Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
General Relativistic Entropic Acceleration at the perturbation level: a CLASS implementation and first Boltzmann-code constraints
Simone D'Onofrio, Dong Ha Lee, Eleonora Di Valentino et al. (+1 more)
General Relativistic Entropic Acceleration (GREA) attributes the late-time acceleration of the Universe to the
entropy growth of the causal cosmological horizon, without a cosmological constant, with a phenomenology fixed by the single $\mathcal{O}(1)$ parameter $\alpha$. The model has so far been confronted with data only at the background level. We present its first implementation within an Einstein-Boltzmann solver: the GREA background is integrated directly into CLASS, while the entropic component is evolved as an effective fluid regulated by the parametrized-post-Friedmann scheme, giving access to the full CMB and matter power spectra. A Markov-chain Monte Carlo analysis with COBAYA against the full primary-CMB likelihoods, DESI DR2 BAO and Type Ia
supernovae constrains the coupling $\alpha \sim 1$, in excellent agreement with the theoretical prediction, with a fit matching $\Lambda$CDM to within $|\Delta\chi^2| \lesssim 6$ despite the addition of a single free parameter. The equation of state inferred from the data agrees with binned, model-independent reconstructions and exhibits a second crossing of the phantom divide at $z \simeq 2$, a distinctive prediction of the thermodynamic dynamics rather than of an imposed parametrization.
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All authors Simone D'Onofrio, Dong Ha Lee, Eleonora Di Valentino, Juan García-Bellido
Astrophysics of Galaxies
Compiling the largest multiwavelength database of known changing-look AGN: Prospects in the Rubin era
Mariangella Camus and Swayamtrupta Panda
Changing-look active
galactic nuclei (CL-AGN) provide a direct way to study
accretion and spectral-state changes on timescales of months to years. Still, the known population remains scattered across heterogeneous literature samples. We present a compilation of a homogenized catalog of known CL-AGN and related candidates, designed as a traceable reference database for time-domain and multiwavelength studies. After coordinate homogenization, duplicate removal, and validation, the optical parent catalog contains 1,438 unique sources, including 987 spectroscopically confirmed CL-AGN and 451 candidate or photometrically selected systems. We augment the catalog with ancillary information from
radio/mm, infrared, ultraviolet, X-ray, and gamma-ray data sets using nway and survey-specific quality criteria. The resulting database includes 188 sources in the broad
radio layer, 9 RFC/VLBI compact-core matches, 16 sources with ALMA archival coverage, 1,353 infrared counterparts, 918 GALEX ultraviolet matches, and 576 X-ray counterparts. We also identify 9
Fermi-LAT candidate associations. Overall, 1,385 sources have at least one non-optical counterpart, and 75 have coverage across the four main ancillary regimes:
radio, infrared, ultraviolet, and X-ray. As a first application, we identify 70 confirmed CL-AGN within the LSST Wide–Fast–Deep footprint and 5 within the Rubin Deep Drilling Fields, and provide the up-to-date, ~116-day ugrizy Rubin lightcurve for SDSS J095902.76+021906.3 (z=0.34579) and discuss the early data inferences. This catalog is envisioned to be community-driven and provides a dynamic, expandable resource for target selection, population comparisons, and future Rubin-era CL-AGN studies.
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Solar and Stellar Astrophysics
Progenitor models of supernovae interacting with their binary companions
Andrea Ercolino
The appearance of nearly all core-collapse (CC)
supernovae (SNe) is largely affected by the interaction between their progenitors and a close binary companion. Using a comprehensive, state-of-the-art grid of single- and binary
stellar evolution models, the relative frequencies of SN types are predicted, as well as the distribution functions of their main properties. SNe that interact with nearby circumstellar material are included, namely those that explode during ongoing binary mass transfer, and are found to account for ~5% of all CCSNe, consistently with observations. The interaction between the newly born compact object and the companion is also investigated, which may produce observable signatures similar to those seen in SN2022jli. These SNe could account for between 3% and 27% of all H-poor CCSNe. These results will help develop strategies for identifying such
supernovae in past and future searches, which will help to constrain uncertain physics in single and binary
evolution models.
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Solar and Stellar Astrophysics
Shear interaction and acceleration of a corotating stream detected by Parker Solar Probe
Andrea Verdini, Simone Landi, Emanuele Papini et al. (+4 more)
Recent analysis of Parker
Solar Probe (PSP) and
Solar Orbiter data indicates that fluctuations energy is transferred to the bulk flow in fast streams of the
solar wind at heliocentric distances between 15 and 120 Rsun. To gain insight into this process, we analyze data collected during the inbound orbit of PSP in Encounter 10, when it is in approximate corotation with the Sun and an accelerating stream is detected between 25 and 45 Rsun. The geometry of the flow indicates that a neighboring very fast streams is colliding with the corotating stream, causing large-scale
magnetic field distortion, density enhancement, and acceleration. However, also deposition of fluctuations' energy can heat and do work on the
solar wind
plasma, resulting in a radial acceleration. We evaluate the energy lost by fluctuations via radial variation of conserved quantities in the corotating stream and find that it is almost equally partitioned into heating and work. While the heating is marginally consistent with the non-adiabatic decrease of
proton temperature, the work exerted on the wind is insufficient to account for the measured
solar wind acceleration. Although limited to this event, observations suggest that shear interaction is capable of accelerating slower streams within relatively short distances from the Sun, possibly leaving its imprint as large-scale density and
magnetic fluctuations.
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All authors Andrea Verdini, Simone Landi, Emanuele Papini, Luca Franci, Petr Hellinger, Roberto Livi, Orlando Romeo
Solar and Stellar Astrophysics
Solar Wind Proton Heating and its Effect on Temperature Anisotropy Evolution between 0.05 and 1 au
Etienne Berriot, Arnaud Zaslavsky, Olga Alexandrova et al. (+3 more)
This study focuses on the radial
evolution of the
solar wind
proton adiabatic invariants and temperature anisotropies in the inner heliosphere. More specifically, we study in-situ measurements provided by the Parker
Solar Probe, between 0.05 au and 0.25 au from the Sun, and
Solar Orbiter spacecraft between 0.3 au and 1 au. Throughout the studied range of radial distances, we observe a significant average heating in the direction perpendicular to the local
magnetic field for both fast and slow
solar wind populations. On the other hand, there is no clear deviation from adiabaticity in the parallel direction regardless of the wind speed. The perpendicular heating is enough to significantly reduce the generation of the temperature anisotropy expected from a double adiabatic
evolution. Despite the heating, an important portion of the
solar wind (especially the slower wind streams) develops substantial anisotropies with higher parallel temperatures, which eventually become constrained by kinetic firehose instabilities.
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All authors Etienne Berriot, Arnaud Zaslavsky, Olga Alexandrova, Pascal Démoulin, Petr Hellinger, Lorenzo Matteini
Astrophysics of Galaxies
Ly$\alpha$ Escape in JWST/NIRCam F430M-Selected H$\alpha$ Emitters at $z\simeq5.5$
Cheng Cheng, Zhen-Ya Zheng, Chunyan Jiang et al. (+8 more)
We study the Ly$\alpha$ escape fraction ($f_{\rm esc}$) in an H$\alpha$-selected sample of
star-forming
galaxies at $z\simeq5.5$, identified via JWST/NIRCam F430M excess and covered by archival VLT/MUSE data. By anchoring the intrinsic Ly$\alpha$ production to H$\alpha$ emission, our approach provides a direct and Ly$\alpha$-unbiased probe of the escape of Ly$\alpha$
photons in
galaxies with SFR $\gtrsim 0.1\,M_\odot\,{\rm yr^{-1}}$ at this epoch. Ly$\alpha$ emission is detected in 3 out of 12
galaxies covered by VLT/MUSE. Combining detections and upper limits, we place a conservative upper bound of $\langle f_{\rm esc}^{\rm Ly\alpha} \rangle < 0.32$ on the population-averaged Ly$\alpha$ escape fraction. We find that Ly$\alpha$ detections are preferentially associated with nearly
dust-free systems, while no clear correlation between SFR and $f_{\rm esc}$, suggesting a
stochastic picture of Ly$\alpha$ escape. Interestingly, three of the four Ly$\alpha$-detected
galaxies reside within a known overdense structure, suggesting that local environment may further facilitate Ly$\alpha$
photons escape. Our H$\alpha$-selected approach establishes a general and scalable framework for probing Ly$\alpha$ escape by combining JWST medium- or narrow-band imaging with ground-based spectroscopic data, enabling systematic and less biased studies of Ly$\alpha$ visibility in typical
star-forming
galaxies during the post-reionization era.
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All authors Cheng Cheng, Zhen-Ya Zheng, Chunyan Jiang, Fengwu Sun, Edo Ibar, Xin Wang, Haojing Yan, Fang-Ting Yuan, Jia-Sheng Huang, Juan Molina, Malte Brinch
Astrophysics of Galaxies
HI Depletion Begins Well Beyond the Virial Radius: A FAST Stacking Study of 36 Galaxy Clusters to 5R200
Cheng Cheng, Chuan-Peng Zhang, Edo Ibar et al. (+10 more)
We present a stacking study of the neutral atomic hydrogen (HI) content in and around 36 local
galaxy clusters at $z<0.07$, using a combination of the FAST all sky HI survey (FASHI) and the extensive spectroscopic catalog mainly from the Dark Energy Spectroscopic Instrument (DESI). We employ spectral stacking techniques to probe the average HI mass and HI-to-
stellar mass ratio ($M_{\rm HI}/M_*$) for member
galaxies down to
stellar masses of $M_*\sim 10^9M_\odot$, spanning a projected cluster-centric distance to $5R_{200}$. Our analysis reveals a pronounced environmental effect: both $M_{\rm HI}$ and $M_{\rm HI}/M_*$ decrease steadily towards the cluster center, dropping by $\sim 0.5$ dex on average from the outskirts to the core. Crucially, we find that $M_{\rm HI}/M_*$ of
galaxies remain lower than the field
galaxies even at the $5R_{200}$. This provides direct, statistical evidence for substantial gas stripping and pre-processing in the cluster outskirts, likely occurring in infalling groups and large-scale filaments. By further splitting the sample by $g-r$ color, we show that the HI deficiency persists at fixed
galaxy color: even the bluest cluster members exhibit $\sim 0.5$~dex lower $M_{\rm HI}/M_*$ than field
galaxies of similar color, reflecting environmental effects on the cold gas reservoir prior to full optical transformation. The total HI mass within clusters and their outskirts agrees broadly with predictions from cosmological simulation. Our results underscore the critical role of the extended cluster environment in quenching
galaxies by depleting their cold gas reservoirs well before they enter the dense cluster core.
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All authors Cheng Cheng, Chuan-Peng Zhang, Edo Ibar, Rory Smith, Weiwei Xu, Hyowon Kim, Jia-Sheng Huang, Wei Zhang, Pei Zuo, Hugo Méndez-Hernández, Juan Molina, Ming Zhu, Qian Yu
Solar and Stellar Astrophysics
High-Frequency Magnetohydrodynamic Waves with Substantial Energy in the Solar Polar Corona
Yuhang Gao, Hui Tian, Richard Morton et al. (+5 more)
The acceleration and heating of the fast
solar wind remain long-standing challenges in space physics. One type of leading theoretical models requires high-frequency magnetohydrodynamic (MHD) waves to transport and dissipate sufficient energy in the corona. However, such high-frequency waves with energetically significant amplitudes have never been unambiguously observed, leaving a key gap between theories and observations. Using high-cadence, high-resolution extreme-ultraviolet imaging from
Solar Orbiter's Extreme Ultraviolet Imager, we identify a previously hidden population of high-frequency MHD waves in coronal plumes of the
solar polar region. An analysis of the detected propagating kink waves shows that over one-third have periods shorter than 100 s, a population largely undetected by earlier instruments. Power spectral analysis demonstrates that these high-frequency waves carry substantial energy flux, which are significantly underestimated in lower-cadence data. These results suggest that high-frequency MHD waves may contribute importantly to the energy budget of the
solar polar corona and could play a role in
solar wind acceleration, highlighting the value of high-resolution observations for probing energy transport in magnetized space and astrophysical
plasmas.
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All authors Yuhang Gao, Hui Tian, Richard Morton, Tom Van Doorsselaere, Daye Lim, Mingzhe Guo, Jiansen He, Zhenyong Hou
Earth and Planetary Astrophysics
Unmasking (44) Nysa: Evidence for a trilobate structure
Kate Minker, Anthony Berdeu, Gianluca Li Causi et al. (+16 more)
Context. (44) Nysa is one of the largest known E-type asteroids. Light curve inversion models have indicated that it may have an elongated shape commonly found in large binary systems. Aims. We aimed to identify the morphology and presence of possible satellites orbiting Nysa. Methods. We observed Nysa with the visible-wavelengths adaptive-optics instruments SHARK-VIS and SPHERE/ZIMPOL in order to image the object with the highest possible spatial resolution, and visually identified surface features on the object. A shape model was constructed from these images and photometric light curves using the ADAM code. Results. Imaging revealed a highly unusual morphology with multiple distinct surface features, including two distinct valleys most easily interpreted as colli. A faint satellite was identified in the deconvolution residuals in multiple
datasets. Conclusions. We determine that (44) Nysa is a binary system most likely consisting of a contact-trinary or highly-irregular, coherent primary object and a small satellite.
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All authors Kate Minker, Anthony Berdeu, Gianluca Li Causi, Josef Hanuš, Michaël Marsset, Al Conrad, Fernando Pedichini, Simone Antoniucci, Piero Vaccari, Nick Moskovitz, Benoit Carry, Tom Polakis, Marin Ferrais, Emmanuël Jehin, Roberto Bonamico, Rhiannon Hicks, Daejhanae Smith, M. Amine Miftah, Ester Marini
Solar and Stellar Astrophysics
JWST/MIRI Detection of Molecular H$_2$ Winds from an Edge-on Class II Source HV Tau C
Vinod Chandra Pathak, P. Manoj, Himanshu Tyagi et al. (+14 more)
The
evolution of protoplanetary disks is regulated by
accretion onto the central
star and mass loss through jets and winds. While atomic and ionized
outflows are commonly observed, molecular winds in evolved Class II disks remain rarely detected. We characterize the spatial, thermal, kinematic, and dynamical properties of molecular hydrogen (H$_2$) emission from the nearly edge-on Class II disk HV Tau C and assess the impact of its molecular wind. We also constrain
accretion using H I recombination lines detected in the same mid-infrared spectrum. Using JWST/MIRI-MRS data from the MINDS Cycle 1 GTO program, we analyze spatially resolved pure-rotational H$_2$ emission. Rotational and position-velocity diagrams constrain excitation and kinematics, from which we estimate wind properties. We detect extended H$_2$ emission tracing a wide-angled, biconical molecular wind extending beyond the near-infrared scattered-light disk, ALMA 887 $\mu$m
dust continuum, and compact $^{12}$CO ($J=3$-$2$) gas disk. The H$_2$ rotational diagram requires warm ($\sim$600K) and hot ($\sim$2000K) components, similar to those in younger protostars. The gas shows outward motions of a few tens of km s$^{-1}$ and dynamical timescales of tens to hundreds of years. The inferred mass-loss rate is $\sim10^{-8}$ M$_\odot$ yr$^{-1}$, while
accretion rates derived from H I lines are $10^{-10}$-$10^{-8}$ M$_\odot$ yr$^{-1}$. The
accretion rate may be underestimated because of the edge-on geometry. Our results show that wide-angled molecular H$_2$ winds can persist into the Class II phase, with
outflow rates comparable to some protostellar systems, suggesting that such winds may remain important for angular momentum removal, disk
evolution, and dispersal. (Abstract modified; see the paper for the full version.)
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All authors Vinod Chandra Pathak, P. Manoj, Himanshu Tyagi, B. Shridharan, Th. Henning, I. Kamp, A. Caratti o Garatti, B. Banerjee, Mayank Narang, E. F. van Dishoeck, Kamber Schwarz, Manuel Güdel, Alice Somigliana, Giulia Perotti, Aditya M. Arabhavi, Sujay Vijay Jadhav, Göran Olofsson
High Energy Astrophysical Phenomena
Pair luminosity and cooling of newborn strange star: Color-flavor-locked and two-flavor color superconducting quarks
Mikalai Prakapenia, Cheng-Jun Xia and Gregory Vereshchagin
Following the previous wor k[1] here we consider early thermal
evolution of hot strange
stars made of color superconducting
quarks in two different pairing states: two-
flavor color
superconductor (2SC) and color-
flavor-locked (CFL) phases, taking into account cooling by
neutrinos and electron-positron pair creation due to the Schwinger process. We show that Schwinger luminosity in the electrosphere is a universal function of temperature, independent of
quark matter phase for
quark chemical potential $\mu_q>280$ MeV. The surface of a strange
star in all the cases cools faster than its interior. This leads to a fast decrease of pair luminosity with time, so that it does not exceed $10^{46}$ erg/s at 1 second after strange
star formation.
Neutrino luminosity dominates over pair luminosity in all the cases except for the CFL phase with a large gap parameter $\Delta>60$ MeV, where there is a strong suppression of
neutrino emission. The total energy emitted in electron-positron pairs is always smaller than the energy emitted in
neutrinos, but they become comparable for the large gap parameter.
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Instrumentation and Methods for Astrophysics
The Lunar Farside Transients and Technology Telescope (LFT3) Mission
David R. DeBoer, Charlie K. Ashe, Owen A. Johnson et al. (+12 more)
We present here an overview of the Lunar Farside Transients and Technology
Telescope (LFT3) mission to take advantage of the extremely clear
radio frequency environment on the lunar farside.
Radio observations performed from the lunar farside effectively and fully mitigate two unavoidable limitations of terrestrial-based
radio telescopes: (i) the prevalence of interfering
radio transmitters from human activity; and (ii) the impact of the Earth's ionosphere. However, in the era of cost-effective access to the Moon, there are many scheduled lunar missions over the next few years, and the window of opportunity to perform
radio interference-free observations from the lunar farside is closing fast. LFT3 is the only mission proposed to go to the lunar farside and exploit this unique opportunity in human history. LFT3 will observe in an uncluttered
radio environment to conduct unambiguous technosignature searches, transient surveys,
solar physics and planetary emissions studies, spectral line observations, and cosmological science observations. LFT3 will provide an important incumbent use of the microwave spectrum for cislunar
radio astronomy.
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All authors David R. DeBoer, Charlie K. Ashe, Owen A. Johnson, Evan F. Keane, Andrew C. Lesh, Richard Lynch, Ella J. Marshall, Steve Prabu, Anže Slosar, Chenoa D. Tremblay, Jake D. Turner, Karl F. Warnick, Andrew P. V. Siemion, Jamie Drew, S. Pete Worden
Astrophysics of Galaxies
Chemical modelling of interstellar MgS
M. Rey-Montejo, I. Jimenez-Serra, T. Millar et al. (+8 more)
The detection of magnesium sulphide (MgS) and sodium sulphide (NaS) towards the
Galactic Center molecular cloud G+0.693 constitutes the first detection of metal sulphides in the interstellar medium (ISM). However, there is scarce information about the key reactions (either in the gas phase or on grains) involved in their formation. In this paper, we model the chemistry of MgS simulating the passage of a low-velocity shock to recover the abundances recently measured towards G+0.693. Through this chemical modelling, we analyse the dominant reactions involved in the formation and destruction of this molecule, their associated chemical time-scales, and the depletion factor needed to recover the observed abundances. We build the initial chemical network of MgS by using SiS as a proxy for this metal sulphide, and we investigate the exothermicity of these and additional, uniquely proposed reactions through
quantum chemical computations. We run a three-phase model (initial translucent cloud, cloud collapse phase and shock interaction stage) that mimics the
evolution and physical conditions of G+0.693. Our results show that a depletion factor of 1000 is required for elemental Mg to recover the observed abundances of MgS. This implies that potentially more than 99.9% of Mg is locked in
dust grains. The dominant reaction leading to the formation of MgS is the neutral-neutral reaction between MgH and S in the gas phase. This work represents the first analysis of the chemistry of the metal-sulphide MgS and suggests that Mg is largely incorporated into
dust grains, most likely in the form of silicates. However, additional laboratory and/or theoretical studies of the key MgS formation reactions are essential to obtain more reliable constraints. Future missions, such as PRIMA, will provide insights into the amount of metal-sulphides locked into interstellar
dust grains.
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All authors M. Rey-Montejo, I. Jimenez-Serra, T. Millar, R.C. Fortenberry, S. Viti, J. Garcia de la Concepcion, G. Vermarien, M. Sanz-Novo, L. Colzi, S. Zeng, V.M. Rivilla
Instrumentation and Methods for Astrophysics
RAISE: A Low-Frequency Space-Based Payload for Solar Radio and RFI Measurements on the SMiLE Mission
Sangeetha A, Harsha Avinash Tanti, Abhirup Datta et al. (+2 more)
We present the
Radio-wave Apparatus for Investigating
Solar & Earth interference (RAISE), a compact low-frequency
radio payload proposed for hosting on the SMiLE mission. Operating from Low Earth Orbit, RAISE targets a spectral regime that is largely inaccessible from the ground due to ionospheric effects. The payload is designed to enable space-based observations of low-frequency
solar radio emissions while simultaneously characterizing terrestrial and ionospheric
radio frequency interference in the near-Earth environment. RAISE employs mode-dependent Earth-pointing and Sun-pointing observations to generate dynamic spectral measurements relevant to space weather studies and low-frequency
radio mission planning. As an experimental and technology demonstration payload, RAISE provides essential heritage for future space-based low-frequency
radio astronomy and space weather missions.
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All authors Sangeetha A, Harsha Avinash Tanti, Abhirup Datta, Anshu Kumari, Rajesh Bodade
Astrophysics of Galaxies
Low-Metallicity Star Formation Survey in Sh2-284 (LZ-STAR): The Core Mass Function
Yu Cheng, Jonathan C. Tan, Morten Andersen et al. (+4 more)
We present an ALMA 1.3~mm
dust continuum study of the dense core mass function (CMF) in Sh2-284, a low
metallicity outer
Galaxy star-forming complex with $Z\sim1/3$–$1/2~Z_\odot$. The observations cover six far-infrared bright subregions at $\sim$0.65" (3000~au) resolution. We identify a total of 91 candidate dense cores and define a robust catalog of 68 cores with Gaussian fitting. The high-mass CMF above 2.5 Msun is well described by a Salpeter-like slope, with a fiducial forward-modeled value of $\alpha=1.22^{+0.24}_{-0.22}$ for $dN/d\log M\propto M^{-\alpha}$. Together with existing constraints on the initial mass function (IMF) of Sh2-284, the Salpeter-like CMF is consistent with a resemblance between the CMF and IMF shapes in the outer
Galaxy environments, suggesting that moderately low
metallicity alone does not strongly reshape the high-mass CMF/IMF slope.
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All authors Yu Cheng, Jonathan C. Tan, Morten Andersen, Alva Kinman, Rubén Fedriani, Kei E. I. Tanaka, Yichen Zhang
Solar and Stellar Astrophysics
Toward 3D orbits of wide sdO/B binaries I. Six composite systems spatially resolved with VLTI/GRAVITY
K. Deshmukh, S. Geier, H. Sana et al. (+7 more)
Hot subdwarf
stars (sdO/Bs) are widely considered to be products of binary
evolution. A significant fraction of them are found in long-period or wide binaries ($P>500$ d) with main sequence (MS) companions, likely resulting from a stable mass transfer episode where the MS companion stripped the hydrogen envelope of the sdO/B progenitor. Consequently, wide sdO/B binaries represent a key population in our pursuit of understanding stable mass transfer. They exhibit a modest range of orbital periods and eccentricities as revealed by long-term spectroscopic campaigns, though the component masses are not well constrained. In this Letter, we present the first long-baseline interferometry campaign to observe wide sdO/B + MS binaries and take the first step toward determining their 3-dimensional (3D) orbits and model-independent component masses. We target six composite sdO/B + MS systems with VLTI/
GRAVITY and spatially resolve all of them. The projected physical separations range between $1-3$ au, with uncertainties between $1-8$%. When combined with complementary information from spectroscopic or astrometric observations, our precise measurements will be crucial to constrain 3D orbits for these systems. Additionally, we also identify a potential third component in BD+10 2357, although additional data will be necessary for confirmation. In light of continued spectroscopic monitoring and the imminent
Gaia Data Release 4, we strongly encourage expanding the interferometric sample presented here to establish new, precise orbital and mass constraints for this key population of binary interaction products.
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All authors K. Deshmukh, S. Geier, H. Sana, H. Dawson, M. Dorsch, A. J. Frost, U. Heber, T. Kupfer, A. Picco, M. Vučković
Solar and Stellar Astrophysics
Herbig AeBe Star AS442A as a UXOR-type system
Nariman Ismailov, Faida Surkhai Huseynova, Volkan Bak{\i}ş et al. (+3 more)
Detailed studies of the physical characteristics of young intermediate-mass Herbig Ae/Be (HAeBe)
stars require extensive sets of homogeneous observational data collected over long periods. In this paper, we present the results of a multi-year study focusing on the faint Herbig Ae/Be
star AS 442A. The goal of this study was to investigate the spectral and photometric variability of the
star, utilizing long-term archival photometry alongside our own spectroscopic observations. The long-term photometric variability was statistically investigated using approximately 3,500 archival measurements spanning 1984 to 2025. Additionally, we examined the
star's spectral variability using data obtained at the Shamakhy Astrophysical Observatory (ShAO) between 2020 and 2024. The three deepest brightness minima were detected in 1990, 2013, and 2023, with amplitudes of approximately ~2 mag in the U-band and up to ~1 mag in other bands. All three observed deep minima were accompanied by smaller brightness dips occurring both before and after the main event. The main light curve and color-magnitude diagrams show the "blueing" effect, which is characteristic of UXOR
stars. A quasi-periodic occurrence of deep brightness minima with a period of P = 3759 +/- 35 days was detected for the first time. Our spectral observations were performed before the last deep light fading, which occurred in 2023. We show that the observed spectral variability, specifically the strengthening of emission lines and the reduction in depths and widths of absorption lines, is primarily related to the
star's brightness variations. We have shown for the first time that the main reason for the UXOR-like brightness dip of the HAeBe
star AS 442A can be explained by a periodic eclipse in a binary system. A close companion as a late-type secondary
star with an orbit semimajor axis (a>7.5 au) likely drives the observed
stellar variability.
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All authors Nariman Ismailov, Faida Surkhai Huseynova, Volkan Bak{\i}ş, Namiq Serdar Dzhalilov, Sabahaddin Amanulla Alishov, Shafaq Kamal Ismayilova
Cosmology and Nongalactic Astrophysics
Robust Ly$\alpha$ forest constraints on reionization from semi-analytic galaxy formation models
Yuxiang Qin and J. Stuart B. Wyithe
The high-
redshift Ly$\alpha$ forest provides one of the most sensitive probes of the final stages of reionization, but its interpretation can depend on how the ionizing sources are modelled. We test the robustness of Ly$\alpha$ forest-inferred reionization histories using Meraxes, a semi-analytic model of
galaxy formation and reionization applied to a cosmological volume of $(210h^{-1}{\rm cMpc})^3$ with merger trees augmented down to the atomic-cooling threshold. We construct a suite of source models in which the
galaxy escape fraction, $f_{\rm esc}^{\rm gal}$, is parameterized as a function of
halo mass,
stellar mass,
star formation rate, specific
star formation rate, or
star-forming disc surface density. We also consider models in which accreting blackholes contribute ionizing
photons, or dense circumgalactic gas further attenuates the escape of ionizing
photons. Each model is calibrated to the observed distribution of Ly$\alpha$ effective optical depths from XQR-30+. These prescriptions redistribute the escaping
photon budget across
halo mass and UV luminosity, introduce scatter in $f_{\rm esc}^{\rm gal}$ at fixed
halo mass, and allow modest variation in the early
evolution of reionization. Nevertheless, all viable calibrated models recover a late and extended EoR, with the midpoint occurring at $z\sim6.2$–6.9 and the final stages at $z\sim5.36$–5.57. Our results indicate that the late reionization history inferred from Ly$\alpha$ forest is robust to physically motivated scatter in the
galaxy–
halo connection, modest AGN contributions, and phenomenological CGM attenuation.
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Astrophysics of Galaxies
SKAO-ALMA Synergies in Star Formation Science
Jan Forbrich, Gary A. Fuller, Mark A. Thompson et al. (+7 more)
We highlight the potential for synergies between the SKA
telescopes and ALMA, which will begin to be significant already with SKA Early Science. Broadly within
star formation science, we focus on 1) (simultaneous) time domain and variability studies (e.g., of (proto-)
stars), which is systematically opening a new observing window that will enable us to better constrain the physics of extreme
stellar flares and their interplay with mass
accretion in young
stars, 2) possibilities for complementary coverage of different transitions of molecules as tracers of the ISM (e.g., H2CO to trace density and temperature), and 3)
radio recombination lines to trace ionised gas at different densities. Furthermore, we address synergies in terms of the spatial resolution of both observatories and new capabilities not only on the SKAO side but extending to the ALMA2030 wideband sensitivity upgrade.
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All authors Jan Forbrich, Gary A. Fuller, Mark A. Thompson, Eleonora Bianchi, Jaime E. Pineda, Marta De Simone, Tomoya Hirota, Katharine Johnston, Steven N. Longmore, Giovanni Sabatini
Cosmology and Nongalactic Astrophysics
Simulation-based tension quantification of the cosmic dipole
Mali Land-Strykowski, Harry T. J. Bevins, Oliver T. Oayda et al. (+1 more)
The
cosmic dipole measured in surveys of cosmologically distant sources consistently exceeds the expectation derived from the
cosmic microwave background, posing a significant challenge to the standard $\Lambda$CDM cosmology. In the era of precision cosmology, quantifying robust tensions is constrained by our ability to model complex, non-linear effects that often result in intractable likelihood functions. In this paper, we present a flexible simulation-based inference (SBI) architecture for measuring the
cosmic dipole tension using Neural Ratio
Estimators (NREs). We design and train an ensemble of NREs to evaluate the log
Bayesian evidence ratio and measure $N\sigma$ tension. We validate our approach against nested sampling, demonstrating that it accurately recovers the ground-truth. Under the kinematic interpretation of the dipole, we apply our approach to Planck, the NRAO VLA Sky Survey (NVSS), the Rapid ASKAP Continuum Survey (RACS), and the Wide-field Infrared Survey Explorer catalogue (CatWISE). Here, leveraging SBI, we measure a $\approx5.7\sigma$ tension between CatWISE and Planck. We demonstrate the extensibility of our approach by applying it to forward-modelled simulations of the CatWISE Eddington bias, revealing a $\approx6.7\sigma$ tension. The methodology proposed here enables robust tension quantification as we enter the era of LSST, Euclid, and the SKA.
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All authors Mali Land-Strykowski, Harry T. J. Bevins, Oliver T. Oayda, Geraint F. Lewis
Solar and Stellar Astrophysics
Project Hephaistos – III. Characterizing anomalous infrared sources identified as Dyson-sphere candidates
Andreas J. Korn, Matías Suazo, Erik Zackrisson et al. (+3 more)
The infrared-flux excess of
stars harbouring Dyson spheres represent one potential technosignature of extraterrestrial intelligence. In a previous Project Hephaistos paper, we highlighted seven M
dwarfs within 300 pc with unusual infrared properties that seem to resemble those expected for Dyson spheres. In the present study, we present an analysis of photometric and, in some cases, spectroscopic data on these seven objects, plus three additional objects with similar properties, to further constrain their nature. The
stellar parameters, derived from calibrated empirical relationships for M
dwarfs, reveal no irregularities with respect to the overall M-
dwarf population of main-sequence
stars. While the infrared properties of our targets resemble those of circumstellar disks in a transitional state, the objects with spectroscopic data show no signs of youth usually associated with such objects. One of our spectroscopic targets does exhibit weak H$\alpha$ emission, but this is more likely attributed to
stellar activity than to the gaseous
accretion disk expected for a young
star. After this analysis, we still find no clear explanation for the infrared excess of these
stars, but note that observations with the JWST and/or the Atacama Large Millimeter/submillimeter Array would be able to probe scenarios in which the infrared excess is due to circumstellar
dust emission or an infrared-bright background source that remains undetected at shorter wavelengths. For two of our
stars, JWST observations have recently revealed superpositions with very red background
galaxies.
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All authors Andreas J. Korn, Matías Suazo, Erik Zackrisson, Pía Cortés-Zuleta, Adam D. Rains, Armin Nabizadeh
Astrophysics of Galaxies
Tracing Obscured AGN Contribution and Number Fraction Across 0 < z < 6 with JWST
Angel Rodriguez Barbosa, Tomotsugu Goto, Daryl Joe D. Santos et al. (+7 more)
Active
galactic nuclei (AGN) are key drivers of
galaxy evolution, yet many remain undetected in ultraviolet and optical surveys due to heavy
dust obscuration. In these systems, absorbed emission is re-radiated at infrared (IR) wavelengths, making IR observations essential for identifying the full AGN population. Tracking the AGN IR contribution and number fraction provides insight into both the dominance and prevalence of AGN activity across
cosmic time. Using the JWST Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES) and the JWST Advanced Deep Extragalactic Survey (JADES), we leverage continuous optical-to-mid-IR coverage (0.4-25 $\mu$m) in the GOODS-S field to identify obscured AGN via multi-wavelength SED fitting with CIGALE. Our sample includes 278 AGN across 0 < z < 6, representing a seven-fold increase in sample size relative to previous studies utilizing the
Cosmic Evolution Early Release Science (CEERS) survey due to the larger 15-pointing SMILES MIRI footprint. We find that both AGN IR contribution and number fraction increase with
redshift, with AGN fractions rising from $\lesssim$ 5% at z < 2 to ~ 30% at higher
redshifts, while the median AGN contribution increases by up to ~ 0.15. In contrast, as a function of total IR luminosity over $\log(L/L_{\odot}) \approx$ 8 - 12, the AGN contribution and AGN number fraction remain fundamentally static. These trends suggest that the prevalence of obscured AGN activity is dependent on
redshift while showing little to no dependence on total infrared luminosity. Our results highlight JWST's ability to uncover previously hidden AGN populations and provide new constraints on AGN-
galaxy co-
evolution.
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All authors Angel Rodriguez Barbosa, Tomotsugu Goto, Daryl Joe D. Santos, Chih-Teng Ling, Tetsuya Hashimoto, Ece Kilerci, Priyanka Jalan, Terry Long Phan Deriyan Senjaya, Vignesh V.V. Rao, Bahareh S. Salmasi
Instrumentation and Methods for Astrophysics
AI's Capability in Assisting Scientific Research in Physics, Astrophysics, and Cosmology I: Literature Review
Anamaria Hell, Kateryna Vovk, Veena Krishnaraj et al. (+18 more)
We investigate how well large
language models (LLMs) can assist with literature reviews for scientific research. We perform a controlled study of eight expert-conceived research projects across the areas of physics, astrophysics, and cosmology. Each project has a defined background and goal, and human experts and AI prompters are asked to perform identical literature review tasks in parallel. We compare the relevant literature selected by humans with that selected by mid-2025 LLMs (ChatGPT-4o, ChatGPT Deep Research, and Gemini). We find the overlap between human- and AI-selected references to be small ($<$6%), indicating that AI models do not yet reproduce a competent expert search on their own, though they have the potential to complement literature searches by humans. We then assess the reliability and completeness of AI-generated candidate references, distinguishing two types of
hallucination: fabrications (references to nonexistent papers) and metadata mismatches (real papers with one or more incorrect fields). We find that while fabricated references make up 3% of the AI-generated references, 64% are real papers with at least one incorrect field (title, author, year, journal, DOI, or link), indicating that the mid-2025 models require systematic verification. However, the performance is significantly improved for the 2026 model ChatGPT Pro 5.5, with a single-project test showing zero fabrication or metadata mismatches.
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All authors Anamaria Hell, Kateryna Vovk, Veena Krishnaraj, Jia Liu, Kosuke Aizawa, Adrian E. Bayer, Linda Blot, Jessica Cowell, Suyog Garg, Jonathan Grée, Ben Horowitz, Masaya Ichikawa, Kanyuni Iemoto, Keigo Kondo, Zacharie Lorsin, Kevin McCarthy, Jamie Robinson, Miguel Ruiz-Granda, Leander Thiele, Ievgen Vovk, Mingshen Zhou
Solar and Stellar Astrophysics
From simulations to observations of cool plasma: What we can learn from synthetic spectra
V. Jerčić, T. A. Kucera, A. G. M. Pietrow et al. (+2 more)
Cool
plasma of coronal rain or prominences and filaments is ubiquitous in the
solar corona. We explored the synthetic spectra of MgII h&k lines in detail and analyse how well a non-adiabatic magnetohydrodynamic (MHD) simulation of condensations in the corona matches observations when comparing the synthetic with the observed spectra. We applied, a Python implemented, non-local thermodynamic
equilibrium (non-LTE) radiative-transfer framework, Promweaver to create synthetic spectra from a 2.5D MHD simulation created with MPI-AMRVAC. The simulation shows a dynamic system of numerous cold, dense thread-like structures that we compare to observations of the $\textit{Interface Region Imaging Spectrograph}$ (IRIS), with a focus on
flare-driven coronal rain. We give a detailed description of the simulation from the aspect of the synthetic spectra. We show how and why the particular spectra form. A single thread already demonstrates great complexity. We further used the quartile analysis to systematically explore the
evolution of observables in the observed and the synthetic spectra. This gives an overview of how the parameters change in time and that the changes seen in the simulation fit with the changes seen in observations. The results show that the simulation, in some aspects, matches particularly well to the observations of
flare-driven coronal rain. Furthermore, we explored relations of parameters of the simulation and the observables. We find significant correlation between intensity and density, but not with temperature (in the studied temperature range of 5 to 20 kK). As a result, there is also a correlation of intensity and pressure. This relation allows us to further relate intensity and the vertical component of the Lorentz force. This brings us a step closer to a better understanding of the connection between the observed spectra and the atmosphere from which it originates.
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All authors V. Jerčić, T. A. Kucera, A. G. M. Pietrow, P. Antolin, J. M. Jenkins
Astrophysics of Galaxies
Distribution of the magnetic field relative to the plane of the Galaxy in the region of the Sagittarius spiral arm
R.R. Andreasyan, H.R. Andreasyan, A. M. Mickaelian et al. (+2 more)
Faraday rotation data for 492
pulsars and more than 2,700 extragalactic
radio sources were used to study the
magnetic field, in detail, in the direction of
Galactic longitude $33^o$ <l< $63^o$, which partially covers the Sagittarius spiral arm region. It was proposed that the Sagittarius spiral arm lies north of the h=-300 pc plane, where h is the distance from the
Galactic plane. The (-) sign indicates that this plane is located in the southern hemisphere of the
Galaxy. The
magnetic field of the Sagittarius spiral arm is directed toward the Sun. This direction is close to the direction of the
magnetic field of the northern hemisphere
halo. The small absolute value of the rotation measures in the region south of the h=-300 pc plane is due solely to the contribution of the
magnetic field of the southern hemisphere
halo, which is directed opposite to the field of the northern hemisphere
halo and the direction of the field in the Sagittarius arm. In the interarm region between the local Orion arm and the Sagittarius arm, the
halo magnetic field extends to the
Galactic plane, where a reversal of the
magnetic fields of the
halos of the northern and southern hemispheres occurs.
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All authors R.R. Andreasyan, H.R. Andreasyan, A. M. Mickaelian, A.G. Suqiasyan, G.M. Paronyan
High Energy Astrophysical Phenomena
Progenitor and Explosion Mechanism of 3C 397 Indicated from XRISM High-resolution Spectroscopy of Fe-group Elements
Hiroshi Nakajima, Yuken Ohshiro, Shing-Chi Leung et al. (+8 more)
We present spatially resolved X-ray spectroscopy of the Type Ia
supernova remnant 3C 397, one of the most promising candidates to have originated from a white
dwarf with a mass close to the Chandrasekhar limit. The remnant was observed during the performance verification phase of the X-ray Imaging and Spectroscopy Mission (XRISM), with the field of view of the Resolve calorimeter array positioned on the eastern half of the remnant. We divide the Resolve field of view into southeastern and northeastern regions and extract spectra from each region for both Resolve and Xtend. The Resolve spectra are characterized by narrow K-shell emission lines from intermediate-mass elements (IMEs) such as Si, S, Ar, and Ca, and by broader K-shell emission lines from iron-group elements (IGEs) such as Cr, Mn, Fe, and Ni. K-shell emission lines from Ti and Cr are also detected, and are found to be locally enhanced in the southeastern region, as reported in previous observations. We model the Resolve and Xtend spectra simultaneously by a non-
equilibrium ionization (NEI)
plasma model with multiple temperatures and ionization states. The observed mass ratios of Ti/Fe and Cr/Fe in the southeastern region can only be explained by nucleosynthesis in a
neutron-rich environment produced by electron-capture reactions in the innermost layers of the exploding white
dwarf. By comparing the observed mass ratios with those predicted by nucleosynthesis models, we constrain the central density to be >= 4.0 x 10^9 g cm^{-3} for the deflagration-to-detonation transition model and >= 6.0 x 10^9 g cm^{-3} for the pure turbulent deflagration model. On the other hand, the observed Ni/Fe mass ratio is globally enhanced across the field of view, suggesting an additional neutronization mechanism beyond electron-capture reactions, such as a higher progenitor
metallicity.
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All authors Hiroshi Nakajima, Yuken Ohshiro, Shing-Chi Leung, Koji Mori, Yoshiaki Kanemaru, Yoshitomo Maeda, Hiroya Yamaguchi, Masayoshi Nobukawa, Kumiko Nobukawa, Manabu Ishida, Yuichiro Ezoe
Solar and Stellar Astrophysics
V407 Vul: a triple star system with an AM CVn detectable by gravitational wave observatories
James Munday, Antonio C. Rodriguez, Nicole Reindl et al. (+23 more)
The AM CVn class includes mass transferring, ultra-compact double white
dwarf binaries with orbital periods on the timescale of minutes. A long-standing puzzle is that none of the roughly fifty ultra-compact, "verification binaries" which are easily detectable in the millihertz gravitational wave regime reside in a triple
star configuration. Much evidence has hinted at V407 Vul being an inspiraling, double white
dwarf AM CVn with an orbital period of 569s. Yet, a decisive confirmation has proved challenging since a main sequence
star dominates its visible spectrum. We present a clear confirmation of the triple
star nature of the source by detecting a significant astrometric wobble of the photocentre on the 569s orbital period of the binary. The AM CVn and the main sequence components are gravitationally bound with a spatial separation of roughly 0.03-0.04”, equating to an orbital separation of approximately 120AU. A total of 23 years of orbital timing constrained the orbital decay of the AM CVn as being precise to the 1% level, critical in understanding if this class of binary survives through a period minimum or coalesce. New Hubble Space
Telescope ultra-violet imaging and spectroscopic data allowed the isolated detection of the AM CVn at shorter wavelengths, revealing an approximately 58000 K accretor white
dwarf, while placing a firm distance constraint of 3510+140-110 pc. At this distance, we predict that the
Laser Interferometer Space
Antenna (LISA) will detect V407 Vul with a 28.4+-9.2 signal-to-noise ratio in a 4yr mission time, making it the first verification binary with an outer tertiary, or "verification triple", detectable for millihertz gravitational wave observatories.
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All authors James Munday, Antonio C. Rodriguez, Nicole Reindl, Nina Mackensen, Tin Long Sunny Wong, S.P. Littlefair, Ingrid Pelisoli, Alex Brown, N. Castro Segura, Joheen Chakraborty, Harry Dawson, V. S. Dhillon, Matti Dorsch, Martin Dyer, James A. Garbutt, Stephan Geier, Matthew Green, Dan Jarvis, Mark R. Kennedy, Paul Kerry, James McCormac, Steven G. Parsons, Jan van Roestel, Dave Sahman, P.-E. Tremblay, Amalie Yates
Earth and Planetary Astrophysics
The Influence of Dust Composition on Accretion Outbursts
Nicolas Kaufmann, Anna B.T. Penzlin, Alfie Robinson et al. (+3 more)
Context: Episodic
accretion outbursts have been shown to occur in protoplanetary discs due to thermal instability at the inner edge of the dead zone. These outbursts periodically heat up the dead zone, significantly altering the composition/chemistry and
accretion onto the
star. Aims: We investigate how these
accretion outbursts affect the inner disc composition and how different
dust compositions and properties affect the outbursts' dynamics. Methods: We run vertically integrated axis-symmetric
dust and gas
evolution models using the TriPoD method, including
dust opacity dependent heating and cooling, a dead zone model, and compositional tracking of
dust, including the evaporation and condensation of volatiles. Results: When considering
dust to be made up of a condensation sequence of silicates and volatiles, the outburst evaporates most of the
dust within 0.5 au. The fast re-condensation and subsequent viscous
evolution reset the disc between bursts. Additionally, we find that the burst cycle period and maximal
accretion rate directly correlate with the
dust sublimation temperature.
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All authors Nicolas Kaufmann, Anna B.T. Penzlin, Alfie Robinson, Alexandros Ziampras, Tilman Birnstiel, Richard Booth
High Energy Astrophysical Phenomena
Timing and Spectral Analysis of the 2024 Outburst of 2S 1553$-$542 with NuSTAR and NICER
Haifan Zhu, Wei Wang, Wen Yang et al. (+4 more)
We report a timing and spectral study of the 2024 outburst of the Be/X-ray binary
pulsar 2S~1553$-$542 using NuSTAR and NICER observations. From the NuSTAR light curve we measure a pulse period of $9.285022\pm0.000001$~s. The energy-resolved pulse profiles are dominated by a single peak and show a wing-like structure most clearly in the $12$–$22$~keV band. The pulsed fraction remains above 60% and increases with energy. The phase-averaged NuSTAR spectrum is described by an absorbed blackbody plus cutoff power-law continuum, together with an iron emission line and a cyclotron absorption feature. Using the cyclabs model, we obtain a cyclotron energy of $E_{\rm cyc}\simeq24.1$~keV, corresponding to a
magnetic field strength of $B\sim3\times10^{12}$~G. Phase-resolved spectroscopy shows that the continuum and cyclotron-line parameters vary with pulse phase, and that the line becomes poorly constrained around the pulse-wing phase. We also searched the short NICER GTIs for transient mHz variability using wavelet analysis and a CEEMDAN-based
Hilbert–Huang transform. Localized excesses near $\sim10$~mHz and $\sim20$~mHz are found, but the short exposures, COI effects, red-noise fluctuations, and the lack of a well-constrained
Fourier peak limit their significance. We therefore treat them as candidate mHz variability rather than firm mHz QPO detections.
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All authors Haifan Zhu, Wei Wang, Wen Yang, Mariano Mendez, Chenxu Gao, Ziyi Xu, Pengfu Tian
High Energy Astrophysical Phenomena
Fast optical spectroscopic observations of PSR J1023+0038 over one orbital period
M. M. Messa, M. C. Baglio, P. D'Avanzo et al. (+8 more)
Transitional millisecond
pulsars (tMSPs) are
neutron-
star binaries that switch between rotation-powered and
accretion-powered states, providing a key link between low-mass X-ray binaries and millisecond
radio pulsars. In their sub-luminous disc state, these systems exhibit complex variability whose origin is still debated. We present high-time-resolution optical spectroscopic observations of the tMSP PSR J1023+0038 obtained during its sub-luminous disc state. Our
dataset covers for the first time a full orbital cycle at minute-timescale cadence. We detect significant variability in the main properties of the optical emission lines, including the equivalent width (EW) and full width at half maximum (FWHM), on timescales of minutes. A comparison between the temporal
evolution of these quantities reveals indications of correlated behaviour, with some FWHM minima coinciding with decreases in the EW. This may point to episodes of matter ejection from the inner regions of the
accretion disc, possibly associated with switches to low modes. The Doppler
tomography of the H$\alpha$ and H$\beta$ emission lines suggests the presence of asymmetric emission structures, consistent with a scenario in which part of the accreting material is expelled from the system. In addition, the optical continuum shows variability consistent with a possible orbital modulation associated with the irradiated companion
star, although its characterisation is limited by the observing conditions. Our results provide new constraints on the short-timescale behaviour of tMSPs in the sub-luminous disc state and support scenarios in which
accretion and
outflow processes coexist. Further multiwavelength observations, particularly including simultaneous X-ray coverage, will be crucial to establish a direct link between the observed optical variability and the high/low mode switches.
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All authors M. M. Messa, M. C. Baglio, P. D'Avanzo, G. Illiano, F. Coti Zelati, K. Alabarta, D. de Martino, Y. D. Hu, A. Miraval Zanon, A. Reguitti, S. Campana