 1.8+_0.3 mag, consistent with a 0.4-0.5 M_sol
star at an age of 2 Myr. Our multi-epoch spectra and u-band photometry indicate a peak
accretion rate of 6.3x10^(-7)M_sol/yr during the outburst, roughly 70 times higher than in quiescence. We report the detection of hot water vapour emission bands, together with TiO, VO, and CO emission features. Using ExoMol models, we measured the inner-disk temperature changed from 3000 K to 2000 K during the fading phase of the outburst. We report a recent EXor outburst in a low-mass Class II YSO. Our observations reveal the transient formation of a hot molecular inner disk, traced by variable water vapour emission during the EXor event. A positive correlation is found between the molecular excitation temperature and the overall
stellar brightness.
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All authors Zhen Guo, Javier Osses, Vitor Fermiano, Yuting Zhou, Min Fang, Gregory Herczeg, Adolfo Carvalho, Vardan Elbakyan, Lynne Hillenbrand, Mutian Wang, Hanpu Liu, Yao Liu, Cesar Briceno, Koshvendra Singh, Valentin D. Ivanov, Joe Ninan, Teresa Giannini, Aldo Aliaga, Calum Morris, Matias Montesinos, He Zhao, Carlos Contreras Pena, Jessy Jose, Tarak Chand, Wen-Ping Chen, Wei-Hao Wang, Yang Huang, Camila Lopez, Pablo Fernandez-Schlosser, Diego Correa-Herrera, Radostin Kurtev, Vania Rodriguez, Carolina Lizana-Vidal, Jura Borissova, Michael Kuhn, Roberto K. Saito, Ram K. Yadav
Solar and Stellar Astrophysics
Wave excitation by a collapsing granule: insights from IFU observations and high-resolution RMHD simulations
J. Buttler, G. Vigeesh, I. Milić et al. (+5 more)
Context. Granular collapse is an ubiquitous process of granular
evolution on the
solar surface, but it is hard to analyze in sufficient spatial, temporal, and spectral detail. Aims. We analyze the change in physical conditions in the photosphere during a specific granular collapse event and the subsequent atmospheric response. Methods. We contrast a high-resolution radiative magneto-hydrodynamic simulation of a granular collapse performed using the CO5BOLD code with the recent integral field unit observations carried out using the MiHI instrument at the Swedish 1-m
Solar Telescope. Results. Our analysis shows that the observed and simulated granular collapse show remarkable similarity. Specifically, they both exhibit the signature of a wave pulse excited in the deep photosphere and visible up to the temperature minimum. This wave is detectable through a blue-wing emission in the observed and synthetic Na i D1 line. We also estimate the acoustic energy flux carried by the wave and analyze its initiation. Conclusions. Combining high-resolution IFU spectropolarimetry and state-of-the-art simulations of the
solar lower atmosphere, this study showcases our current capabilities in identifying specific physical processes taking place during the granular collapse and their impact on the atmosphere above.
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All authors J. Buttler, G. Vigeesh, I. Milić, M. van Noort, S. M. Díaz Castillo, C. J. Díaz Baso, F. Riva, O. Steiner
Cosmology and Nongalactic Astrophysics
Modified Cosmological Expansion and the JWST CMB Optical Depth Tension in Self Interaction Gravity
Subhadeep Mukherjee, Shashank Shekhar Pandey and A. S. Majumdar
Recent James Webb Space
Telescope (JWST) observations favor an earlier and more efficient reionization history, leading to Thomson-scattering optical depths larger than those inferred from the
cosmic microwave background (CMB). We investigate whether this tension can be alleviated within the framework of self-interaction (SI)
gravity by modifying the cosmological expansion history while retaining the standard astrophysical description of reionization. The SI
gravity parameters are constrained through a
Bayesian MCMC analysis of the Union3 Type Ia
supernova and DESI DR2
Baryon Acoustic Oscillations (BAO) data. The resulting expansion history is then used to predict the ionization history and Thomson optical depth. We find that the predicted optical depth decreases from $\tau_{\rm{CMB}}\simeq0.076$ in $\Lambda$CDM to $\tau_{\rm{CMB}}\simeq0.061$, consistent with the Planck PR4 measurement within $1\sigma$, thereby substantially reducing the optical-depth tension.
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Cosmology and Nongalactic Astrophysics
SCRIPT in the Cosmic Dawn: Distinguishing Redshift-Evolving Galaxy Populations with 21-cm Fluctuations
Janakee Raste and Tirthankar Roy Choudhury
Recent James Webb Space
Telescope (JWST) observations suggest an unexpectedly high abundance of luminous
galaxies at $z \gtrsim 10$, challenging traditional models of
star formation. The 21-cm signal of neutral hydrogen offers a complementary, volume-averaged probe of these early epochs. In this work, we present a major extension to the explicitly
photon-conserving semi-numerical framework SCRIPT, enabling the self-consistent calculation of
spin temperature fluctuations driven by inhomogeneous Lyman-$\alpha$ coupling and X-ray heating during the
Cosmic Dawn. Using this framework, we compare a JWST-informed fiducial
galaxy model, featuring a
redshift-evolving
star-formation efficiency, against a static baseline model. We demonstrate that the global 21-cm signal is highly degenerate: a static
galaxy population can replicate the absorption trough of an evolving population if a steep, mass-dependent X-ray efficiency is invoked to shift intergalactic medium heating toward highly abundant, low-mass
halos. However, this degeneracy is definitively broken by the 21-cm power spectrum. Because spatial fluctuations retain a structural
memory of the clustering bias of the source
halos, the tuned static model predicts a substantially lower power spectrum amplitude across all characteristic peaks. We conclude that combining global and fluctuation measurements is essential to robustly constrain the
redshift evolution of high-
redshift galaxies.
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