High Energy Astrophysical Phenomena
On the Apparent Correlation between X-ray and Neutrino Luminosities of Active Galactic Nuclei
Jian-Jun Luo, Ming-Xuan Lu and Yun-Feng Liang
Recent studies have reported a linear correlation between the hard X-ray and high-energy
neutrino luminosities of active
galactic nuclei (AGN), suggesting a possible physical connection between these two messengers. In this work, we challenge this interpretation by demonstrating that the observed correlation may arise purely from selection effects. We analyze 10 years of IceCube public data for a sample of Seyfert
galaxies and blazars from the Swift BAT catalog. While our data reproduces the apparent $L_\nu$–$L_X$ correlation for sources with mild (but not significant)
neutrino evidence, we show through Monte Carlo simulations that the same correlation appears even when analyzing random sky positions with no astrophysical sources. The key issue is that TS-based source selection effectively restricts the
neutrino flux to a narrow range (a factor of several), while the luminosity distance of the sample spans $\sim4$ orders of magnitude. This causes the luminosity $L = 4\pi D_L^2 F$ to be dominated by the distance term rather than intrinsic flux variations, creating an artificial correlation. While a robust flux correlation ($F_\nu$–$F_X$) for high-significance sources may indicate a genuine physical link, our results demonstrate that a luminosity-luminosity correlation alone is insufficient to establish a physical relationship between
neutrino and X-ray emission in AGN.
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Cosmology and Nongalactic Astrophysics
UNIONS-3500 Weak Lensing: I. A Galaxy Shape Catalogue in the Northern Sky
F. Hervas-Peters, S. Guerrini, M. Kilbinger et al. (+15 more)
Weak gravitational
lensing has become a widely used effect to characterise the dark-matter distribution on large scales in the Universe by measuring
galaxy ellipticities and their statistical correlations. We present the first weak gravitational
lensing catalogue for
cosmic-shear cosmology of the Ultraviolet Near Infrared Optical Northern Survey (UNIONS). We analyse approximately $3\,500$ square degrees of sky area in the Northern Hemisphere, observed in the $r$-band by MegaCam on the Canada-France Hawai'i
Telescope, achieving a median seeing of 0.7 arcsec. Starting from images calibrated for astrometry and photometry, we describe the steps from image processing to catalogue creation. These steps include masking, source detection and selection,
star selection, point spread function (PSF) modelling, shape measurement, and calibration. We conduct extensive validation tests, particularly to assess and mitigate the leakage of PSF ellipticity into
galaxy shapes. We demonstrate the robustness of the catalogue by investigating correlations between ellipticity and other observational variables as well as structural elements, such as observer-frame image positions and proximity to bright
stars. The final
galaxy catalogue contains $62$ million
galaxies, corresponding to an effective source density of $4.96$ arcmin$^{-2}$. The ellipticity dispersion, commonly referred to as shape noise, is $\sigma_\epsilon = 0.27$. Initiating the first major cosmological analysis by the UNIONS collaboration, this is the first in a series of five papers which cover the various aspects of a robust
cosmic shear analysis. Two companion papers discuss the robustness of the catalogue, one through the level of $B$-mode contamination and another by producing and analysing dedicated image simulations for shear calibration, while the other two present cosmological results in real and harmonic space.
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All authors F. Hervas-Peters, S. Guerrini, M. Kilbinger, L. Baumont, A. Guinot, C. Daley, C. Bonini, A. Wittje, C. Murray, L. W. K. Goh, A. Paradis, A. Tersenov, M. J. Hudson, L. Van Waerbeke, H. Hildebrandt, S. Fabbro, J.-C. Cuillandre, A. W. McConnachie
Cosmology and Nongalactic Astrophysics
UNIONS-3500 Weak Lensing: III. 2D Cosmological Constraints in Configuration Space
L. W. K. Goh, S. Guerrini, C. Daley et al. (+13 more)
We present the first cosmological constraints from the
cosmic shear analysis of the UNIONS-3500 weak
lensing galaxy catalogue in configuration space. The Ultraviolet Near Infrared Optical Northern Survey (UNIONS) is the largest and deepest photometric survey of the northern hemisphere to date, with the UNIONS-3500 catalogue using high-quality $r$-band imaging across 3500 deg2 of the sky. We perform a 2D
cosmic shear analysis with a single tomographic bin, using the two-point correlation function (2PCF) statistic. Assuming a flat LCDM model, we obtain constraints on the clustering amplitude of S_8 = 0.831^{+0.067}_{-0.078}, which is consistent with constraints from Planck CMB measurements and precedent
cosmic shear results within 1sigma. We outline the construction of our cosmological inference pipeline, including the estimation of the source
redshift distribution, shear calibration, and covariance
matrix, and describe methodologies for the mitigation of systematic effects arising from PSF systematics and B-modes. We demonstrate that our results are robust to variations in analysis choices, including scale cuts, prior ranges, and nonlinear modelling. This paper is part of a coordinated release which collectively demonstrates the maturity and readiness of UNIONS to deliver competitive cosmological results, positioning it as a key stepping stone towards the forthcoming era of Stage IV weak
lensing experiments.
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All authors L. W. K. Goh, S. Guerrini, C. Daley, F. Hervas-Peters, M. Kilbinger, A. Wittje, C. Murray, S. Fabbro, H. Hildebrandt, M. J. Hudson, L. van Waerbeke, A. H. Wright, T. de Boer, J.-C. Cuillandre, E. Magnier, A. W. McConnachie
Cosmology and Nongalactic Astrophysics
No evidence for phantom crossing: local goodness-of-fit improvements do not persist under global Bayesian model comparison
Bikash R. Dinda, Roy Maartens and Shun Saito
Recent cosmological data have been interpreted as indicating deviations from $\Lambda$CDM within the standard $w_0w_a$ parametrization, including hints of phantom crossing and dynamical dark energy. However, such inferences can be parametrization-dependent and need not imply a statistically robust detection. We test these claims by comparing $\Lambda$CDM, $w_0w_a$, and thawing quintessence models, using the Deviance Information Criterion (DIC) and the
Bayesian evidence $\ln \mathcal{Z}$. We find that $w_0w_a$ can provide a slightly improved local fit; however, this improvement is confined to a limited region of the parameter space. The global
Bayesian evidence does not support it once the full prior volume is accounted for. In particular, cases with $\Delta{\rm DIC}<0$ but $\Delta \ln \mathcal{Z}<0$ indicate that these improvements are not statistically significant. We show that all models are statistically indistinguishable, and that there is no statistically consistent evidence across different
datasets for either dynamical dark energy or phantom crossing.
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Cosmology and Nongalactic Astrophysics
UNIONS-3500 Weak Lensing: IV. 2D cosmological constraints in harmonic space
S. Guerrini, L. W. K. Goh, F. Hervas-Peters et al. (+14 more)
The Ultraviolet Near Infrared Optical Northern Survey (UNIONS) is a photometric survey in the northern sky. The quality of the data in the $r$ band provides precise shape measurements to measure the growth of structures using
cosmic shear. This work aims to constrain cosmological parameters using a harmonic-space
estimator of the
cosmic shear signal, known as pseudo-$C_\ell$, in a non-tomographic analysis. We perform our analysis in the context of the standard $\Lambda$CDM cosmology. We model astrophysical systematic effects such as baryonic feedback and intrinsic
alignments of
galaxies. We verify that the point spread function systematic contribution does not affect our results. We assess the impact of different scale cuts and modelling choices on the constraints. We find $S_8 \equiv \sigma_8 \sqrt{\Omega_{\rm m}/0.3} = 0.891^{+0.057}_{-0.084}$, consistent at the $0.79 \, \sigma$ level with Planck and between $0.87$ to $1.51 \, \sigma$ with other weak
lensing surveys. Our results are robust to analysis choices, and we use lognormal simulations to assess the consistency between configuration and harmonic space results, finding a $2.18 \, \sigma$ agreement between the two statistics. The degeneracy between $S_8$ and the amplitude of the intrinsic
alignment, $A_{\rm IA}$, sampled from a prior obtained from direct measurements, is one of the largest sources of uncertainty. This work is part of the first cosmological analysis of the UNIONS survey using
cosmic shear and paves the way for future tomographic and $3 \times 2$ point cross-correlation analyses, exploiting the unique overlap of UNIONS with deep spectroscopic surveys in the northern hemisphere.
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All authors S. Guerrini, L. W. K. Goh, F. Hervas-Peters, C. Daley, M. Kilbinger, A. Wittje, C. Murray, L. Baumont, S. Fabbro, H. Hildebrandt, M. J. Hudson, L. van Waerbeke, A. H. Wright, T. de Boer, J.-C. Cuillandre, E. Magnier, A. W. McConnachie
Solar and Stellar Astrophysics
Spectropolarimetric analysis of waves linked to FIP
M. Murabito and M. Stangalini
High-resolution spectropolarimetry has opened new avenues for understanding how chromospheric waves shape coronal
plasma composition. All modeling efforts so far highlight wave activity and, in particular, the ponderomotive force associated to Alfvénic perturbations, as a key ingredient. Over recent years, studies based on spectropolarimetric measurements in the
solar chromosphere have identified
magnetic perturbations associated to waves linked to regions in the corona with enhanced FIP bias. Building on this established framework, the present work explores the diagnostic potential of Stokes V amplitude asymmetries as an alternative diagnostic tool for investigating wave behavior relevant to compositional fractionation processes.
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Astrophysics of Galaxies
COOL-LAMPS IX: A Rare Duo of Quasars Each Lensed by a Single Massive Galaxy Cluster
Erik Solhaug, Michael D. Gladders, Andi M. Kisare et al. (+20 more)
Wide-separation lensed
quasars (WSLQs) are rare systems that arise from the chance
alignment of two objects: a
galaxy cluster and a background
quasar. After two decades, only seven WSLQs have been found. Here, we report the discovery of COOLJ1153+0755 by the COOL-LAMPS collaboration in DECaLS imaging and its confirmation with follow-up observations with the Magellan
Telescopes and the Nordic Optical
Telescope. This system features two multiply-imaged
quasars each lensed into four images by the same $z=0.4301$ cluster: a classic broad-line Type I
quasar at $z=1.524$ (COOLJ1153A) and a
dust-obscured Type II
quasar at $z=1.939$ (COOLJ1153B), with maximum image separations of $25.''6$ and $26.''0$, respectively. We construct a lens model to estimate a projected cluster mass of $M(<500\,{\rm kpc})\sim3.3\times10^{14}{\rm M}_{\odot}$ and relative time delays between the three brightest images of each
quasar of $\Delta t_{\rm \,A3,A1}\sim800$, $\Delta t_{\rm \,A2,A1}\sim1200$, $\Delta t_{\rm \,B1,B3}\sim800$, and $\Delta t_{\rm \,B2,B3}\sim1000$ days. COOLJ1153A resides in a dense environment with three nearby
galaxies, two of which are also strongly lensed. We identify COOLJ1153+0755 without making a morphological cut in the DECaLS catalog; none of its multiple images are classified as point sources in those data, implying that morphology-based selection would miss such systems. COOLJ1153+0755 expands the WSLQ sample from 7 to 8 systems (9 individual
quasars), adding two powerful laboratories for probing black hole-
galaxy co-
evolution at
Cosmic Noon and for time-delay cosmography constraints on the Hubble constant, $H_0$.
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All authors Erik Solhaug, Michael D. Gladders, Andi M. Kisare, Simon D. Mork, Matthew B. Bayliss, Aidan P. Cloonan, Håkon Dahle, Isaiah R. Escapa, Michael K. Florian, Gourav Khullar, Guillaume Mahler, Natalie Malagon, Kate Napier, Allison Noble, Jane R. Rigby, Riley Rosener, T. Emil Rivera-Thorsen, Keren Sharon, Antony A. Stark, Kabelo Tsiane, Grace C. Wagner, Brian Welch, Yifan "Megan" Zhao
Astrophysics of Galaxies
First Light And Reionization Epoch Simulations (FLARES) XXI: The UV Indices of Galaxies in the Early Universe
Connor Sant Fournier, Stephen M. Wilkins, Joseph Caruana et al. (+5 more)
UV absorption line indices trace chemical enrichment and
star formation histories in high-
redshift galaxies, yet their reliability as quantitative
stellar metallicity, Z*, diagnostics remains uncertain. In this work, we combine synthetic spectral modelling with cosmological simulations to assess the behaviour of rest-frame UV indices in the early Universe. Using the forward-modelling package Synthesizer, we compute equivalent widths for UV indices based on BPASS
stellar population synthesis models and examine their sensitivity to
metallicity,
star formation history, nebular emission, and model assumptions. We first investigate idealised
stellar populations to establish the
metallicity dependence of each index. Most indices show increasing equivalent width with
metallicity, although the strength and linearity of this relation varies between features. The 1719 Angstrom index exhibits one of the most stable correlations with
stellar metallicity, while the 1460 Angstrom index shows stronger sensitivity to nebular emission, bursty
star formation, and model-dependent effects at high
metallicity. We then apply these models to
galaxies from the First Light and Reionization Epoch Simulations,
FLARES, which provide realistic
star formation and chemical enrichment histories. The simulated
galaxy populations reproduce a
stellar mass-
metallicity relation and allow the UV indices to be tested in composite spectra. Although scatter increases due to population mixing and
stochastic enrichment, the overall
metallicity trends remain largely preserved. These predictions provide a theoretical framework for interpreting rest-frame UV spectra from JWST and future surveys, supporting the use of UV absorption indices as complementary tracers of
stellar metallicity in early
galaxies.
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All authors Connor Sant Fournier, Stephen M. Wilkins, Joseph Caruana, Kristian Zarb Adami, Conor M. Byrne, William J. Roper, Jack C. Turner, Aswin P. Vijayan
High Energy Astrophysical Phenomena
The impact of flickering variability and magnetisation on the dynamics, stability and morphology of radio-loud AGN jets
Emma L. Elley, James H. Matthews, Henry Whitehead et al. (+1 more)
The physics governing the morphology of
radio-loud AGN jets is not fully understood. We investigate how magnetization, flickering jet power and their interplay affects the morphology of
radio galaxies. We present a grid of relativistic magnetohydrodynamic simulations using the PLUTO code covering constant and variable jets with two levels of magnetisation. We find that the constant high magnetisation jets can lead to highly asymmetrical cocoon morphologies, whilst the variable high magnetisation jet can exhibit a broken morphology, caused by a discontinuous jet beam. Our work highlights the importance of magnetisation and variability on the stability and resulting morphology of
radio-loud AGN jets, suggesting both are significant factors in addition to jet power or environment. Furthermore, we show that the interaction between magnetisation and variability can lead to the development of localised kink instabilities along the jet beam. Finally, we discuss the effects of hydrodynamic mixing in low magnetisation jets and the role of viewing angle dependence in comparisons between our simulations and observed sources. To facilitate this comparison we present a library of simulated
radio images at different times in the simulations and from various viewing angles, which highlight a diverse set of complex morphologies.
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All authors Emma L. Elley, James H. Matthews, Henry Whitehead, Alex J. Cooper
Earth and Planetary Astrophysics
Self-gravity in thin protoplanetary discs: 2. Numerical convergence solved and revealing the overestimation in mass of formed planets with softening
S. Rendon Restrepo
The Gravitational Instability (GI) is a leading theory for explaining early
planet formation in massive discs. In the early 2010s, 3D SPH simulations of GI failed to converge, initially attributed to resolution-dependent viscosity but later appearing in 2D SPH and grid-based simulations, suggesting a numerical artifact inherent to the 2D approximation of
gravity. Recently, we derived from first principles a much improved prescription for
gravity in 2D discs (via a Bessel kernel). This prescription introduces a characteristic length below which
gravity smoothly transitions from a 3D to a 2D scaling. This cannot be captured by standard smoothing length approaches, widely used in 2D simulations. We employ this new prescription to resolve the convergence issue of GI in 2D, and compare the outcomes of GI in runs using the Bessel kernel with those obtained using softening prescriptions at high resolution. We conducted numerical simulations with the FargoCPT code, where the Bessel prescription was implemented. The 2D Bessel formalism of
gravity effectively resolves the convergence issues encountered in 2D simulations. When compared to simulations employing softened or unsoftened potentials, I observe that a small softening parameter tends to overestimate gravitational effects. This results in an artificially high number of fragments, leading to final fragment masses that are overestimated by a factor of 2-3. Conversely, employing large softening parameters inhibits gravitational effects. Although our analysis initially suggests that a softening parameter of 0.6 H might offer the best compromise, in reality, the resulting fragments fail to remain gravitationally bound-a behavior not observed when using the Bessel kernel. Our findings strongly suggest that the Bessel prescription should be adopted to ensure a consistent and accurate treatment of
gravity in thin discs.
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Solar and Stellar Astrophysics
VLTI/PIONIER imaging of post-AGB binaries. An INSPIRING hunt for inner rim substructures in circumbinary discs
Toon De Prins, Akke Corporaal, Jacques Kluska et al. (+10 more)
We image the detailed inner rim morphology for a sample of post-AGB circumbinary discs observed using NIR interferometry. At resolutions down to ~1-2 mas (corresponding to ~1-10 AU), we aim to reveal potential substructures that may trace perturbations from the binary or embedded substellar companions, or that arise from hydrodynamical instabilities. We developed an image reconstruction workflow using the SPARCO approach together with the ORGANIC reconstruction
algorithm. This was applied to VLTI/PIONIER data of eight diverse post-AGB binaries, providing high-fidelity images of
dust continuum emission at the inner rim. Extensive tests were applied to assess the robustness of the recovered image features. The dusty disc rim is well-resolved for all targets. Only one of the images can be fully accounted for by simple radiative transfer effects due to disc inclination, while in several others indications of potential substructures are detected. Strikingly, four exhibit robust azimuthal brightness enhancements at locations not expected from inclination effects alone. These can indicate strong radiative or dynamical responses to the binary, or
vortices formed via hydrodynamical instabilities. One target displays an even more puzzling morphology, showing a single large-scale outer flux arc and several small-scale arcs closer to the binary, possibly revealing
accretion streams onto the binary, a misaligned innermost disc, or a spiral feature located in the disc or in an
outflow. This work presents the first homogeneous interferometric imaging survey of the inner regions of post-AGB circumbinary discs, enabling direct comparison of inner rim morphologies across a representative sample. The inner disc regions are highly diverse and dynamic, harbouring a significant amount of substructure candidates. Multi-wavelength and time-series imaging will be essential in uncovering their physical origins.
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All authors Toon De Prins, Akke Corporaal, Jacques Kluska, Devika Kamath, Hans Van Winckel, Kateryna Andrych, Javier Alcolea, Narsireddy Anugu, Jean-Philippe Berger, Valentin Bujarrabal, Ivan Gallardo Cava, Stefan Kraus, Hans Olofsson
High Energy Astrophysical Phenomena
Magnetar-powered long gamma-ray bursts and connection to superluminous supernovae and fast radio bursts
Yu-Qi Zhou, Shuang-Xi Yi, Yu-Peng Yang et al. (+4 more)
Based on X-ray afterglow observations from the Swift satellite, we construct a sample of 169 long gamma-ray bursts (LGRBs) exhibiting the canonical magnetar plateau signature, i.e., a plateau followed by a $t^{-2}$ decay. We derive the plateau luminosity $L_0$ and break time $t_b$ for each burst by performing Markov Chain Monte Carlo (MCMC) fits to the light curves, and estimate pseudo-
redshifts for bursts lacking known
redshifts via the Amati relation. The fundamental magnetar parameters are subsequently inferred: the surface polar
magnetic field strength $B_p \in [0.39,\ 23.08] \times 10^{15}$G and the initial
spin period $P_0 \in [0.95,\ 13.79]$ms. Statistical analysis shows that both the known-
redshift subsample and the full sample follow the Dainotti correlation between $L_0$ and $t_b$ with a slope close to $-1$, supporting a constant energy injection rate during the plateau phase. Furthermore, we identify a significant correlation between $B_p$ and $P_0$: $B_p \propto P_0^{0.83 \pm 0.09}$ for the full sample and $B_p \propto P_0^{0.80 \pm 0.16}$ for the known-
redshift subsample, with both slopes consistent within uncertainties. Compared to magnetars powering superluminous
supernovae (SLSNe), GRB magnetars possess systematically stronger
magnetic fields (by approximately one order of magnitude), suggesting fundamental differences in their progenitor systems or collapse conditions; while their
magnetic field strengths show no significant difference from those powering fast
radio bursts (FRBs), suggesting a possible common evolutionary pathway. This study provides a physics-motivated, model-consistent sample of magnetar-candidate GRBs, offering a robust foundation for statistical investigations within the magnetar central engine model and placing new observational constraints on the birth properties of these extreme compact objects.
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All authors Yu-Qi Zhou, Shuang-Xi Yi, Yu-Peng Yang, Yan-Kun Qu, Ning Gai, Yan-Ke Tang, Fa-Yin Wang
Cosmology and Nongalactic Astrophysics
Latent-Space Gaussian Processes for Dark-Energy Reconstruction from Observational \(H(z)\) Data
Jia-yan Jiang, Wei Hong and Tong-jie Zhang
Using the 37-point
cosmic-chronometer subset of observational Hubble parameter (OHD) data, we develop a
Bayesian Gaussian-process framework to reconstruct the normalized dark-energy density \(f(z)\) and equation of state \(w(z)\), focusing on how the choice of latent space affects the inference. We compare a Gaussian-process prior placed directly on \(f(z)\) with the conventional latent-\(H\) formulation, and also test a log-\(f\) branch that enforces \(f(z)>0\). We further analyze OHD-like mock data generated from fiducial \(\Lambda\)CDM and mildly evolving \(w_0w_a\) models, using both the observed
redshift distribution and a higher-quality high-
redshift setup. For real OHD, leave-one-out cross-validation shows no strong predictive preference between latent-\(f\) and latent-\(H\) reconstructions. The inferred \(f(z)\), \(w(z)\), and \(Om(z)\) remain consistent with \(\Lambda\)CDM across the tested external priors, while apparent \(Om(z)\) trends are prior sensitive and not robust evidence for dark-energy
evolution. Residual differences between the two latent constructions are small, sign mixed, prior dependent, and mainly confined to the weakly constrained high-
redshift tail. We therefore interpret the real-data results primarily as a methodological assessment. In mock tests, the framework responds to injected mild
evolution in the reconstructed dark-energy quantities and \(Om(z)\), with detectability depending on method and data coverage. Improved high-
redshift OHD reduces the discrepancy between latent constructions and makes the \(Om(z)\) response more consistently detectable. The latent-\(f\) approach is therefore a viable alternative to latent-\(H\), while current constraints are limited mainly by sparse high-
redshift OHD and dependence on external priors.
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Earth and Planetary Astrophysics
Comet 1P/Halley Completes 15 Orbits in 1,151 Years: Commensurability with the Solar System Quasi-Period and Evidence for Jupiter-Saturn Dynamical Coupling
Carlos Baiget Orts
I investigate whether comet 1P/Halley participates in the 1,151-year planetary quasi-period T* identified in a companion paper (Baiget Orts 2026a, arXiv:2604.03049). Using historical perihelion records spanning 2,225 years (30 apparitions, 239 BCE to 1986 CE), I find that Halley's mean orbital period P_bar = 76.713 yr satisfies T*/P_bar = 15.004, yielding an angular residue of +1.43 degrees – the smallest of any
Solar System body examined, including all seven
planets that participate in T* (Mercury, Venus, Earth, Mars, Jupiter, Saturn, and Neptune; p = 0.009). No other Halley-type comet participates: all examined HTCs exhibit residues of 80–130 degrees, comparable to Uranus (108 degrees), the sole planetary non-participant. Four independent statistical tests establish that Jupiter and Saturn couple to Halley's orbital period through distinct mechanisms. Jupiter acts through phase-dependent modulation: its angular position at each perihelion predicts the period deviation (p = 0.027–0.04, three methods). Saturn acts through distance-amplitude modulation: closer approaches produce larger deviations regardless of sign (r = -0.496, p = 0.007), specific to Saturn's actual orbital phase (random-phase control p = 0.133). After 15 orbits, the cumulative period deviation is only 9.4% of the random-walk expectation – direct evidence of coherent perturbation cancellation over one T* cycle. The orbit-to-orbit chaos (Lyapunov time ~70 yr) and the long-term mean stability are not contradictory: the same Jupiter-Saturn forces that cause individual-orbit variability cancel coherently over the T* baseline, anchoring the mean period at the millennium scale.
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Astrophysics of Galaxies · Cross-listed from gr-qc
Geodesics Structure and Thermodynamic Properties of Gaussian Black Hole in Quadratic Ricci Scaler Gravity
M. Haditale and B. Malekolkalami
The geodesic structure and thermal properties of Gaussian Black Holes (GBH)s in modified and Einstein gravities are studied and compared. In the geodesic part, motion of a test particle (massive and massless) are discussed, specially properties of the circular motion are considered. In the thermodynamic part, the mass,
entropy and temperature functions are considered and discussed. The local and global stability is also analyzed through the Heat Capacity (HC) and Gibbs Energy (GE). The results show the thermodynamic differences are more than geodesic ones in the two theories of
gravity with the note that the modified
gravity is more consistent with the physical world.
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Solar and Stellar Astrophysics
Full non-LTE multi-level radiative transfer II. The case of a 5-level Ca ii atom with broadened excited levels
T. Lagache, M. Sampoorna and F. Paletou
The so-called full non-local thermodynamic
equilibrium (FNLTE) radiative transfer problem allows us to take into account not only deviations of the radiation field from the Planckian but also deviations of the densities and velocity distributions of massive particles from Maxwell-Boltzmann statistics. This article discusses the extension of this formalism to physically realistic multi-level atoms, including natural broadening of the excited levels. In practice, we must solve self-consistently a coupled set of kinetic equations and determine, for each line, an emission and absorption profile by convolving a non-Lorentzian atomic profile with a non-Maxwellian velocity distribution at each iteration. To solve this numerically challenging problem, we have developed a new efficient iterative method based on well-known approximate operator techniques. After validating our numerical strategy, we present the results obtained for the H & K lines and the infrared triplet of the Ca II. Under the conditions studied, for this particular atomic model and for a simplified atmosphere, we find that the standard NLTE with partial redistribution is sufficient to describe the formation of Ca II spectral lines. The more exact treatment of FNLTE is unnecessary in the case of Ca II H & K, and infrared triplet lines, even when accounting for velocity-changing collisions.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Fixing the Renormalization of Inflationary Loops via Ward Identities
Cheng-Jun Fang and Zong-Kuan Guo
Evaluating
quantum loop corrections to
curvature perturbations in non-attractor inflation presents theoretical ambiguities. A crucial aspect of this challenge lies in the unconstrained finite contributions in renormalization counterterms and regularization scheme dependence. In this work, we derive exact Ward identities via the path integral formalism based on the large gauge
symmetry of the background-perturbation split. These identities are shown to impose strict, model-independent constraints on the renormalization procedure. Provided the ultraviolet completion respects this
symmetry, the Ward identities non-perturbatively govern the infrared
evolution of the power spectrum. This
symmetry-based framework offers a systematic resolution to recent theoretical discrepancies concerning one-loop corrections in ultra-slow-roll inflation.
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Earth and Planetary Astrophysics
Fizzy water ice in space: CO$_2$ adsorption, binding energies and its fate in a protoplanetary disk
Alicja Bulik, V. Bariosco, E. Mates-Torres et al. (+4 more)
CO2 is the third most abundant ice component found on
dust grains in
star-forming regions and a common ingredient of
exoplanet atmospheres. Characterization of its adsorption properties on ices through the binding energy (BE) is essential for accurate astrochemical modelling and understanding chemical inheritance in
planet formation. We aim to derive an accurate BE distribution of CO2 on water ices. Our goal is to understand the impact of the BE distribution on the abundance of gaseous and frozen CO2 in a generic protoplanetary disk and the spectral absorption features of frozen CO2. The ACO-FROST procedure is used for computing the BE distribution, where CO2 molecules are adsorbed on several sites of an amorphous water ice grain model. The BEs are computed using an ONIOM scheme. The BEs of CO2 follow a bimodal Gaussian distribution characterised by the following parameters: {\mu}1 = 1648K, {\sigma}1=229K, {\mu}2=2339K, {\sigma}2=274K.For each BE bin, the pre-exponential factor was estimated using two models and the Polanyi-Wigner relationship. Comparison with previous studies, both experimental and computational, show good agreement on the range of the BEs. The impact of the adsorption on water ice on the spectral features of CO2 molecule is evaluated. The coverage simulation shows the non-wetting properties of CO2 on the water ice surface. We discuss the impact of using a BE distribution and different pre-exponential factors to calculate the partitioning between the ice and gas in a generic protoplanetary disk. We confirm that the use of BE distribution to model the gas and ice fractionation in a protoplanetary disk causes the gas fraction to be significantly more extended. Furthermore, we show that the prefactor has a significant impact on where the snowline forms and on the final extent of the gas fraction in the disk.
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All authors Alicja Bulik, V. Bariosco, E. Mates-Torres, P. Ugliengo, K. Furuya, C. Ceccarelli, A. Rimola
Cosmology and Nongalactic Astrophysics
Probing nonlinear structure formation beyond $\Lambda$CDM with the LSS bootstrap: a joint power spectrum and bispectrum analysis
Giorgia Biselli, Marco Marinucci, Guido D'Amico et al. (+1 more)
We present the first MCMC-derived constraints on the parameters of the Large Scale Structure (LSS) bootstrap, a model-independent framework that captures deviations from $\Lambda$CDM using
symmetry arguments alone. Focusing on modifications to the linear growth rate and to the quadratic perturbation-theory kernel – quantified by the fractional parameters $\varepsilon_f$ and $\varepsilon_{d_{\gamma}}$, respectively – we carry out a joint analysis of the one-loop
galaxy power spectrum and the tree-level bispectrum multipoles within the EFTofLSS, employing the PyBird code extended to implement the bootstrap parametrization. We apply this analysis pipeline to two
datasets: the BOSS DR12 LRG sample and the large-volume “PT Challenge” simulations. For BOSS, combining the power spectrum with the bispectrum monopole yields $\sim 7\%$ constraints on $\varepsilon_f$ and $\sim 57\%$ constraints on $\varepsilon_{d_{\gamma}}$. For the PT Challenge, whose survey volume is about 100 times larger, we reach $\sim 1\%$ precision on $\varepsilon_f$ and $\sim 25\%$ on $\varepsilon_{d_{\gamma}}$, including the bispectrum quadrupole in the analysis. Our results underscore the complementary roles of $\varepsilon_f$ and $\varepsilon_{d_{\gamma}}$ in separating changes to the background expansion from those affecting nonlinear structure formation, and they show that the LSS bootstrap offers a competitive, model-agnostic method for probing physics beyond $\Lambda$CDM with existing and upcoming
galaxy surveys.
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All authors Giorgia Biselli, Marco Marinucci, Guido D'Amico, Massimo Pietroni
High Energy Astrophysical Phenomena
Revisiting the 2021 Outburst of the BHC MAXI J1803-298 Using NICER, NuSTAR, and Insight-HXMT Data
Kaushik Chatterjee and Sujoy K. Nath
We present a broadband spectral and timing study of the black hole candidate MAXI J1803-298 during its 2021 outburst using simultaneous observations from NICER, NuSTAR, and Insight-HXMT. The combined multi-instrument coverage allows us to investigate the
evolution of low-frequency quasi-periodic oscillations (LFQPOs) together with the spectral properties of the source over a wide energy range. During the early observation epoch, the source exhibits a hard or hard-intermediate spectral state dominated by Comptonized emission with reflection features. Spectral modeling within the framework of the two-component advective flow (TCAF) model indicates the presence of a sub-Keplerian
halo and a Keplerian disk with a shock located at 130 Schwarzschild radii, and provides an independent estimate of the black hole mass. A prominent LFQPO is detected during this epoch with a centroid frequency evolving from 0.35 Hz to 0.5 Hz and extending up to 100 keV. The energy-dependent fractional rms variability suggests that the modulation originates primarily from the Comptonizing inner
accretion flow. In contrast, a later observation epoch shows a softer spectral state characterized by stronger disk emission and a steeper
photon index, during which no LFQPO is detected. We also demonstrate that cospectral analysis effectively mitigates dead-time-induced distortions in NuSTAR timing studies, confirming the intrinsic nature of the detected variability. The combined spectral and timing results support a scenario in which LFQPOs in MAXI J1803-298 arise from the dynamically evolving inner
accretion flow.
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Astrophysics of Galaxies
Survival of Molecular Complexity under Recent Supernova Feedback: Detection of Hot Cores in RX J1713.7-3946
Takashi Shimonishi, Hidetoshi Sano, Kenji Furuya et al. (+1 more)
Protostellar cores located near
supernova remnants are considered potential analogues of the birth environment of the
solar system. However, the extent to which
supernovae influence their chemical
evolution remains unclear. We report the first detection of hot molecular cores in a
supernova remnant using the Atacama Large Millimeter/submillimeter Array. The detected hot cores (HC1 and HC2) are located inside the X-ray shell of the young
supernova remnant RX J1713.7-3946, and both sources are associated with Class I intermediate-mass protostars. This paper focuses on a detailed chemical analysis of HC1, in which a variety of carbon-, oxygen-, nitrogen-, sulfur-, and silicon-bearing species are detected. Excitation analyses indicate that HC1 harbors dense (~10^7 cm-3), compact (<500 au), and high-temperature (>100K) molecular gas. Despite being located within a
supernova-feedback region, the column density ratios of complex organic molecules (HCOOCH3/CH3OH, CH3OCH3/CH3OH, and CH3CHO/CH3OH), a deuterated molecule (CH2DOH/CH3OH), and sulfur- and nitrogen-bearing species (OCS/CH3OH and C2H5CN/CH3CN) in HC1 are indistinguishable from those observed in hot cores/corinos in more typical
star-forming environments. HC1 is located near the outer edge of the
supernova shell, and the surrounding region has likely begun to be exposed to such a harsh environment only recently. The elapsed time since the onset of exposure to high-energy particles and
photons may be too short for the chemical composition of the hot core to be significantly altered, and/or the hot-core region may be shielded by
magnetic fields amplified by
supernova feedback, which could suppress the penetration of enhanced
cosmic rays.
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All authors Takashi Shimonishi, Hidetoshi Sano, Kenji Furuya, Yoko Oya
Astrophysics of Galaxies
Comparative analysis of missing data imputation methods for CSST survey: Impact on photometric redshift estimation performance
Ling Wang, Zhu Chen, Zhijian Luo et al. (+42 more)
Improving the accuracy of photometric
redshifts (photo-$z$) is essential for reliable statistical studies of cosmology and
galaxy evolution. However, missing photometric bands are a common observational challenge that can significantly degrade photo-$z$ estimation accuracy. In this work, we present a systematic evaluation of data imputation methods aimed at improving photo-$z$ performance. We
benchmark a range of representative machine learning (ML) and deep learning (DL) architectures, identifying k-nearest neighbors (KNN) and the
attention-based SAITS model as the leading performers. These models are then applied to China Space Station Survey
Telescope (CSST) mock data to assess their performance under realistic observational conditions. Our results show that KNN yields the highest accuracy under idealized missing completely at random (MCAR) conditions with complete training sets, whereas robustness tests reveal that SAITS significantly outperforms KNN when training data is incomplete or when applied to realistic mixed-mechanism scenarios. We find that domain consistency between training and testing missingness patterns is a prerequisite for optimal performance, highlighting the risks of domain shift in supervised regression tasks. Furthermore, our analysis demonstrates that while general imputation models are highly effective for MCAR and missing at random (MAR) data, they are detrimental when applied to missing not at random (MNAR) data arising from flux limits, as statistical models fail to capture the physical information inherent in these non-detections. Consequently, we advocate for more sophisticated architectures capable of disentangling
stochastic missingness from physical non-detections to address these distinct mechanisms individually.
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All authors Ling Wang, Zhu Chen, Zhijian Luo, Liping Fu, Zuhui Fan, Wei Du, Yaoming Lei, Zhang Ban, Yuedong Fang, Yi Hu, Xin Ji, Guoliang Li, Xiaobo Li, Jiaqi Lin, Chenxiaoji Ling, Chao Liu, Dezi Liu, Changqing Luo, Yu Luo, Bin Ma, Xianmin Meng, Jundan Nie, Juanjuan Ren, Li Shao, Jianing Tang, Hao Tian, Feng Wang, Chengliang Wei, Peng Wei, Shoulin Wei, Kaichao Wu, You Wu, Yun-Ao Xiao, Zhou Xie, Yibo Yan, Su Yao, Yan Yu, Bo Zhang, Shengwen Zhang, Tianmeng Zhang, Xiaoli Zhang, Xin Zhang, Bowei Zhao, Zhimin Zhou, Hu Zou
Solar and Stellar Astrophysics
Diversity in Evolutionary Status and Magnetic Activity among Solar-Type Twin Detached Eclipsing Binaries
Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian et al. (+9 more)
We present a combined photometric and spectroscopic analysis of four detached eclipsing binaries (KIC 8957954, KIC 10593759, KIC 8302455, and TIC 207398432), all of which exhibit composite G-type spectra and nearly equal mass ratios. Based on survey data and our own observations, we measured radial velocities with the broadening function method, applied the fd3 program for spectral disentangling, and modeled the light curves with the Wilson-Devinney code to determine accurate absolute parameters. The results reveal significant differences in evolutionary stages and
magnetic activity despite their nearly equal masses. Both components of KIC 8957954 and KIC 8302455 are on the main sequence; KIC 10593759 has evolved to the subgiant stage; and in TIC 207398432, the secondary has entered the red
giant phase. Stronger
magnetic activity is observed in KIC 10593759 and TIC 207398432, characterized by rapid O'Connell Effect Ratio variations, with the latter also exhibiting multiple superflare events. In addition, the spectral characteristics of TIC 207398432 suggest that it may be part of a hierarchical triple system. This study provides precise absolute parameters for twin binaries and offers important observational evidence for understanding their evolutionary diversity,
magnetic activity, and the possible presence of tertiary companions.
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All authors Fang-Bin Meng, Li-Ying Zhu, Sheng-Bang Qian, Lin-Jia Li, David Mkrtichian, Nian-Ping Liu, Ahmet Dervişoğlu, Er-Gang Zhao, Boonrucksar Soonthornthum, Sergey Zvyagintsev, Somsawat Rattanasoon, Jia Zhang
Solar and Stellar Astrophysics
The Accretion Process on Protostars
Eleonora Fiorellino and Alice Somigliana
The process of mass
accretion onto Young
Stellar Objects (YSOs) plays a fundamental role in determining the final
stellar mass and setting the initial conditions for
planet formation. Despite its critical role, our understanding of
accretion remains fragmented, particularly for what concerns the earliest, protostellar phases (Class 0/I). While the community has consolidated a comprehensive knowledge of the
accretion process of the later-stage Classical T Tauri
Stars (CTTSs), a similar level of understanding is critically lacking for the protostellar phase, where the bulk of the mass is assembled. This work aims to review recent major results, both from the observational and numerical point of view, bridging the gap between the two approaches and providing an updated, complete assessment of
accretion in protostellar sources. We present different techniques to measure
accretion on protostars, analyze how methodological differences affect parameter estimation, discuss the caveats in comparing with numerical models, and suggest the next steps to take towards an ever more exhaustive picture of the protostellar phase.
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Solar and Stellar Astrophysics
Discovery and Characterization of White Dwarf-FGK Main-Sequence Binaries within the Optical Main-Sequence Locus
Mingkuan Yang, Hailong Yuan, Xiaozhen Yang et al. (+12 more)
White
dwarf main-sequence (WDMS) binaries provide important laboratories for studying binary
evolution and the formation of low-mass white
dwarfs. In this work, we identify 654 reliable WDMS candidates with FGK-type companions from an initial set of 772 ultraviolet-excess sources, selected using
stellar atmospheric parameters from LAMOST spectroscopy and subsequently refined with
Gaia DR3 astrometry and photometry together with ultraviolet data from GALEX. Candidates were selected based on ultraviolet excess relative to the
Gaia main-sequence locus and refined using isochrone constraints to exclude systems inconsistent with MS companions. Binary spectral energy distribution fitting yields effective temperatures and radii for both components, as well as distance and extinction estimates. The MS companions are dominated by G-type
stars (\(\sim52\%\)), with comparable fractions of F- and K-type companions, and no A-type primaries. Using white-
dwarf evolutionary cooling models, we find that the WD components are predominantly low-mass (\(M_{\rm WD}\,\sim\,0.2\text{--}0.4\,M_\odot\)), including a substantial population of extremely low-mass (\(<0.3\,M_\odot\)) WDs likely produced through binary interaction. The WDs are generally hot (\(\sim1.5\times10^4\,\mathrm{K}\)), consistent with the ultraviolet selection bias favoring luminous, large-radius WDs. Multi-epoch LAMOST radial velocities show larger amplitudes than those of a comparison sample of MS
stars, supporting the close-binary nature of these systems. Although subject to strong selection effects, the catalog offers a clean and well-characterized sample of FGK+WD binaries.
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All authors Mingkuan Yang, Hailong Yuan, Xiaozhen Yang, Zhongrui Bai, Yuji He, Jianping Xiong, Jiao Li, Mengxin Wang, Yiqiao Dong, Ziyue Jiang, Qian Liu, Ganyu Li, Ming Zhou, Haotong Zhang, Xuefei Chen
Solar and Stellar Astrophysics
Resonant shear-flow instability in anisotropic supersonic plasmas with heat flux
Namig S. Dzhalilov
This work is devoted to the study of the influence of temperature anisotropy and parallel heat flux on the stability of supersonic shear flow in collisionless
plasmas. Within a fluid-based framework, we employ the 16-moment transport equations – derived from the Vlasov-Maxwell system – to describe the
plasma dynamics. By performing a modal analysis we investigate the oblique propagation of linear disturbances within a magnetized
plasma characterized by a shear flow of arbitrary profile aligned with the ambient
magnetic field. In the unperturbed state, both the
plasma density and the
magnetic field are assumed to be homogeneous. For a smooth,
hyperbolic velocity profile representing supersonic shear, the governing wave equation is reduced to a form amenable to an exact analytical solution. Analytical solutions are expressed in terms of special functions that yield an infinite discrete spectrum of complex eigenfrequencies ($n = 0, 1, 2, \dots$). The instability is identified as resonant, peaking when the wave phase velocity matches the mean flow velocity, with the growth rate decreasing for higher-order modes. The results indicate that, while heat flux exerts a negligible influence under conditions of supersonic flow, the growth rate decreases and approaches an asymptotic value as the Mach number increases. Notably, the instability vanishes in the
vortex sheet limit, distinguishing it from the classical Kelvin-Helmholtz mechanism. These findings suggest that this specific instability holds significant potential for explaining the problem of observed boundaries between isotropic and anisotropic
proton temperature regions in a low-beta
solar wind
plasma.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
The Gravitational Spectral Radio Forest: A Signature of Primordial Black Holes
P. George Christopher, K. Hari and S. Shankaranarayanan
We propose a novel gravitational signature to detect
Primordial Black Hole (PBH) dark matter by treating interstellar hydrogen as a
quantum sensor for spacetime
curvature. Focusing on H II regions, we demonstrate that the Riemann
tidal tensor of an asteroid-mass PBH induces a symmetric splitting of the $2P_{3/2}$ state in bound hydrogen atoms. This relativistic effect redistributes $9.9\,\mathrm{GHz}$ absorption line into a gravitational spectral
radio forest with a bandwidth $\sim 2\,\mathrm{GHz}$. By accounting for active
accretion of Hydrogen atoms and the resulting density-squared emission measure within the Bondi radius, we find a relatively enhanced absorption spectrum. This feature presents a concrete, high-contrast target for upcoming
radio-surveys to constrain PBH populations in the dark matter sector.
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Solar and Stellar Astrophysics
Height Variations of Magnetoacoustic Cutoff Frequency in the Solar Atmosphere
Pradeep Kayshap, Gayathri Hegde, Z. E. Musielak et al. (+2 more)
The determination of the cutoff frequency in real
solar observations under different local physical conditions is an important and insufficiently explored aspect of waves in
solar physics. This work utilizes the near ultraviolet (NUV) spectrum of the QS, observed by the Interface Region Imaging Spectrograph (IRIS) on November 16th, 2013, in sit-n-stare mode. It contains several absorption and emission lines that form at different heights between the photosphere and chromosphere. Cross-wavelet analysis is performed on Doppler velocity time series of pairs of spectral lines sampling different atmospheric layers to estimate the cutoff frequency at six different heights between the photosphere and chromosphere. It is found that the cutoff frequency increases with height from around 3.0 mHz at 0.38 Mm (photosphere) to around 8.5 mHz at 1.2 Mm (chromosphere). Higher chromospheric heights show indications of standing oscillations. The presented observational results are compared with those previously obtained, and serve as a
benchmark to refine theoretical models that predict variations of cutoff frequencies in the
solar atmosphere.
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All authors Pradeep Kayshap, Gayathri Hegde, Z. E. Musielak, Kris Murawski, Tob{\i}as Felipe
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Inspiral gravitational waveforms from charged compact binaries with scalar hair
Antonio De Felice and Shinji Tsujikawa
We investigate gravitational waveforms from compact binary systems in Einstein-scalar-Maxwell (ESM) theories, where a scalar field $\phi$ couples to a $U(1)$ gauge field $A_\mu$ through a field-dependent function $\mu(\phi)$. In this framework, compact objects – black holes (BHs),
neutron stars (NSs), and exotic compact objects (ECOs) – can carry both vector and scalar charges, with the latter arising as secondary hair induced by the former. Modeling the binary as electrically charged point particles with scalar-field-dependent masses, we derive the conservative dynamics in the near zone and compute the radiative fields in the far zone. The tensor waveform is modified through the effective dynamics and radiation-reaction-driven phase
evolution, while scalar and vector modes introduce additional energy-loss channels. From the energy fluxes of tensor, scalar, and vector radiation, we construct the frequency-domain waveform using the stationary phase approximation. Dipole radiation sourced by differences in scalar and vector charge-to-mass ratios yields a leading $-1$ post-Newtonian correction. The deviation from general relativity is characterized by a single parameter $b$, which controls both amplitude and phase modifications. We further examine constraints from the orbital-period decay of binary
pulsars, showing that current observations already place stringent bounds on $b$ for
neutron star binaries. In addition, we evaluate $b$ for representative BH-BH, NS-NS, ECO-ECO binaries realized in ESM theories. Our results provide a unified framework for gravitational-wave signatures of charged compact binaries and offer a means of testing dark-sectorscalar and vector charges with current and future observations.
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Cosmology and Nongalactic Astrophysics
Revisiting constraints on primordial vector modes and implications for sourced magnetic fields and observed $EB$ power spectrum
Kaito Yura, Shohei Saga, Shuichiro Yokoyama et al. (+1 more)
We revisit regular
primordial vector modes sustained by the anisotropic stress of free-streaming
neutrinos. We consider two classes of
neutrino-sector initial conditions, the
neutrino velocity isocurvature mode ($\nu\mathrm{VI}$) and the
neutrino octupole mode ($\nu\mathrm{OCT}$). We update their observational constraints using current cosmological data, and examine the impact of including the BICEP/Keck 2018 $B$-mode polarization data. From an MCMC analysis, we obtain the 95% C.L. upper bounds on the vector-to-scalar ratio as $r_\mathrm{v}<1.55\times10^{-4}$ and $r_\mathrm{v}<1.04\times10^{-2}$ for the $\nu\mathrm{VI}$ and $\nu\mathrm{OCT}$ modes at the vector pivot scale $k_{0} = 0.01\,{\rm Mpc}^{-1}$, respectively. We then study two consequences of these bounds. First, we estimate the
magnetic fields inevitably generated in the pre-recombination
plasma associated with the vector modes. We find that the
magnetic-field amplitude at recombination with a coherent length of $1~{\rm Mpc}$ is bounded by $B\sim\mathcal{O}(10^{-23})\,{\rm G}$ and $B\sim\mathcal{O}(10^{-21})\,{\rm G}$ for the $\nu\mathrm{VI}$ and $\nu\mathrm{OCT}$ modes, respetively, which is too small to provide the seed of
magnetic fields observed today. Second, assuming the helical vector mode, we compute the induced CMB $EB$ spectrum. We show that even a fully helical
primordial vector mode cannot reproduce the currently observed $EB$ signal while remaining consistent with parity-even CMB constraints.
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All authors Kaito Yura, Shohei Saga, Shuichiro Yokoyama, Kiyotomo Ichiki