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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 16 June

High Energy Astrophysical Phenomena

MeV Gamma-Ray Lines from Radioactive Nuclei in Magnetar Giant Flares

Wu-Zimo Qiumu, Meng-Hua Chen, Qiu-Hong Chen et al. (+4 more)

The rapid neutron-capture process (r-process) is widely regarded as the dominant mechanism responsible for the synthesis of heavy elements in the universe, yet its astrophysical sites remain an open question. Recent studies suggest that the high-entropy, rapidly expanding baryonic material ejected by magnetar giant flares may provide favorable conditions for r-process nucleosynthesis, while the late-time gamma-ray emission observed from the magnetar SGR 1806-20 offers direct observational support for this scenario. In this work, we perform nuclear reaction network simulations to investigate the nucleosynthesis yields of magnetar giant flares and to characterize the associated nuclear gamma-ray line emission arising from the radioactive decay of heavy nuclei. The nuclei synthesized in magnetar giant flares are found to be mainly distributed near the first and second r-process abundance peaks. Owing to this nuclide composition, the gamma-ray opacity is found to be strongly energy-dependent with the opacity in the keV band exceeding that in the MeV band by approximately three orders of magnitude. The nuclear gamma-ray emission is dominated by MeV photons at early times and gradually extends toward the sub-MeV and keV bands as time progresses, thereby offering a diagnostic of heavy element enrichment in the ejecta. The gamma-ray spectrum exhibits a peak near 1 MeV with major contributions from $^{88}$Kr and $^{92}$Sr, whose radioactive decays produce several bright gamma-ray lines with fluxes exceeding $\sim10^{-8}$ erg cm$^{-2}$ s$^{-1}$, making them the most promising lines for detection by MeV gamma-ray detectors. Because magnetar giant flares occur in the Galaxy at a rate roughly three orders of magnitude higher than neutron star mergers and their gamma-ray lines are accessible to current MeV instruments, they offer new and valuable science opportunities for MeV gamma-ray astronomy.
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All authors Wu-Zimo Qiumu, Meng-Hua Chen, Qiu-Hong Chen, Fei Xie, Hou-Jun Lü, Xiang-Gao Wang, En-Wei Liang

Cosmology and Nongalactic Astrophysics

Constraints on the Sum of Neutrino Masses from ACT DR6 and DESI DR2 Considering Isocurvature Initial Conditions

Hongsheng Hou, Sai Wang, Zhi-Chao Zhao et al. (+1 more)

We present a robust assessment of cosmological constraints on the sum of neutrino masses ($\sum m_\nu$) when relaxing the standard assumption of purely adiabatic primordial initial conditions. Allowing for a neutrino density isocurvature (NDI) component alongside the adiabatic mode, we analyse the latest CMB-SPA combination (Planck 2018, ACT DR6, and SPT-3G), DESI DR2 baryon acoustic oscillation data, and the DES Year 5 supernova sample. Within the $\Lambda$CDM model, the 95% upper limit weakens only marginally from $\sum m_\nu < 0.052$ eV (purely adiabatic) to $< 0.057$ eV (including NDI), with the NDI amplitude consistent with zero. In the CPL dynamical dark energy model, the adiabatic limit is $< 0.111$ eV, shifting to $< 0.115$ eV with NDI, yet the isocurvature mode remains undetected. While these limits are robust against the inclusion of isocurvature perturbations, they are highly sensitive to both the assumed dark energy equation of state and the prior lower bound on $\sum m_\nu$. Notably, the adiabatic $\Lambda$CDM limit of $0.052$ eV lies below the minimum sum required by the normal neutrino mass hierarchy ($0.05878$ eV), indicating that this bound is an artifact of the statistical prior extending to zero. Imposing a physically motivated hierarchy-informed prior raises the limit to $< 0.092$ eV. Our results demonstrate that current data show no evidence for NDI modes and that the inferred neutrino mass upper limit is robust against this extension, but a definitive, model-independent bound requires addressing prior dependencies and dark energy uncertainties. This work provides the first joint constraint on $\sum m_\nu$ and NDI using the full CMB-SPA+DESI DR2+DES dataset.
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All authors Hongsheng Hou, Sai Wang, Zhi-Chao Zhao, Xin Zhang

Cosmology and Nongalactic Astrophysics

Weak-lensing mass calibration of Planck Sunyaev–Zel'dovich clusters with HSC-SSP Year~3

Andrés Alejandro Plazas Malagón, Hironao Miyatake, Surhud More et al. (+3 more)

We present a weak gravitational lensing mass calibration of 19 Planck Sunyaev–Zel'dovich (SZ) selected galaxy clusters using shape measurements from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Year 3 shape catalog. We measure the stacked weak-lensing signal $\Delta\Sigma(R)$ using per-cluster lensing weights that match the measurement pipeline's stacking scheme, and construct an analytical covariance matrix that includes shape noise and projected large-scale structure contributions. Our primary constraint on the SZ mass bias comes from a forward-modeling approach that integrates over the halo mass function while accounting for the Planck SZ selection function, Eddington bias from log-normal scatter in the SZ mass proxy, and cluster miscentering. Fitting four free parameters, the log mass bias $\ln(1-b)$, the miscentered fraction $f_{\rm mis}$, the offset scale $\sigma_{\rm off}$, and the SZ scatter $\sigma_{\ln M}$, over the radial range $0.5$–$5.0\,h^{-1}\,\mathrm{Mpc}$, we obtain $1-b = 0.73^{+0.10}_{-0.11}$ with $\chi^2/\mathrm{dof} = 5.2/5$ at an effective redshift $z_{\rm eff}\simeq 0.24$. This measurement is consistent with recent weak-lensing calibrations of SZ-selected clusters and supports the picture that significant mass bias corrections are required to reconcile cluster abundance measurements with primary cosmic microwave background constraints on cosmological parameters.
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All authors Andrés Alejandro Plazas Malagón, Hironao Miyatake, Surhud More, Nicholas Battaglia, Eunseong Lee, Neta Bahcall

High Energy Astrophysical Phenomena

Kes 75 with IXPE: Detection of Nebular X-ray Polarization and Change in Pulsar Lightcurve

Josephine Wong, Jack T. Dinsmore, Roger W. Romani et al. (+16 more)

We present the first X-ray polarization measurements of the PSR/PWN complex within SNR Kes 75. Two $\rm {\sim}\,500\,ks$ IXPE observations were conducted in October/November 2024 and April 2025. The second observation yields a significant phase-average 2-8 keV polarization degree $\rm PD = 9.9\% \pm 2.5\%$ at $\rm PA=36.8^\circ \pm 7.3^\circ$, implying a toroidal field aligned with the PWN symmetry axis. The first epoch, however, has only a polarization upper limit. During this epoch, an additional pulsed component is visible at $\Delta \phi \approx 0.5$, detected at ${\sim}\,3.7\sigma$. An unbinned phase-resolved analysis reveals a high-PD rotating vector model PA sweep at the ${\sim}\,99.5\%$ confidence level, with angles fixed at those inferred from the PWN morphology; this can explain the loss of phase-average polarization. Additional observations are needed to pin down the nature of the anomalous pulse.
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All authors Josephine Wong, Jack T. Dinsmore, Roger W. Romani, Stefano Silvestri, Shumeng Zhang, Ruolan Jin, Matteo Bachetti, C. Y. Ng, Niccolo Di Lalla, Wei Deng, Fei Xie, Patrick Slane, Niccolo Bucciantini, Philip Kaaret, Tsunefumi Mizuno, Maura Pilia, Yi-Jung Yang, Silvia Zane, Martin C. Weisskopf

High Energy Astrophysical Phenomena

An atypical X-ray variability component in the black hole candidate AT2019wey

Pengcheng Yang, Mariano Méndez, Sandeep K. Rout et al. (+5 more)

Recent studies have revealed a notable timing feature in several black hole X-ray binaries (BHXBs) during the soft-to-hard transition at the outburst decay. Within a narrow frequency range, the phase lags between high- and low-energy X-ray light curves exhibit a sudden increase, accompanied by a drop in the coherence function. These narrow features have been associated with a quasi-periodic oscillation (QPO) appearing only in the imaginary part of the cross spectrum (CS). This QPO remains undetected in the power density spectrum (PDS) and is known as imaginary QPO. Motivated by these results, we analyse five years of NICER observations of the BHXB AT2019wey during its low-hard state (LHS) and hard-intermediate state (HIMS). We find an imaginary QPO in the CS of AT2019wey, with similar characteristics as those found in other BHXBs, making AT2019wey the fifth BHXB in which such QPOs have been found. As the source hardens, the frequency of the imaginary QPO drops from $\sim$ 5 Hz to $\sim$ 1 Hz, while its phase lag rises from $\sim$ 0.3 rad to $\sim$ 0.7 rad during the HIMS and from $\sim$ 0.5 rad to $\sim$ 0.6 rad during the LHS. During the HIMS, the phase-lag energy spectrum of the imaginary QPO shows a typical U-shaped profile, while the shape changes in the LHS. The rms spectrum of the imaginary QPO rises below $\sim$ 2 keV, peaks at around $\sim$ 2 keV and decreases at higher energies, which may be associated with the presence of a relatively cool corona. We compare the properties of the imaginary QPO with those of the type-B and C QPOs in BHXBs and find a tentative connection to type-C QPOs. Combining the imaginary QPOs detected in AT2019wey with those reported in other sources, we find a systematic increase of QPO phase lags with QPO frequency. However, we cannot conclude whether the phase lags of imaginary QPOs exhibit the inclination dependence previously observed in type-C QPOs.
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All authors Pengcheng Yang, Mariano Méndez, Sandeep K. Rout, Candela Bellavita, Federico García, Diego Altamirano, Ole König, Federico A. Fogantini

Cosmology and Nongalactic Astrophysics

Data-Driven Discovery of a Simple Phantom-Crossing Dark Energy Parametrization

Giulia Borghetto, Ameek Malhotra, Simran Arora et al. (+4 more)

We develop a data-driven reconstruction programme for the dark-energy equation of state within VCDM, a minimally modified gravity framework in which both background and linear perturbations can be consistently evolved across the phantom divide. Using CMB, BAO, and type-Ia supernova data, we first perform a Bayesian spline reconstruction of $w(a)$, finding a preference for smooth, monotonic phantom-crossing trajectories. Bayesian evidence disfavors increasingly complex spline models, indicating that current observations exhibit a statistical preference for low-complexity dark-energy dynamics. Motivated by this result, we apply Exhaustive Symbolic Regression, an interpretable machine-learning technique that systematically searches over analytic expressions of fixed complexity, identifying the remarkably simple one-parameter form $w(a)={w_0}/{\sqrt a}$, which reproduces the reconstructed behaviour and fits the data at a level comparable to standard two-parameter parametrizations such as CPL. The model naturally crosses the phantom divide for $w_0<0$, suppresses early dark energy, and predicts a transient accelerating and phantom phase without a future big-rip singularity. As a one-parameter model, it is highly predictive, being a genuinely dynamical deformation of the cosmological constant rather than containing it as a limit. Bayesian model comparison yields mild-to-moderate support for this parametrization relative to standard two-parameter alternatives, and stronger evidence relative to $\Lambda$CDM. Our results suggest that current observations favour surprisingly simple dark-energy dynamics and illustrate how Bayesian reconstruction and symbolic regression can be combined into a principled model-discovery framework for cosmology.
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All authors Giulia Borghetto, Ameek Malhotra, Simran Arora, Antonio De Felice, Shinji Mukohyama, Gianmassimo Tasinato, Ivonne Zavala

Earth and Planetary Astrophysics

A simplified engineering algorithm for collision risk assessment and classification of LEO satellites

Federico Toson

Collision risk in low Earth orbit is now a sustainability constraint, not only a mission-level concern. Current standards (ECSS, NASA) classify risk in discrete per-mission categories and yield no continuous index that can be aggregated across missions or fed into broader sustainability assessments. This paper develops an engineering algorithm in which the expected number of collisions is estimated from the kinetic theory of the debris flux and combined with a severity term to give a continuous, dimensionally consistent risk index. An individual index, weighted by replacement cost, captures the expected loss to the operator; a collective index with homogeneous per-target severity captures the burden imposed on the operational population at the mission altitude band, independent of the mission's own value. Applied with a May 2026 Celestrak snapshot to three cases (ENVISAT, Sentinel-6, Starlink V2 Mini), the collective index exceeds the individual one by over two orders of magnitude for the constellation element: operator-centred assessment understates the collective cost of large constellations. A random sample of 100 LEO satellites, swept over 100 seeds, confirms the asymmetry as structural, and it survives the swap to a mass-based severity weight, which widens rather than closes the constellation gap. The construction is checked against a snapshot proxy of the ECOB family (rank correlation 0.91 on 103 objects) and against published ECOB values for MetOp-A and Sentinel-2, matched within a factor of two. A parametric analysis gives an explicit replacement-cost threshold per altitude band, about one to five million USD across the operational LEO bands, below which any satellite is structurally underestimated by operator-centred frameworks. The index is released as an open MATLAB toolchain and is intended as the orbital component of a multi-domain sustainability assessment.
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Cosmology and Nongalactic Astrophysics · Cross-listed from stat.CO

Nested Sampling: A Critical and Comprehensive Theoretical Guide

Luca Martino and Fernando Llorente

The nested sampling (NS) technique has gained widespread attention, particularly in cosmology and astronomy, due to its ability to efficiently explore high-likelihood regions - a feature akin to an implicit likelihood optimization that underlies its success. While the full theoretical derivation of NS is complex and involves several approximations, the central challenge lies in sampling from the likelihood-constrained priors, which is crucial for its performance. This work provides a comprehensive and detailed exposition of NS derivation, clarifying both its theoretical foundations and practical challenges. We provide a thorough description of the NS procedure, emphasizing both its strengths and potential limitations. The connections between NS, importance sampling (IS), and vertical Monte Carlo are also discussed in detail. In doing so, this work seeks to deepen understanding of the method and to foster the development of future enhancements, novel variants, and more efficient implementations across a wide range of scientific applications. Thus, the main contribution of this work is twofold: it serves both as a tutorial for newcomers to the field and as a critical review for experienced practitioners.
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Solar and Stellar Astrophysics

Detectability of deuterium in spectra of early-type stars

Veronika Mitrokhina, Colin P. Folsom, Mihkel Kama et al. (+1 more)

Context: Deuterium is easily destroyed in stellar interiors through nuclear fusion. It is therefore usually not expected to be present in stellar photospheres. Early-type stars, with radiative envelopes that mix slowly, may provide a favourable environment for the survival of recently accreted deuterium. Aims: In this study, we explore the detectability of deuterium in B-, A-, and F-type stars, which possess radiative envelopes that can delay the mixing and destruction of recently accreted material. Methods: We used synthetic spectra to generate model observations including deuterium, focusing on Balmer line regions, for stars with effective temperatures between 7 500 K and 12 500 K and a surface gravity of log g = 4.0. To assess the detectability of deuterium, we employed a Markov Chain Monte Carlo framework over a range of signal-to-noise ratios between 100 and 1000. We then applied this method to observed spectra of the A9 star HD 32115 and the B9.5 star 21 Peg. Results: We show how detection limits of deuterium abundance depend on signal-to-noise ratio, effective temperature, and projected rotational velocity. For example, for a 10 000 K star, the detection limit decreases from D/H = -4.6 dex to -5.5 dex, as the signal-to-noise ratio increases from 100 to 1000. For HD 32115, we find an upper limit of D/H < -5.5 dex, and for 21 Peg < -4.9 dex. We conclude that the detection of deuterium on early-type stars may be possible in some heavily accretion-contaminated cases, providing a new diagnostic tool for the study of proto- or exo-planetary material.
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All authors Veronika Mitrokhina, Colin P. Folsom, Mihkel Kama, Anna Aret

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Hybrid Stars with Post-Merger Rotation Profiles

Kalin V. Staykov, Violetta Sagun, Lorenzo Cipriani et al. (+2 more)

We study the effect of differential rotation on hybrid stars with the first-order deconfinement phase transition from hadronic to color superconducting quark matter. The differential rotation is introduced within a realistic, four-parameter phenomenological rotation law, in which the maximum angular velocity of the rotating configuration is shifted away from the center. We focus on two classes of differentially rotating solutions, namely quasi-toroidal (type C) and quasi-spherical (type A), and study the changes in the star global properties and angular velocity profiles due to the presence of a phase transition. Thus, we demonstrate the existence of quasi-toroidal hybrid star configurations in which deconfined quark matter forms a ring around the center of mass, while hadronic matter remains at the center and outer layers. Furthermore, we show that when increasing the angular momentum $J$ the turning points of the $J=const$ sequences shift towards lower energy densities, shrinking considerably the region where differentially rotating neutron stars with phase transitions exists. Interestingly, for both type A and type C solutions, the angular velocity profile is continuous throughout the star despite the discontinuity in the energy density. Moreover, we show that at the crossing points where the mass-radius curves for different equations of state intersect, the rotational profiles of the solutions are very close despite large differences in the energy density profiles. This reveals a possible degeneracy between the post-merger remnant properties for models with and without phase transitions, emphasizing the need for complementary multi-messenger observables to distinguish between them.
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All authors Kalin V. Staykov, Violetta Sagun, Lorenzo Cipriani, Daniela D. Doneva, Stoytcho S. Yazadjiev

High Energy Astrophysical Phenomena · Cross-listed from physics.space-ph

High-energy Particle Transport in Three-dimensional Anisotropic Turbulent Magnetic Fields

Daniela Maci, Rony Keppens and Fabio Bacchini

The understanding and modeling of high-energy particles transport in turbulent magnetic fields is an important open question in space- and astrophysics. The multiscale, nonlinear nature of turbulence, and the high variability of turbulence properties across different environments, make it particularly challenging to reach a full understanding of the interactions between particles and turbulent fluctuations. Using synthetic, realistically looking turbulent magnetic field realizations generated by the BxC toolkit, we investigate how the scattering of particles is affected by anisotropic fluctuations in strongly turbulent fields. We find evidence that, in the absence of a uniform background or guide magnetic field, the scattering process is not governed by the turbulence correlation length. We then further verify this hypothesis by studying particle transport in the presence of a guide field. We find evidence of a different scattering mechanism than the usual pitch-angle diffusion used to describe scattering in strong-guide-field settings.
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Cosmology and Nongalactic Astrophysics

Two-population model of type Ia supernovae and their associations with host galaxies in ZTF DR2

Radosław Wojtak, Lucas Hallgren and Jens Hjorth

We constrain type Ia supernova intrinsic properties, extinction, and probabilistic supernova-host associations using the volume-limited sample from the Zwicky Transient Factory DR2, the largest selection-free data set of type Ia supernovae to date. We employ Bayesian hierarchical modelling to jointly analyse the distribution of SALT2 light-curve parameters and global host-galaxy properties (stellar mass and rest-frame g-z colour). The adopted model is a mixture of distributions representing two supernova populations corresponding to two distinct modes of the stretch-parameter distribution, and two host-galaxy populations corresponding to two modes in the host-galaxy parameter space (red/massive and blue/less massive). Motivated by observations, high-stretch supernovae are allowed to populate both host-galaxy populations, whereas low-stretch supernovae are assumed to be exclusively associated with the red/massive host-galaxy population. The apparent non-linearity of the supernova magnitude-stretch relation implies a luminosity gap between the supernova populations, with the low-stretch population being Delta MB=0.14+/-0.03 mag brighter at x1=0, and different slopes (Delta alpha=0.064+/-0.023, steeper for the low-stretch population). The mean extinction coefficient is RB=3.89+/-0.29 (consistent with typical Milky Way values) in the blue/less massive host-galaxy population, which contains 68 per cent of high-stretch supernovae, and RB=3.08+/-0.08 in the red/massive host-galaxy population. Host-galaxy step corrections, both in stellar mass and colour, naturally emerge from the way the two supernova populations, characterised by different intrinsic luminosities and exctinctions, are distributed across host-galaxy populations. The adopted framework for modelling supernova populations and supernova-host associations makes host-galaxy step corrections redundant.
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High Energy Astrophysical Phenomena

Effective description of lensed gravitational waves diffracted by stellar fields

Miguel Zumalacárregui and Xikai Shan

As natural telescopes, Gravitational lenses enable the observation of sources that would otherwise be too distant and faint. Stellar-mass objects, or microlenses, act as impurities in the lens, producing subtle distortions of the source. These effects are necessary to correctly interpret observations, and may in some cases be themselves evidence of gravitational magnification. Gravitational waves (GWs) observed by ground detectors and magnified by galaxies and clusters will undergo microlensing by fields of stars and remnants: describing these systems requires not only considering a large number of small-scale lenses (microlenses), but also including wave-optics effects, leading to frequency-dependent modulations of the signal. Here we present novel models for Reduced-Order Stochastic Diffraction (ROSD), which overcome these challenges in the search for GW lensing signatures: an effective description is synthesized from numerical simulations of wave-optics lensing by stellar fields via a singular value decomposition. The procedure yields an optimized orthonormal basis to describe microlensing distortions – capturing the dominant "tones" of the stellar field, or stellar timbre – and a probability density function for the coefficients, which can be used as priors or to verify the consistency with stellar-field lensing. We present SVD-stellar-I5-aLIGO as an example of this model category, discuss the role of truncation order and demonstrate how it can be applied to GW data via injection and recovery in Bayesian parameter estimation. ROSD can be tailored to account for detector sensitivity and the type of source under analysis, and extended to different microlens populations and external potentials. ROSD models open a new window to probe small-scale objects (stars, remnants and potentially dark matter) and facilitate the discovery of the most distant compact binary mergers.
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Astrophysics of Galaxies

Tracing the very early disruption of the Sagittarius dwarf galaxy in the distant Milky Way halo

Manuel Bayer, Else Starkenburg, Akshara Viswanathan et al. (+3 more)

Current models predict that at distances beyond 80 kpc in the Milky Way halo, we can find the earliest escaped stars from the merging Sagittarius dwarf galaxy. However, observational data on the Sagittarius stream at these distances is limited. This study examines an overdensity of red giant branch (RGB) stars potentially linked to Sagittarius merger debris. Using the Magellan Inamori Kyocera Echelle spectrograph of Las Campanas Observatory's Clay Telescope, we measured the radial velocities and metallicities of these stars. We compared their properties with model predictions of Sagittarius' disruption and other stellar tracers from the Dark Energy Spectroscopic Instrument Data Release 1 and RR Lyrae catalogs. Our spectral analysis confirms the significant tight clustering of four of these RGBs in full 6D phase space. This tight clump is embedded within a larger spur-like feature of the Sagittarius stream in the southern sky. A comparison with Sagittarius stream models further strengthens this hypothesis and shows that this far spur could be composed of stars originally in the halo of the Sagittarius dwarf galaxy, stripped in the earliest phases of the interaction. The metallicity dispersion of the four stars of $0.15 ^ {+0.17} _ {-0.08}$ around the average of [Fe/H] = $-1.46 ^ {+0.11} _ {-0.09}$ is very low. This study provides the first spectroscopic view of the distant southern spur of Sagittarius, composed of stars likely stripped from Sagittarius's halo.
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All authors Manuel Bayer, Else Starkenburg, Akshara Viswanathan, Vedant Chandra, Alexander P. Ji, Guillaume F. Thomas

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Intrinsic handedness in O1-O4a black-hole mergers: probing orbital precession, remnant retention in dense environments and cosmological mirror asymmetry

Juan Calderón Bustillo, Adrián del Rio, Nicolás Sanchis-Gual et al. (+1 more)

Precessing binary black-holes generically produce an imbalance of right- and left- handed gravitational waves, reflecting the breaking of mirror symmetry by the merger dynamics. We study this phenomenon using the observer-independent quantity $V_{\rm GW}$, a gravitational analogue of the optical Stokes parameter that quantifies the intrinsic handedness of the emitted radiation. Using 91 LIGO-Virgo-KAGRA black-hole mergers from the O1-O4a observing runs, we find that $92\%$ of the analyzed events favour non-vanishing $V_{\rm GW}$, indicating a predominance of precessing dynamics across the events. Through a recently established relation between $V_{\rm GW}$ and the remnant black hole recoil, we further constrain the retention of merger remnants in dense stellar environments, finding that at most $8\%$ could remain gravitationally bound to globular or nuclear star clusters and subsequently participate in hierarchical merger channels. We finally investigate the cosmological distribution of black-hole merger handedness. The observed $V_{\rm GW}$ distribution is consistent with symmetry under $V_{\rm GW}\rightarrow -V_{\rm GW}$, and yields an average value $\langle V_{\rm GW}\rangle=-1.9^{+6.1}_{-6.6}\times10^{-3}$ ($90\%$ credibility), consistent with the absence of a preferred handedness and with expectations from large-scale statistical isotropy. In particular, the inclusion of O4a events reduces uncertainties in $\langle V_{\rm GW} \rangle$ by $\sim 40\%$ with respect to O1-O3 events. These results establish black-hole merger handedness as a unified probe of orbital precession, remnant recoil, hierarchical formation, and cosmological mirror symmetry.
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All authors Juan Calderón Bustillo, Adrián del Rio, Nicolás Sanchis-Gual, Koustav Chandra

Cosmology and Nongalactic Astrophysics

Alleviating the Hubble tension with the $\Lambda_{\omega_s}$CDM model

Youri Carloni

We formulate a novel extension of the $\Lambda$CDM model, named $\Lambda_{\omega_s}$CDM, in which we consider an additional term at early times in order to alleviate the Hubble tension. This additional component, referred to as matter with pressure, indicates a barotropic fluid that is subdominant to dust and radiation as the Universe expands, thereby recovering the $\Lambda$CDM paradigm at late times. We constrain the $\Lambda_{\omega_s}$CDM cosmology by performing a Markov Chain Monte Carlo analysis with Planck 2018 CMB, DESI DR2, and Pantheon+SH0ES data. The results suggest that the barotropic factor and the normalized density of the new fluid are given, respectively, by $\omega_s=0.294_{-0.004(0.023)}^{+0.014(0.015)}$ and $10^{5}\Omega_s=1.62_{-0.56(0.91)}^{+0.36(1.02)}$. With these two additional parameters, the Hubble constant is increased to $H_0 = 71.51^{+0.72(1.43)}_{-0.74(1.46)}$ km/s/Mpc, alleviating de facto the Hubble tension.
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Earth and Planetary Astrophysics

Shape, Orientation and Colors Combined approach for Asteroids (SOCCA)

K. O. Xenos, B. Carry, J. Peloton et al. (+3 more)

Large photometric surveys provide sparse multi-band photometry for millions of Solar System objects, offering an opportunity to jointly constrain their physical and compositional properties. However, current phase function models do not account for rotational variability, limiting their ability to retrieve accurate parameters. Similarly, methods that recover shape and rotational parameters remain both computationally and observationally expensive. We present a model capable of simultaneously retrieving the absolute magnitude, phase parameters, spin state, and shape proportions of SSOs from sparse photometric data, while remaining computationally efficient. We introduce the Shape, Orientation and Colors Combined approach for Asteroids (SOCCA), which extends the HG1G2 formalism by incorporating the projected surface of a rotating triaxial ellipsoid. The model jointly fits multi-band photometry, and includes a dedicated treatment of rotational period determination. We implement the model on a 10-year LSST simulation as well as on real data of asteroid (45) Eugenia for validation purposes. SOCCA significantly improves the fit to photometric data, reducing the mean residuals to half, compared to previous models. It retrieves the absolute magnitude with a scatter about three times smaller than existing approaches, and improves the determination of phase parameters by a similar factor. It also recovers the sidereal rotation period, spin axis orientation and the axes ratios of the best fitting ellipsoid. The inclusion of shape and rotation increases the number of physically meaningful solutions by 10-20% per filter, leading to an overall success rate of 53%. Its performance and scalability make it well suited for current and upcoming large surveys such as the Zwicky Transient Facility and the recently started Legacy Survey of Space and Time.
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All authors K. O. Xenos, B. Carry, J. Peloton, M. Mahlke, J. Berthier, P.-A. Mattei

Cosmology and Nongalactic Astrophysics

A rare sextuple-merging brightest cluster galaxy system in a disturbed galaxy cluster observed with the Einstein Probe Follow-up X-ray Telescope

Z. L. Wen, S. M. Jia, Z. S. Yuan et al. (+12 more)

The evolutionary processes of galaxy clusters influence the properties of their member galaxies. We present a joint X-ray–optical analysis of the galaxy cluster WHY J050106.2+013714 at $z_{\rm c}=0.151$. X-ray observations with the Einstein Probe Follow-up X-ray Telescope indicate that the cluster is dynamically young. The cluster displays an average X-ray temperature of $2.8^{+0.4}_{-0.3}$ keV and a total luminosity of 9.4$\pm0.3\times10^{43}$ erg s$^{-1}$, consistent with the scaling relation of typical disturbed clusters. Remarkably, the cluster hosts a multi-merging brightest cluster galaxy (BCG) system composed of six massive galaxies, with a total stellar mass of $1.16\times10^{12}M_{\odot}$. We detected a well-defined intracluster light component extending to a size of 310 kpc. A systematic search for merging BCGs in the DESI Legacy Surveys reveals that this sextuple-merging BCG is extremely rare in the local Universe. Additionally, other merging BCGs are also likely to form in moderately disturbed clusters, which provides valuable insights into the formation of BCGs.
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All authors Z. L. Wen, S. M. Jia, Z. S. Yuan, M. T. Shen, Y. Chen, C. K. Li, C. Ge, L. M. Song, H. Feng, J. Guan, C. C. Jin, C. Z. Liu, Y. Liu, S. N. Zhang, H. S. Zhao

High Energy Astrophysical Phenomena

A catalogue of TeV pulsar environments

Tina Wach, Tim Linden, Alison M.W. Mitchell et al. (+1 more)

Pulsars and their environments represent a major class of Galactic gamma-ray sources. Their complex evolution, shaped by the interactions of the pulsar outflow with the supernova remnant (SNR) and the surrounding interstellar medium (ISM), produces diverse morphological and spectral characteristics observable from radio to PeV energies. This work collects and homogenizes data from all major operating TeV observatories, presenting the first comprehensive catalogue of TeV gamma-ray properties of pulsar environments. The catalogue is created from information regarding all gamma-ray sources that have been classified as pulsar-associated sources in published results from H.E.S.S., MAGIC, VERITAS, HAWC, and LHAASO. For each source, the observed gamma-ray properties are cross-matched with pulsar properties from the ATNF catalogue and Fermi-LAT pulsar catalogue. The final catalogue comprises all currently known TeV sources associated with pulsars, spanning all evolutionary stages. The sample consists of 128 gamma-ray sources, connected to 66 different pulsars. It reflects that the TeV-detected population is dominated by young and energetic pulsars located near the Galactic plane, but includes a growing number of middle-aged systems detected as extended halos. Only a weak correlation is found between TeV luminosity and pulsar characteristic age, indicating that TeV evolution is driven by environmental and transport effects rather than by spin-down age alone. Additionally, 5 pulsars which should host a PWN detectable by CTAO are identified as prime targets for future observation to improve our understanding of properties inhibiting the formation of a TeV nebula. This publicly available catalogue provides a uniform foundation for future population studies and for constraining models of particle transport and energy losses in pulsar environments.
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All authors Tina Wach, Tim Linden, Alison M.W. Mitchell, Samuel T. Spencer

Solar and Stellar Astrophysics

Observational Evidence of Solar Spicules Associated with Microfilament Eruptions Using DKIST

Qifan Dong, Xiaoli Yan, Zhike Xue et al. (+8 more)

The formation mechanism of spicules is fundamentally important for understanding mass and energy transport from the chromosphere into the corona. Recent studies suggested that spicules may be powered by microfilament eruptions. However, direct observational evidence remains limited due to insufficient spatial resolution. Using high-resolution H$\alpha$ broadband observations from the Visible Broadband Imager (VBI) onboard the Daniel K. Inouye Solar Telescope (DKIST), we identify 30 spicule events triggered by microfilament eruptions in a quiet Sun region near the solar disk center on 2023 August 29. The detected microfilaments have an average length of $0.93\pm0.46$ Mm and a minimum length of 0.17 Mm, substantially smaller than previously reported minifilaments. We identify two distinct morphological classes of ejecta: individual spicules associated with smaller microfilaments, and enhanced spicular activities associated with larger microfilaments. Moreover, some events exhibit apparent twisting motions. All these high-resolution observations provide compelling evidence that spicules can be triggered by microfilament eruptions.
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All authors Qifan Dong, Xiaoli Yan, Zhike Xue, Liheng Yang, Jincheng Wang, Yadan Duan, Zhe Xu, Yian Zhou, Xinsheng Zhang, Zongyin Wu, Guotang Wu

Astrophysics of Galaxies

Galaxy groups within voids

M. Argudo-Fernández, G. Torres-Ríos, P. Vásquez-Bustos et al. (+18 more)

In this work, we aim to identify and characterise a sample of galaxy groups within voids in the local Universe (z\,<\,0.08), taking into account the peculiarities of these vast and empty structures. The void galaxies used in this study are selected from a well-defined void galaxy sample, from which the parent sample of the Calar Alto Void Integral-field Treasury surveY (CAVITY) legacy project was drawn. To identify galaxy groups, we applied a fiends-of-friends (FoF) like group finder algorithm to the selected sample, ensuring a certain degree of gravitational binding among group members. The same algorithm has been applied to identify a control sample of groups not in clusters nor voids, referred as NCNV groups. The catalogue of groups consists on 1367 physically bound groups, with a total of 3040 galaxies, plus 14672 galaxy singlets. Most of the galaxies in voids are singlets (59%), in contrast, most of the NCNV galaxies in the control sample are in groups (60%). To consider the dynamical stage of the groups we used the parameters harmonic radius ($\rm R_H$), radial velocity dispersion ($\rm \sigma_{v_r}^2$), dimensionless crossing time ($\rm H_0 t_c$), and group virial mass ($\rm M_{vir}$). We also used the total optical ($r$-band) luminosity, L$_r$, to estimate the mass-to-light ratio ($\rm M/L$) of the groups. We studied the relations of void properties and these parameters with the group richness. Galaxy groups can be found in any void in the local Universe, with no dependency of group richness on the density of voids. The densest groups in the studied sample of voids are composed of six galaxies, therefore, voids generally contain small groups, in comparison to denser structures such as filaments, walls, and galaxy clusters. Galaxy groups within voids are typically loose groups, in an early stage of their evolution.
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All authors M. Argudo-Fernández, G. Torres-Ríos, P. Vásquez-Bustos, S. Verley, I. Pérez, S. Duarte Puertas, A. Jiménez, R. García-Benito, A. Zurita, M. Alcázar-Laynez, B. Bidaran, A. Conrado, D. Espada, E. Florido, R. González Delgado, M. Hernández-Sánchez, I. del Moral-Castro, J. Román, L. Sánchez-Menguiano, S. Subramanian, P. Villalba-González

Astrophysics of Galaxies

TOPoS VII. Age-metallicity relation in the Galactic halo and assembly of the Milky Way

P. Bonifacio, Y. Lebreton, I. Koutsouridou et al. (+8 more)

One technique for determining stellar ages is to compare the position of a star in the Hertzsprung-Russell diagram to theoretical stellar evolutionary tracks. The sub-giant evolutionary stage is the one that is most sensitive to age and allows the most precise evolutionary age estimates. The TOPoS sample of stars with metallicities derived from low-resolution Sloan Digital Sky Survey spectra contains a large subset of sub-giant stars with precise parallaxes from the Gaia mission, for which evolutionary ages can be determined. Our aim is to use this stellar sample to investigate the age-metallicity relation in the Galactic halo. We use the Bayesian inference code SPInS and theoretical BaSTI stellar evolutionary tracks to determine the ages for TOPoS stars. There is a clear increase in metallicity with decreasing age, albeit with a considerable scatter at any given age. At ages larger than 8 Ga, the scatter is so large that in fact, over this range, age and metallicity appear to be uncorrelated. At any given age, the metallicity distribution is multi-modal, with up to three distinct peaks. These peaks trace three age-metallicity relations that we tentatively identify with the halo, thick-disc, and thin-disc. Our data demonstrate the important role of mergers in the evolution of the Galaxy, up to 8 Ga ago. In more recent times, the spread in metallicity drops. One possibility is that the major merger Gaia-Sausage-Enceladus may have perturbed the galaxies in the Milky Way vicinity in such a way as to decrease the merger rate. Chemical evolution models and cosmological models of the Local Group both support the importance of mergers in the early evolution of the Milky Way. Larger, unbiased samples, or at least with well-understood biases, of stars with accurate ages are required for a quantitative comparison between models and data.
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All authors P. Bonifacio, Y. Lebreton, I. Koutsouridou, Y. Zou, D. Romano, S. Salvadori, L. Sbordone, L. Monaco, E. Caffau, M. Spite, P. François

Instrumentation and Methods for Astrophysics

A fast spectral-multigrid Poisson solver in non-Cartesian geometries

Ankush Mandal, Oliver Gressel, Udo Ziegler et al. (+1 more)

Accurate and efficient computation of self-gravity is essential in astrophysical fluid dynamics, particularly in spherical and cylindrical geometries where large radial dynamic ranges and non-axisymmetric structures arise. Poisson solvers in such settings must simultaneously achieve high accuracy, scalability, and flexibility across a wide range of grid configurations and physical regimes. We present a robust and scalable Poisson solver for three-dimensional non-Cartesian geometries, supporting both spherical and cylindrical coordinates with either uniform or logarithmic radial discretizations. The method employs azimuthal Fourier decomposition to transform the 3D Poisson equation into a set of independent 2D Helmholtz equations. These are solved using a geometrically consistent multigrid algorithm that preserves second-order accuracy on both uniform and non-uniform grids. Vacuum boundary conditions are implemented through a screening-mass approach, enabling accurate solutions in domains with open boundaries, inner cavities, and strongly non-axisymmetric mass distributions. Owing to the differing convergence rates of Fourier modes – where higher-order modes converge more rapidly – the solver allows efficient mode-by-mode treatment. The combination of spectral decomposition and multigrid acceleration provides an efficient and flexible computational framework. The solver is implemented in the PLUTO code and validated against both analytical solutions and dynamical test problems in spherical and cylindrical geometries. Results demonstrate second-order convergence and excellent agreement with reference solutions. Weak-scaling tests up to 4096 cores show strong parallel performance, with the Poisson solve remaining subdominant to magnetohydrodynamic update cost. This makes the method well suited for large-scale simulations of star formation, accretion disks, and gravitational instabilities.
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All authors Ankush Mandal, Oliver Gressel, Udo Ziegler, Andrea Mignone

Cosmology and Nongalactic Astrophysics

PSZ: The meta-catalogue of Planck Sunyaev-Zeldovich sources

P. Tarrío, M. Arnaud, J.-B. Melin et al. (+2 more)

We present the PSZ, a meta-catalogue of 1962 clusters and cluster candidates produced by the Planck Collaboration. The PSZ contains fully-updated validation information for all official Planck catalogue detections, together with redshift estimates for confirmed clusters, with no duplicate entries. The validation is derived from optical and X-ray follow-up campaigns, supplemented by cross-matching with external catalogues with redshift information, and with XMM-Newton archive data. The external catalogues considered include the all-sky X-ray catalogue MCXC-II, the eROSITA X-ray cluster catalogue, the RASS-MCMF and PSZ-MCMF catalogues, and the extended Planck catalogues of Burenin. A total of 281 clusters are newly-confirmed owing to this process; conversely, 262 Planck candidates are invalidated. Of the 1500 confirmed clusters, 274 have updated redshifts, and 278 have newly-assigned redshifts. An MCXC-II counterpart is assigned to 631 clusters, updating the MCXC cross-match published in the Planck catalogues. Differences with the PSZ2 update of Bahk & Hwang are discussed. We further introduce a new, homogeneously-derived mass estimate, corrected for selection effects owing to intrinsic scatter and the properties of the underlying mass function. New posterior probability contours in the $Y_{5R500}-\theta_s$ plane are provided for all sources, in addition to the corresponding $M_{500}(z)$ degeneracy curves. PSZ includes both corrected and uncorrected $M_{500}$ values for confirmed clusters. A methodology for cross-identification between catalogues is presented. We show that simple fixed-distance matching is insufficient for this task, and demonstrate the need for additional consistency checks based on mass proxies, redshifts, and distance versus angular size comparisons. The final PSZ comprises 1500 confirmed clusters, 262 noise-dominated detections, and 200 candidates awaiting validation.
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All authors P. Tarrío, M. Arnaud, J.-B. Melin, G.W. Pratt, T. Sadibekova

Cosmology and Nongalactic Astrophysics

Synergy between CSST and future gravitational-wave detectors: Probing primordial black holes by cross-correlating dark sirens with galaxies

Ya-Nan Du, Ji-Yu Song, Jing-Fei Zhang et al. (+1 more)

Gravitational-wave (GW) events and galaxies both trace the cosmic matter distribution, but the mergers of astrophysical black holes and primordial black holes (PBHs) are expected to populate different environments and therefore to cluster with different biases. The GW clustering bias is thus a statistical observable that can separate the two populations. We assess how well this can be done by cross-correlating the photometric galaxy survey of the Chinese Space-station Survey Telescope (CSST) with mock GW catalogs from two future detector networks: the third-generation ET2CE network (the Einstein Telescope and two Cosmic Explorer detectors) and the multi-band BDET2CE network, which adds the space-based baseline Decihertz Interferometer Gravitational-Wave Observatory. We find that CSST combined with 10 years of ET2CE observations can reveal a PBH contribution once its fraction in the total merger rate exceeds about $40\%$, while the much sharper sky localization of BDET2CE lowers this threshold to about $20\%$. The improvement comes from recovering the small-scale clustering information that localization errors would otherwise erase. These results show that combining future GW detector networks with CSST galaxy clustering offers a promising and largely independent route to identifying PBHs statistically.
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All authors Ya-Nan Du, Ji-Yu Song, Jing-Fei Zhang, Xin Zhang

Cosmology and Nongalactic Astrophysics

Joint reconstruction of $H(z)$ and $f\sigma_8(z)$ with physics informed neural networks

Konstantinos F. Dialektopoulos

We present a model-independent joint reconstruction of the Hubble parameter $H(z)$ and the growth rate $f\sigma_8(z)$ using a dual-head physics-informed neural network trained on four complementary late-universe datasets: Cosmic Chronometers, Redshift-Space Distortions, the DESI DR2 BAO mean vector and full covariance, and the Pantheon$+$SH0ES supernova compilation. The two output heads share a backbone and are coupled through the linear growth equation of general relativity, penalizing the ODE residual at 1000 collocation points per training step via automatic differentiation. Uncertainty is quantified by an ensemble of 100 networks, each trained on an independent parametric-bootstrap resample of the data and its own draw of the fiducial cosmological parameters from Planck 2018 priors, so that the ensemble spread captures data-noise, initialization, and fiducial-cosmology systematics simultaneously. The physics coupling weight $\lambda$ is selected via an L-curve analysis over six values; the curve is nearly flat in total data $\chi^2$, indicating that the joint dataset is intrinsically consistent with the growth ODE. Without any $H_0$ prior, the free reconstruction yields $H_0 = 69.0 \pm 4.7$\,km\,s$^{-1}$\,Mpc$^{-1}$, consistent with the Planck 2018 CMB value and with the DESI DR2 inverse distance-ladder determination, and approximately $0.9\sigma$ below the SH0ES local measurement. The reconstructed $H(z)$ lies systematically below the flat $\Lambda$CDM prediction at $z \sim 0.7$-$0.8$, consistent with the dark energy evolution suggested by DESI DR2. As conditional analyses, we also anchor $H_0$ to the SH0ES value $73.04 \pm 1.04$\,km\,s$^{-1}$\,Mpc$^{-1}$ and the Local Distance Network consensus $73.50 \pm 0.81$\,km\,s$^{-1}$\,Mpc$^{-1}$; both anchored reconstructions yield a suppressed $f\sigma_8$, illustrating the propagation of the $H_0$–$\sigma_8$ link through the ODE coupling.
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Astrophysics of Galaxies

OQ~208: A New Fe~II Changing-look Active Galactic Nucleus and Implications for the Nature of the Changing-look Phenomenon

J. Wang, W. K. Zheng, D. W. Xu et al. (+5 more)

In addition to the traditional hydrogen Balmer emission lines, here we extend the optical changing-look (CL) phenomenon occurring in some active galactic nuclei (AGNs) to the optical FeII complex. Multiepoch spectroscopy allows to identify OQ~208, a local flat-spectrum radio source, as a new FeII CL-AGN owing to the disappearance of both its strong FeII complex (RFe $\equiv$ FeII/H$\beta =0.64$) and its Balmer broad-line emission on a timescale of $\sim14$\,yr. The simultaneous disappearance implies that in this object, both the FeII and Balmer emission come from the same region exposed to the ionizing continuum. We further identify an anticorrelation between the FeII strength and the continuum (and also Eddington ratio) during the CL events in dozens of CL-AGNs recently studied by Panda & Sniegowska (2024), suggesting a negative response of RFe to both $L_{5100}$ and $L_{\mathrm{bol}}/L_{\mathrm{Edd}}$; this can be understood by the Comptonization process in a hot, optically thin accretion flow.
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All authors J. Wang, W. K. Zheng, D. W. Xu, T. G. Brink, C. Gao, A. V. Filippenko, Z. H. Yao, J. Y. Wei

Astrophysics of Galaxies

The Incidence of Large Ionized Bubbles at Redshift 13

Peter Ziwei Hu, Massimo Stiavelli and Colin Norman

Ionized bubbles around the first galaxies link early galaxy growth, ionizing photon escape, intergalactic-medium topology, Ly{\alpha} visibility, 21 cm structure, and the timing of reionization. With JWST now constraining both the abundance of luminous galaxies at $z\gtrsim 10$ and rare Ly$\alpha$ emitters deep in the neutral era, it is timely to ask how often galaxy populations produce large ionized environments. We model the incidence of galaxy-driven ionized bubbles at $z\approx 13$ using JWST UV luminosity functions, taking the Ly$\alpha$ source reported by Witstok et al. (2025) as a benchmark for the relevant bubble scale. We quantify the incidence of regions with comoving radius $R\ge 2.5$ cMpc through the sky surface density $\Sigma_{\ge 2.5}$ at $z\approx 13$. For our fiducial case (UVLF from Donnan et al. 2024 with $f_{\mathrm{esc}}=0.2$, $\log\xi_{\mathrm{ion}}=25.5$, $f_{\mathrm{duty}}=1$, and $C=3$), we find $\Sigma_{\ge 2.5}\simeq 1.33\times 10^{-2}$ arcmin$^{-2}$ per $\Delta z=1$. Because bubbles are treated as independent spheres with random source positions and no union of overlaps, this is a conservative baseline for the abundance of connected ionized environments. We conclude that Witstok-sized regions are plausible in UVLF-calibrated galaxy-driven models. This is a population-level statement, however, and the specific Witstok source may still require unusual effective ionizing efficiency, recent fading or burstiness, or a non-stellar ionizing contribution.
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High Energy Astrophysical Phenomena

A MUSE View of the Optical Torus within the Supernova Remnant 1E 0102.2-7219

Janette Suherli, Samar Safi-Harb, Ivo R. Seitenzahl et al. (+6 more)

We present new MUSE Narrow Field Mode with Adaptive Optics observations of the optical torus surrounding a Central Compact Object (CCO) candidate within the oxygen-rich supernova remnant 1E 0102.2-7219 (E0102) located in the Small Magellanic Cloud. These data provide nearly an order-of-magnitude improvement in spatial resolution over previous MUSE Wide Field Mode observations. The improved spatial resolution resolved the previously identified torus into a cavity-like structure with a sharply defined inner edge and diffuse, outer filamentary substructure. The emission shows continuous velocity connectivity, broad intrinsic line widths, and co-spatial contributions from neutral and partially ionized species, including O I, Ne I, [O I], [O II], and [O III]. Spatially resolved line-ratio maps indicate that the emission arises from a multiphase, non-equilibrium medium rather than a single homogeneous component. Comparison with photoionization and shock models shows that no single-component model within the explored parameter space can simultaneously reproduce both the strong neutral and high-ionization diagnostics, indicating that multiple physical conditions must coexist. We favor an interpretation in which shocks propagating through density inhomogeneities in the ejecta shape the observed morphology and excitation, while also considering alternative mechanisms linked to the central source, binary evolution, or interaction with an embedded object within the remnant.
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All authors Janette Suherli, Samar Safi-Harb, Ivo R. Seitenzahl, Frédéric P. A. Vogt, Parviz Ghavamian, Ralph Sutherland, Chuan-Jui Li, Ashley J. Ruiter, Gilles Ferrand

Solar and Stellar Astrophysics

Characterizing Orbital Parameters of Hot Subdwarf Binaries with Multiple Spectroscopic Surveys

XInlin Zhao, Song Wang, Zhenxin Lei et al. (+5 more)

Hot subdwarfs (HSDs) provide critical insights into the physical mechanisms governing binary evolution. In this work, we conduct a systematic analysis of 157 HSDs, selected from Gaia EDR3 and characterized using multi-survey spectroscopic data. Atmospheric parameters of these HSDs are derived via a convolutional neural network (CNN) method and template-matching method. Based on the atmospheric parameters from CNN method, these HSDs exhibit a median mass of $0.45^{+0.19}_{-0.17} M_{\odot}$ and radius of $0.18^{+0.04}_{-0.05} R_{\odot}$, consistent with earlier work. Orbital parameters of 23 systems are determined through the fitting of radial velocity data and light curves, with 11 of them being new solutions. We find that reflection-dominated binaries typically have periods longer than 0.1 d and host low-mass main-sequence companions ($\sim$ 0.2 $M_{\odot}$) with rotation-inflated radii. In contrast, binaries including an HSD and a white dwarf show very short periods ($P < 0.2$ d), with the closest systems hosting more massive white dwarfs. Most of these systems share a similar mass–period distribution with that of post-common-envelope binaries, supporting a common-envelope origin.
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All authors XInlin Zhao, Song Wang, Zhenxin Lei, Yangyang Dong, Buhui Lv, Chuanjie Zheng, Xiaohong Yang, Jifeng Liu