High Energy Astrophysical Phenomena
Reversible-jump MCMC reveals binary black hole subpopulations with distinct redshift evolution
April Qiu Cheng, Alexandre Toubiana, Sylvia Biscoveanu et al. (+1 more)
Analyses of the growing catalog of binary black hole (BBH) mergers observed by the LIGO-Virgo-KAGRA detectors are beginning to resolve features in their population-level mass,
spin, and
redshift distributions, revealing imprints of the astrophysical processes driving their formation and
evolution. We present a novel method to search for subpopulations in the data using reversible-jump Markov chain Monte Carlo, providing interpretable results while making minimal prior assumptions. We find evidence for three subpopulations: a narrow subpopulation in primary mass at $\sim 10~M_\odot$ with preferentially aligned
spins and unequal masses, consistent with isolated binary
evolution; a subpopulation broadly distributed around $\sim 30~M_\odot$ with isotropically-distributed
spins and a strong preference for equal mass ratios, consistent with dynamical formation in clusters; and a high-
spin subpopulation spanning the continuum in mass, which we interpret as the confluence of multiple subdominant formation channels. When we allow for the independent
redshift evolution of each subpopulation, we find that the subpopulation encompassing the $10~M_\odot$ peak evolves more quickly than the $30~M_\odot$ subpopulation, with implications for the delay-time distribution and
metallicity-dependent BBH formation efficiency. Our work lays the foundation for a novel data-driven framework to infer the formation mechanisms of BBHs.
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All authors April Qiu Cheng, Alexandre Toubiana, Sylvia Biscoveanu, Jonathan Gair
Instrumentation and Methods for Astrophysics
Building on SVOM : the CATCH satellite constellation for transient astronomy
Stéphane Schanne
Building on the success of the French-Chinese SVOM mission, our consortium proposes CATCH (Chasing All Transients Constellation of Hunters), targeting Gamma-Ray Bursts and X-ray transients. Its first step, CATCH-PM (Precursor Mission), consists of three satellites: (i) the Trigger Scout Satellite (TSS), providing real-time detection and localization of transients from soft X-rays to gamma-rays; (ii) the X-ray Hunter Satellite (XHS), performing rapid X-ray afterglow follow-up and refined localization with Wolter-I optics; and (iii) the Infrared Hunter Satellite (IHS), enabling precise localization and follow-up in the visible and near-infrared, including obscured and high-
redshift transients. CATCH-PM is both a technological demonstrator and a standalone time-domain astrophysics mission. In addition to Scout triggers, it will accept numerous external Targets of Opportunity and conduct a broad observing program. By reusing available spare hardware, a launch within five years is feasible. Operating alongside SVOM and EinsteinProbe, it would significantly enhance the overall scientific return.
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Solar and Stellar Astrophysics
Chronos: Towards a self-consistent and absolute stellar age scale. I. A Bayesian hierarchical lithium-age model: Validation on the Pleiades cluster
L. González-Ramírez, D. Barrado, J. Olivares et al. (+3 more)
Context. Establishing a self-consistent age scale for
stellar populations requires physically well-calibrated chronometers. Among these, lithium-based diagnostics, particularly the lithium depletion boundary (LDB), provide one of the most robust age constraints for
stellar populations in the low-mass regime. However, their application is limited by heterogeneous temperature scales and astrophysical dispersion, especially among FGK
stars, where rotation can significantly affect lithium abundances. Aims. As a first step towards a self-consistent age scale, our aim has been to formulate Chronos, the first version of a
Bayesian hierarchical lithium-based age-dating model combined with a neural network trained on
stellar evolutionary models. Methods. We implemented a
Bayesian hierarchical model that jointly infers
stellar effective temperatures, lithium abundances, and the global age of a
stellar association. The theoretical LDB is provided by a pre-trained multilayer perceptron based on BT–Settl evolutionary models. The model incorporates a temperature-dependent transition between fully convective ultra-cool
dwarfs (UCDs) and FGKM
dwarf stars, together with a two-component FGK mixture to account for rotation-induced lithium enhancement. We applied the method to the Pleiades cluster and performed a validation using synthetic
datasets. Results. For the Pleiades cluster, Chronos yields a posterior age distribution centred at $\mathrm{Age}=124.53_{-2.70}^{+3.34}$ Myr, consistent with classical LDB estimates, while simultaneously constraining both global and
stellar-level rotation parameters. Conclusions. This work demonstrates that lithium-based
stellar chronology can be recast as a coherent hierarchical inference problem, providing a flexible and statistically robust framework for making age determinations for young (1–600 Myr)
stellar populations.
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All authors L. González-Ramírez, D. Barrado, J. Olivares, A. Berihuete, L. M. Sarro, F. J. Palmero
Solar and Stellar Astrophysics
Gaia FGK Benchmark Stars: Impact of Spectral Resolution on Stellar Abundances
Ivanna Hernández-Araya, Claudia Aguilera-Gómez, Paula Jofré et al. (+5 more)
In the era of large Milky Way spectroscopic surveys, calibrating and standardizing
stellar parameters and abundance measurements is crucial. The
Gaia benchmark stars (GBS) are key references points characterized by well-defined parameters derived from fundamental relations independent of spectroscopy. We analyze 30 GBS with spectra data at three different resolutions. Our goal is to evaluate the impact of spectral resolution on the measurements of the
stellar parameters and chemical abundances. We also present a line selection suitable for both metal-poor and metal-rich
stars. We used R~190000 (R190), R~42000 (R42), R~28 000 (R28), and R190 degraded to R28 (R190-R28) spectral data to measure abundances with synthetic fitting and equivalent widths (EW) methods, testing the needed resolution to obtain consistent results. Our comparative analysis between R28 and R190-R28 shows that gaps in wavelength coverage can lead to discrepancies in the derived
stellar parameters, particularly log g. These effects are not primarily driven by resolution, but rather by the limited spectral coverage and line availability. We find overall similar abundance, emphasizing the importance of line selection for spectroscopic studies. However, some elements (e.g, Ti II, Sc II) show larger discrepancies, possibly due to blending that becomes more pronounced as resolution decreases or is HFS-sensitive. Our comparative analysis shows that the abundances for Fe I, Ni I, Ti I, and Si I present less scatter across all resolutions, including R28. Our findings indicate that for some elements, synthetic fitting and the EW method give similar abundances, especially at the highest resolution. However, we also find that the highest resolution is not always essential for chemical abundance measurements. Our results provide practical guidelines for upcoming large surveys to reconstruct the chemical history of the Milky Way.
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All authors Ivanna Hernández-Araya, Claudia Aguilera-Gómez, Paula Jofré, Sara Vitali, Laia Casamiquela, Caroline Soubiran, Ulrike Heiter, Sergi Blanco-Cuaresma
Solar and Stellar Astrophysics
Diversity of morphology of type II spicules in MURaM-ChE simulations
Sanghita Chandra, Robert Cameron, Damien Przybylski et al. (+1 more)
Spicules are ubiquitous, small-scale features in the
solar atmosphere, exhibiting a jet-like appearance most clearly identified by their apparent motion in off-limb observations. While they are often interpreted as narrow, thread-like structures, their true three-dimensional (3D) structure remains unknown. We aim to uncover the 3D morphology and dynamics of fast-evolving spicules (type II) using a MURaM-ChE simulation. We use a H$\alpha$ proxy that has been developed using non-
equilibrium (NE) hydrogen populations in MURaM-ChE. The proxy, modelled as an escape probability, is synthesised to isolate on-disc as well as off-limb H$\alpha$ wing features. The 3D structure of these features is investigated using the 3D information on opacity in H$\alpha$. We identify type II spicules, with unique 3D morphologies: the dominant being thread-like and slab-like. The appearance of spicules as slabs or threads is a function of time and Doppler velocity. The spicules extending above the spicule-forest (2Mm -3Mm above the surface) tend to be located at quasi-separatrix layers (QSLs). We find that the spatially resolved contributions to the opacity of spicules are often similar for spicules synthesised in the horizontal direction, and their on-disk rapid blueshifted excursion (RBE) synthesised in the vertical direction at the same Doppler velocity of 37km/s. This confirms that RBEs are indeed the on-disc counterparts of spicules. Furthermore, our analysis indicates that cross-field motions can significantly contribute to spicule dynamics. Spicules exhibit a range of morphologies, including both slab-like and thread-like structures. Their observed appearance depends strongly on line-of-sight projection and Doppler sampling. Spicules are preferentially located at QSLs, highlighting the role of
magnetic topology in driving spicular dynamics.
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All authors Sanghita Chandra, Robert Cameron, Damien Przybylski, Sami K. Solanki
High Energy Astrophysical Phenomena
B. Mueller and B. Sykes
Core-collapse
supernovae are the terminal explosions of massive
stars. After successive phases of
nuclear fusion proceeding up to silicon burning, these
stars form an iron core that is supported by electron degeneracy pressure. The core eventually collapses to a proto-
neutron star, and in most cases the outer layers of the
star are ejected by a shock wave, with a kinetic energy of order $10^{51}\,\mathrm{erg}$.
Neutrinos and multi-dimensional fluid flow play a key role in extracting energy from the collapsed core to drive the explosion. After adumbrating the astrophysical context of
stellar evolution and transient observations, this chapter sketches the modern theory of
neutrino-driven
supernova explosions, and discusses the key role of
nuclear physics and
neutrino interaction rates in the
supernova problem. It also outlines the role of
neutrinos and gravitational waves as probes into the
supernova core.
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Instrumentation and Methods for Astrophysics
skysurvey: a pure python package to simulate the transient sky
M. Rigault, M. Ginolin, L. Dellazzeri et al. (+12 more)
Accurate simulation of astronomical observations is a critical element for any modern analyses, be it to measure event rates, analyses population properties, validate or train pipelines, account for selection effects, or correct biases. We present a novel pure python package named skysurvey made to enable the user to quickly simulate astrophysical transients as observed by a survey. The package is structured to make the implementation of any complex population modeling fast and easy. The skysurvey package relies on three core objects: a Target, that models how an astrophysical target exists in nature, a Survey, that specifies how the sky has been observed and, a
DataSet that combine these two to generate data as they would have been acquired. In addition, we present a side stand-alone package named modeldag that contains the core structure that simplifies the parameter modeling. We present in this paper how skysurvey is structured and we clearly illustrate how the code can straightforwardly be used to simulate complex populations, such as Type Ia
Supernovae with varying color-brightness $\beta$ term. We also illustrate how the package can be made to replicate the rate and
redshift distribution of the ZTF SNe Ia DR2
dataset. The skysurvey package, already used in recent scientific publications, is now ready for general usage and paves the way for future use of simulations such as simulation based inference.
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All authors M. Rigault, M. Ginolin, L. Dellazzeri, B. Popovic, J. O. Hjortlund, A. Gilles-Lordet, S. Conseil, M. Coughlin, F. Ruppin, M. Smith, A. Townsend, A. Trigui, C. Barjou-Delayre, R. Kebadian, J. Nordin
High Energy Astrophysical Phenomena
The transitional Type Ibn/IIn SN 2022pda, with pre-explosion outbursts and a double-peaked light curve
Y.-Z. Cai, A. Pastorello, R. Chiba et al. (+65 more)
We report the results of a photometric and spectroscopic follow-up campaign of the unusual interacting
supernova (SN) 2022pda. Precursor variability lasting $\sim 100$ days is observed before the explosion. The SN light curve has a double peak shape. It reached a first maximum of $M_{\rm{r}} = -19.6 \pm 0.2$\,mag, followed by an initial two-month decline and a second, broad peak lasting about six months. The early spectra show a blue continuum with dominant H and He emission lines. A high-resolution pre-maximum spectrum shows that the profile of the \Hei~$\lambda$5876 line consists of a moderately narrow ($\sim 1900$ \kms) P~Cygni absorption superposed on a broader ($\sim 3300$ \kms) component. In the blue region, several spectral features are identified, including C iii/N iii/O ii blends. Two broad bumps at 4600–5200 Å, 6400–6800~Å\ regions reveal a complex profile, which are likely due to blends of H, He, and other emission lines. Late-time spectra are still dominated by prominent and broad H and He lines in emission. Shock-driven model fits to the bolometric light curve suggest that the SN is powered by interaction with a massive CSM with enhanced mass loss rates $\sim 5$ \msun yr$^{-1}$, expelled during two events occurred $\sim 1$ and $\sim 0.2$ years before the explosion. The overall SN
evolution indicates that SN\,2022pda is a transitional event between a H-rich SN IIn (SN\,2009ip-like) and a He-rich SN Ibn. Our findings suggest that the progenitor was likely a Luminous Blue Variable transitioning towards a Wolf–Rayet stage.
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All authors Y.-Z. Cai, A. Pastorello, R. Chiba, T. J. Moriya, A. Reguitti, L. Tartaglia, S. Moran, S. Campana, Z.-Y. Wang, J.-W. Zhao, J. P. Anderson, S. Benetti, S. J. Brennan, E. Cappellaro, K. C. Chambers, T.-W. Chen, Z.-H. Chen, T. de Boer, Y.-Z. Dong, J. Duarte, N. Elias-Rosa, M. Fraser, W.-P. Gan, H. Gao, M. Gromadzki, G. Hosseinzadeh, D. A. Howell, C. Inserra, T. Kangas, E. Kankare, T. Kravtsov, L.-P. Li, C.-C. Lin, T. B. Lowe, P. Lundqvist, E. A. Magnier, K. Matilainen, P. A. Mazzali, C. McCully, P. Minguez, T. E. Müller-Bravo, M. Newsome, E. Padilla Gonzalez, C. Pellegrino, P. J. Pessi, T. Petrushevska, G. Pignata, R. P. Santos, S. Schulze, S. J. Smartt, I. A. Smith, K. W. Smith, J. Sollerman, S. Srivastav, M. D. Stritzinger, G. Terreran, G. Valerin, R. Wainscoat, S.-Q. Wang, D. R. Young, L. Galbany, Z. Li, I. Salmaso, S. Zha, J.-M. Bai, B. Wang, X.-F. Wang, J.-J. Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Polarized Anisotropic Stochastic Gravitational Wave Background Search with Ground-Based Detector Networks
Töre Boybeyi and Vuk Mandic
Gravitational waves admit a Stokes decomposition into intensity ($I$), circular polarization ($V$), and linear polarization ($Q$, $U$), analogous to
Cosmic Microwave Background (CMB) polarimetry. We implement a full-Stokes maximum-likelihood SGWB map-making analysis for ground-based detector networks, promoting the standard cross-correlation data products used in existing pipelines to a joint reconstruction of $I$, $V$, $Q$, $U$. Applied to LVK O3 data, we constrain the polarized angular spectra $C^{VV}_\ell$, $C^{EE}_\ell$, $C^{BB}_\ell$ and $|C^{IV}_\ell|$. We show that an intensity-only model is biased when polarized sky components are present, since the detector-network Fisher inner product does not generally make the Stokes responses orthogonal. For transient CBC foregrounds, polarized shot noise is not parametrically suppressed relative to ordinary CBC intensity shot noise. The full Stokes framework separates the Stokes sectors while providing access to polarized anisotropies invisible to conventional intensity-only searches.
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Solar and Stellar Astrophysics
Lithium-rich M-dwarfs at the ZAMS: Evidence for planetary engulfment?
R. D. Jeffries, R. J. Jackson and I. Baraffe
We identify 6 early M-
dwarfs, in 3 open clusters (NGC 2451a, Blanco 1 and NGC 2516) at ages of 50-200 Myr, that are anomalously enriched in lithium compared with Li-depleted siblings of similar spectral type. The Li-rich outliers represent 2-3 per cent of
stars with $3560 < T_{\rm eff}/{\rm K} < 4045$ in clusters at those ages but are otherwise indistinguishable in their positions, parallaxes and kinematics from other cluster members; their placement in absolute colour-magnitude diagrams is incompatible with being much younger Li-rich interlopers, only one shows evidence of binarity and they are all slow rotators. The enhanced Li abundances are consistent with the engulfment of 3-10 $M_\oplus$ of volatile-depleted planetary material after the formation of a radiative core has ended rapid pre main sequence Li depletion. Published planetary formation simulations featuring engulfment via dynamical interactions, and the preponderance of Earth-like
exoplanets in close orbits around M-
dwarfs, offer some support to this scenario. The observed occurrence rate would be a lower limit to the frequency with which such engulfment events occur between ages of $\sim (30-200)$ Myr, that depends in the timescale for ongoing Li depletion at the ZAMS.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.plasm-ph
Pulse magnet of 10 T for power laser experiments with x-ray free-electron laser diagnostics
Akihiko Ikeda, Kosuke Noda, Yutaro Yamanaka et al. (+22 more)
The importance of investigating magnetized
plasmas/solids in extreme conditions has grown over the last decades, particularly in the field of high energy density physics (HEDP), such as laboratory astrophysics and inertial confinement fusion. However, up to now, the unique capabilities of an X-ray free-electron
laser (XFEL), such as high brilliance and low divergence have never been exploited for this type of research. In this paper, we present the first platform developed at SACLA, Japan, that combines a high-power optical
laser for generating matter under extreme conditions of pressure and temperature, an XFEL probe, and an external
magnetic field. The high current is produced using a 2 kV, 4.8 kJ pulsed power system giving a maximum current of 10 kA which is synchronized with the optical
laser and XFEL in a
vacuum environment. It flows through a split-pair coil to generate a high
magnetic field (10 T at 6 kA) which has 1 cm access every 45$^{\circ}$ in the equatorial plane and 90$^{\circ}$ in the poloidal one. This platform offers new opportunities to study high-energy-density matter in strong
magnetic fields, including shock propagation, instability growth, and turbulent
plasma dynamics.
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All authors Akihiko Ikeda, Kosuke Noda, Yutaro Yamanaka, Yuma Urabe, Keiichiro Kawai, Yasuhiro H. Matsuda, Hirotaka Nakamura, Ryusuke Yamamoto, Yoshiki Naito, Yasuhiro Kuramitsu, Kai Taketoshi, Naoki Yamagata, Norimasa Ozaki, Tatiana Pikuz, Yoichi Sakawa, Takayoshi Sano, Ryosuke Kodama, Taichi Morita, Tomoya Ogawa, Kohei Miyanishi, Toshinori Yabuuchi, Rigon Gabriel, Bakandreas Stavros, Koenig Michel, Bruno Albertazzi
Astrophysics of Galaxies
Beyond the [OIII]$\lambda$4363 auroral line: [NeIII]$\lambda$3868 as a direct tracer of electron temperature
Borja Pérez-Díaz, José M. Vílchez, Marco Castellano et al. (+9 more)
Auroral lines enable accurate measurements of chemical abundances in ionized gaseous nebulae thanks to their sensitivity to electron temperature. However, metal-enriched systems remain a challenge, as even deep observations cannot retrieve auroral lines due to their intrinsic faintness. To overcome this limitation, we present a novel approach to estimate electron temperatures in the conditions where the [OIII]$\lambda$4363 auroral line is barely detectable ($T_{e} < 11,000$ K). This approach relies on the detection of [NeIII]$\lambda$3868 and [OIII]$\lambda$4959,5007, which are among the brightest rest-frame optical emission lines. By means of detailed photoionization models, we derive a tight relation between the O3Ne3$\equiv$[OIII]$\lambda$4959,5007/[NeIII]$\lambda$3868 ratio and the electron temperature weighted in the O$^{++}$ dominated region. We test the validity of this relation in a large sample of
galaxies that cover a wide range of
redshifts z$\sim$0-9 and extragalactic HII regions. Our results show that the O3Ne3 ratio, in combination with the O3O2 ratio (tracer of ionization), yields electron temperature estimates consistent within the uncertainties with those based on [OIII]$\lambda$4363. The proposed relation can be used to estimate electron temperature in the cool (equivalently high-metal) regime [6,000, 13,500 K] where the emissivity of [OIII]$\lambda$4363 drops drastically.
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All authors Borja Pérez-Díaz, José M. Vílchez, Marco Castellano, Ricardo Amorín, Davide Bevacqua, Adriano Fontana, Giovanni Gandolfi, Antonio Giménez-Alcázar, Laura Pentericci, Enrique Pérez-Montero, Paola Santini, Roberta Tripodi
Astrophysics of Galaxies
Extreme color-magnitude variability: connection to changing-look AGNs
Litao Zhu, Zhongxiang Wang, Alok C. Gupta et al. (+5 more)
Context. Changing-look active
galactic nuclei (CL-AGNs) challenge the unified model of AGNs and offer key insights into the physics of the
accretion processes of super-massive black holes. While systematic spectroscopic comparisons have successfully identified large samples of CL-AGNs, photometric selection based on variability features provides an efficient alternative. Methods. We use the colour–magnitude (CM) variability method to continue our identification of the CL transition in AGNs, which utilizes the slope ($k$) of the CM variations to identify strong bluer-when-brighter behavior, while the variation amplitudes in optical and mid-infrared bands are also considered. The candidates thus selected from the Type-2 AGNs given in the Sloan Digital Sky Survey catalog are spectroscopically observed using the 3.6-m DOT and the 2-m HCT. Results. We confirm seven turn-on CL-AGNs among 12 candidates. Comparing them with both the general AGN populations and the spectroscopically identified CL-AGN sample, the CL-AGNs showed larger optical and MIR variations and $k$ values. The extreme CM variabilities of these sources (with optical magnitude changes $>$ 0.9) occurred recently. For four sources,
flare-like brightening episodes were temporally associated with the turn-on transitions within 3–7 years, suggesting that these
flares may trace short-timescale
accretion enhancement, central brightening, and BLR re-illumination. Conclusions. The extreme CM variability serves as a highly efficient criterion for finding CL-AGNs. The properties of the CL-AGNs thus found suggest that they may represent AGNs at a pivotal state, which likely occur CL transitions due to enhanced
accretion activity, while the cause of the
accretion activity, determined to have a time scale of several years, remains to be investigated.
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All authors Litao Zhu, Zhongxiang Wang, Alok C. Gupta, P. U. Devanand, Ruoheng Yang, Qiangmeng Huang, Man Lang, Jiawen Li
High Energy Astrophysical Phenomena
Reassessing high-energy emission correlations in gamma-ray bursts using a large, homogeneous sample of X-ray afterglows
A. A. Vigliano, F. Longo and Ž. Bošnjak
Gamma-ray bursts (GRBs) show diverse X-ray afterglow light-curves, including breaks and plateaus, whose physical origins remain debated. Previous claims linked high-energy ($E \ge 100$ MeV) detection to X-ray afterglow complexity or plateau incidence, but they were often based on small or heterogeneous samples. We present a large-scale, uniform, model-independent analysis of the complete Swift-XRT GRB afterglow catalog, including more than 1400 events. Our automated pipeline performs
flare removal and segmented power-law fitting consistently across the sample. We find that both light-curve complexity and plateau incidence are strongly governed by the XRT observation start time, $t_{XRT}$. Apparent correlations between high-energy emission and X-ray morphology arise when $t_{XRT}$ is ignored, but vanish when the sample is stratified or controlled for this variable. X-ray complexity and plateaus are therefore not directly coupled to high-energy detectability, and early X-ray morphology is not predictive of high-energy emission. These results resolve conflicting claims in the literature and show that controlling for $t_{XRT}$ is essential in large-sample GRB studies. The automated pipeline provides a reproducible basis for future analyses of GRB afterglows from Swift and upcoming missions such as SVOM, Einstein Probe, and THESEUS.
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Solar and Stellar Astrophysics
Machine Learning-based Separation of the He I 10830Å Chromospheric Signal: Quantitative Analysis of Chromosphere-Corona Intensity in the Quiet Sun
Huaiming Li, Fangyu Xu, Yi Bi et al. (+1 more)
The He I 10830Å line, a crucial optically thin chromospheric line, is frequently used to study coronal heating and vertical coupling across the chromosphere-corona interface. However, its images are severely contaminated by the strong photospheric background signal, hindering the analysis of fine chromospheric structures. Given the morphological differences between the Active Region (AR) and the Quiet Sun (QS), we proposed separating the He I 10830Å chromospheric signal using two deep learning CNN models. Our model utilizes TiO images and cross-band learning to infer the He I 10830Å photospheric background. The output is combined with an exponential absorption model to achieve quantitative analysis of the pure chromospheric component. Joint analysis of
Solar Dynamics Observatory (SDO) data and the separated QS structures reveals a strong spatial negative correlation between chromospheric He I 10830Å intensities(R approx -0.84 in 304Å ), and significant layered coupling with EUV (171, 193, and 304Å) radiation. Furthermore, strong He I 10830Å absorption areas are highly correlated with regions of strong
magnetic fields, while 171Å radiative enhancement areas extend to the strong
magnetic field edges and the mixed-polarity regions. These findings quantify the radiation intensity relationship between He I 10830Å and EUV bands in the Quiet Sun. It also demonstrates the differences in heating characteristics between unipolar and mixed-polarity
magnetic fields.
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All authors Huaiming Li, Fangyu Xu, Yi Bi, Zhenyu Jin
High Energy Astrophysical Phenomena
Superfluid fraction and effective ion mass in the crystalline crust of a neutron star: role of interband response
Nicolas Chamel
Neutron superfluidity in the inner crust of a
neutron star is further investigated, focusing on the role of the interband response in the superfluid fraction and the effective mass of crustal ions induced by their motion through the superfluid. Calculations are performed within the linear response theory of the self-consistent time-dependent Hartree-Fock-Bogoliubov equations with Skyrme
nuclear energy density functionals in the Bardeen-Cooper-Schrieffer approximation. The absence of interband response in previous analyses is clarified. The
neutron superfluid density is formally shown to be consistent with the entrainment
matrix derived earlier in homogeneous
neutron-
proton superfluid mixture, thus providing a unified description of entrainment effects in the inner crust and outer core of a
neutron star within the same microscopic framework. The relative importance of the intraband and interband responses in different regions of the crust is numerically assessed from three-dimensional band-structure calculations, taking into account
quantum zero-point motion of ions about their
equilibrium position. The
neutron superfluid fraction is found to be enhanced by the interband response, resulting in effective ion masses that remain close to the mass of
quantum mechanically bound nucleons for realistic
neutron pairing gaps. Results are compared to predictions from classical hydrodynamics with different prescriptions for the permeability of ions to superfluidity.
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High Energy Astrophysical Phenomena
Legacy analysis of Milky Way dwarf spheroidal satellite galaxies: an update
A. Circiello, M. Di Mauro, M. Ajello et al. (+3 more)
Studies of
Fermi-Large Area
Telescope (LAT) data coincident with
dwarf spheroidal satellite
galaxies (dSphs) of the Milky Way (MW) have put the most stringent constraints on models of annihilating dark matter (DM) with candidate masses in the GeV-TeV range. Recent results found the presence of small, local significance excesses from these targets, at the 2-3 sigma level. However, these excesses disagree on the predicted properties of the DM candidate, and their significance vanishes when considering the correction factors for the number of trials. In this work, we apply key improvements to the analysis of the dSphs. We use stricter cuts on the data, implement a method to adaptively model the background, and assume an updated framework for DM annihilation. We find that our improved background modeling leads to a better agreement between the model and the data. This produces an increase in the local and global significance of the dSphs excess compared to previous studies. Finally, we find that the DM properties obtained in this work are less dependent on the sample of dSphs being considered compared to previous studies, while remaining in agreement with the predictions from the
Galactic center excess observed by the
Fermi-LAT and the antiproton excess observed by the Alpha
Magnetic Spectrometer (AMS-02). Considering our improvements, a future significant increase in the number of
dwarfs may lead to a definitive confirmation or exclusion of the DM interpretation of the
Galactic center excess.
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All authors A. Circiello, M. Di Mauro, M. Ajello, C. Karwin, A. Drlica-Wagner, M. Á. Sánchez-Conde
Astrophysics of Galaxies
The Gas-Phase Mass-Metallicity Relation of Dwarf Galaxies Across Large-Scale Environments Using the CAVITY Parent Sample
Bahar Bidaran, Salvador Duarte Puertas, Isabel Pérez et al. (+13 more)
The gas-phase mass-
metallicity relation (MZR) of
galaxies shows a noticeable break in slope and increased scatter at low
stellar masses, suggesting that the physical processes governing chemical enrichment differ between
dwarf and high-mass systems.
Dwarf galaxies are highly susceptible to internal and environmental mechanisms due to shallow potential wells. We assess whether a single MZR describes
dwarf galaxies across diverse large-scale environments using the CAVITY parent sample. We examine the MZR and
star formation rate (SFR) of
dwarfs with
stellar masses 8.9 < log(M_
star/M_sun) < 9.5. Using SDSS optical spectra, we measured emission line fluxes via the pyPipe3D pipeline to derive the MZR and SFR for 353, 311, and 22
dwarf galaxies in voids, filaments, and clusters, respectively. We find a systematic variation in the MZR slope, which is steeper in voids (0.28 +/- 0.03) and progressively flatter in clusters (0.17 +/- 0.08), indicating an environmental dependence in this mass regime. When separated by local environment, isolated and non-isolated
dwarfs in voids show no significant differences. Isolated
dwarfs in filaments exhibit properties similar to void counterparts. However, non-isolated filament
galaxies display flatter MZR slopes, comparable to cluster
dwarfs. We report both large- and local-scale environmental dependencies in the gas-phase
metallicity and MZR slope. Consistent with the pre-processing framework, our results indicate that the local environment becomes significant within
cosmic web filaments, affecting the chemical enrichment and
star formation of low-mass systems. This suggests that part of the MZR scatter in
dwarf galaxies arises from environmental effects.
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All authors Bahar Bidaran, Salvador Duarte Puertas, Isabel Pérez, Almudena Zurita, Daniel Espada, María Argudo-Fernández, Rubén García-Benito, Laura Sánchez-Menguiano, Simon Verley, Sebastián F. Sánchez, Jesús Falcón-Barroso, Anna Ferré-Mateu, Pedro Villalba-Gonzalez, Andoni Jiménez, Reynier F. Peletier, Tomás Ruiz-Lara
Solar and Stellar Astrophysics
Long-Term Clustering Pattern of Solar Active Regions and Their Potential Connection with Magneto-Rossby Waves
Junwei Zhao, Ruizhu Chen and Aimee A Norton
Large
solar active regions (ARs) tend to be long lived and spatially clustered, with repeated emergence occurring in persistent
solar activity nests over extended timescales. By analyzing long-term spatiotemporal
magnetic flux maps constructed from near-side
magnetic field observations and far-side helioseismic AR maps, we investigate the recurrence and clustering properties of large ARs during
Solar Cycle 24. We find that, in both hemispheres, over 63% of
magnetic fluxes emerge and cluster within or near three distinct bands in the spatiotemporal maps, two of which rotate faster than the Carrington rate and one more slowly. These bands closely correspond to low-order nonaxisymmetric modes, primarily the azimuthal order m=1 mode. The drift rates of the three spatiotemporal bands are in good agreement with the phase speeds inferred for these modes. The frequencies of the dominant modes are consistent with slow magneto-Rossby waves originating in the
solar tachocline, associated with odd harmonic degrees $\ell$ and a toroidal
magnetic field strength of approximately 4.0 kG. Our results suggest that magneto-Rossby waves play an important role in modulating both the timing and longitudinal localization of major AR emergence. Rieger-type periodicities may arise from interactions between a dominant mode and weaker modes, while longer quasi-periodic variations on 0.6–4 yr timescales are likely linked to intersections of multiple major modes. These findings point to a potential connection between surface
magnetic flux patterns and dynamical processes in the tachocline.
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Instrumentation and Methods for Astrophysics
Constraining the inclination of binary system orbits with the astrometric excess noise from Gaia DR3
Shilong Liao, Ye Ding, Shangyu Wen et al. (+2 more)
Orbital inclination is crucial in determining the binary mass. The astrometric excess noise contains the orbital motion information, which can be used to constrain the inclination. We aim to constrain the orbital inclination of a binary system by combining radial velocity measurements with the astrometric excess noise from the
Gaia DR3 solution. The astrometric excess noise is directly related to the orbital parameters. For a binary system with a radial velocity solution, it can be treated as a function of the orbital inclination. Using the
Gaia nominal scanning law and the estimated centroid uncertainties, we simulate
Gaia astrometric epoch observations to reproduce the expected excess noise. By sampling different inclinations and comparing the resulting simulated excess noise with the value reported in
Gaia DR3, we can constrain the inclination to a specific interval. We have developed a method to constrain the orbital inclination within a specific range, enabling a more accurate determination of the binary mass, particularly for spectroscopic binaries. Internal and external validations demonstrate the robustness of the method, although certain limitations remain. It is most reliable for systems exhibiting a strong astrometric signal of binary motion, while caution is required when applying it to binaries with weak astrometric wobbles or poorly sampled orbits.
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All authors Shilong Liao, Ye Ding, Shangyu Wen, Zhaoxiang Qi, Qiqi Wu
High Energy Astrophysical Phenomena
Discovery of Molecular and Atomic Gas associated with HESS J1646-458 (Westerlund 1): Spatial TeV Gamma-Ray and Interstellar Proton Correspondence
H. Sano, Y. Fukui, S. Fujimori et al. (+21 more)
We report CO and HI studies of molecular and atomic gas toward the TeV gamma-ray source HESS J1646$-$458, widely considered to be associated with the young massive cluster Westerlund 1 (Wd1). We found that molecular clouds at $V_\mathrm{LSR} \sim$$-32$ km s$^{-1}$ coincide with arc-like structures seen at 8 $\mu$m, likely illuminated by strong FUV radiation from Wd1. $^{12}$CO($J$ = 3-2) emission at the same velocity reveals a cavity-like structure with an expansion velocity of $\sim$$5$ km s$^{-1}$ toward the central region of Wd1, suggesting a recently formed wind-blown bubble driven by the cluster. We also identify a complementary spatial distribution between the $V_\mathrm{LSR} \sim$$-55$ and $\sim$$-32$ km s$^{-1}$ clouds, connected by an intermediate-velocity component at $V_\mathrm{LSR} \sim$$-44$ km s$^{-1}$. These characteristics are consistent with signatures of triggered
star formation through a cloud-cloud collision and imply that both clouds are physically associated with Wd1. On larger scales, the total interstellar
proton column density at $V_\mathrm{LSR}$ $\sim$$-36$-$-23$ km s$^{-1}$ shows a moderate spatial correspondence with the TeV gamma-ray shell. Together with this correlation, a substantial gas mass of $\sim$$1.6 \times 10^6$ $M_\odot$, and the absence of bright synchrotron X-rays, the TeV gamma-ray emission surrounding Wd1 is consistent with the hadronic origin. The present finding allows us to calculate the total energy of accelerated
cosmic-ray
protons to be $\sim$$6 \times 10^{49}$ erg.
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All authors H. Sano, Y. Fukui, S. Fujimori, T. Murase, R. Z. E. Alsaberi, M. D. Filipović, G. Rowell, M. Aruga, Y. Asano, R. G. Bhuvana, F. Demachi, S. Einecke, N. Fukaya, R. Hamada, H. Inoue, T. Kamazaki, S. Lazarević, T. Minamidani, Z. J. Smeaton, H. Sudou, K. Tachihara, H. Takaba, K. Tsuge, R. I. Yamada
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Gravitational Wave Propagation in K-essence Cosmology: Theory and Observational Constraints
Sougata Bhunia, Goutam Manna, Eduardo Guendelman et al. (+3 more)
Gravitational waves (GWs) provide a powerful, theory-independent probe of the dynamical structure of spacetime and the cosmological background. We investigate the propagation of linearized tensor modes in k-essence cosmology, where the dark sector is described by a non-canonical scalar field. Working in the high-frequency (short-wavelength) limit on a Friedmann-Lemaître-Robertson-Walker background and restricting to the transverse-traceless sector, we obtain a modified
evolution equation in which the GW speed remains strictly luminal (compatible with GW170817), while the background field $\bar{\phi}$ generates a time-dependent effective mass term $m_{\rm eff}$. This background-induced mass alters the dispersion relation without introducing extra propagating degrees of freedom, producing an accumulated, frequency-dependent phase shift over cosmological distances. We show that $m_{\rm eff}$ is uniquely determined by background cosmological parameters and can be expressed as a
redshift-dependent function $m_{\rm eff}(z)$, providing a direct connection between GW observables and scalar-field dynamics. The GW luminosity distance stays identical to the electromagnetic one, preserving standard-siren consistency. We confront the model with a joint
Bayesian analysis combining
cosmic chronometers, BAO, Pantheon+SH0ES, and standard-siren measurements from GWTC-2.1/3/4, and assess performance using $\chi^2$, $\chi^2_{\rm red}$, AIC, BIC, and DIC. The reconstruction is consistent with current data, reproduces the late-time expansion history, and provides data-driven constraints on the
redshift evolution of $m_{\rm eff}(z)$.
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All authors Sougata Bhunia, Goutam Manna, Eduardo Guendelman, Debashis Gangopadhyay, Ramón Herrera, Abhijit Bhattacharyya
High Energy Astrophysical Phenomena
Compact dusty starbursts at cosmic noon linked to high-energy neutrinos
Yuji Urata, Kuiyun Huang, Bunyo Hatsukade et al. (+7 more)
The origin of high-energy astrophysical
neutrinos remains unresolved, and secure electromagnetic counterparts to individual events are rare despite rapid follow-up. Dusty
star-forming
galaxies (DSFGs) at
cosmic noon (z ~ 1-4) are natural
cosmic-ray calorimeters, yet observational links between DSFGs and
neutrinos have remained elusive. Here we report a compact-core DSFG within an IceCube localization, JCMT0402-0424, a quadruply lensed
galaxy at z = 2.988 located inside the 90% containment region of the IceCube event IC 210922A. ALMA imaging and lens modeling resolve a highly magnified, compact starburst with no bright gamma-ray or X-ray counterpart above current sensitivity limits. Considering the positional agreement, the low chance-coincidence probability (less than about 1%) for such an extreme submillimeter source, the absence of equally plausible alternatives in the field, and the compact, gas-rich core revealed by ALMA, JCMT0402-0424 is the most plausible electromagnetic counterpart candidate within the IC 210922A localization. In a population context, compact-core starbursts at
cosmic noon can provide a non-negligible population-level contribution to the diffuse high-energy
neutrino background, even though the
neutrino yield from any single DSFG is modest. This result connects high-energy
neutrino production to the peak epoch of
cosmic star formation, opening a new avenue to probe
galaxy evolution and
cosmic-ray acceleration across
cosmic time.
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All authors Yuji Urata, Kuiyun Huang, Bunyo Hatsukade, Mansi Kasliwal, Shigeo S. Kimura, Yuichi Matsuda, Yusuke Miyamoto, Hiroshi Nagai, Kouichiro Nakanishi, Robert Stein
Instrumentation and Methods for Astrophysics · Cross-listed from physics.plasm-ph
Bayesian Estimation of Spectroscopic Parameters: Application to the Atomic Nitrogen Bound-Bound System
Tae Woong Jeong and Sung Min Jo
Atomic nitrogen bound-bound radiation is a major component of the radiative heat flux on hypersonic vehicles entering nitrogen-dominated atmospheres, yet its prediction is limited by substantial parametric uncertainty in the published Einstein coefficients and Stark broadening coefficients. In the present study, these spectroscopic parameters are inferred and their uncertainty is quantified through
Bayesian inversion of
equilibrium spectral radiance measured in the NASA Ames Electric-Arc Shock Tube for two shots of the Test 62 campaign at shock speeds of 10.32 and 10.72 km/s. The inference is restricted to the post-shock
equilibrium region, where the Boltzmann assumption closes the species population degree of freedom. The residual uncertainty in the post-shock temperature and species number densities is incorporated as a coupled nuisance parameter distribution. A hybrid principal component analysis and
polynomial chaos expansion surrogate model and a likelihood formulated jointly over the two shots enable tractable Markov chain Monte Carlo sampling across multiple wavelength regions. Eighteen parameters in total, ten Einstein coefficients and eight Stark broadening coefficients, are inferred across eight wavelength regions, with posterior uncertainties significantly reduced relative to the prior literature bands. Forward propagation of the joint posterior through the stagnation-line flow field around a 3 m radius sphere at entry velocities of 10, 12, and 14 km/s demonstrates a reduction in the standard deviation of the predicted radiative heat flux by approximately a factor of five compared with the prior, in particular at 14 km/s, it drops from 10.4 to 1.94 W/cm$^{2}$.
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Astrophysics of Galaxies
A Unified [CII] Morpho-Kinematic Corpus for 31 Star-Forming Galaxies at z = 4.26-5.68: The High-z Kinematic Corpus Z1
David C. Flynn
CORRECTION (August 2026): The $\omega$ values originally reported were computed with a parenthesization error not matching Eq. 6 of Flynn & Cannaliato (2025). Under the corrected formula, all 8 Tier-1 Z1 rotators yield positive $\omega$ values (median $+12.621$ rad Gyr$^{-1}$; $+12.341$ km s$^{-1}$ kpc$^{-1}$). The previously reported sign reversal does not reproduce. See the GitHub repository for full details. Corrected corpus at Zenodo DOI: 10.5281/zenodo.21834678. We present the High-z Kinematic Corpus Z1, a structured machine-readable
dataset of ALMA [CII] 158 $\mu$m morpho-kinematic data for 31
star-forming
galaxies at $z = 4.26-5.68$ drawn from the ALPINE survey (Jones et al. 2021; Le Fevre et al. 2020). The corpus is the fifth entry in the EPS Research RAG Astrophysics Corpus Series, extending coverage to the epoch approaching
cosmic reionization. Eight confirmed rotators carry quality tier 1 per-ring rotation curves from 3DBarolo tilted-ring fits (Di Teodoro & Fraternali 2015), with 2-3 rings per
galaxy, $V_{\rm rot}$ and $\sigma$ per ring, and dynamical mass estimates; the remaining 23 carry morpho-kinematic classification only (tier 2). All entries include
stellar mass (Faisst et al. 2020),
star formation rate, Wisnioski disk criteria, and
geometric parameters. Distributed as a structured JSON, flat CSV, RAG-ready JSONL, and per-
galaxy ZIP. Jupyter notebooks demonstrate single-
galaxy [CII] analysis, population statistics, and cross-corpus application of the $\omega$ kinematic correction. Corrected result: Applying canonical Eq. 6 to all 8 tier-1 rotators yields positive $\omega$ values (median $+12.621$ rad Gyr$^{-1}$)[cite: 1]. The previous negative values (median $-13.05$ rad Gyr$^{-1}$) were a formula artifact and are withdrawn. Publicly available under CC BY 4.0[cite: 1].
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Solar and Stellar Astrophysics
Signs of Sulphur fractionation under high magnetic field strength
Dominik Orlovskij, Andy S. H. To and David M. Long
Sulphur, with a first ionisation potential (FIP) of 10.36 eV, lies at the boundary between low- and high-FIP elements, making it particularly sensitive to fractionation processes in the
solar atmosphere. Sulphur exhibits variable behaviour across
solar environments, with coronal remote sensing studies often observing it as a high-FIP element while in-situ measurements sometimes detect low-FIP-like enhancement. Sulphur also exhibits variable behaviour during
flares and
magnetic restructuring. To understand sulphur's variations, we quantify how sulphur's FIP bias depends on potential field source surface (PFSS)-derived loop properties. We analyse nine Hinode/EUV Imaging Spectrometer (EIS) raster observations using four diagnostic line pairs (Si X 258.37 A / S X 264.23 A, S XI 188.68 A / Ar XI 188.81 A, Ca XIV 193.87 A / Ar XIV 194.40 A, and Fe XVI 262.98 A / S XIII 256.69 A), with FIP biases derived using differential emission measures (DEM) calculated via regularised inversion. Our results show that abundances of low-FIP elements, including sulphur, decrease above approximately 150 G relative to the high-FIP element Ar, while showing no dependence on loop length. This provides evidence that FIP fractionation is modulated by mean
magnetic field strength of coronal loops.
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