High Energy Astrophysical Phenomena
Far-infrared synchrotron properties of the inner lobes of the radio galaxy Centaurus A revealed with the Herschel observatory
Naoki Isobe, Motoki Kino, Takao Nakagawa et al. (+3 more)
Diffuse far-infrared synchrotron emission filling the northern inner lobe of the
radio galaxy Centaurus A is investigated with the Spectral and Photometric Imaging Receiver onboard the Herschel observatory at its three photometric bands. The far-infrared flux density spatially integrated over the lobe is measured as $S_{\rm \nu} = 1.63 \pm 0.05$ Jy at the wavelength of $500$ $\mu$m (the frequency of $600$ GHz). A comparison between the far-infrared spectral index derived with Herschel ($\alpha = 1.32 \pm 0.19$) and the
radio index ($\alpha = 0.66 \pm 0.04$) suggests a spectral break between these frequency ranges. The change of the spectral index through the break is indicated to be consistent with that of the standard cooling break ($\Delta \alpha = 0.5$) predicted for particle acceleration under the continuous energy injection condition. A broken power-law model incorporating the standard cooling break yields the break frequency as $\nu_{\rm b} = 218 \pm 83$ GHz. From the measured cooling break frequency, the
magnetic field of the northern inner lobe is evaluated as $B \gtrsim 100$ $\mu$G. It is quantitatively estimated that the adiabatic cooling puts only a minor impact on the derived
magnetic field. This
magnetic field is higher than that under the minimum-energy condition by more than a factor of $5$. In addition, the derived
magnetic field of the lobe is suggested to be at least by a factor of $4$ stronger than that of the inner-jet region implied in the previous very-high-energy gamma-ray study. Even if the line-of-sight orientation of the lobe is considered in its possible extreme case, the
magnetic field is found to be reduced only by a factor of 2, and the above arguments about the strong
magnetic field basically holds. The science impact of this result is discussed from the viewpoints of jet energetics, and of ultra-high energy
cosmic rays.
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All authors Naoki Isobe, Motoki Kino, Takao Nakagawa, Shunsuke Baba, Makoto Tashiro, Hiroshi Nagai
Astrophysics of Galaxies
Subarcsecond Multi-line Observations of NH$_3$ with VLA toward the Class 0 Source IRAS 16293-2422
Yoshihide Yamato, Yuri Aikawa, Kenji Furuya et al. (+2 more)
Ammonia (NH$_3$) is one of the key volatiles that plays a central role in nitrogen chemistry and its
evolution during the epoch of
star and
planet formation. We present subarcsecond ($\sim0.\!\!^{\prime\prime}5$) resolution observations of NH$_3$ molecular emission lines with Karl G. Jansky Very Large Array (VLA) toward the Class 0 multiple system IRAS 16293-2422 including source A and source B as major components. This comprises the most comprehensive set of NH$_3$ line observations in protostellar sources to date, which includes 17 inversion transitions with a wide range of upper state energies ($E_\mathrm{u}$) spanning from $\sim$23 K to $\sim$1,580 K. We detect spatially resolved emission of a number of transitions, and find that the high-$E_\mathrm{u}$ ($\gtrsim$1,000 K) lines show compact distributions in the vicinity of protostars while low-$E_\mathrm{u}$ ($\lesssim$150 K) lines exhibit more extended emission. Utilizing a two-component model, we constrain the rotation temperature and NH$_3$ column density for both source A and source B. The rotation temperature of the warmer component reaches $\sim$200-300 K, indicating that the high-$E_\mathrm{u}$ lines selectively trace the inner hot region. We suggest that this hot NH$_3$ gas in source A is originated from the local shock heating based on the comparison with the previous high-resolution ALMA observations, while that in source B could be explained by the mass
accretion heating in the innermost hot region. We also briefly discuss the chemistry related to NH$_3$ based on the abundance ratios relative to major icy molecules derived using literature values.
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All authors Yoshihide Yamato, Yuri Aikawa, Kenji Furuya, John J. Tobin, Jes K. Jørgensen
High Energy Astrophysical Phenomena
On the Faint Early-time Radio and X-ray Emissions in TDE2025aarm
Tatsuya Matsumoto and Tsvi Piran
TDE2025aarm is a nearby
tidal disruption event whose early
radio and X-ray emissions are exceptionally faint compared with previously observed TDEs. We examine whether these weak signals can be explained within standard
outflow and disk-emission scenarios. The
radio detection at $15\,\rm GHz$ with $\sim10^{36}\,\rm erg\,s^{-1}$ around $40\,\rm days$ after discovery is inconsistent with synchrotron emission from a quasi-spherical disk wind for reasonable circum-
nuclear densities and
outflow velocities. Instead, the low luminosity and inferred self-absorbed spectrum imply a narrowly collimated
outflow with a solid angle $\lesssim0.1\,\rm sr$, naturally identified with the unbound
stellar debris. The X-ray emission is likewise unusually faint, with $L_{\rm X}\sim10^{39-40}\,\rm erg\,s^{-1}$ during the first few months. If interpreted as thermal emission from an obscured
accretion disk, the inferred emitting area would correspond to an implausibly small X-ray-transparent region expected to vary on short dynamical timescales that are not observed. Alternatively, the same shock responsible for the
radio emission can accelerate relativistic electrons that produce X-rays through synchrotron radiation and/or inverse-Compton scattering of optical/UV
photons. Both mechanisms can explain the early faint X-ray emission, although their temporal
evolution differs. Continued
radio and X-ray monitoring of TDE2025aarm will provide a sensitive probe of the unbound debris, circum-
nuclear medium, and high-energy emission mechanisms in optical TDEs.
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High Energy Astrophysical Phenomena
JWST Reveals Large Reservoirs of Dust and Ongoing Circumstellar Interaction in SN Ibn/Icn 2023xgo over a Year Post-Explosion
Kyle W. Davis, Kirsty Taggart, Samaporn Tinyanont et al. (+23 more)
We present infrared (IR) photometric and spectroscopic observations of SN 2023xgo, a recent and nearby Type Ibn/Icn
supernova (SN Ibn/Icn) which shows shock interaction with a He/C-rich and H-poor circumstellar medium (CSM). Although interacting SNe are predicted to produce large amounts of
dust, the rarity of SNe Ibn and Icn has resulted in few opportunities to observe these objects in the IR at late times. Here, we report observations of SN 2023xgo from JWST (NIRSpec and MIRI), WISE, and Gemini taken out to +377 days post-explosion. At +377 days, the JWST spectrum is consistent with both emission from cool (~300-600 K) silicate
dust with $M \gtrsim 3 \times 10^{-2}$ M$_{\odot}$ at a radius similar to the shock radius ($2.3 \times 10^{16}$ cm), and optically thin carbonaceous
dust with $M = 8 \times 10^{-3}$ M$_{\odot}$. We also detect narrow (FWHM = 520+/-130 km s$^{-1}$) He I $\lambda$2.06 micron emission at +377 days, indicating that the SN shock continues to encounter material shed from the
star to this late epoch. The emission line is blueshifted from the rest frame by 340+/-40 km s$^{-1}$. The Gemini and WISE observations at ~70-100 days reveal emission from 6.8$\times$10$^{-5}$ M$_{\odot}$ of hot (~1300 K)
dust, which we interpret as a lower limit of the total
dust mass at that phase. Molecular gas emission is not detected in any data, though emission line profiles in the optical and NIR taken at ~70 days after explosion show progressively less redshifted emission, attributed to attenuation from
dust and suggesting that some
dust is rapidly forming interior to the unshocked CSM. The large
dust mass and rapid onset of
dust formation observed in SN 2023xgo show that the unique physical environments of SNe Ibn/Icn facilitate substantial
dust formation both before and after the SN.
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All authors Kyle W. Davis, Kirsty Taggart, Samaporn Tinyanont, Ryan J. Foley, Jeonghee Rho, Katie Auchettl, Diego Farias, Ori D. Fox, Joel Johansson, Charles D. Kilpatrick, Kishore C. Patra, Craig Pellegrino, Enrico Ramirez-Ruiz, David A. Coulter, Yize Dong, Alexander T. Gagliano, T. R. Geballe, Wynn V. Jacobson-Galán, Jenna Karcheski, Ravjit Kaur, Ryan M. Lau, Thomas Moore, Seong Hyun Park, Armin Rest, Tamás Szalai, Qinan Wang
Astrophysics of Galaxies
Ultraviolet diversity of Little Red Dots as a probe for direct-collapse black hole ages
Elia Cenci, Melanie Habouzit and Dale D. Kocevski
Little Red Dots (LRDs) uncovered by the James Webb Space
Telescope have been proposed as candidate
galaxies hosting embedded accreting direct-collapse black holes (DCBHs), yet the relative ultraviolet (UV) emission of their host
galaxy remains highly uncertain and diverse across the population. Using a large-scale cosmological hydrodynamical simulation from the \textsc{meli$\odot$ra} suite, we investigate the contribution of PopIII
stars and accreting DCBHs in LRD candidates at $z>8.5$, in the rest-frame $0.2-0.6~\mu\mathrm{m}$ band. We find that the UV emission from the host
galaxy evolves rapidly over the first $\sim 30~\mathrm{Myr}$ following DCBH formation, reflecting the build-up of
stellar mass and metal enrichment. This
evolution consists of a rapid transition from initially BH-dominated systems, with negligible
stellar mass, low
metallicity, and high
accretion rates, to progressively more developed hosts in which rapid
star formation enhances the UV output and
metallicity increases. After $\sim 30~\mathrm{Myr}$, the
stellar continuum typically overwhelms the accreting DCBH contribution, producing bluer colours and more extended
stellar distributions. As a result, UV-bright LRDs are predicted to host older DCBHs, have higher gas-phase
metallicities, lower BH-to-
stellar mass ratios, and lower Eddington ratios. The short-lived nature of the LRD phase places strong constraints on their emergence over
cosmic time. Overall, our results suggest that DCBH ages can be constrained from the host
galaxy contribution to the UV-optical spectrum of LRDs, relative to that of the accreting DCBH, and support the picture in which a DCBH evolutionary sequence is systematically encoded in emission line properties, gas-phase
metallicities, and
accretion states.
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Earth and Planetary Astrophysics
Magnesium Silicate Clouds in the Atmosphere of HD 209458b from a Rule-Based Tree-Structured Data Reduction
Katy L. Chubb, David Grant, Hannah R. Wakeford et al. (+14 more)
HD 209458b is the canonical hot Jupiter: the first to have its atmosphere measured and the first to hint at the role of aerosols in
exoplanet atmospheres through the muting of Na absorption signatures in the optical. Here we present JWST MIRI/LRS transmission observations of HD 209458b from 5-12 microns, directly measuring the absorption signatures of its clouds for the first time. The observations indicate the presence of magnesium silicates, most likely Mg2SiO4 or a mixture of Mg2SiO4 and MgSiO3. We also present a new methodology to reduce observational data, whereby the analysis is formulated as a rule-based model with a tree structure, enabling key decisions to be identified and uncertain decisions to be incorporated into subsequent modeling. With this data reduction, and using a combination of ARCiS free
retrievals and PICASO+Virga self consistent forward models, we are able to show that amorphous Mg2SiO4 clouds explain the LRS data to high significance over either a clear (Delta ln(Z)=16.63) or gray cloud atmosphere (Delta ln(Z)=22.26). By combining the LRS
dataset with archival JWST NIRCam and HST optical and near-infrared observations, we are able to more robustly constrain the properties of the magnesium silicate condensates, finding particle sizes of approximately 0.1 microns and atmospheric pressures of the clouds of roughly 1-10 millibar. Our results add to the growing detections of silicate clouds as a dominant atmospheric component of hot Jupiters, with the exact silicate species contextualizing the atmospheric chemistry and potentially formation conditions of these
planets.
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All authors Katy L. Chubb, David Grant, Hannah R. Wakeford, Sarah E. Moran, Natasha E. Batalha, Arika Egan, Charlotte Fairman, Diana Powell, Kevin B. Stevenson, Lili Alderson, Peter Gao, Tiffany Kataria, Nikole K. Lewis, Ryan J. MacDonald, Mark Marley Elijah Mullens, David K. Sing, Jeff A. Valenti
Cosmology and Nongalactic Astrophysics
Eigenvalue formulation of Stochastic Inflation and application to large perturbation generating inflationary features
Swagat S. Mishra, Edmund J. Copeland and Anne M. Green
Stochastic inflation is a powerful technique for calculating the probability distribution function (PDF) of large inflationary perturbations, which may collapse to form
Primordial Black Holes. The PDF, $P({\cal N})$, of the
stochastic number of e-folds, ${\cal N}$, satisfies an adjoint Fokker-Planck Equation. We develop a new self-contained
eigenvalue technique which can be used to determine $P({\cal N})$. First we apply this method to the simple case of
quantum diffusion along a flat potential without any classical drift. We recover the expression for the PDF that has previously been found using characteristic functions, with an exponential tail, and a power-law behaviour, $P({\cal N}) \propto {\cal N}^{-3/2}$, in the intermediate regime between the peak and the tail of the PDF. Finally we apply the method to constant drift inflation, in the narrow- and broad-well limits. In the narrow-well limit, there is an analytic solution and the PDF is similar to the drift-free case, with a mildly suppressed tail. In the broad-well limit, determining the full set of
eigenvalues and eigenfunctions requires a piecewise construction of the spectrum, and the broad-well PDF is qualitatively different, with an enhanced peak and a strongly suppressed tail.
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Instrumentation and Methods for Astrophysics
Astronomical Advantages of a Boost Mission to Facilitate HST Science into the 2030s: Imaging the Circumgalactic Medium of Galaxies
Matthew J. Hayes, Kate H. R. Rubin, Michelle A. Berg et al. (+20 more)
We present the case for imaging ultraviolet line emission from highly ionized metals and HI Lya in the circumgalactic medium of
galaxies, should the Hubble Space
Telescope receive an orbital boost. Hubble can uniquely probe emission lines with ionization potentials between 13 and 200 electron-volts (Lya, CIV, OVI, NeVIII, etc). Spatial mapping of the diffuse material traced by these transitions is critical to constraining the physics of feedback and the energetic exchange between
galaxies and their circumgalactic environments, as well as basic morphologies of the dominant mass component. Deep high-resolution mapping of these features will not be possible with any other observatory, existing or planned, until HWO is launched, which leaves HST as a critical observatory to test key science drivers for HWO. If HST receives an orbital boost, it can (a) provide the first statistical constraints on the spatial distribution of warm-hot CGM and (b) provide important avenues for science case development, as well as target/pointing selection, for HWO's upcoming spectroscopic facilities.
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All authors Matthew J. Hayes, Kate H. R. Rubin, Michelle A. Berg, Kevin France, Sally Oey, Ramona Augustin, Joseph N. Burchett, Cody A. Carr, Alison L. Coil, Sophia R. Flury, Cameron Hummels, Varsha P. Kulkarni, Stephan R. McCandliss, Matilde Mingozzi, Dylan Nelson, Zixuan Peng, Michael Rutkowski, Alberto Saldana-Lopez, Jason Tumlinson, Sarah Tuttle, Freeke van de Voort, Bart P. Wakker, Jessica K. Werk
Cosmology and Nongalactic Astrophysics
Gravitational Waves from hybrid defects as probe of Flavor symmetry breaking: Machine-Learning Approach
Anish Ghoshal, Ilia Gogoladze and Amit Tiwari
We present a novel possibility that a network of domain walls bounded by
cosmic strings generates a
stochastic gravitational wave background (SWGB) signal originating from the spontaneous breaking of a gauged $U(1)_F$
flavor symmetry and the subsequent breaking of discrete $Z_2$
symmetry that accommodates dark matter. The gravitational wave (GW) spectrum produced by the string-bounded-wall network can be detected for high $U(1)_F$ breaking scales in forthcoming GW detectors including LISA, ET and SKA. The GW signal exhibits a distinctive frequency slope, in the infrared, compared to the standard
cosmic-string case, in the frequency range between micro-hertz and hertz. We develop a possible strategy to distinguish and characterize GW spectrum of the hybrid defect from from other defects, such as stable
cosmic strings, via employing the exact calculation with a machine-learning surrogate, based on a multilayer perceptron (MLP), trained on spectra obtained from the full numerical treatment. This is then used for rapid inference in the detector-specific signal-to-noise ratio (SNR) computation which also makes the process fast and efficient. We also discuss some possible complementarity between GW searches and
Flavor observables in the laboratory.
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High Energy Astrophysical Phenomena
Insights on the Gamma-Ray Bursts variability in their cosmological rest frame
Giovanni Della Casa, Fabrizio Fiore, Giuseppe Dilillo et al. (+2 more)
Gamma-ray bursts temporal profile can be extremely variable, going from a single pulse of a few seconds duration to multiple superimposed pulses occurring over tens or even hundreds of seconds. The variability displayed in the lightcurve of each gamma-ray burst can be the result of the activity taking place in the central engine that generates these violent phenomena, as well as due to
magnetic reconnection activities at larger distances. The objective of this work is to find the shortest variability hidden in the lightcurves of the GRBs, with particular focus for the ones with measured
redshift, on timescales as short as few milliseconds. This variability will then be related to physical characteristics of the central engine, and evidences of its relation with the spectral parameters of the burst, such as the isotropic energy and peak energy, will be presented. This research is even more relevant in view of the future generation of satellites with improved timing resolution, that will allow us to explore the possible variability in the microsecond region.
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All authors Giovanni Della Casa, Fabrizio Fiore, Giuseppe Dilillo, Simonetta Puccetti, Andrea Vacchi
High Energy Astrophysical Phenomena
Expanding the Population of Short Gamma-Ray Transients with a Coherent Fermi/GBM Search. A 13-year catalog of short GRBs
Ariel Perera, Barak Zackay and Tejaswi Venumadhav
In this paper, we present an archival search for short gamma-ray bursts (sGRBs) over 13 years (2013-2025) of
Fermi/GBM data using a Poisson matched-filter pipeline that performs a fully coherent analysis across all detectors and energy channels, significantly improving sensitivity relative to the onboard triggering
algorithms. A central component of the analysis is the empirical estimation of trigger significance using 'timeslided' data, allowing each candidate to be assigned a probability of astrophysical origin. We also developed a new parameter-estimation framework based on the Poisson matched filter, which uses the global structure of the detected event across spectral, temporal, and spatial parameter spaces. This enables us to systematically classify bursts and distinguish between GRBs, soft gamma repeaters, terrestrial gamma-ray flashes, and
solar flares. We identify 568 new GRB candidates with $p_{\text{astro}}\geq0.9$ and thousands of magnetar bursts, significantly expanding the known short-transient population in GBM data. To further strengthen the significance of the GRB candidates, we performed a targeted follow-up search in Swift/BAT rate data. Applying the followup to all of our triggers - including triggers below the detection threshold yielded 1736 temporally coincident events with association probability above $90\%$. The resulting probabilistically ranked catalog substantially expands the population of short GRBs and magnetar
flares detected in GBM data and provides a statistically robust framework for multimessenger searches.
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Astrophysics of Galaxies
Reconciling the Fundamental Plane of Early-Type Galaxies with hydrodynamical simulations: The case of IllustrisTNG100-1
Pedro de Araujo Ferreira, Nicola R. Napolitano, Crescenzo Tortora et al. (+2 more)
The Fundamental Plane (FP) of Early-Type
Galaxies (ETGs) encapsulates a tight correlation among their structural and dynamical properties and provides an important
benchmark for
galaxy formation models. However, cosmological hydrodynamical simulations have historically struggled to reproduce the observed FP tilt, with discrepancies often attributed to to flawed feedback physics or insufficient resolution. Using the IllustrisTNG100-1 simulation, we show that adopting observationally motivated measurements, including Sérsic-derived photometric parameters and dynamically inferred velocity dispersions designed to minimise softening-length effects, substantially reduces the discrepancy between simulated and observed FPs. We further explore the impact of non-universal, mass-dependent Initial Mass Function (IMF) variations through forward modelling of their effects on
galaxy structural and dynamical quantities. In particular, bottom-heavy IMF variations produce FP coefficients fully consistent with observational constraints for both direct and orthogonal fits. Our results suggest that a significant fraction of the long-standing FP tension arises from how
galaxy observables are extracted and interpreted in simulations, although residual discrepancies may still reflect limitations in the underlying baryonic physics. These findings highlight the importance of observational realism and IMF variations for interpreting
galaxy scaling relations and for improving the predictive power of hydrodynamical simulations of ETG formation.
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All authors Pedro de Araujo Ferreira, Nicola R. Napolitano, Crescenzo Tortora, Luciano Casarini, Francisco Villaescusa-Navarro
Earth and Planetary Astrophysics · Cross-listed from math.DS
Orbital Networks in the Three-Body Problem
Abdullah Braik and Shane D. Ross
Orbital transfers in multi-body systems are often studied as isolated trajectory design problems, making it difficult to identify the larger transport structure connecting families of periodic orbits, including which families act as hubs, gateways, relays, or persistently difficult-to-access regions. This work introduces a reachable-set-based framework for constructing orbital networks in the circular restricted three-body problem. Finite-$\Delta V$ and finite-time-of-flight reachable-set overlaps are used to infer accessibility relationships between representative periodic orbit families on a common Jacobi energy
manifold and to assemble these relationships into a weighted orbital network. Applied to the Earth-Moon system, the resulting network reveals distinct accessibility regimes in which direct reachability, graph connectedness, and feasible multileg closure emerge separately. The analysis identifies multi-orbiter cycler orbits as the dominant hub, gateway, and relay families, with the (3,2)-cycler dominating across much of the sampled budget plane and the short-period (1,1)-cycler dominating in the low-time-of-flight regime, while the stable 2:1 resonant orbit remains persistently difficult to access. Although the maximum-budget network is nearly complete in a binary sense, its weighted accessibility remains strongly non-uniform. Selected proxy-supported connections are refined into concrete trajectories through differential correction, with corrected transfer costs remaining below the proxy estimates in all tested cases. Together, the results demonstrate how reachable-set overlap geometry can expose large-scale transport structure in nonlinear gravitational systems without requiring exhaustive pairwise trajectory optimization.
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Solar and Stellar Astrophysics
Harmonics as a Hidden Window into the Turbulent Convective Envelope of non-Blazhko RRab Stars
Jia-Shu Niu
Harmonics in pulsating
stars have traditionally been regarded as mere
Fourier artifacts, fully determined by their parent mode. Recent observations of high-amplitude $\delta$ Scuti
stars, however, have revealed the existence of disharmonized harmonics, which exhibit amplitude and frequency variations uncorrelated with their parent pulsation mode. Here we test the universality of this phenomenon by examining a class of
stars long considered pulsationally stable: non-Blazhko RRab
stars. Using short-cadence Kepler photometric data, we not only identify a distinct hump structure formed by harmonics of the primary pulsation mode in their frequency spectra, but also find significant amplitude and frequency variations associated with the harmonics around the onset and in the tail of the hump structure. These findings are consistent with the interpretation that the hump structure originates from the turbulent convective envelope of the
star. Interestingly, several important phenomena can be understood within this framework as a working hypothesis. Thus, the hump structure of harmonics and their intrinsic variability could constitute a hidden window into the
stellar convective envelope, potentially tracing energy injection at the convection-pulsation interaction and
stochastic perturbations from turbulent convection – although detailed modeling is required to confirm this interpretation.
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Earth and Planetary Astrophysics
Mind the Companion : Demographics of Transiting S-type Exoplanets
Lina Y. Messamah, François Bouchy, Julia Venturini et al. (+2 more)
Exoplanet demographic studies rely on large and homogeneous catalogues, yet
stellar multiplicity remains incompletely characterised in many
planet samples. We update the
PlanetS catalogue of transiting
exoplanets by systematically identifying gravitationally bound
stellar companions using
Gaia data release 3 (DR3), constructing a matched control sample of single hosts to mitigate selection and observational biases. Using this curated
dataset of 860 transiting
exoplanets including 133 S-type
planets, we perform a comparative demographic analysis as a function of host multiplicity,
stellar mass, and binary separation. We find a binary fraction of 19.4% relative to the control sample, consistent with previous estimates but derived from a larger and more homogeneous
dataset. In the
giant planet regime, less affected by observational biases,
planets in binaries tend to be more massive than their single-
star counterparts and orbit closer to their host
stars, making their radii more inflated. In particular, 53% of
giant planets orbiting M-
dwarfs reside in binary systems with separations < 1000 AU, a 2.6{\sigma} excess compared to FGK-type hosts, suggesting that
stellar multiplicity plays a key role in the formation or survival of
giant planets around low-mass
stars.
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All authors Lina Y. Messamah, François Bouchy, Julia Venturini, Léna Parc, Arianna Nigioni
Solar and Stellar Astrophysics
Frequency-time-resolved Imaging Spectroscopy of Fine Structures in a Solar Radio Noise Storm
Daniel L. Clarkson and Eduard P. Kontar
Solar radio noise storms are common phenomena, composed of broadband continuum emission embedded with diverse fine structures, yet their unusually compact apparent sizes remain unexplained. We present frequency-time-resolved imaging spectroscopy of a near-disk-center noise storm observed by LOFAR between 30–40 MHz, together with anisotropic
radio-wave scattering simulations. The continuum forms a bright, spatially compact source that drifts across the
solar disk over tens of minutes. Across the band, the measured apparent major axis is $\sim8.0^\prime$ to $\sim4.3^\prime$ between 31.3 and 38.4~MHz, less than half the size of typical type III burst sources at comparable frequencies. Embedded type I bursts, S-bursts, and spikes exhibit a range of dynamic spectra appearances, yet share nearly identical apparent sizes within uncertainties, suggesting a common size-determining mechanism. Using anisotropic scattering simulations, we show that compact apparent source sizes naturally arise for emission embedded within closed
magnetic field structures, where anisotropic
turbulence directs radiation away from the observer's line of sight. Additional modifications arise from enhanced coronal densities, steeper density gradients, reduced
turbulence levels, and strong fluctuation anisotropy, but these exert secondary influence. Our results provide a unified explanation for the similar apparent sizes of diverse fine structures in noise storms, and demonstrate that the compactness of type I storm sources is governed primarily by the large-scale coronal environment rather than intrinsic differences in emission processes, where the
magnetic topology plays a crucial role in determining the observed source size.
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Astrophysics of Galaxies
Dynamics of tidal tails of open clusters: I. effects of bar, spiral arms and giant molecular clouds
Janez Kos, Jovana Risojević and Samo Ilc
Open clusters gradually dissolve, and their
stars disperse into the
Galactic field. Lost
stars form
tidal tails-elongated streams that trace the cluster orbit ahead of and behind its core. From the shape and orientation of the
tidal tails, it is possible to infer the shape of the gravitational potential governing the cluster's motion. The orbits of open clusters, including those in the
Solar neighbourhood, are sensitive to the gravitational potential of the inner
Galaxy, which is dominated by the
Galactic bar. Using n-body simulations of synthetic and real open clusters, we investigate how sensitive the shapes and orientations of
tidal tails are to variations of the gravitational potential of the Milky Way. We consider the effects of the bar as well as spiral arms,
giant molecular clouds (GMCs) and satellite
galaxies. We analyse the
stellar distributions within
tidal tails using statistical metrics that quantify the differences between tail morphologies. Such non-parametric approach enables us to efficiently explore
tidal tails across a large parameter space of gravitational potential models. We find that the
Galactic bar-particularly its pattern speed-has a strong influence on the orbits of open clusters and the shape of their tails. Spiral arms have a limited effect, and satellite
galaxies do not disturb the
tidal tails of nearby open clusters. Perturbations by GMCs affect most clusters, with distortions stronger than those by the bar observed in old and in-plane clusters. We identify nearby open clusters that are most sensitive to the pattern speed of the bar. By observing the
tidal tails of a handful of well-selected nearby clusters, we should be able to measure the pattern speed of the bar with a precision in the order of $1\ \mathrm{km\,s^{-1}\,kpc^{-1}}$ independently from length and orientation of the bar. We will present the observability of
tidal tails in paper II.
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Astrophysics of Galaxies
Enhancing Galaxy Classification with U-Net Variational Autoencoders. III. Disk-like Galaxy Identification in JWST Samples of up to redshift 4
Sergey S. Mirzoyan and Arno Avagyan
In this third study of the series, we extend our U-Net Variational Autoencoder-based
galaxy classification framework to a significantly larger JWST sample spanning the
redshift range $0.5 < z < 4$. Focusing on massive systems with
stellar masses exceeding $10^{10}\,M_\odot$, we analyze 1,380
galaxies that satisfy these criteria and apply our previously developed denoising and classification pipeline to identify disk-like morphologies across
cosmic time. Within this population, our classifier detects 382 disk-like
galaxies, with a subset showing uncertain features consistent with the expected performance limits of current deep-learning models. This expanded
dataset allows us to examine the distribution of disk-like systems in a statistically meaningful high-
redshift regime, including epochs where well-ordered disks are traditionally expected to be rare. The results demonstrate that disk-like structures persist across a broad range of
redshifts and
stellar masses, suggesting that massive disks may be more common in the early universe than previously assumed. These findings emphasize the value of combining advanced denoising techniques with machine-learning-based morphological analysis for characterizing
galaxy populations in large JWST surveys.
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Astrophysics of Galaxies
COSMOS-Web: Galaxy Size and Surface Brightness Evolution at Rest-Frame 1.22 $\mu$m Since $z=3$
Si-Yue Yu, Andreas L. Faisst, Taotao Fang et al. (+7 more)
We present the
evolution of
galaxy size and surface brightness in the rest-frame $J$ band (1.22 $\mu$m), tracing the
stellar mass distribution, over $0.5 \leq z \leq 3$, using a sample of 15,420
galaxies with
stellar masses $M_\star=10^{10}$-$10^{11.5}\ M_{\odot}$ from the JWST COSMOS-Web survey. The rest-frame $J$-band effective radius ($R_{e,J}$) is obtained from previous measurements and mapped from the available JWST/NIRCam filters, while the surface brightness ($\mu_J$) is corrected for
dust extinction and cosmological dimming. At a characteristic mass of $M_\star = 5 \times 10^{10}\ M_{\odot}$,
star-forming
galaxies exhibit a size
evolution of $R_{e,J} \propto (1+z)^\beta$ with $\beta = -0.92 \pm 0.04$, falling between previously reported shallower and steeper measurements. Quiescent
galaxies evolve more rapidly, with $\beta = -1.34 \pm 0.05$, consistent with earlier studies. Among
star-forming
galaxies, lower-mass systems ($10^{10}$ to $10^{10.5}\ M_{\odot}$) show slower ($\beta=-0.66\pm0.02$) size
evolution compared to their higher-mass counterparts. Furthermore, the surface brightness brightens toward higher
redshifts, scaling as $\mu_J \propto -2.5 \log(1+z)^\gamma$. We find $\gamma = 3.07 \pm 0.08$ for
star-forming
galaxies and $\gamma = 3.70 \pm 0.08$ for quiescent
galaxies. We also find that massive
star-forming
galaxies ($M_\star > 10^{10.5}\ M_{\odot}$) exhibit similar $\mu_J$ values at fixed
redshift, independent of mass. Finally, we demonstrate that the observed surface brightness
evolution is driven by the combined
evolution of
galaxy luminosity and size.
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All authors Si-Yue Yu, Andreas L. Faisst, Taotao Fang, Greta Toni, Lauro Moscardini, Maximilien Franco, Rasha M. Samir, Michaela Hirschmann, Xiaoxia Zhang, Gavin Leroy
Astrophysics of Galaxies
MAUVE-MUSE: When Metallicity Follows or Fights Star Formation – A Mass-Dependent Inversion in Virgo Galaxies
Rongjun Huang, Luca Cortese, Barbara Catinella et al. (+11 more)
Although globally-integrated studies often find that, at fixed
stellar mass, high
star formation rate (SFR)
galaxies are relatively metal-poor while lower-SFR systems are more metal-rich, the corresponding coupling between gas-phase
metallicity ($Z_{\rm gas}$) and
star formation on sub-
galactic scales remains poorly constrained. In this study, we analyse 14 Virgo spirals from the MAUVE-MUSE survey to revisit the resolved mass-
metallicity relation (rMZR) and its secondary dependence on SFR surface density ($\Sigma_\mathrm{SFR}$) at $\sim 100$\,pc scales. We construct co-spatial maps of
stellar mass surface density ($\Sigma_*$), $\Sigma_\mathrm{SFR}$, and oxygen abundance. MAUVE-MUSE
galaxies follow a standard rMZR, but when binned by $\Sigma_*$, we find a mass-dependent inversion in the $Z_\mathrm{gas}$-$\Sigma_\mathrm{SFR}$ relation using O3N2 calibrations: the standard anti-correlation is confined to low-$\Sigma_*$ bins, while high-$\Sigma_*$ regions show a positive correlation, inverting at $\log_{10}(\Sigma_*/M_\odot\,\mathrm{kpc}^{-2})\simeq 7.5$-8.0. Correlated and anti-correlated \ion{H}{ii} regions coexist within the same discs; the mass dependence emerges only when grouping spaxels by $\Sigma_*$. We develop a spatially resolved gas-regulator model showing this $Z_\mathrm{gas}$-$\Sigma_\mathrm{SFR}$ (anti-)correlation arises from competition between
star-formation-driven and gas-supply-driven variability. This framework naturally extrapolates to the integrated scenario, providing a unified explanation for resolved and global relations. However, the presence and strength of the $Z_\mathrm{gas}$-$\Sigma_\mathrm{SFR}$ (anti-)correlation depend strongly on the
metallicity indicator used, highlighting the challenge of disentangling physical secondary trends within
metallicity scaling relations.
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All authors Rongjun Huang, Luca Cortese, Barbara Catinella, Luke J. M. Davies, Toby Brown, Andrei Ristea, Alessandro Boselli, Andrew J. Battisti, Vicente Villanueva, Kristine Spekkens, Sara L. Ellison, Daniel A. Dale, Sabine Thater, Amirnezam Amiri
Instrumentation and Methods for Astrophysics
Refining the Gaia DR3 Parallax Zero-point: A Hybrid Approach Combining Global Parametric Correction with Local Refinement
Ye Ding, Shilong Liao, Zhaoxiang Qi et al. (+3 more)
The
Gaia Data Release 3 (GDR3) parallaxes are affected by a complex bias that depends on
stellar magnitude, color, and celestial position, with amplitudes reaching tens of microarcseconds ($\mu$as). Standard global parametric models (e.g., Lindegren et al. 2021, hereafter L21) effectively remove large-scale trends but struggle to resolve small-scale spatial systematics due to functional
rigidity. We aim to construct a flexible, data-driven calibration map that eliminates these residual local systematics without imposing rigid functional forms. We propose a "Global Pre-correction + Local Refinement" hybrid strategy. First, we utilize the L21 model as a baseline to remove the dominant magnitude and color-dependent biases. Second, we model the residual zero-point using a Local Non-parametric method based on a Sliding Window technique. This approach fits local trends using k-nearest neighbors from
quasars (for faint
stars, G>18) and wide binaries combined with Large Magellanic Cloud (LMC) (for bright
stars, G < 18). Our hybrid model demonstrates significant improvements over the standard L21 solution. Validation against different samples reveals a remarkably flat residual map with near-zero bias across the full sky. Our mathematical attempt at calibrating the parallax zero-point is expected to provide a useful reference for the zero-point correction in future
Gaia DR4, and to help move towards a physical resolution of this issue.
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All authors Ye Ding, Shilong Liao, Zhaoxiang Qi, Qiqi Wu, Qi Xu, Keyu Zhu
High Energy Astrophysical Phenomena
Collective Winds of Massive Star Clusters as the Dominant PeVatrons for Galactic Cosmic Rays
Zijian Qiu, Sujie Lin and Lili Yang
The knee feature in the
cosmic-ray energy spectrum around 4 PeV is widely believed to have a
Galactic origin, but the acceleration mechanism and identification of PeVatrons remain key open questions in high-energy astrophysics. Recent precise measurements by LHAASO reveal that the
proton and helium spectra exhibit a common
rigidity-dependent spectral break at ~ 3.5 PV, imposing a stringent constraint on source models. In this work, we construct, for the first time, a time-dependent
cosmic-ray injection model that incorporates the full
evolution of massive
stars together with the dynamical development of wind termination shocks. We find that
stellar winds of individual massive
stars cannot explain the common spectral break observed by LHAASO, as they yield distinct
rigidity cutoffs for
protons and helium. By contrast, collective winds of massive
star clusters naturally reconcile this discrepancy through the mixing effect of
stars at different evolutionary stages. We propose a
stellar-dominated model in which
supernova remnants dominate the GeV-TeV range, individual
stellar winds dominate the TeV range, and collective cluster winds dominate the PeV knee region. This model successfully reproduces the
rigidity-dependent spectral features of various species near 100 GV and 0.1 PV. It further makes two testable predictions for future observations. Around 0.5 PV, the energy spectra of carbon and oxygen are expected to exhibit hardening similar to that of helium, which can be verified by LHAASO observations. In the multi-TV range, the energy spectrum of magnesium is not expected to show hardening similar to that observed for helium, carbon, and oxygen, which can be tested by DAMPE observations.
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Cosmology and Nongalactic Astrophysics
Gravothermal Collapse: Robust Against Baryonic Feedback
Demao Kong and Hai-Bo Yu
We perform a stress test of gravothermal collapse in self-interacting dark matter (SIDM)
halos under baryonic feedback using a semi-analytical oscillating-potential model in controlled N-body simulations. For high-concentration
halos, where the SIDM thermalization timescale is short, gravothermal collapse is only mildly delayed and never stalled, even under extremely strong feedback. In contrast, the collapse of a median-concentration
halo can be significantly delayed, but it resumes once feedback ceases. The final density profile of such
halos depends sensitively on the episodic feedback history, producing a broad diversity in central densities. These results strengthen the interpretation of dense compact perturbers identified in recent strong-
lensing observations as core-collapsed SIDM
halos.
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Cosmology and Nongalactic Astrophysics
Time-reversed stochastic inflation in the quantum well
Chiara Animali, Baptiste Blachier, Nanoka Okada et al. (+3 more)
Time-reversed
stochastic inflation solves the
stochastic evolution of the inflationary universe backward in time, by counting the number of e-folds from the end of
quantum diffusion towards some initial state. The point of view of observers attached to the end-of-inflation hypersurface is thus enforced. In this work, we exactly solve time-reversed
stochastic inflation in a flat and bounded potential, the so-called
quantum well. At given lifetime, the field behaviour is found to be either indistinguishable from the one obtained in a semi-infinite flat potential, or, subject to enhanced stochasticity where any
memory of the initial state is erased. The derived distribution of
curvature perturbations reduces to the semi-infinite result for small fluctuations while it develops exponential tails for the large ones. Such tails arise for both positive and negative values, and decay twice as fast as the one obtained in the standard forward
stochastic inflation. These differences may have important consequences for tail-sensitive phenomena, such as
primordial black hole formation.
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All authors Chiara Animali, Baptiste Blachier, Nanoka Okada, Christophe Ringeval, Tomo Takahashi, Koki Tokeshi
Instrumentation and Methods for Astrophysics
An Automated Photometric Pipeline for the 80cm Xizang University Telescope
Chao Xu, Jie Zheng, Tian-Lu Chen et al. (+5 more)
Processing astronomical data can take up a significant amount of researchers' time. The 80cm
telescope at Xizang University is currently in its trial operation phase; however, it lacks a data processing program, which makes efficient handling of the data it generates an urgent concern. To address this issue, we have developed an automatic pipeline for processing photometric data and extracting light curves using Python 3. This pipeline has several advantages, including high speed, ease of use, and modularity. The differential photometric accuracy of this pipeline is comparable to that of data processing programs used by other similar
telescopes. This development effectively overcomes the limitations of manually processing data, providing efficient and reliable support for future studies of variable
stars. The pipeline has already been integrated into the
telescope's operational system.
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All authors Chao Xu, Jie Zheng, Tian-Lu Chen, Lin-Qiao Jiang, Hua Bao, Ying-Gang Li, SuoNan-DaJi, Xing-Lan Feng
Solar and Stellar Astrophysics
Ongoing and Post-Mass-Transfer Binaries: A Living Catalog and Unified Review of Binary Mass Transfer Products
Lieke A. C. van Son, Natsuko Yamaguchi, Pranav Nagarajan et al. (+6 more)
Mass transfer is arguably the most defining interaction in binary
stellar systems, yet many aspects of its physics remain poorly understood, from stability to endpoints and observable products. Comparing theory and observations is challenging because post-mass-transfer systems are studied across largely independent communities with different methods, nomenclature, and evolutionary frameworks. % We present a unified review and catalog of ongoing and post-mass-transfer binaries spanning the full
stellar mass range, but restricted to systems likely to have experienced only a single episode of mass transfer (i.e., only one component is evolved). We review 16 observational classes of binary interaction products and compile a curated sample of 5,452 systems into a publicly available, community-driven catalog at https://binary-observations.github.io/post_mt_catalog/. % Using this catalog, we investigate global trends in orbital periods, eccentricities, masses, and mass ratios across post-mass-transfer binaries. We find I) non-zero eccentricities are common at all periods and system classes, with both median values and scatter increasing with period, II) the $e(\log P)$ relation depends on donor progenitor mass, with
neutron-
star and black-hole binaries showing the highest median eccentricities, likely reflecting effects of natal kicks, III) period distributions are broad and overlapping across evolutionary channels, and IV) the
Gaia BH and NS systems are extreme in mass ratio but otherwise consistent with the general post-mass-transfer population. Together, these results support a unified empirical view of post-mass-transfer binaries that highlights several tensions between theory and observations.
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All authors Lieke A. C. van Son, Natsuko Yamaguchi, Pranav Nagarajan, Tomer Shenar, Koushik Sen, Alexander Laroche, Emily M. Leiner, Hugues Sana, Onno R. Pols
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Neutrino helicity oscillations in astrophysical environments: A many-body approach
Yiheng Xu, Julien Froustey, George M. Fuller et al. (+2 more)
Neutrino rest mass enables left-handed states to "flip" to right-handed states and vice versa. In-medium effects can enhance the probability for such
spin-flip. We demonstrate that a full many-body calculation of this process in
neutrino-dense environments can lead to
spin-flip probabilities that exceed by orders of magnitude those calculated with mean-field treatments. We study simple configurations with a few
neutrinos in well-defined momentum states, for which we show that the helicity conversion enhancement is connected to many-body momentum exchange. Such an effect would therefore be missed in a calculation that considers only forward processes. We speculate on the potential astrophysical implications of these results and the range of applicability of our calculation and its limitations.
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All authors Yiheng Xu, Julien Froustey, George M. Fuller, Lukáš Gráf, Amol V. Patwardhan
High Energy Astrophysical Phenomena
Neutron Star Equation of State via Physics Informed Neural Network
Gabriel Bezerra, Veronica Dexheimer and Rodrigo Negreiros
We present the first application, to the best of our knowledge, of Physics-Informed Neural Networks (PINNs) to the
neutron star equation-of-state (EOS) inverse problem. Two interacting networks – one representing the EOS $P(\varepsilon)$ as a continuous, non-parametric function, the other solving the Tolman-Oppenheimer-Volkoff (TOV) equations – are trained jointly on NICER X-ray timing posteriors and
pulsar mass measurements. The TOV equations enter as a mean-square ODE residual enforced via automatic differentiation at every training step, rooted in the Neural Differential Equation framework. The inferred EOS satisfies
nuclear saturation properties, causality, and perturbative QCD bounds simultaneously; $\chi$EFT consistency at $1$–$2\rhoz$ emerges without explicit enforcement, providing a non-trivial self-consistency check. Across $N=15$ independent training runs, we find a
neutron star maximum mass $M_\mathrm{max}=2.06^{+0.07}_{-0.09}$ and radius and
tidal deformability of a 1.4 $M_\odot$
star $R_{1.4}=12.85^{+0.03}_{-0.06}$~km and $\Lambda_{1.4}=684$, respectively, with 68% CI, in agreement with recent
Bayesian analyses. Most interestingly, the speed of sound exhibits a reproducible softening at $2$–$4\,\rhoz$, consistent with a
quark-
hadron crossover.
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High Energy Astrophysical Phenomena
High-redshift GRB 140304A at z = 5.282 with flaring activity: A multi-wavelength study
Shashi. B. Pandey, Amit. K. Ror, A. J. Castro-Tirado et al. (+48 more)
Context. This article presents a detailed multi-wavelength analysis of GRB 140304A at z = 5.282, having uncommon late-time flaring features. The aim is to study GRB 140304A and other similar bursts to understand
stellar evolution and formation processes at high-z. Aims. GRBs at high-z, possible flaring activities at different frequencies seen at relatively late-times, help to constrain temporal correlation among contemporaneous
flares. In the present study, we plan to constrain such a temporal and spectral study for a sample of high-z bursts, including GRB 140304A. Methods. We use Swift,
Fermi, and ground-based observations to constrain the temporal and spectral properties of the
prompt and afterglow emissions. Using the cross-correlation function, we calculate the spectral lag in the light curves observed in two energy bands of Swift's Burst Alert
Telescope (BAT) and X-ray
Telescope (XRT). Results. Parameter
evolution of the
prompt emission analysis reveals a hard-to-soft
evolution of the spectral peak energy (Ep) and the
magnetic field strength (B), consistent with the typical population of long GRBs. For GRB 140304A, a rare pattern of spectral lag
evolution having positive lag in the early BAT light curves, but no lag is observed in the XRT light curves. We have also observed systematic time delays among the peak times of
flares in three different bands, but the optical
flares exhibit a morphological correspondence with X-ray or gamma-ray
flares. Conclusions. Our analysis shows that the observed positive spectral lag in GRB 140304A is closely related to the hard-to-soft spectral
evolution during the
prompt emission phase, as seen in some of the other long GRBs. Additionally, there is a clear connection between gamma-ray, X-ray and optical
flares with
prompt emission, which are produced through synchrotron radiation during rapid bulk acceleration within the emitting region.
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All authors Shashi. B. Pandey, Amit. K. Ror, A. J. Castro-Tirado, A. Pozanenko, V. Lipunov, S. Jeong, I. H. Park, R. Sanchez-Ramirez, B.-B. Zhang, D. Xu, N. R. Butler, C. G. Mundell, S. R. Oates, P. Y. Minaev, A. Volnova, J. Bai, J. Bloom, N. Budnev, A. Castellon, Ch. Cui, M. D. Caballero-Garcia, Maria Gritsevich, G. Garcia-Segura, D. Hiriart, A. Valeev, S. Castillo-Carrion, Yash Sharma, Y. Fan, E. Gorbovskoy, O. Gress, S. Guziy, Y.-D. Hu, Brajesh Kumar, Amar Aryan, Rahul Gupta, E. V. Klunko, V. Kornilov, A. Kutyrev, G. Antipov, A. Kuznetsov, William H. Lee, C. Perez del Pulgar, R. Querel, M. G. Richer, S. E. Schmalz, N. Tiurina, N. Tungalag, K. Zhirkov, A. M. Watson, Ch. Wang, P. Balanutsa
Earth and Planetary Astrophysics
Metamorphoses of carbon and oxygen in protoplanetary discs: how chemistry and radial drift transform inner disc C/O ratios
Tamara Molyarova, Richard A. Booth and Catherine Walsh
The chemical composition of a protoplanetary disc is sensitive to its thermal structure and
dust properties, and can provide insights into the disc
evolution. Recent observations with the James Webb Space
Telescope (JWST) reveal correlations of the inner disc compositions with disc size,
accretion rate and
stellar mass, explained by the key role of
dust radial drift in redistributing
primordial volatiles. We explore how chemical reactions change the composition of ices carried with pebbles and how they affect the inner disc C/O ratios in a disc around a
solar mass
star. We consider different drift efficiencies set by
dust fragmentation velocity and include
dust traps at different locations. We vary the incident
cosmic ray ionisation rate $\zeta$ and the efficiency of
cosmic ray dissociation of ices, and consider the effect of carbon grain destruction. We find that methane depletion within $<1$ Myr prevents the delivery of carbon-rich gas to the inner disc and yields $\mathrm{C/O} \lesssim1$ for $\zeta\geq10^{-17}$ s$^{-1}$.
Dust traps collect water and carbon-rich ices formed via methane destruction, further lowering the inner disc
metallicity and C/O ratio.
Cosmic-ray driven photodissociation of ices can convert water to O$_2$ and carbon-bearing molecules to CO, allowing ices to escape the trap if $\gtrsim10 \%$ of the dissociated products can participate in surface reactions. We discuss the observational implications and conclude that
cosmic rays and their effect on ices are the key factors that determine the impact of chemistry on the inner disc composition.
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