Instrumentation and Methods for Astrophysics
Overview of the Canadian Hydrogen Observatory and Radio Transient Detector (CHORD) Project
The CHORD Collaboration: Kevin Bandura, Leonid Belostotski, Lindsay Berkhout et al. (+48 more)
The Canadian Hydrogen Observatory and
Radio-transient Detector (CHORD) is a next-generation wideband
radio interferometer currently being constructed and commissioned at the Dominion
Radio Astrophysical Observatory in British Columbia, Canada. CHORD is designed for precision 21\,cm cosmology, fast
radio transient discovery, spectral line
galaxy surveys, and
pulsar science using a highly redundant large-N, small-diameter drift-scan array architecture. The
telescope consists of a 512-element core array of 6\,m dishes operating from 300–1500\,MHz in drift-scan mode, together with two 64-dish outrigger stations located at the Hat Creek
Radio Observatory and the Green Bank Observatory for long-baseline transient localization. The instrument supports multiple simultaneous digital backends for interferometric correlation, FRB detection,
pulsar beamforming, and high spectral resolution surveys. CHORD is designed with an emphasis on precision beam control and stable instrumental response, incorporating lessons learned from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) while providing a substantial increase in sensitivity. Initial performance has been evaluated using a three-dish engineering array, and a 64-dish pathfinder array is currently being commissioned. The full array will be commissioned in 2028.
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All authors The CHORD Collaboration: Kevin Bandura, Leonid Belostotski, Lindsay Berkhout, Gianni Bernardi, Akanksha Bij, Duncan Cameron-Steinke, Arnab Chakraborty, Hsin Cynthia Chiang, Jean-Francois Cliche, Sophia Da Costa, Evan Davies-Velie, Matt Dobbs, Emmanuel Fonseca, Simon Foreman, Qwin Goodwin, Ian Hendricksen, Jason Hessels, Alex S. Hill, Mohammad Islam, Michael Jafs, Aditya Krishna Karigiri Madhusudhan, Gordon Lacy, Dustin Lang, Calvin Leung, Jessie Lin, Adrian Liu, Vincent MacKay, Kiyoshi W. Masui, Juan Mena-Parra, James Mertens, Daniele Michilli, Kenzie Nimmo, Robert Pascua, Maura Pilia, Andrea Possenti, Aniket Prasad, Andre Renard, Sophia D'Agostino Rubens, Mawson Sammons, Erik Schnetter, Paul Scholz, Seth Siegel, Jonathan Sievers, Kendrick Smith, Kristine Spekkens, Shronim Tiwari, Martin Topinka, Matteo Trudu, Keith Vanderlinde, Dallas Wulf, Yifan Zhao
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Bayesian inference of the dense matter equation of state built upon extended Skyrme interactions: A generalization
Mikhail V. Beznogov and Adriana R. Raduta
The nonrelativistic theory of
nuclear matter (NM) based on Brussels-Skyrme interactions is employed to develop models for dense and
neutron-rich matter within a
Bayesian framework. We employ the following set of constraints: the four best-known
nuclear empirical parameters, density dependence of the energy per particle in pure
neutron matter (PNM), density dependence of the Landau effective mass ($m_\mathrm{eff}$) of
neutrons in PNM and symmetric NM, and a lower limit on the maximum gravitational mass that
neutron stars (NSs) can sustain. In addition, a number of “sanity checks” are added: the values of the speed of sound,
neutron and
proton Landau effective masses and
Fermi velocities are constrained up to the central density of the most massive NS configuration and for isospin asymmetries $\delta=(n_n-n_p)/(n_n+n_p)$ ranging from 0 to 1. Our ensemble of models fully explores the capacity of non-relativistic Brussels-Skyrme effective interactions to describe NM at densities exceeding several times the
nuclear saturation density. This is a necessary step toward a better understanding of the properties of dense matter and possible correlations between the parameters of NSs and the parameters of NM. Due to pronounced U-shaped density-dependencies of $m_\mathrm{eff}$, all our models exhibit a non-monotonic “rise-and-fall” behavior of the thermal pressure ($p_\mathrm{th}$) as a function of density, which in extreme cases leads to $p_\mathrm{th} < 0$. This work is a generalization of [Beznogov and Raduta, Phys. Rev. C 110, 035805 (2024)].
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Astrophysics of Galaxies
Effect of Ice Charging on the Astrochemistry of Interstellar Sulfur Bearing Species on Amorphous Solid Water
T. Vorsselmans, I. Grubova, K. Verhagen et al. (+4 more)
We aim to derive statistically robust and physically interpretable BE distributions for atomic S and the sulfur-bearing molecules H$_2$S, SO$_2$, and OCS on neutral and negatively charged ASW, and assess how excess negative charge alters their retention and potential role in the sulfur reservoir of cold dense molecular clouds. Basis set superposition error (BSSE) and zero-point energy (ZPE) corrected BEs of S, SO$_2$, OCS and H$_2$S, are calculated by density functional theory (DFT), using the ORCA software. Molecule-specific DFT levels of theory were first selected from
benchmark calculations on neutral and charged small water complexes, against coupled-cluster reference energies. The selected protocols were then applied to study adsorption on neutral and charged ASW clusters. A range of adsorption sites were sampled on five independent amorphous ice clusters, yielding BE distributions that account for the site heterogeneity of ASW. Neutral ASW yields broad, site-dependent BE distributions consistent with previous water-ice estimates. On charged ASW, three general cases are identified: the BE will either always increase due to electron transfer (S-atom, SO$_2$), the BE increases slightly without any electron transfer (H$_2$S) or the BE remains the same unless an electron transfer occurs under specific conditions (OCS). These findings are inherently linked to the molecular properties of these molecules.
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All authors T. Vorsselmans, I. Grubova, K. Verhagen, T. Guldentops, R. Buimer, C. King, E. C. Neyts
Earth and Planetary Astrophysics
The GAPS Programme with HARPS-N at TNG LXXVII. Occurrence rates of small close-in planets in the presence of cold Jupiters
A. Ruggieri, S. Desidera, M. Pinamonti et al. (+18 more)
Context. The architecture of our
Solar System, with inner small
planets (ISPs) and outer
giants, may or may not be common. Understanding whether a correlation exists between ISPs and outer cold
giants is key to evaluating how common systems with a similar architecture to our own are. Aims. This study aims to build a large, homogeneous sample of systems hosting cold Jupiters (CJs, a > 1 au, msini > 0.1 M$_J$) detected via radial velocities (RVs), and to assess the presence of additional ISPs (P < 400 d, 3 < msini < 31.7 M$_{\oplus}$), studying the correlation between these two types of objects. Methods. We selected 137
stars known to host a CJ, including 23 which also harbor a hot Jupiter and were treated separately. Data from various instruments were compiled, including unpublished data gathered with HARPS-N within the GAPS program, and consistently fitted using PyORBIT. We derived RV detection maps and calculated occurrence rates for ISPs, cross-validating results with two independent codes. The sample was divided into subgroups to evaluate how system parameters influence
planet occurrence. Results. We confirmed the 213 already known
planets in the 137 systems and also identified six new candidates. We divided them, based on mass and period, into Neptunes (10 < m sin i < 31.7 M$_{\oplus}$) and Super-Earths (3 < m sin i < 10 M$_{\oplus}$), and into hot (1 < P < 10 d), warm (10 < P < 100 d), and cool (100 < P < 400 d). We found occurrences of 5%, 13%, and 12% for hot, warm, and cool Neptunes, respectively, and 11% and 16% for hot and warm Super-Earths, respectively. Systems with dynamically stable inner regions show higher rates of small
planets. These findings are consistent with previous studies showing no strong correlation between ISPs and CJs at average
stellar metallicity and mass, and suggest that HJs may be more commonly associated with external
giants.
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All authors A. Ruggieri, S. Desidera, M. Pinamonti, D. Barbato, A. Sozzetti, A. S. Bonomo, L. Naponiello, M. Damasso, S. Benatti, I. Carleo, R. Gratton, K. Biazzo, A. F. Lanza, G. Piccinini, N. Nari, G. Mantovan, J. Maldonado, D. Nardiello, A. Fiorenzano, A. Ghedina, A. Bignamini
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The significance of first post-adiabatic contributions for scalar charge measurements with intermediate and extreme mass ratio inspirals
Susanna Barsanti, Ollie Burke, Andrea Maselli et al. (+3 more)
We present the first self-force-based beyond-GR waveform model incorporating post-adiabatic orbital
evolution for intermediate- and extreme-mass-ratio inspirals in theories of
gravity with additional scalar fields. Focusing on quasi-circular inspirals into a non-spinning primary, we combine a first post-adiabatic (1PA) gravitational sector with leading-order scalar field effects and use
Bayesian injection-recovery studies to assess the impact of waveform systematics on the inference of scalar charges with LISA. We find that neglecting 1PA effects in the gravitational sector can bias the inference of intrinsic binary parameters, while scalar-charge measurements remain robust across a wide range of mass ratios. In contrast, analysing signals from binaries in which the secondary carries a scalar charge using pure-GR templates leads to significant biases and underestimated uncertainties due to unmodelled correlations between the scalar charge and the binary parameters. We also investigate the role of secondary
spin and find no significant correlation between the secondary
spin and the scalar charge. Notably, up to a mass ratio of $10^{-4}$, the secondary
spin itself remains unconstrained even in the pure-GR case, in contrast with previous claims in the literature. Finally, we show that modelling scalar emission with a leading-order dipolar post-Newtonian approximation – for quasi-circular inspirals into a non-spinning primary – introduces negligible systematic errors relative to fully relativistic scalar fluxes.
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All authors Susanna Barsanti, Ollie Burke, Andrea Maselli, Thomas P. Sotiriou, Andrew Spiers, Niels Warburton
Astrophysics of Galaxies
Structural Diversity Among the Milky Way's Dwarf Spheroidal Satellites
Matthew G. Walker, Raphaël Errani, Andrew B. Pace et al. (+3 more)
We fit a flexible double power-law (`$\alpha\beta\gamma$') model to the
stellar density fields observed for the Milky Way's known
dwarf spheroidal satellite
galaxies. We show that where standard criteria for model selection are decisive, the $\alpha\beta\gamma$ model is favored over the special case of the Plummer model, and also over the \sersic\ model and its special case, the exponential. The Milky Way's dSph population exhibits a diverse range of
stellar density profile shapes, as quantified by the values we infer for outer and inner power-law indices $\beta$ and $\gamma$. Several of the most massive dSphs (e.g., Eridanus II, Fornax, Leo I, Leo II) have steeply-declining outer profiles, with $\beta\gtrsim 8$; others (e.g., Sextans, Boötes I) fade slowly, with $\beta\lesssim 4$. The inner profiles of dSphs with
stellar mass $\gtrsim 10^5 M_{\odot}$ are consistent with `cores' of uniform
stellar density ($\gamma\approx 0$). At lower masses the slopes of inner density profiles are poorly constrained, except in a few ultrafaint dSphs (e.g., Hercules, Ursa Major II) where we infer steep
stellar cusps, with $\gamma\gtrsim 1.5$. Owing to the $\alpha\beta\gamma$ model's flexibility, the inferred halflight radii and total
stellar masses are significantly more uncertain than previous estimates, with halflight radii larger by up to an order of magnitude in some cases. Finally, we demonstrate that allowing for flexibility in the shape of the
stellar density profile is crucial for dSph mass modeling, where systematic errors associated with choice of
stellar density profile can outweigh random errors in the observed velocity dispersions.
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All authors Matthew G. Walker, Raphaël Errani, Andrew B. Pace, Jorge Peñarrubia, Sofia Splawska, Eduardo Vitral
Instrumentation and Methods for Astrophysics
Enhancing the Cherenkov Telescope Array Observatory high-level performance through an event-type-based analysis
Juan Bernete, Silvia García-Soto, Tarek Hassan et al. (+4 more)
The analysis traditionally employed by Imaging Atmospheric Cherenkov
Telescopes involves optimizing quality cuts to select a sub-sample of high-quality events. These events are used for the scientific interpretation of the data, employing a single set of Instrument Response Functions (IRFs). All selected events are treated equally and assumed to be well represented by these IRFs, while the rest are discarded. An alternative approach, successfully applied in experiments such as
Fermi-LAT, is an event-type-based analysis. This method divides
datasets into subsamples, each containing events of a given expected reconstruction quality. IRFs are computed for each subsample independently, improving the accuracy with which IRFs represent the reconstruction quality of each event. The high-level analysis of these subsamples is performed treating them as independent observations, each with their own set of IRFs, and analyzed jointly. In this work we present a proof-of-concept implementation of an event-type-based analysis for the future CTAO using simulated data. A neural network (specifically a multi-layer perceptron) is trained to predict the direction reconstruction error of each event, and the simulated
dataset is divided into event types based on this predicted variable. We compute IRFs for each event type and compare them with those from the standard analysis (without event types). Finally, we simulate observations using these event-type-wise IRFs and analyze them with high-level analysis tools to test the performance of both approaches. This implementation demonstrates notable improvements: 25% to 50% boost in spatial resolving power and ~25% in sensitivity. This boost in performance will have strong implications in the scientific exploitation of the CTAO data, especially in crowded regions such as the
Galactic Plane or searching for spectral signatures like Dark Matter annihilation lines.
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All authors Juan Bernete, Silvia García-Soto, Tarek Hassan, Orel Gueta, Maximilian Linhoff, Atreyee Sinha, Gernot Maier
Cosmology and Nongalactic Astrophysics
Primordial Black Hole mass growth from neutrinos during the radiation era
Maël Gonin
We present a new picture of
primordial black holes mass
evolution through
neutrino absorption. Using semi-classical approach and a closer look at the kinetic of the early
plasma we revisit the thermal absorption of radiation by a population of
primordial black holes ranging from $10^{-3}-10^9 M_\odot$ embedded in a thermal bath. We find significant mass growth of intermediate mass and supermassive PBHs, the effect shift the predicted $e^+e^-$ peak from thermal history. Depending on the value of the collapse fraction an additional peak around the intermediate mass range, might become significant. Moreover, because PBH grow from the thermal bath the fraction of DM in PBH $f_{\rm PBH}$ also change. These results revise the previous view on mass
evolution of PBH and have implications for dark matter PBH observations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Leptogenesis with sub-electroweak-scale reheating temperature
Basabendu Barman, Arindam Basu, Debasish Borah et al. (+1 more)
We study the generation of the
baryon asymmetry of the Universe via leptogenesis during the post-inflationary reheating epoch, considering reheating temperatures below the temperature of sphaleron freeze-out. Within the framework of a monomial inflaton potential during reheating, we analyze three perturbative reheating scenarios in which the inflaton decays into (i) a pair of Standard Model (SM)-like
bosons, (ii) a pair of SM-like
fermions, or (iii) exclusively into a pair of heavy right-handed
neutrinos, which eventually decays into the SM final states after briefly dominating the energy density of the Universe. For each case, we identify the regions of parameter space that successfully reproduce the observed
baryon asymmetry consistently tracking the sphaleron interaction rate during reheating, while satisfying existing cosmological constraints. We also highlight the potential of future
primordial gravitational wave observations to probe this class of scenarios.
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All authors Basabendu Barman, Arindam Basu, Debasish Borah, Nayan Das
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
In-medium hyperon potentials and the quarkyonic hyperon onset: charged $\Sigma$'s in $\beta$-equilibrium and the neutrino connection
Jaroslaw Nowak
Quarkyonic matter resolves the
neutron-
star hyperon puzzle statistically:
neutrons fill low-momentum $d$-
quark phase space, shifting the $S=-1$ threshold from $\muB=M_Y$ to $2M_Y-M_N$ and suppressing residual softening by $1/\Nc^3$ in the Fujimoto–Kojo–McLerran (FKM) mechanism. We dress FKM's IdylliQ model with in-medium potentials, constrained by hypernuclear data and
neutrino-induced hyperon FSI, and find: (i) the dressed onset, $\muB^{\rm onset}=(2M_Y{-}M_N)+2U_Y-\UN$, carries $U_Y$ at weight 2, with $dn_{\rm onset}/dU_Y\simeq0.3\,\nz$ per $10\MeV$, twice the leverage. (ii) A self-consistent
neutron potential enters at weight $-2$, so protection needs $\UN(n_{\rm onset})\lesssim+96\MeV$. (iii) With
leptons in $\beta$
equilibrium, the $\Sigma^-$ ($dds$) onset becomes $\mue\ge258\MeV+\US-\UN$, never reached inside a $2\,\Msun$ core: $\Sigma^-$ switches from first hyperon to forbidden and the $\Sigma$ ordering inverts. (iv) The $\kY\ge\kbu$ continuation gives TOV softening below $0.05\,\Msun$ in the FKM ansatz family and below $0.025\,\Msun$ for the realistic interacting
star, $4$–$8$ below hadronic models. In the family this is a ceiling; generally it is a floor, since hyperons above $\kbu$ are omitted. (v) In an interacting low-density sector calibrated to $\Mmax=2.12\,\Msun$, core strangeness is controlled by $(\UL(\nz),c_\Lambda)$: at $\UL(\nz)=-28\MeV$, the maximum-mass
star is hyperon-free once the supra-saturation $YNN$ turn-over exceeds a few-MeV threshold $c^*_\Lambda$. Projected SBND+DUNE FSI precision pins $\UL(\nz)$ but leaves $c_\Lambda$ – to which
neutrino data are blind – decisive: with the heavy-ion prior, $P({\rm hyperon\mbox{-}free\ core})=0.90$, versus $0.89$ from priors alone, prior-dominated rather than measured. The sharpest observable is differential: $d\Mmax/dU_Y$ is an order of magnitude smaller than in mean-field models, discriminating the two resolutions.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Neutrino-induced hyperon final-state interactions as constraints on the in-medium hyperon potential
Jaroslaw Nowak
Hyperon single-particle potentials $U_Y(\rho)$ control propagation in
nuclei and hyperon onset in dense matter, where they soften the
neutron-
star equation of state and reduce the maximum mass – the “hyperon puzzle”. We show that charged-current accelerator (anti)
neutrino interactions on $^{40}$Ar, producing $\Lambda$ and $\Sigma$ inside the
nucleus, can constrain these potentials. At SBND and DUNE energies, the trapped-$\Lambda$ fraction and escaping-hyperon momenta vary monotonically with $U_\Lambda$ and $U_\Sigma$, with a kaon-vetoed FSI-$\Sigma^+$ tag adding sensitivity. Inserted in a GM1 relativistic mean-field equation of state at established hypernuclear/$\Sigma$-atom depths, the same potentials give $M_{\rm max} = 1.94\,M_\odot$ and $\Lambda_{1.4}=1034$, below the heaviest
pulsars and above the GW170817 bound typical of GM1-class mean fields. A detector-level Fisher forecast yields $\delta U_\Lambda \simeq 0.3\,$MeV and $\delta U_\Sigma \simeq 3$-$4\,$MeV for fixed low-density exponent $\gamma$. Since hyperons are produced below saturation, $U_\Lambda(\rho_0)$ and $\gamma$ are 99.8% anti-correlated; marginalising over $\gamma$ degrades the anchor to $\delta U_\Lambda \simeq 5.6\,$MeV ($1.3\,$MeV with a $\pm 0.2$ prior), while $\delta U_\Sigma$ is unchanged. For $U_\Lambda$, comparable systematics arise from hyperon-nucleon final-state cross sections ($-5/{+}2\,$MeV) and the exit-shift/gradient transport prescription ($-6\,$MeV). For $U_\Sigma$, the same $YN$ uncertainty biases the fit by $\mathcal{O}(150)\,$MeV; removing the $\Sigma^+$ tag does not cure this, because the $\Lambda$ momentum spectrum carries most $U_\Sigma$ information and is itself $YN$-sensitive. The low-density $U_\Lambda$ anchor is a robust handle, at several-MeV rather than sub-MeV precision. A joint fit with terrestrial and heavy-ion priors gives $M_{\rm max} = 2.21^{+0.04}_{-0.15}\,\,$Msun, set mainly by the external $c_\Lambda$ prior.
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Solar and Stellar Astrophysics
Structure of the Stellar Neighborhood of CQ Tau in the Presence of a Companion in an Elongated Orbit
Tatiana Demidova
There are indirect signs of the presence of a companion near the
star CQ\,Tau. A period of 10\;years was found in the brightness changes. The image of the disk shows an extensive cavity with a size of about 25~AU, surrounded by a
dust ring with a distribution maximum near 53~AU. A simulation of the interaction of
dust and gas in the vicinity of the
star with the CQ\,Tau parameters was carried out, assuming the existence of a companion in an orbit with a period of 10\;years. It was shown that an M-class
star in a highly elongated orbit is capable of forming a region of reduced density around the center of mass of the system, with a size close to the observed one. However, the
dust ring-like structure in this case is located noticeably closer to the
star than observed. Evidence has been obtained that a massive
planet in an outer, relatively binary orbit, could form a ring-shaped
dust structure at a distance similar to that observed.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Accelerator neutrinos as a probe of in-medium hyperon potentials
Jaroslaw Nowak
Charged-current (anti)
neutrino interactions create $\Lambda$ and $\Sigma$ hyperons inside the
nucleus, making hyperon final-state interactions a terrestrial probe of the in-medium potentials that govern hyperon onset in
neutron stars. In the StrangeMC simulation the trapped-$\Lambda$ fraction, escaping hyperon momenta, and a kaon-vetoed $\Sigma^+$ tag respond monotonically to $U_\Lambda$ and $U_\Sigma$ at SBND and DUNE. Marginalised over the low-density slope, a forecast gives $\delta U_\Lambda\approx6\MeV$ with systematics distinct from hypernuclear data; $U_\Sigma$ is limited by hyperon–nucleon cross sections.
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Cosmology and Nongalactic Astrophysics
Cosmological Constraints on the DGP Model in light of DESI DR2 2025 Data
Xinyi Dai, Yupeng Yang and Yicheng Wang
We present updated constraints on both flat and non-flat Dvali-Gabadadze-Porrati (DGP) cosmological models using the latest
baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument Data Release 2 (DESI DR2), in combination with
cosmic chronometer (CC), Type Ia
supernova (SNIa), and
cosmic microwave background (CMB) distance priors. For the non-flat DGP model, we obtain $H_0 = 64.05 \pm 0.27\, \rm{kms^{-1}Mpc^{-1}}$, $\Omega_m = 0.3264 \pm 0.0043$, and $\Omega_k = 0.0088 \pm 0.0016$, corresponding to a transition
redshift $z_t \sim 0.41$. For the flat case, the constraints are $H_0 = 63.28 \pm 0.25\, \rm{kms^{-1}Mpc^{-1}}$ and $\Omega_m = 0.3303 \pm 0.0036$. In both scenarios, the inferred Hubble constant is significantly lower than the Planck $\mathrm{\Lambda}$CDM value, indicating that the DGP framework does not alleviate the Hubble tension. Current observations strongly disfavor the DGP framework, primarily due to its inability to simultaneously accommodate DESI BAO and CMB constraints.By incorporating the latest high-precision DESI observations within a unified analysis framework, this work provides updated and more stringent limits on the DGP scenario, offering a consolidated assessment of its viability in the context of current cosmological data.
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Astrophysics of Galaxies
Performance of morphological classifiers for galaxy mergers compared to current machine learning methods
Aidan P. Cotter, William J. Pearson, Subhrata Dey et al. (+3 more)
Aims. Non-parametric morphological statistics can be used for efficient classification of
galaxy mergers. This work aims to compare the performance of morphological merger classifiers to state-of-the-art machine learning (ML) models. A secondary aim is to produce updated criteria for mergers based on non-parametric morphological statistics. Methods. The Gini coefficient (G), $M_{20}$ statistic, and concentration ($C$) were calculated for mock Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) images based on the IllustrisTNG and Horizon-AGN simulations, and observations from HSC-SSP. The IllustrisTNG images were used to find the line which best separates mergers and non-mergers in 2D morphological space with a Markov Chain Monte-Carlo (MCMC) method. Results. Based on the MCMC results, we classified
galaxies with $G>(-0.267\pm0.081)M_{20}+(0.143\pm0.012)$ or $G>(0.162\pm0.048)C-(0.149\pm0.12)$ as mergers, these criteria had precisions of 69.5% and 72.3% respectively when applied to previously unseen IllustrisTNG mock HSC-SSP images. The precisions of the morphological classifications are consistent with state-of-the-art ML methods. The morphological classifiers were found to be effective at selecting only pre-mergers; post-merger
galaxies are indistinguishable from non-mergers in terms of their $G$, $M_{20}$, and $C$ values. Morphological classifiers displayed a similar robustness to new data to ML methods up to a
redshift of $\sim0.52$ and maintained robustness better than ML methods based on convolutional neural networks in the
redshift range $0.52<z<1$. Conclusions. This work presents updated morphological classifiers which achieve similar precisions to ML based merger classifiers with a high robustness to new data. New morphological statistics are needed to identify the features of post-merger
galaxies.
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All authors Aidan P. Cotter, William J. Pearson, Subhrata Dey, Berta Margalef-Bentabol, Alejandro Guzmán-Ortega, Vicente Rodriguez-Gomez
Solar and Stellar Astrophysics · Cross-listed from nucl-th
The impact of nuclear uncertainties on the p-process nucleosynthesis in Supernovae
S. Martinet, S. Goriely and A. Choplin
The p-process is responsible for the production of the stable
neutron-deficient
nuclei heavier than iron observed in the
solar system. However, important
nuclear uncertainties still limit our understanding of this nucleosynthesis process. Among the most significant are the
nuclear level densities (NLDs) and
photon strength functions (PSFs) entering the calculation of photodisintegration rates under
supernova conditions. We investigate both model (systematic) and parameter (statistical) uncertainties affecting NLDs and PSFs and quantify their impact on p-process nucleosynthesis in type-Ia and type-II
supernovae. Correlated model uncertainties are estimated using several NLD and PSF models that reproduce available experimental observables. Uncorrelated parameter uncertainties are evaluated with a backward-forward Monte Carlo approach, in which parameter variations are constrained by measured reaction rates before being propagated to unknown cross sections of
neutron-deficient
nuclei. The resulting uncertainties are propagated through p-process calculations while preserving model correlations. To identify the reactions driving abundance uncertainties, we combine regularized linear-response modeling, stability analysis, and contribution and interaction decompositions. We find that photoneutron-emission uncertainties dominate the overall uncertainty budget. The leading source of uncertainty arises from local parameter variations still compatible with current experimental constraints, highlighting the lack of constraining
nuclear data in the
neutron-deficient region. For many p-
nuclei, the dominant contribution originates either from the photoneutron emission of the p-
nucleus itself or from a nearby $(\gamma,n)$ reaction along the same isotopic chain. While improved
nuclear models remain important, many key reactions involve stable or near-stable
nuclei and should be experimentally accessible.
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Cosmology and Nongalactic Astrophysics
Environmental dependence of Type Ia supernova standardization on the local luminosity-weighted age
Yuhui Zhang, Xiangcun Meng, Jingxiao Luo et al. (+3 more)
Context. The dependence of Type Ia
supernova (SN Ia) standardised luminosity on host
galaxy properties is a major source of uncertainty in cosmology. As next-generation surveys like LSST and HLTDS reduce statistical uncertainties, cosmological precision will be limited by astrophysical systematics. However, the empirical mass step, an indirect global proxy, may obscure the physical link to the progenitor environment. Aims. We test whether local luminosity-weighted age (LWA), used as a statistical proxy for the age of the
stellar population associated with SN Ia progenitors, is more closely related to the physical driver of standardised-luminosity variations than host
galaxy mass. Methods. Using SDSS-MaNGA Pipe3D, we extracted local LWA within a 1 kpc aperture for 56 SNe Ia and performed a joint likelihood analysis of local age and mass effects on Hubble residuals. Results. SNe Ia in younger environments are significantly fainter than those in older ones, with a step amplitude of 0.163 mag (5.2 sigma) after standardisation. Global and local mass steps are initially observed (0.071 mag, 2.0 sigma and 0.087 mag, 2.4 sigma), but both become insignificant when age and mass are fitted simultaneously: the global mass step decreases to 0.028 mag (0.9 sigma), while the age step remains robust at 0.156 mag (4.9 sigma). Similarly, the local mass step becomes insignificant (0.012 mag, 0.3 sigma), whereas the age step persists at 0.157 mag (4.4 sigma). The weighted Hubble residual decreases from 0.1550 to 0.1376 mag after introducing the local LWA step. Conclusions. The mass step is substantially reduced when local LWA is included. The inferred dark energy equation of state parameter (w) could be affected by local LWA, highlighting the importance of environmental effects for next-generation SN Ia cosmology.
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All authors Yuhui Zhang, Xiangcun Meng, Jingxiao Luo, Xiejin Li, Yunkun Han, Fenghui Zhang
Instrumentation and Methods for Astrophysics · Cross-listed from cond-mat.supr-con
Tunable responsivity and bandwidth in microwave kinetic inductance detectors via readout current nonlinearity
Maclean Rouble, Peter Day, Matt Dobbs et al. (+3 more)
Microwave kinetic inductance detectors (MKIDs) are generally read out with microwave readout tones of high enough amplitude to adequately suppress the noise contribution of the first-stage amplifier. At high readout power, the detector's resonant frequency is altered as a result of the dependence of the kinetic inductance on the internally circulating microwave current. With the tone placed below the resonant frequency, the nonlinear frequency shift results in a positive feedback effect that can significantly enhance the responsivity of the detector, to both optical and microwave power. We report a factor of 10 enhancement in optical response by tuning the readout power and frequency to close to the resonator's bifurcation point. A corresponding decrease in the bandwidth of the resonator is observed under these conditions. We show that the strength of the feedback effect can be easily selected by adjusting the excitation, and provide a map of possible operational states to do so. Operation of MKIDs in this mode could be used to improve sensitivity when non-intrinsic noise sources are significant.
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All authors Maclean Rouble, Peter Day, Matt Dobbs, Joshua Montgomery, Sofiia Savchyn, Graeme Smecher
Instrumentation and Methods for Astrophysics
Masking Algorithm for CCD Bleeding in Korea Microlensing Telescope Network Images
Jiseop Shin, Mankeun Jeong, Myungshin Im et al. (+3 more)
Astronomical CCD images are often affected by bleeding from bright sources, producing column-aligned streaks that degrade source detection and photometry. We present a pixel-level masking
algorithm for bleeding in Korea Microlensing
Telescope Network (KMTNet) images, in which these streaks extend along detector columns away from the readout register. The
algorithm identifies bleed-generating pixels using a conservative bleeding threshold and a bleeding index that quantifies excess signal along the expected bleeding direction. The extent of each bleed trail is then determined by termination criteria based on a background-relative detection threshold and a continuity condition. To optimize these termination parameters, we generate multiple candidate masks and evaluate them with an F-beta-like score that favors high purity while preserving recovery of sources whose photometry is biased by bleeding. Using the final mask, we apply interpolation-based cleaning and assess the performance in terms of completeness and photometric accuracy in a crowded KMTNet field, using
Gaia DR3 as a reference. The source completeness improves from 94.08% to 98.61%, primarily by enabling proper aperture placement that was previously hindered by bleeding. For selected bleeding-affected sources, the root-mean-square photometric offset decreases from 0.623 mag to 0.068 mag. These results demonstrate that the
algorithm provides a practical framework for mitigating bleeding artifacts in KMTNet images. We further examine the stability of the
algorithm across different observing conditions and discuss limitations of the current masking and cleaning procedure.
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All authors Jiseop Shin, Mankeun Jeong, Myungshin Im, Seo-Won Chang, Sang-Mok Cha, Seong-Kook Lee
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Minimal Majoron Dark Matter from a Discrete $Z_N$ Gauge Symmetry
Subaru Fujisawa, Qiuyue Liang, Shigeki Matsumoto et al. (+2 more)
We investigate majoron dark matter in a minimal setup, where the Standard Model is extended by three right-handed
neutrinos and a complex scalar field. The theory is defined by an exact discrete gauge
symmetry, $Z_N\subset U(1)_{B-L}$, while the global $U(1)_{B-L}$
symmetry emerges only as an accidental
symmetry at low energies. For nontrivial choices of the discrete
symmetry $Z_N$, such as $Z_5$, $Z_7$, $Z_{11}$, and $Z_{13}$, Planck-suppressed operators explicitly break this accidental
symmetry and generate a small majoron mass, making the resulting pseudo-Nambu–Goldstone
boson a well-motivated dark matter candidate. We study its production via the misalignment mechanism after inflation, considering both radiation-dominated and early matter-dominated cosmological histories, and confront the viable parameter space with isocurvature bounds, cosmological constraints, and indirect dark matter searches. We find that the $Z_5$ model is excluded by limits on the dominant dark matter decay into
neutrinos, whereas the other models remain viable. In particular, the $Z_7$ scenario predicts a majoron mass in the $1$–$10\,{\rm MeV}$ range and can be sensitively probed by future MeV gamma-ray observations, especially with COSI, through the 511$\,$keV line from the majoron decay into an electron–positron pair and the monochromatic gamma-ray line from its decay into two
photons.
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All authors Subaru Fujisawa, Qiuyue Liang, Shigeki Matsumoto, Michiru Uwabo-Niibo, Tsutomu T. Yanagida
High Energy Astrophysical Phenomena
Effects of dark matter and magnetic field on neutron star properties in relativistic mean-field theory: A single-fluid approach
Neeshu Rani, M. Mishra, Deepak Kumar et al. (+1 more)
Neutron stars, due to their extremely high matter density and strong
magnetic field, provide the best environment for exploring new physics beyond the Standard Model of particle physics. In this work, we study the effect of pre-existing dark matter component and an internal
magnetic field on the structural properties of
neutron stars. We employed relativistic mean field theory based equations of state and used a single fluid approach for solving the Tolman-Oppenheimer-Volkoff (TOV) equation to compute properties like mass-radius,
tidal deformability, compactness, and non-radial oscillation frequencies. We consider the following two scenarios for equation of state (EoS): (1) density-independent couplings along with non-linear interactions of
mesons, and (2) density-dependent couplings, with only considering linear interactions for
mesons. These
mesons mediate the interactions between nucleonic constituents of a
neutron star. In the dark matter sector we consider a massive fermionic dark matter which interacts with the nucleons through a
Higgs portal interaction. We explore parameter regions for
Fermi momentum of dark matter in the range $k_F = 0.01$ GeV - $0.06$ GeV, and two different values of the mass of fermionic dark matter, $M_\chi = 200$ GeV and $300$ GeV. We consider two values of the central
magnetic field, $B_c = 7\times10^{17}$ Gauss, $9 \times 10^{17}$ Gauss, for a magnetized
neutron star. Finally, we compare the theoretical predictions with the observed mass-radius and
tidal deformability data of
pulsars obtained from gravitational wave observations.
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All authors Neeshu Rani, M. Mishra, Deepak Kumar, Arpan Das
Cosmology and Nongalactic Astrophysics
Climbing the $N$-point Ladder Part I: Information in the Higher-Order Configuration-Space Clustering of Dark Matter Halos
Sumi Kim, Cristiano G. Sabiu and Inkyu Park
We quantify the information content of the configuration-space two-, three-, and connected four-point correlation functions of Quijote dark-matter
haloes at $z=0$ and fixed number density. We build Fisher forecasts for $\{\Omega_m, \Omega_b, h, n_s, \sigma_8, M_\nu\}$ in real and
redshift space from ${\sim}38{,}000$ GPU-accelerated $N$-point measurements. Treating the statistics as a ladder, $\mathrm{2PCF} \rightarrow +\mathrm{3PCF} \rightarrow +\zeta^{(4)}_{\mathrm{conn}}$, we report the information gained at each rung. The 3PCF supplies most of the accessible higher-order information: it tightens every parameter, most strongly $\sigma_8$ and $M_\nu$, whose degeneracy it partially breaks, by factors of $1.6$–$6.3$ over the
redshift-space $\{\xi_0,\xi_2\}$ baseline with per-parameter gains consistent with those of the
Fourier-space
halo bispectrum on the same simulations. The 3PCF gains persist under conservative, modelling-motivated scale cuts: restricted to the tree-level-validated regime with minimum triangle side $\ge40\,h^{-1}{\rm Mpc}$, it still improves $M_\nu$ by $3.9\times$. The connected 4PCF adds a further $\sim1.2$–$1.5\times$, an increment insensitive to whether the quadrupole is included in the baseline but traceable to small-scale configurations with sides $\lesssim30\,h^{-1}{\rm Mpc}$. This rung-to-rung increment is stable against derivative-sample noise and compression regularization, whereas the absolute constraints remain limited by the finite simulation ensembles and are reported as preliminary. The configuration-space ladder thus offers an independent and complementary route to the higher-order information probed by the
Fourier-space poly-spectra.
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High Energy Astrophysical Phenomena
Physics and Astrophysics of Black Holes with eXTP
Cosimo Bambi
The enhanced X-ray Timing and Polarimetry (eXTP) mission will combine spectral, timing, and polarimetric techniques to study accreting black holes, measure their masses and
spins, and test Einstein's theory of General Relativity in the strong-field regime. In this contribution, I review the capabilities of eXTP to advance our current understanding of black hole physics and astrophysics.
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High Energy Astrophysical Phenomena
Fast Radio Bursts Trace Cosmic Star Formation with Little Delay
Yi-Ying Wang, Yin-Jie Li and Yi-Zhong Fan
The progenitor channels of fast
radio bursts (FRBs) remain debated, with a central question being whether their
cosmic rate traces
star formation promptly or instead follows it with the long time-delay characteristic of compact-binary mergers. We perform a forward-modeling, hierarchical
Bayesian analysis of the CHIME/FRB population, jointly fitting the catalog sample, baseband fluences, and localized host
redshifts, while self-consistently incorporating the survey selection function through the injection framework. Across a range of delay-time models, the reconstructed FRB rate robustly peaks at the same
redshift as the
cosmic star-formation history, with a mean delay of only $0.1-0.3$ Gyr that remains consistent with a
prompt, zero-delay origin at the $2\sigma$ level. For dominant FRB population, this finding rules out the multi-Gyr delays reported previously and interpreted as the evidence for compact binary merger origin, and instead points toward progenitor systems linked to young
stellar remnants, most notably magnetars formed in core-collapse
supernovae.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Unscreened multipole moments of the fifth force in the EFT of dark energy
Tsutomu Kobayashi and Toshiki Takadera
It has been argued that degenerate higher-order scalar-tensor theories and the effective field theory (EFT) of dark energy are endowed with the Vainshtein mechanism, resulting in a screened fifth force in the exterior of a gravitational source. However, spherical
symmetry has been assumed in most of the discussions so far. In this paper, we study whether the Vainshtein mechanism operates in the EFT of dark energy beyond spherical
symmetry, focusing in particular on the role of the “beyond Horndeski” EFT parameters. Assuming that deviations from spherical
symmetry are small, we compute multipole moments of the gravitational potential for a given nonspherical source. For a generic choice of the “beyond Horndeski” EFT parameters, it is shown that the multipole moments of the fifth force are not screened in the region where the monopole component is screened. Rather, the gravitational potential shows a characteristic oscillatory behavior in its multipole components. In the special case where the EFT parameters are tuned so that graviton decay into dark energy is practically absent, the behavior of the multipole moments is qualitatively different from that in the generic case. However, also in this case, the Vainshtein mechanism is not efficient enough to screen the fifth force around the source.
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High Energy Astrophysical Phenomena
Effects of Differential Rotation on the Maximum Mass of Neutron Stars
Hyukjin Kwon, Jinho Kim and Kazuyuki Sekizawa
The maximum mass of
neutron stars provides a key constraint on the equation of state (EoS) of dense matter. Recent observations, including the ${\approx}2 M_{\odot}$
pulsar PSR~J0740+6620, have placed strong constraints on a large class of soft EoSs, while the possible existence of a compact object with a mass of $2.50$ - $2.67$ $M_{\odot}$ in GW 190814 further challenges our understanding of dense matter. Moreover, the inclusion of hyperonic degrees of freedom generally softens the EoS, making it difficult to support massive
neutron stars even when the $2$ $M_{\odot}$ constraint is satisfied (a problem known as the hyperon puzzle). In this work, we investigate whether differential rotation can enhance the maximum mass of
neutron stars constructed with an EoS including hyperons, thereby addressing the maximum-mass constraints imposed by current observations. We employ the Cook-Shapiro-Teukolsky (CST) approach, a numerically improved reformulation of the Komatsu-Eriguchi-Hachisu (KEH) scheme, to construct
equilibrium configurations of differentially rotating
neutron stars. For the
nuclear matter EoS, we adopt a relativistic mean-field (RMF) model incorporating hyperonic degrees of freedom through an SU(6) symmetric coupling scheme. We find that differential rotation can substantially increase the maximum mass, yielding configurations consistent with the mass range inferred from GW 190814. However, a sufficiently soft EoS fails to satisfy the constraint from PSR~J0740+6620 (346 Hz) even with differential rotation applied. We also present a systematic analysis of the internal structure of the resulting
equilibrium configurations. Furthermore, we demonstrate the existence of quasi-toroidal configurations and present
equilibrium sequences incorporating the full
baryon octet under extreme differential rotation.
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Astrophysics of Galaxies
In the Eye of the Storm: The Third Giant X-ray Outburst of the Extreme Changing-look AGN IC 3599
D. Grupe, S. Komossa, W. Zheng et al. (+10 more)
We report the discovery and multiwavelength follow-up observations of a
giant (factor >100) X-ray outburst of the exceptional changing-look active
galactic nucleus (AGN) IC 3599. This is the third such outburst after two previous ones serendipitously discovered in 1990 and 2010. Based on our dedicated long-term monitoring of IC 3599 with Swift, the third outburst was detected while it was happening, and we triggered multiple follow-up observations within days to weeks for the first time. The Swift outburst spectra are supersoft and almost no
photons are detected beyond 2.5 keV. The XMM-Newton short-term light curve shows a remarkable apparent oscillatory pattern that is reminiscent of quasiperiodic oscillations (QPOs). The optical high-state spectra reveal a multitude of bright coronal emission lines that have dramatically brightened and were absent or much fainter in low-state spectra. The new results eliminate outburst scenarios that require a constant time interval of repetitions (like certain variants of repeat
tidal stripping, or of an orbiting supermassive black hole impacting the inner
accretion disk), but remain in excellent agreement with an
accretion disk radiation-pressure instability when assuming that local conditions in the disk of this long-lived AGN affect the onset time of each new instability. The combination of recurrent,
giant, supersoft outbursts on decadal timescales, the exceptional emission-line response, and the rapid, candidate quasiperiodic, short-term variability on an hours timescale makes IC 3599 unique among AGN, and establishes it as a key system for studying
accretion physics under extreme conditions and at the Eddington limit.
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All authors D. Grupe, S. Komossa, W. Zheng, A.V. Filippenko, T.G. Brink, N. Schartel, J. Wang, V. Oknyansky, A.V. Dodin, S. Wolsing, E. Elien, C. Tapper, P. Lynam
High Energy Astrophysical Phenomena
Interplanetary scintillation-informed heliospheric modelling for the MeerKAT Pulsar Timing Array 4.5 yr dataset
Saurav Mishra, Daniel J. Reardon, Andrew Zic et al. (+9 more)
Heliospheric density variations impart delays on pulse times of arrivals from millisecond
pulsars. Improper modelling of these variations may affect gravitational wave detection and characterisation by
pulsar timing arrays (PTAs). Currently, PTAs typically employ a time-varying, spherically symmetric heliosphere model, which does not capture the full spatial and temporal complexity of the heliosphere. Instead, we investigate whether a three-dimensional, time-dependent model of the inner heliosphere from interplanetary scintillation (IPS) measurements - the IPS-UCSD model - can be employed to mitigate the
solar wind in PTA analyses. We applied the IPS-UCSD model to the MeerKAT PTA 4.5-year
dataset to assess whether it could correct for heliospheric density variations, and the impact on GW sensitivity compared to a spherically-symmetric model. We find that the model does not accurately correct for heliosphere-induced timing distortions, leading to bias in recovered GW parameters. Using simulations, we show that the spherically symmetric heliosphere model also fails to fully capture heliospheric density variations like those in the IPS-UCSD model. However, if interstellar dispersion measure (DM) variations are also modelled, then the heliospheric model errors are partially absorbed by DM variations, reducing contamination of the GW signal. Therefore we find that a time-varying spherically symmetric model is sufficient to mitigate the effect of heliospheric time delays on recovered GW results at typical PTA
radio frequencies, provided other signal components are also modelled. We propose that the most precisely timed
pulsars may be used to improve data-driven heliospheric density models in the future.
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All authors Saurav Mishra, Daniel J. Reardon, Andrew Zic, Matthew Bailes, John Morgan, Atharva D. Kulkarni, Matthew T. Miles, Ryan M. Shannon, Caterina Tiburzi, Mark Cheung, Michael Kramer, Ruoyao Ni