Showing 1–50 of 1,246 results for author: Wang, L

Revisiting Mars' Induced Magnetic Field and Clock Angle Departures under Real-Time Upstream Solar Wind Conditions

Authors: Zhihao Cheng, Chi Zhang, Chuanfei Dong, Hongyang Zhou, Jiawei Gao, Abigail Tadlock, Xinmin Li, Liang Wang

Abstract: Mars lacks a global intrinsic dipole magnetic field, but its interaction with the solar wind generates a global induced magnetosphere. Until now, most studies have relied on single-spacecraft measurements, which could not simultaneously capture upstream solar wind conditions and the induced magnetic fields, thereby limiting our understanding of the system. Here, we statistically re-examine the pro… ▽ More Mars lacks a global intrinsic dipole magnetic field, but its interaction with the solar wind generates a global induced magnetosphere. Until now, most studies have relied on single-spacecraft measurements, which could not simultaneously capture upstream solar wind conditions and the induced magnetic fields, thereby limiting our understanding of the system. Here, we statistically re-examine the properties of Mars' induced magnetic field by incorporating, for the first time, real-time upstream solar wind conditions from the coordinated MAVEN and Tianwen-1 observations. Our results are show that both solar wind dynamic pressure and the interplanetary magnetic field (IMF) magnitude enhance the strength of the induced magnetic field, but they exert opposite effects on the compression ratio: higher dynamic pressure strengthens compression, while stronger IMF weakens it. The induced field is stronger under quasi-perpendicular IMF conditions compared with quasi-parallel IMF, reflecting a stronger mass-loading effect. We further investigate the clock angle departures of the induced fields. They remain relatively small in the magnetosheath near the bow shock, increase gradually toward the induced magnetosphere, and become significantly larger within the induced magnetosphere. In addition, clock angle departures are strongly enhanced under quasi-parallel IMF conditions. Their dependence on upstream drivers further shows that, within the magnetosheath, clock angle departures are minimized under low dynamic pressure, high IMF magnitude, and low Alfven Mach number conditions. These results may enhance our understanding of solar wind interaction with Mars, and highlight the critical role of multi-point observations. △ Less

Submitted 21 December, 2025; originally announced December 2025.

Comments: 27 pages, 8 figures, accepted for publication in Journal of Geophysical Research: Space Physics

Physics-Informed Neural Networks for Modeling the Martian Induced Magnetosphere

Authors: Jiawei Gao, Chuanfei Dong, Chi Zhang, Yilan Qin, Simin Shekarpaz, Xinmin Li, Liang Wang, Hongyang Zhou, Abigail Tadlock

Abstract: Understanding the magnetic field environment around Mars and its response to upstream solar wind conditions provide key insights into the processes driving atmospheric ion escape. To date, global models of Martian induced magnetosphere have been exclusively physics-based, relying on computationally intensive simulations. For the first time, we develop a data-driven model of the Martian induced mag… ▽ More Understanding the magnetic field environment around Mars and its response to upstream solar wind conditions provide key insights into the processes driving atmospheric ion escape. To date, global models of Martian induced magnetosphere have been exclusively physics-based, relying on computationally intensive simulations. For the first time, we develop a data-driven model of the Martian induced magnetospheric magnetic field using Physics-Informed Neural Network (PINN) combined with MAVEN observations and physical laws. Trained under varying solar wind conditions, including B_IMF, P_SW, and θ_cone, the data-driven model accurately reconstructs the three-dimensional magnetic field configuration and its variability in response to upstream solar wind drivers. Based on the PINN results, we identify key dependencies of magnetic field configuration on solar wind parameters, including the hemispheric asymmetries of the draped field line strength in the Mars-Solar-Electric coordinates. These findings demonstrate the capability of PINNs to reconstruct complex magnetic field structures in the Martian induced magnetosphere, thereby offering a promising tool for advancing studies of solar wind-Mars interactions. △ Less

Submitted 17 December, 2025; originally announced December 2025.

AMKID -- a large KID-based camera at the APEX telescope

Authors: N. Reyes, A. Weiss, S. J. C. Yates, A. M. Baryshev, I. C. mara-Mayorga, S. Dabironezare A. Endo, L. Ferrari, A. Görlitz, G. Grutzeck, R. Güsten, C. Heiter, S. Heyminck, S. Hochgürtel, H. Hoevers, S. Jorquera, A. Kovàcs, D. Koopmans, C. König, N. Llombart, K. M. Menten, V. Murugesan, M. Ridder, A. Schmitz, D. J. Thoen, A. J. van der Linden , et al. (4 additional authors not shown)

Abstract: The thermal emission at sub-millimeter wavelengths carries unique information in many astronomical applications ranging from disks and planet formation around young stars, to galaxy evolution studies at cosmological distances. Advancing on the mapping speed to detect this faint emission in ground-based astronomy has been a technical challenge for decades. The APEX Microwave Kinetic Inductance Dete… ▽ More The thermal emission at sub-millimeter wavelengths carries unique information in many astronomical applications ranging from disks and planet formation around young stars, to galaxy evolution studies at cosmological distances. Advancing on the mapping speed to detect this faint emission in ground-based astronomy has been a technical challenge for decades. The APEX Microwave Kinetic Inductance Detector (AMKID) camera was designed to accomplish this task. The instrument is a wide field-of-view camera based on kinetic inductance detectors. It is installed on the 12~meter APEX telescope in Chile at 5.100~meters above see level. The instrument operates dual color, covering simultaneously the 350~GHz and 850~GHz atmospheric windows. It has a large field-of-view of 15.3'x15.3', and an unprecedented number of pixels: 13.952~detectors in the high frequency band and 3.520~detectors in the low frequency band. Here we present a complete description of the instrument design and construction together with results of the successful low frequency array (LFA) commissioning campaign executed during the last year. The LFA performance is in good agreement with design parameters, with detector sensitivity of 2.2~mK$\sqrt{s}$ and diffraction limited beam sizes of 17.0''. On-sky measurements demonstrate a sensitivity of 70-90~mJy$\sqrt{s}$ per detector when operating under good atmospheric conditions (PWV below 1.0mm). With this performance the LFA regularly achieve a mapping sensitivity of 25~mJy when mapping a square degree in an hour. AMKID on APEX with its dual color observing capabilities, high sensitivity, large field-of-view and high angular resolution holds the promise to open a new range of science with the APEX telescope. △ Less

Submitted 16 December, 2025; originally announced December 2025.

Comments: Submitted to Astronomy & Astrophysics 17 pages, 19 figures

XID+PRIMA, II: Stepping Through Hyperspectral Imaging to Deblend PRIMAger Beyond the Extragalactic Confusion Limit

Authors: J. M. S. Donnellan, B. Pautasso, S. J. Oliver, M. Béthermin, L. Bing, A. Bolatto, L. Ciesla, D. Koopmans, A. Pope, S. Serjeant, L. Wang

Abstract: The PRobe far-Infrared Mission for Astrophysics concept aims to map large areas with spectral coverage and sensitivities inaccessible to previous FIR space telescopes, covering 25-235um. We synthesise images representing a deep imaging survey, with realistic instrumental and confusion noise, reflecting the latest PRIMAger instrument specifications. We present a new Bayesian modelling approach XID+… ▽ More The PRobe far-Infrared Mission for Astrophysics concept aims to map large areas with spectral coverage and sensitivities inaccessible to previous FIR space telescopes, covering 25-235um. We synthesise images representing a deep imaging survey, with realistic instrumental and confusion noise, reflecting the latest PRIMAger instrument specifications. We present a new Bayesian modelling approach XID+stepwise that exploits PRIMAger's hyperspectral imaging to derive self-consistent, informative flux priors by sequentially propagating constraints from short to long wavelengths. With Euclid-like prior source positions, this method recovers fluxes to within 20% to 0.2-0.7 mJy across 45-84 um, which correspond to factors of 1.3-3.4 fainter than the confusion limit. For the most confusion-dominated channels, accurate fluxes are measured to 0.9, 2.5, 7.6 and 14.8 mJy at 92, 126, 183 and 235 um, respectively, which are factors of 3-5 better than the confusion limit. Using a deeper Euclid-based prior catalogue and weak ancillary flux priors at 25 um yields further improvements, reaching up to a factor ~7 fainter than the confusion limit at 96 um. Additionally, we demonstrate that positional priors from blind source detection followed by deblending via XID+ enables PRIMAger to achieve sensitivity beyond the confusion limits using PRIMAger data alone. We show that IR-luminous galaxies at z~2 are robustly detected in a large fraction of the PRIMAger channels (>98% in 12 out of the 16 considered channels), providing dense sampling of the FIR SED even for sources several factors below the confusion limit. We explore the impact on our results for a range of systematic effects, including cirrus contamination, optical degradation, and calibration uncertainties. These findings indicate that confusion noise will not limit the key science from PRIMA extragalactic imaging surveys when employing XID+. △ Less

Submitted 15 December, 2025; originally announced December 2025.

Comments: Submitted to Open Journal of Astrophysics. Comments welcome! 20 pages, 16 figures

Super-resolving Herschel - a deep learning based deconvolution and denoising technique

Authors: Dennis Koopmans, Lingyu Wang, Berta Margalef-Bentabol, Antonio La Marca, Matthieu Bethermin, Laura Bisigello, Zhen-Kai Gao, Claudia del P. Lagos, Lynge Lauritsen, Stephen Serjeant, F. F. S. van der Tak, Wei-Hao Wang

Abstract: Dusty star-forming galaxies (DSFGs) dominate the far-infrared and sub-millimetre number counts, but single-dish surveys suffer from poor angular resolution, complicating mult-wavelength counterpart identification. Prior-driven deblending techniques require extensive fine-tuning and struggle to process large fields. This work aims to develop a fast, reliable deep-learning based deconvolution and de… ▽ More Dusty star-forming galaxies (DSFGs) dominate the far-infrared and sub-millimetre number counts, but single-dish surveys suffer from poor angular resolution, complicating mult-wavelength counterpart identification. Prior-driven deblending techniques require extensive fine-tuning and struggle to process large fields. This work aims to develop a fast, reliable deep-learning based deconvolution and denoising super-resolution (SR) technique. We employ a transformer neural network to improve the resolution of Herschel/SPIRE 500 $μ$m observations by a factor 4.5, using Spitzer/MIPS 24$μ$m and Herschel/SPIRE 250, 350, 500$μ$m images. Trained on SIDES and SHARK simulations, we injected instrumental noise into the input simulated images, while keeping the target images noise-free to enhance de-noising capabilities of our method. We evaluated the performance on simulated test sets and real JCMT/SCUBA-2 450 $μ$m observations in the COSMOS field which have superior resolution compared to Herschel. Our SR method achieves an inference time of $1s/deg^2$ on consumer GPUs, much faster than traditional deblending techniques. Using the simulation test sets, we show that fluxes of the extracted sources from the super-resolved image are accurate to within 5% for sources with an intrinsic flux $\gtrsim$ 8 mJy, which is a substantial improvement compared to blind extraction on the native images. Astrometric error is low ($\lesssim$ 1" vs 12" pixel scale). Reliability is $\gtrsim$ 90% for sources $>$3 mJy and $>$90% of sources with intrinsic fluxes $\gtrsim5$ mJy are recovered. Applied to real 500 $μ$m observations, fluxes of the extracted sources from the super-resolved map agree well with SCUBA-2 measured fluxes for sources $\geq$10 mJy. Our technique enables SR over hundreds of $deg^2$ without the need for fine-tuning, facilitating statistical analysis of DSFGs. △ Less

Submitted 18 December, 2025; v1 submitted 15 December, 2025; originally announced December 2025.

Comments: Submitted to Astronomy & Astrophysics. Contains: 16 pages, 16 figures, 1 table

Measurement of the cosmic ray nickel energy spectrum from 10 GeV/n to 2 TeV/n with the DAMPE

Authors: F. Alemanno, Q. An, P. Azzarello, F. C. T. Barbato, P. Bernardini, X. J. Bi, H. V. Boutin, I. Cagnoli, M. S. Cai, E. Casilli, J. Chang, D. Y. Chen, J. L. Chen, Z. F. Chen, Z. X. Chen, P. Coppin, M. Y. Cui, T. S. Cui, I. De Mitri, F. de Palma, A. Di Giovanni, T. K. Dong, Z. X. Dong, G. Donvito, J. L. Duan , et al. (123 additional authors not shown)

Abstract: Nickel, one of the most stable elements alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of c… ▽ More Nickel, one of the most stable elements alongside iron, is the most abundant heavy element beyond iron in cosmic rays. With DAMPE's excellent charge resolution and broad energy range, a high-precision energy spectrum provides valuable insights into the acceleration sources of heavy nuclei and their propagation through the interstellar medium. In this analysis, we report the direct measurement of cosmic-ray nickel spectrum from 10 GeV/n to 2 TeV/n with nine years of flight data. The nickel spectrum is consistent with a single power law with spectral index -2.60 +/- 0.03 from 40 GeV/n to 1 TeV/n. This work provides an accurate measurement of differential flux of nickel with kinetic energy extending to TeV/n for the first time. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Efficient pulsar distance measurement with multiple nanohertz gravitational-wave sources

Authors: Si-Ren Xiao, Ji-Yu Song, Yue Shao, Ling-Feng Wang, Jing-Fei Zhang, Xin Zhang

Abstract: In recent years, pulsar timing arrays (PTAs) have reported evidence for a nanohertz gravitational-wave (GW) background. As radio telescope sensitivity improves, PTAs are also expected to detect continuous gravitational waves from individual supermassive black hole binaries. Nanohertz GWs generate both Earth and pulsar terms in the timing data, and the time delay between the two terms encodes the p… ▽ More In recent years, pulsar timing arrays (PTAs) have reported evidence for a nanohertz gravitational-wave (GW) background. As radio telescope sensitivity improves, PTAs are also expected to detect continuous gravitational waves from individual supermassive black hole binaries. Nanohertz GWs generate both Earth and pulsar terms in the timing data, and the time delay between the two terms encodes the pulsar distance. Precise pulsar distance measurements are critical to fully exploiting pulsar-term information, which can improve the measurement precision of GW sources' sky position parameters and thus enhance the GW sky-localization capability. In this work, we propose a new pulsar distance estimation method by using pulsar-term phase information from GWs. We construct two-dimensional distance posteriors for pulsar pairs based on the simulated GW signals and combine them to constrain individual pulsar distances. Compared with the existing one-dimensional method, our approach reduces the impact of source-parameter uncertainties on pulsar distance measurements. Considering four GW sources and a PTA of 20 pulsars with a white-noise level of 20 ns, we find that a significant fraction of pulsars at distances $\lesssim 1.4$ kpc can achieve sub-parsec distance precision over a 15-year observation. △ Less

Submitted 11 December, 2025; originally announced December 2025.

Comments: 13 pages, 4 figures

EP250827b/SN 2025wkm: An X-ray Flash-Supernova Powered by a Central Engine and Circumstellar Interaction

Authors: Gokul P. Srinivasaragavan, Dongyue Li, Xander J. Hall, Ore Gottlieb, Genevieve Schroeder, Heyang Liu, Brendan O'Connor, Chichuan Jin, Mansi Kasliwal, Tomás Ahumada, Qinyu Wu, Christopher L. Fryer, Annabelle E. Niblett, Dong Xu, Maria Edvige Ravasio, Grace Daja, Wenxiong Li, Shreya Anand, Anna Y. Q. Ho, Hui Sun, Daniel A. Perley, Lin Yan, Eric Burns, S. Bradley Cenko, Jesper Sollerman , et al. (69 additional authors not shown)

Abstract: We present the discovery of EP250827b/SN 2025wkm, an X-ray Flash (XRF) discovered by the Einstein Probe (EP), accompanied by a broad-line Type Ic supernova (SN Ic-BL) at $z = 0.1194$. EP250827b possesses a prompt X-ray luminosity of $\sim 10^{45} \, \rm{erg \, s^{-1}}$, lasts over 1000 seconds, and has a peak energy $E_{\rm{p}} < 1.5$ keV at 90% confidence. SN 2025wkm possesses a double-peaked lig… ▽ More We present the discovery of EP250827b/SN 2025wkm, an X-ray Flash (XRF) discovered by the Einstein Probe (EP), accompanied by a broad-line Type Ic supernova (SN Ic-BL) at $z = 0.1194$. EP250827b possesses a prompt X-ray luminosity of $\sim 10^{45} \, \rm{erg \, s^{-1}}$, lasts over 1000 seconds, and has a peak energy $E_{\rm{p}} < 1.5$ keV at 90% confidence. SN 2025wkm possesses a double-peaked light curve (LC), though its bolometric luminosity plateaus after its initial peak for $\sim 20$ days, giving evidence that a central engine is injecting additional energy into the explosion. Its spectrum transitions from a blue to red continuum with clear blueshifted Fe II and Si II broad absorption features, allowing for a SN Ic-BL classification. We do not detect any transient radio emission and rule out the existence of an on-axis, energetic jet $\gtrsim 10^{50}~$erg. In the model we invoke, the collapse gives rise to a long-lived magnetar, potentially surrounded by an accretion disk. Magnetically-driven winds from the magnetar and the disk mix together, and break out with a velocity $\sim 0.35c$ from an extended circumstellar medium with radius $\sim 10^{13}$ cm, generating X-ray breakout emission through free-free processes. The disk outflows and magnetar winds power blackbody emission as they cool, producing the first peak in the SN LC. The spin-down luminosity of the magnetar in combination with the radioactive decay of $^{56}$Ni produces the late-time SN LC. We end by discussing the landscape of XRF-SNe within the context of EP's recent discoveries. △ Less

Submitted 10 December, 2025; originally announced December 2025.

Comments: 43 pages, 20 Figures, Submitted to ApJ Letters

Euclid Quick Data Release (Q1): Euclid spectroscopy of QSOs. 1. Identification and redshift determination of 3500 bright QSOs

Authors: Euclid Collaboration, Y. Fu, R. Bouwens, K. I. Caputi, D. Vergani, M. Scialpi, B. Margalef-Bentabol, L. Wang, M. Bolzonella, M. Banerji, E. Bañados, A. Feltre, Y. Toba, J. Calhau, F. Tarsitano, P. A. C. Cunha, A. Humphrey, G. Vietri, F. Mannucci, S. Bisogni, F. Ricci, H. Landt, L. Spinoglio, T. Matamoro Zatarain, D. Stern , et al. (331 additional authors not shown)

Abstract: The slitless spectroscopy mode of the NISP onboard Euclid has enabled efficient spectroscopy of objects within a large FoV. We present a large and homogeneous sample of bright quasars identified from the Euclid Quick Data Release (Q1) by combining high-purity candidate selections from Gaia and WISE with the NISP spectra. Through visual inspection of the Euclid spectra of these quasar candidates, w… ▽ More The slitless spectroscopy mode of the NISP onboard Euclid has enabled efficient spectroscopy of objects within a large FoV. We present a large and homogeneous sample of bright quasars identified from the Euclid Quick Data Release (Q1) by combining high-purity candidate selections from Gaia and WISE with the NISP spectra. Through visual inspection of the Euclid spectra of these quasar candidates, we identify approximately 3500 quasars with reliable redshifts at $0<z\lesssim 4.8$. We generate the first Euclid composite spectrum of quasars covering rest-frame NUV to NIR wavelengths without telluric lines, which will be pivotal to NIR quasar spectral analysis. We obtain an empirical spectroscopic depth of $J_{\rm E}\lesssim 21.5$ and $H_{\rm E}\lesssim 21.3$ at the sensitivity of the Wide Field Survey, beyond which the number of securely identified quasars declines sharply. We analyse VIS morphologies using Sersic and CAS metrics, and a deep-learning PSF fraction to track nuclear dominance. At low redshift ($z<0.5$), obvious host structures are common and a single Sersic model fits about half of the sources; at intermediate redshift ($0.5<z<2$), the nuclear component dominates, with 90% of the Sersic fits saturating at the upper index limit. In this intermediate redshift regime, $f_{\rm PSF}$ is available, and we use it as a more reliable compactness measure than the single-Sersic and CAS parameters to quantify nuclear versus host emission. We also explore the novel Euclid NIR colour space and discuss the role of these quasars in refining AGN selection techniques for future Euclid data releases. Our results highlight the potential of Euclid spectroscopy to advance quasar surveys and enable the construction of more complete AGN catalogues. The spectroscopic bright quasar catalogue of this work, and the composite quasar spectrum, will be available at https://cdsarc.cds.unistra.fr/. (abridged) △ Less

Submitted 9 December, 2025; originally announced December 2025.

Comments: 24 pages, 15 figures, 5 tables, submitted to A&A Euclid Quick Data Release (Q1) special issue

Line Polarization of Si II $λ$6355 Å in Type Ia Supernovae: A New Statistical Approach to Probe the Explosion Physics and Diversity

Authors: Aleksandar Cikota, Peter Hoeflich, Dietrich Baade, Ferdinando Patat, Lifan Wang, J. Craig Wheeler, Yi Yang, Elham Fereidouni, Divya Mishra

Abstract: Spectropolarimetry provides a unique probe of ejecta asphericities, offering direct insights into the underlying explosion physics of Type Ia supernovae (SNe Ia). We analyze the statistical properties of pre-maximum spectropolarimetric data for 24 SNe Ia observed with VLT/FORS, focusing on the Si II $λ$6355 Åline. Previous studies have revealed a correlation between the peak Si II polarization deg… ▽ More Spectropolarimetry provides a unique probe of ejecta asphericities, offering direct insights into the underlying explosion physics of Type Ia supernovae (SNe Ia). We analyze the statistical properties of pre-maximum spectropolarimetric data for 24 SNe Ia observed with VLT/FORS, focusing on the Si II $λ$6355 Åline. Previous studies have revealed a correlation between the peak Si II polarization degree and the expansion velocity. Here, we combine these observations with multi-dimensional non-LTE radiative transfer simulations. We consider two asphericity classes: (i) lopsided abundance distributions produced by off-center delayed-detonation transitions in near-$M_{Ch}$ white dwarfs or, for example, WD collisions (Class I), and (ii) global, axisymmetric density asphericities such as those arising from explosions of rapidly rotating WDs or mergers (Class II). Our model grid spans normal to subluminous SNe Ia and successfully reproduces the observed Si II velocity-polarization trend, with higher velocities associated with stronger asphericities. Consistent with observations, transitional SNe Ia and the faint end of the normal SNe Ia population show the highest Si II polarization and are best explained by Class I scenarios. In contrast, subluminous SNe Ia are dominated by Class II asphericities, characterized by lower Si II polarization but significant continuum polarization. The observed distribution of Si II polarization depends on both the observer's viewing angle $θ$ and the intrinsic asphericity. Statistical analysis of these spectropolarimetric snapshots enables the separation of Class I and Class II contributions and highlights the intrinsic diversity among SNe Ia. Our results imply viewing-angle-dependent luminosities in our local sample, which may have implications when using high-redshift SNe Ia as evidence for the need of non-standard cosmology. △ Less

Submitted 3 December, 2025; originally announced December 2025.

Comments: Accepted for publication in ApJL

Kratos-polrad: Novel GPU system for Monte-Carlo simulations with consistent polarization calculations

Authors: Haifeng Yang, Lile Wang

Abstract: Polarized radiation serves as a vital diagnostic tool in astrophysics, providing unique insights into magnetic field geometries, scattering processes, and three-dimensional structures in diverse astrophysical scenarios. To address these applications, we present Kratos-polrad, a novel GPU-accelerated Monte Carlo Radiative Transfer code built upon the heterogeneous computing framework of Kratos, des… ▽ More Polarized radiation serves as a vital diagnostic tool in astrophysics, providing unique insights into magnetic field geometries, scattering processes, and three-dimensional structures in diverse astrophysical scenarios. To address these applications, we present Kratos-polrad, a novel GPU-accelerated Monte Carlo Radiative Transfer code built upon the heterogeneous computing framework of Kratos, designed for self-consistent and efficient polarization calculations. It utlizes comprehensive treatment of Stokes parameters throughout photon propagation, featuring transforms the grain-lab frame transforms using quaternion algebra and consistent non-linear polarization extinction in cells, which are useful in modeling radiative transfer processes with scatterings by aligned dust grains. The code implements two-step polarimetry imaging that decouples Monte Carlo sampling of scattering physics from imaging geometry, enabling efficient synthesis maximizing the utilization of photon packets. Extensive validation against analytical solutions and established codes demonstrates accurate treatment of diverse polarization phenomena, including self-scattering polarization, dichroic extinction in aligned dust grains, and complex polarization patterns in twisted magnetic field configurations. By leveraging massive GPU parallelism, optimized memory access patterns, and analytical approaches for optically thick cells, Kratos-polrad achieves performance improvements of $\sim 10^{2}$ times compared to CPU-based methods, enabling previously prohibitive studies in polarimetric astrophysics. △ Less

Submitted 1 December, 2025; originally announced December 2025.

Comments: 13 pages, 7 figures, submitted to ApJ

Searching Stochastic Gravitational Wave Background Landscape Across Frequency Bands

Authors: Yunjia Bao, Tore Boybeyi, Vuk Mandic, Lian-Tao Wang

Abstract: Gravitational wave (GW) astrophysics is entering a multi-band era with upcoming GW detectors, enabling detailed mapping of the stochastic GW background across vast frequencies. We highlight this potential via a new physics scenario: hybrid topological defects from a two-step phase transition separated by inflation. We develop a general pipeline to analyze experimental exclusions and apply it to th… ▽ More Gravitational wave (GW) astrophysics is entering a multi-band era with upcoming GW detectors, enabling detailed mapping of the stochastic GW background across vast frequencies. We highlight this potential via a new physics scenario: hybrid topological defects from a two-step phase transition separated by inflation. We develop a general pipeline to analyze experimental exclusions and apply it to this model. The model offers a possible explanation of the pulsar timing array signal at low frequencies, and future experiments (LISA/Cosmic Explorer/Einstein Telescope) will confirm or rule it out via the higher-frequency probes, showcasing the power of multi-band constraints. △ Less

Submitted 24 November, 2025; originally announced November 2025.

Comments: 9+14 pages, 1+12 figures, 1 table

Report number: P2500693

Performance Simulations for Kola: Achieving High-Resolution, Visible-Light AO Correction Over a 1 Arcminute Field

Authors: Brianna Peck, Jessica R. Lu, Lianqi Wang, Brooke DiGia, Richard Dekany, Antonin H. Bouchez, Peter Wizinowich, Maxwell A. Millar-Blanchaer, Mark Chun, Philip Hinz, Charles-Antoine Claveau

Abstract: We present performance simulations for a proposed visible-light, multi-conjugate adaptive optics system for the 10-meter W. M. Keck I telescope that aims to deliver near diffraction-limited angular resolution at optical wavelengths. Our proposed architecture, the Keck Optical Laser Guide Star Adaptive Optics System (KOLA), combines multiple laser guide stars (LGS) and deformable mirrors to enable… ▽ More We present performance simulations for a proposed visible-light, multi-conjugate adaptive optics system for the 10-meter W. M. Keck I telescope that aims to deliver near diffraction-limited angular resolution at optical wavelengths. Our proposed architecture, the Keck Optical Laser Guide Star Adaptive Optics System (KOLA), combines multiple laser guide stars (LGS) and deformable mirrors to enable wide-field correction across a 60 arcsecond field of view. Simulations were conducted using the open-source Multi-Threaded Adaptive Optics Simulator (MAOS), which we validated against on-sky data for the current Keck I adaptive optics system. We evaluated KOLA performance across a range of design parameters and report key point spread function metrics, including Strehl ratio, full width at half maximum, and encircled energy radius. Example science-driven requirements include resolving black hole spheres of influence, probing crowded stellar fields, and imaging protoplanetary disks. Trade studies on actuator count and laser guide star configuration help inform future design decisions. We present a nominal KOLA design (10 LGS, 3 tip-tilt natural guide stars (TTNGS), and 3600 actuators on the adaptive secondary mirror). Performance simulations show a 15 mas angular resolution with a Strehl ratio of 34% at 652 nm on-axis. More work is needed to explore alternative LGS/TTNGS asterisms, optimize conjugation heights for high-altitude deformable mirrors, and test performance under poorer seeing conditions. △ Less

Submitted 21 November, 2025; originally announced November 2025.

Comments: 18 pages, 9 figures

Comparing galaxy merger orbits in hydrodynamical simulation and in dark-matter-only simulation

Authors: Yahan Pu, Lan Wang, Guangquan Zeng, Lizhi Xie

Abstract: To investigate how the presence of baryons in simulations affects galaxy merger orbits, we compare in detail the merger timescales and orbits of the matched merger pairs in TNG100 hydrodynamical simulations and their corresponding dark-matter-only simulations, for different resolution levels. Compared with the mergers in the TNG100-1-Dark simulation without baryons, the matched mergers in the TNG1… ▽ More To investigate how the presence of baryons in simulations affects galaxy merger orbits, we compare in detail the merger timescales and orbits of the matched merger pairs in TNG100 hydrodynamical simulations and their corresponding dark-matter-only simulations, for different resolution levels. Compared with the mergers in the TNG100-1-Dark simulation without baryons, the matched mergers in the TNG100-1 simulation have similar infall time, but have statistically earlier merger times and therefore shorter merger timescales. The merger orbits for the matched pairs in the TNG100-1 and the TNG100-1-Dark simulations are similar right after infall, and both evolve to more head-on orbits at final stages, with smaller changes in the hydrodynamical simulation. In the final 2 Gyr before merger, the collision angles that represent merger orbits quantitatively are smaller in TNG100-1 than those in TNG100-1-Dark, by around 6$^\circ$ to 10$^\circ$, depending on the mass ratios and galaxy masses investigated. Our results demonstrate that the presence of baryons accelerates a bit the merger processes, and results in more spiral-in orbits for both major and minor mergers in galaxies with various stellar masses. These effects are less obvious in simulations with lower resolutions. △ Less

Submitted 21 November, 2025; originally announced November 2025.

Comments: 18 pages, 8 figures, submitted to RAA

A Comprehensive Analysis of the Panchromatic Transmission Spectrum of the Hot-Saturn WASP-96 b: Nondetection of Haze, Possible Sodium Limb Asymmetry, Stellar Characterization, and Formation History

Authors: Le-Chris Wang, Zafar Rustamkulov, David K. Sing, Joshua Lothringer, Patrick McCreery, Daniel Thorngren, Munazza K. Alam

Abstract: We conduct a reanalysis of the JWST NIRISS/SOSS observation of the hot-Saturn WASP-96 b. Initial analysis of this data revealed an enhanced Rayleigh scattering slope at the blue end of the transmission spectrum, suggesting the presence of hazes at high altitudes. In this work, we report non-detection of this slope, confirming an atmosphere clear of high-altitude aerosols consistent with the pre-JW… ▽ More We conduct a reanalysis of the JWST NIRISS/SOSS observation of the hot-Saturn WASP-96 b. Initial analysis of this data revealed an enhanced Rayleigh scattering slope at the blue end of the transmission spectrum, suggesting the presence of hazes at high altitudes. In this work, we report non-detection of this slope, confirming an atmosphere clear of high-altitude aerosols consistent with the pre-JWST results. Also contrary to the initial result, our results indicate the presence of gray cloud deck, although at relatively low altitudes/high pressures. We further combined the NIRISS/SOSS spectrum with VLT, HST, and Spitzer to produce a transmission spectrum from 0.35 $μ$m to 5 $μ$m. We constrain the mass fraction of multiple chemical species, including: H$_2$O$=-2.62^{+0.43}_{-0.42}$, K$=-5.76^{+1.05}_{-1.13}$, and Na$=-3.40^{+0.90}_{-0.92}$. C/O ratio and metallicity are tentatively constrained at substellar values (C/O$_{planet}=0.57^{+0.07}_{-0.12}$ and [Fe/H]$_{planet}=0.01^{+0.46}_{-0.52}$ compared to C/O$_{star}=0.92\pm0.25$ and [Fe/H]$_{star}=0.24\pm0.05$). Inputing these composition constraints to interior models, we constrain a core mass of $43^{+8}_{-15}$ M$_\oplus$. This, in addition to our inferred super-stellar refractory-to-oxygen ratio ($Δ\log_{10}(R/O)=1.48^{+0.57}_{-0.62}$) and substellar C/O ratio, suggests that the core of WASP-96 b likely formed outside of water iceline, underwent disk-driven migration, and accreted its atmosphere inside the carbon soot line. We find evidence of atmospheric leading-trailing terminator asymmetries in the broadened sodium absorption feature with a transit time offset of 50 seconds, while the water features appear symmetric. CH$_4$, CO, and CO$_2$ remain unconstrained due to spectral coverage limits. Upcoming JWST NIRSpec/G395H observations (ID 4082, PI: M. Radica) will be crucial for constraining these carbon-bearing species. △ Less

Submitted 20 November, 2025; originally announced November 2025.

Comments: 27 pages, 19 figures, 6 tables. accepted to AJ

Aql X-1 from dawn 'til dusk: the early rise, fast state transition and decay of its 2024 outburst

Authors: A. Marino, F. Coti Zelati, K. Alabarta, D. M. Russell, Y. Cavecchi, N. Rea, S. K. Rout, T. Di Salvo, J. Homan, Á. Jurado-López, L. Ji, R. Soria, T. D. Russell, Y. L. Wang, A. Anitra, M. C. Baglio, H. Feng, S. Fijma, S. Guillot, Y. F. Huang, G. Illiano, M. Imbrogno, C. Jin, F. Lewis, Y. F. Liang , et al. (14 additional authors not shown)

Abstract: Transient Low-Mass X-ray Binaries (LMXBs) are usually first detected by all-sky X-ray monitors when they enter new outbursts, typically at X-ray luminosities above $\sim$10$^{36}$ erg/s. Observations of these sources during the early rise of the outbursts have so far been very limited. However, the launch of the Einstein Probe (EP) has greatly improved our ability to detect fainter X-ray activity,… ▽ More Transient Low-Mass X-ray Binaries (LMXBs) are usually first detected by all-sky X-ray monitors when they enter new outbursts, typically at X-ray luminosities above $\sim$10$^{36}$ erg/s. Observations of these sources during the early rise of the outbursts have so far been very limited. However, the launch of the Einstein Probe (EP) has greatly improved our ability to detect fainter X-ray activity, unlocking access to the outburst early rise. In September 2024, EP detected the early onset of a new outburst from the neutron star LMXB Aql X-1, catching the source at a luminosity below 10$^{35}$ erg/s. In this paper we present results from a comprehensive, multi-wavelength campaign of this event, combining data from EP, NICER, NuSTAR, Swift and Las Cumbres Observatory covering the full outburst from its early rise through its decay. By comparing X-ray and optical light curves obtained with Las Cumbres Observatory during the initial rise, we show that the start of the X-ray emission lagged the optical rise by, at most, 3 days. Time-resolved X-ray spectroscopy revealed how the geometry and the physical properties of the accretion flow evolve during this early stage of the outburst, as well as at higher luminosities as the source transitioned through the canonical X-ray spectral states - hard, intermediate and soft. These data show that the source underwent a very rapid, about 12-h long, transition from the hard to the soft state about two weeks after the optical onset of the outburst. The evolution of the temperature and physical sizes of both the inner region of the disk and a black body near the NS surface suggest that at the state transition, a boundary and spreading layer likely formed. We discuss these results in the context of time-scales for outburst evolution and state transitions in accreting neutron stars and black holes. △ Less

Submitted 20 November, 2025; originally announced November 2025.

Comments: 13 pages, 9 figures, submitted to A&A

A Method for Gamma-Ray Energy Spectrum Inversion and Correction

Authors: Zhi-Qiang Ding, Xin-Qiao Li, Da-Li Zhang, Zheng-Hua An, Zhen-Xia Zhang, Roberto Battiston, Roberto Iuppa, Zhuo Li, Yan-Qiu Zhang, Yan Huang, Chao Zheng, Yan-Bing Xu, Xiao-Yun Zhao, Lu Wang, Ping Wang, Hong Lu

Abstract: Accurate spectral analysis of high-energy astrophysical sources often relies on comparing observed data to incident spectral models convolved with the instrument response. However, for Gamma-Ray Bursts and other high-energy transient events observed at high count rates, significant distortions (e.g., pile-up, dead time, and large signal trailing) are introduced, complicating this analysis. We pres… ▽ More Accurate spectral analysis of high-energy astrophysical sources often relies on comparing observed data to incident spectral models convolved with the instrument response. However, for Gamma-Ray Bursts and other high-energy transient events observed at high count rates, significant distortions (e.g., pile-up, dead time, and large signal trailing) are introduced, complicating this analysis. We present a method framework to address the model dependence problem, especially to solve the problem of energy spectrum distortion caused by instrument signal pile-up due to high counting rate and high-rate effects, applicable to X-ray, gamma-ray, and particle detectors. Our approach combines physics-based Monte Carlo (MC) simulations with a model-independent spectral inversion technique. The MC simulations quantify instrumental effects and enable correction of the distorted spectrum. Subsequently, the inversion step reconstructs the incident spectrum using an inverse response matrix approach, conceptually equivalent to deconvolving the detector response. The inversion employs a Convolutional Neural Network, selected for its numerical stability and effective handling of complex detector responses. Validation using simulations across diverse input spectra demonstrates high fidelity. Specifically, for 27 different parameter sets of the brightest gamma-ray bursts, goodness-of-fit tests confirm the reconstructed spectra are in excellent statistical agreement with the input spectra, and residuals are typically within $\pm 2σ$. This method enables precise analysis of intense transients and other high-flux events, overcoming limitations imposed by instrumental effects in traditional analyses. △ Less

Submitted 19 November, 2025; originally announced November 2025.

Comments: The Astrophysical Journal has accepted

How accurately can obscured galaxy luminosities be measured using spectral energy distribution fitting of near- through far-infrared observations?

Authors: Duncan Farrah, Kiana Ejercito, Andreas Efstathiou, David Leisawitz, Athena Engholm, Irene Shivaei, Matteo Bonato, David L. Clements, Sara Petty, Lura. K. Pitchford, Charalambia Varnava, Jose Afonso, Carlotta Gruppioni, Evanthia Hatziminaoglou, Andrew Hoffman, Mark Lacy, Brenda C. Matthews, Conor Nixon, Chris Pearson, Berke Vow Ricketti, Dimitra Rigopoulou, Loren Robinson, Locke D. Spencer, Lingyu Wang, David B. Sanders , et al. (1 additional authors not shown)

Abstract: Infrared-luminous galaxies are important sites of stellar and black hole mass assembly at most redshifts. Their luminosities are often estimated by fitting spectral energy distribution (SED) models to near- to far-infrared data, but the dependence of these estimates on the data used is not well-understood. Here, using observations simulated from a well-studied local sample, we compare the effects… ▽ More Infrared-luminous galaxies are important sites of stellar and black hole mass assembly at most redshifts. Their luminosities are often estimated by fitting spectral energy distribution (SED) models to near- to far-infrared data, but the dependence of these estimates on the data used is not well-understood. Here, using observations simulated from a well-studied local sample, we compare the effects of wavelength coverage, signal-to-noise (S/N), flux calibration, angular resolution, and redshift on the recovery of starburst, AGN, and host luminosities. We show that the most important factors are wavelength coverage that spans the peak in a SED, with dense wavelength sampling. Such observations recover starburst and AGN infrared luminosities with systematic bias below $20\%$. Starburst luminosities are best recovered with far-infrared observations while AGN luminosities are best recovered with near- and mid-infrared observations, though the recovery of both are enhanced with near/mid-infrared, and far-infrared observations, respectively. Host luminosities are best recovered with near/far-infrared observations, but are usually biased low, by $\gtrsim20\%$. The recovery of starburst and AGN luminosity is enhanced by observing at high angular resolution. Starburst-dominated systems show more biased recovery of luminosities than do AGN-dominated systems. As redshift increases, far-infrared observations become more capable, and mid-infrared observations less capable, at recovering luminosities. Our results highlight the transformative power of a far-infrared instrument with dense wavelength coverage from tens to hundreds of microns for studying infrared-luminous galaxies. We tabulate estimates of systematic bias and random error for use with JWST and other observatories. △ Less

Submitted 17 November, 2025; originally announced November 2025.

Comments: ApJ accepted. Tables A1 and A2 contain bias estimates for observations of infrared-luminous galaxies over 0<z<5 with JWST and other observatories

Mock Observations for the CSST Mission: Integral Field Spectrograph--Instrument Simulation

Authors: Zhao-Jun Yan, Jun Yin, Lei Hao, Shi-Yin Shen, Wei Chen, Shuai Feng, Yi-Fei Xiong, Chun Xu, Xin-Rong Wen, Lin Lin, Chao Liu, Lin Long, Zhen-Lei Chen, Mao-Chun Wu, Xiao-Bo Li, Zhang Ban, Xun Yang, Yu-Xi Jiang, Guo-Liang Li, Ke-Xin Li, Jian-Jun Chen, Nan Li, Cheng-Liang Wei, Lei Wang, Bai-Chuan Ren , et al. (3 additional authors not shown)

Abstract: The Chinese Space Station Survey Telescope (CSST) is a next-generation Stage-IV facility renowned for its wide field of view, high image quality, and multi-band observational capabilities. Among the five instruments onboard the CSST, the Integral Field Spectrograph (IFS) offers the unique ability to simultaneously capture spatial and spectral information across a field of view of no less than… ▽ More The Chinese Space Station Survey Telescope (CSST) is a next-generation Stage-IV facility renowned for its wide field of view, high image quality, and multi-band observational capabilities. Among the five instruments onboard the CSST, the Integral Field Spectrograph (IFS) offers the unique ability to simultaneously capture spatial and spectral information across a field of view of no less than $6^{''}\times6^{''}$. Key advantages of the IFS include a high spatial resolution of $0.2^{''}$ and a broad spectral coverage from 350 to 1000 nm, making it an ideal instrument for studying physical processes in the vicinity of supermassive black holes within galaxies. To more accurately assess the technical and scientific performance of the CSST-IFS, it is essential to develop a simulation tool that incorporates realistic effects from all optical components. Such a simulation will form an integral part of the CSST-IFS data and pipeline system, enabling the development of the data reduction pipeline well ahead of actual observations. This paper presents an end-to-end simulation workflow for the CSST-IFS, incorporating a wide range of instrumental effects that may influence its spectral and imaging performance. The simulation accounts for optical diffraction effects introduced by all components, such as image slicers and slit array, as well as sub-pixel effects from gratings. It also includes various detector noises, frame-shifting effects, and charge-transfer inefficiency. Real observational conditions--such as target Doppler shift, cosmic rays, and other in-orbit operational effects--are also considered. We describe the technical implementation of the simulation and present results that quantitatively characterize key instrument parameters. △ Less

Submitted 16 November, 2025; originally announced November 2025.

Comments: 24 pages, 17 figures, accepted by RAA

Mock Observations for the CSST Mission: Multi-Channel Imager--Instrument Simulation

Authors: Zhao-Jun Yan, Huan-Yuan Shan, Zhen-Ya Zheng, Xi-Yan Peng, Zhao-Xiang Qi, Chun Xu, Lin Lin, Xin-Rong Wen, Chun-Yan Jiang, Li-Xin Zheng, Jing Zhong, Fang-Ting Yuan, Zhen-Lei Chen, Wei Chen, Mao-Chun Wu, Zhen-Sen Fu, Ke-Xin Li, Lin Nie, Chao Liu, Nan Li, Qiao Wang, Zi-Huang Cao, Shuai Feng, Guo-Liang Li, Lei Wang , et al. (18 additional authors not shown)

Abstract: The Chinese Space Station Survey Telescope (CSST), a two-meter aperture astronomical space telescope under China's manned space program, is equipped with multiple back-end scientific instruments. As an astronomical precision measurement module of the CSST, the Multi-Channel Imager (MCI) can cover a wide wavelength range from ultraviolet to near-infrared with three-color simultaneous high-precision… ▽ More The Chinese Space Station Survey Telescope (CSST), a two-meter aperture astronomical space telescope under China's manned space program, is equipped with multiple back-end scientific instruments. As an astronomical precision measurement module of the CSST, the Multi-Channel Imager (MCI) can cover a wide wavelength range from ultraviolet to near-infrared with three-color simultaneous high-precision photometry and imaging, which meets the scientific requirements for various fields. The diverse scientific objectives of MCI require not only a robust airborne platform, advanced optical systems, and observing facilities but also comprehensive software support for scientific operations and research. To this end, it is essential to develop realistic observational simulation software to thoroughly evaluate the MCI data stream and provide calibration tools for future scientific investigations. The MCI instrument simulation software will serve as a foundation for the development of the MCI data processing pipeline and will facilitate improvements in both hardware and software, as well as in the observational operation strategy, in alignment with the mission's scientific goals. In conclusion, we present a comprehensive overview of the MCI instrument simulation and some corresponding performances of the MCI data processing pipeline. △ Less

Submitted 16 November, 2025; originally announced November 2025.

Comments: 28 pages, 21 figures, accepted by RAA

Gravitational wave standard sirens from GWTC-3 combined with DESI DR2 and DESY5: A late-universe probe of the Hubble constant and dark energy

Authors: Ji-Yu Song, Guo-Hong Du, Tian-Nuo Li, Ling-Feng Wang, Jing-Zhao Qi, Jing-Fei Zhang, Xin Zhang

Abstract: Recently, the combination of the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) baryon acoustic oscillation (BAO) data and the Planck cosmic microwave background (CMB) measurements has shown a $\sim$3$σ$ preference for a dynamical dark energy model with a phantom-crossing behavior. However, such a phantom-crossing dark energy evolution further exacerbates the already severe Hubbl… ▽ More Recently, the combination of the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) baryon acoustic oscillation (BAO) data and the Planck cosmic microwave background (CMB) measurements has shown a $\sim$3$σ$ preference for a dynamical dark energy model with a phantom-crossing behavior. However, such a phantom-crossing dark energy evolution further exacerbates the already severe Hubble tension in the $Λ$CDM model. Moreover, there exists a $\sim2σ$ tension between the DESI DR2 BAO and CMB datasets. Therefore, it is essential to measure the Hubble constant and dark-energy equation-of-state (EoS) parameters using only late-universe observations. In this work, we investigate a novel late-universe data combination: gravitational-wave (GW) standard sirens, BAO, and Type Ia supernovae (SNe Ia). This combination provides a fully distance-ladder- and CMB-independent determination of the Hubble constant and the dark-energy EoS. Using 47 GW standard sirens from the third Gravitational-Wave Transient Catalog, the DESI DR2 BAO data, and DESY5 SNe Ia data, in the $w_0w_a$CDM model, we obtain $H_0=74.8^{+6.3}_{-8.9}$ km s$^{-1}$ Mpc$^{-1}$, $Ω_{\rm m}=0.320^{+0.015}_{-0.012}$, $w_0=-0.775^{+0.072}_{-0.074}$, and $w_a=-0.80\pm0.47$, indicating a mild phantom-crossing behavior within the $1σ$ credible interval with an $H_0$ value consistent with the distance ladder measurements. Our analysis demonstrates the power of GW standard sirens in breaking parameter degeneracies, and this novel data combination provides joint constraints on the Hubble constant and the dark-energy EoS parameters. △ Less

Submitted 14 November, 2025; originally announced November 2025.

Comments: 10 pages, 3 figures

Mock Observations for the CSST Mission: Main Surveys -- the Mock Catalogue

Authors: Cheng-Liang Wei, Yu Luo, Hao Tian, Ming Li, Yi-Sheng Qiu, Guo-Liang Li, Yue-Dong Fang, Xin Zhang, De-Zi Liu, Nan Li, Ran Li, Huan-Yuan Shan, Lin Nie, Zizhao He, Lei Wang, Xi Kang, Dongwei Fan, Yang Chen, Xiaoting Fu, Chao Liu

Abstract: The Chinese Space Station Survey Telescope (CSST) is a flagship space mission, designed to carry out a large-area sky survey to explore the nature of dark matter and dark energy in the Universe. The onboard multi-band imaging and slitless spectroscopic modules will enable us to obtain photometric data for billions of galaxies and stars, as well as hundreds of millions of spectroscopic measurements… ▽ More The Chinese Space Station Survey Telescope (CSST) is a flagship space mission, designed to carry out a large-area sky survey to explore the nature of dark matter and dark energy in the Universe. The onboard multi-band imaging and slitless spectroscopic modules will enable us to obtain photometric data for billions of galaxies and stars, as well as hundreds of millions of spectroscopic measurements, advancing various scientific analyses such as galaxy clustering and weak gravitational lensing. To support the image simulations for the main survey of the CSST mission, we present a mock catalogue of stars and galaxies. For stars, the mock catalogue is generated using either Galaxia or TRILEGAL, both of which provide a range of stellar properties to meet the requirements of CSST image simulations. For galaxies, we built a mock light-cone up to redshift z~3.5 from the cosmological Nbody simulation and populated the mock galaxy catalogue from the dark mater haloes using a semi-analytical galaxy formation model. We then performed a full-sky ray-tracing simulation of weak gravitational lensing to obtain lensing shear at the position of each galaxy in the light-cone. To support both multi-band imaging and slitless spectroscopic simulations, we computed the spectral energy distribution (SED) for each galaxy based on its star formation history using a supervised deep-learning model and determined the magnitudes in each band using the CSST throughputs. Finally, the properties of our mock galaxies include positions, redshifts, stellar masses, shapes, sizes, SEDs, lensing shears and magnifications. We have validated our mock catalogue against observational data and theoretical models, with results showing good overall agreement. The catalogue provides a flexible dataset for the development of CSST image processing and can support a wide range of cosmological analyses within the CSST mission. △ Less

Submitted 13 November, 2025; originally announced November 2025.

Comments: 17 pages, 17 figures, accepted in RAA. Our mock catalog is available upon request

fiDrizzle-MU: A Fast Iterative Drizzle with Multiplicative Updates

Authors: Shen Zhang, Lei Wang, Huanyuan Shan, Ran Li, Xiaoyue Cao, Yunhao Gao

Abstract: We propose fiDrizzleMU, an algorithm for co-adding exposures via iterative multiplicative updates, replacing the additive correction framework. This method achieves superior anti-aliasing and noise reduction in stacked images. When applied to James Webb Space Telescope data, the fiDrizzleMU algorithm reconstructs a gravitational lensing candidate that was significantly blurred by the pipeline's re… ▽ More We propose fiDrizzleMU, an algorithm for co-adding exposures via iterative multiplicative updates, replacing the additive correction framework. This method achieves superior anti-aliasing and noise reduction in stacked images. When applied to James Webb Space Telescope data, the fiDrizzleMU algorithm reconstructs a gravitational lensing candidate that was significantly blurred by the pipeline's resampling process. This enables the accurate recovery of faint and extended structures in high-resolution astronomical imaging. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 12 pages, 5 figures, published in RAA

Adsorption of volatiles on dust grains in protoplanetary disks

Authors: Lile Wang, Feng Long, Haifeng Yang, Ruobing Dong, Shenzhen Xu

Abstract: The adsorption of volatile molecules onto dust grain surfaces fundamentally influences dust-related processes, including condensation of gas-phase molecules, dust coagulation, and planet formation in protoplanetary disks. Using advanced ab-initio density functional theory with r$^2$SCAN+rVV10 van der Waals functionals, we calculate adsorption energies of H$_2$, H$_2$O, and CO on carbonaceous (grap… ▽ More The adsorption of volatile molecules onto dust grain surfaces fundamentally influences dust-related processes, including condensation of gas-phase molecules, dust coagulation, and planet formation in protoplanetary disks. Using advanced ab-initio density functional theory with r$^2$SCAN+rVV10 van der Waals functionals, we calculate adsorption energies of H$_2$, H$_2$O, and CO on carbonaceous (graphene, amorphous carbon) and silicate (MgSiO$_3$) surfaces. Results reveal fundamentally different adsorption mechanisms: weak physisorption on carbonaceous surfaces ($|Δε_{\rm ad}|\sim 0.1-0.2~{\rm eV}$) versus strong chemisorption on silicates ($|Δε_{\rm ad}|\sim 0.5-1.5~{\rm eV}$) via coordination bonds. Kinetic Monte Carlo simulations incorporating these energies demonstrate divergent surface evolution: carbonaceous grains exhibit distinct condensation radius compared to silicates, while the cocrystal of H$_2$O and CO significantly increases the desorption temperature of CO. The actual radii of gas-phase molecule depletion could thus be a comprehensive result of temperatures, chemical compositions, and even evolution tracks. Meanwhile, silicates maintain chemisorbed molecular coatings throughout most disk regions. Such dichotomy in surface coverage could also provide a natural mechanism for carbon depletion in inner planetary systems. △ Less

Submitted 13 November, 2025; v1 submitted 12 November, 2025; originally announced November 2025.

Comments: 15 pages, 5 figures, submitted to ApJ

An axisymmetric shock breakout indicated by prompt polarized emission from the type II supernova 2024ggi

Authors: Yi Yang, Xudong Wen, Lifan Wang, Dietrich Baade, J. Craig Wheeler, Alexei V. Filippenko, Avishay Gal-Yam, Justyn Maund, Steve Schulze, Xiaofeng Wang, Chris Ashall, Mattia Bulla, Aleksandar Cikota, He Gao, Peter Hoeflich, Gaici Li, Divya Mishra, Ferdinando Patat, Kishore C. Patra, Sergiy S. Vasylyev, Shengyu Yan

Abstract: The death of massive stars is triggered by an infall-induced bounce shock that disrupts the star. How such a shock is launched and propagates through the star is a decade-long puzzle. Some models assume that the shock can be reenergized by absorbing neutrinos, leading to highly aspherical explosions. Other models involve jet-powered shocks that lead to bipolar explosions reflected in the geometry… ▽ More The death of massive stars is triggered by an infall-induced bounce shock that disrupts the star. How such a shock is launched and propagates through the star is a decade-long puzzle. Some models assume that the shock can be reenergized by absorbing neutrinos, leading to highly aspherical explosions. Other models involve jet-powered shocks that lead to bipolar explosions reflected in the geometry of the shock-breakout emission. We report measurement of the geometry of the shock breakout through unprecedentedly early spectropolarimetry of the nearby type II supernova 2024ggi starting ~1.2 days after the explosion. The measurement indicates a well-defined symmetry axis of the shock breakout, which is also shared by the hydrogen-rich envelope that emerged after the circumstellar matter was engulfed by the ejecta, revealing a persisting and prominent symmetry axis throughout the explosion. These findings suggest that the physical mechanism driving the explosion of massive stars manifests a well-defined axial symmetry and acts on large scales. △ Less

Submitted 11 November, 2025; originally announced November 2025.

Comments: Science Advances: https://www.science.org/doi/10.1126/sciadv.adx2925 ESO PR: https://www.eso.org/public/news/eso2520/

Mock Observations for the CSST Mission: Main Surveys--An Overview of Framework and Simulation Suite

Authors: Cheng-Liang Wei, Guo-Liang Li, Yue-Dong Fang, Xin Zhang, Yu Luo, Hao Tian, De-Zi Liu, Xian-Ming Meng, Zhang Ban, Xiao-Bo Li, Zun Luo, Jing-Tian Xian, Wei Wang, Xi-Yan Peng, Nan Li, Ran Li, Li Shao, Tian-Meng Zhang, Jing Tang, Yang Chen, Zhao-Xiang Qi, Zi-Huang Cao, Huan- Yuan Shan, Lin Nie, Lei Wang , et al. (4 additional authors not shown)

Abstract: The Chinese Space Station Survey Telescope (CSST) is a flagship space-based observatory. Its main survey camera is designed to conduct high spatial resolution near-ultraviolet to near-infrared imaging and low-resolution spectroscopic surveys. To maximize the scientific output of CSST, we have developed a comprehensive, high-fidelity simulation pipeline for reproducing both imaging and spectroscopi… ▽ More The Chinese Space Station Survey Telescope (CSST) is a flagship space-based observatory. Its main survey camera is designed to conduct high spatial resolution near-ultraviolet to near-infrared imaging and low-resolution spectroscopic surveys. To maximize the scientific output of CSST, we have developed a comprehensive, high-fidelity simulation pipeline for reproducing both imaging and spectroscopic observations. This paper presents an overview of the simulation framework, detailing its implementation and components. Built upon the GalSim package and incorporating the latest CSST instrumental specifications, our pipeline generates pixel-level mock observations that closely replicate the expected instrumental and observational conditions. The simulation suite integrates realistic astrophysical object catalogs, instrumental effects, point spread function (PSF) modeling, and observational noises to produce accurate synthetic data. We describe the key processing stages of the simulation, from constructing the input object catalogs to modeling the telescope optics and detector responses. Furthermore, we introduce the most recent release of simulated datasets, which provide a crucial testbed for data processing pipeline developments, calibration strategies, and scientific analyses, ensuring that CSST will meet its stringent requirements. Our pipeline serves as a vital tool for optimizing CSST main survey strategies and ensuring robust cosmological measurements. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 38 pages, 22 figures, accepted for publication in RAA. The image simulation code is now publicly accessible at https://csst-tb.bao.ac.cn/code/csst-sims/csst_msc_sim

Mock Observations for the CSST Mission: Multi-Channel Imager--The Cluster Field

Authors: Yushan Xie, Xiaokai Chen, Shuai Feng, Zhaojun Yan, Nan Li, Huanyuan Shan, Yin Li, Chengliang Wei, Weiwei Xu, Zhenya Zheng, Ran Li, Wei Chen, Zhenlei Chen, Chunyan Jiang, Dezi Liu, Lin Nie, Xiyan Peng, Lei Wang, Maochun Wu, Chun Xu, Fangting Yuan, Shen Zhang, Jing Zhong

Abstract: The Multi-Channel Imager (MCI), one of the instruments aboard the China Survey Space Telescope (CSST), is designed to simultaneously observe the sky in three filters, covering wavelengths from the near-ultraviolet (NUV) to the near-infrared (NIR). With its large field of view ($7.5^{\prime}\times7.5^{\prime}$), MCI is particularly well-suited for observing galaxy clusters, providing a powerful too… ▽ More The Multi-Channel Imager (MCI), one of the instruments aboard the China Survey Space Telescope (CSST), is designed to simultaneously observe the sky in three filters, covering wavelengths from the near-ultraviolet (NUV) to the near-infrared (NIR). With its large field of view ($7.5^{\prime}\times7.5^{\prime}$), MCI is particularly well-suited for observing galaxy clusters, providing a powerful tool for investigating galaxy evolution, dark matter and dark energy through gravitational lensing. Here we present a comprehensive simulation framework of a strong lensing cluster as observed by MCI, aiming to fully exploit its capabilities in capturing lensing features. The framework simulates a strong lensing cluster from the CosmoDC2 catalog, calculating the gravitational potential and performing ray-tracing to derive the true positions, shapes and light distribution of galaxies within the cluster field. Additionally, the simulation incorporates intra-cluster light (ICL) and spectral energy distributions (SEDs), enabling further strong lensing analyses, such as ICL seperation from galaxy light and mass reconstruction combining strong and weak lensing measurements. This framework provides a critical benchmark for testing the MCI data pipeline and maximizing its potential in galaxy cluster research. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 17 pages, 7 figures, accpeted by RAA

Charge-dependent spectral softenings of primary cosmic-rays from proton to iron below the knee

Authors: DAMPE Collaboration, Francesca Alemanno, Qi An, Philipp Azzarello, Felicia-Carla-Tiziana Barbato, Paolo Bernardini, Xiao-Jun Bi, Hugo Valentin Boutin, Irene Cagnoli, Ming-Sheng Cai, Elisabetta Casilli, Jin Chang, Deng-Yi Chen, Jun-Ling Chen, Zhan-Fang Chen, Zi-Xuan Chen, Paul Coppin, Ming-Yang Cui, Tian-Shu Cui, Ivan De Mitri, Francesco de Palma, Adriano Di Giovanni, Tie-Kuang Dong, Zhen-Xing Dong, Giacinto Donvito , et al. (124 additional authors not shown)

Abstract: In most particle acceleration mechanisms, the maximum energy of the cosmic rays can achieve is charge dependent. However, the observational verification of such a fundamental relation is still lack due to the difficulty of measuring the spectra of individual particles from one (kind of) source(s) up to very high energies. This work reports direct measurements of the carbon, oxygen, and iron spectr… ▽ More In most particle acceleration mechanisms, the maximum energy of the cosmic rays can achieve is charge dependent. However, the observational verification of such a fundamental relation is still lack due to the difficulty of measuring the spectra of individual particles from one (kind of) source(s) up to very high energies. This work reports direct measurements of the carbon, oxygen, and iron spectra from ~ 20 gigavolts to ~ 100 teravolts (~ 60 teravolts for iron) with 9 years of on-orbit data collected by the Dark Matter Particle Explorer (DAMPE). Distinct spectral softenings have been directly detected in these spectra for the first time. Combined with the updated proton and helium spectra, the spectral softening appears universally at a rigidity of ~ 15 teravolts. A nuclei mass dependent softening is rejected at a confidence level of > 99.999%. Taking into account the correlated structures at similar energies in the large-scale anisotropies of cosmic rays, one of the most natural interpretations of the spectral structures is the presence of a nearby cosmic ray source. In this case, the softening energies correspond to the acceleration upper limits of such a source, forming the so-called Peters cycle of the spectra. The results thus offer observational verification of the long-standing prediction of the charge-dependent energy limit of cosmic ray acceleration. △ Less

Submitted 10 November, 2025; v1 submitted 7 November, 2025; originally announced November 2025.

Comments: This update corrects typos in the tables

Massive stars exploding in a He-rich circumstellar medium XII. SN 2024acyl: A fast, linearly declining Type Ibn supernova with early flash-ionisation features

Authors: Y. -Z. Cai, A. Pastorello, K. Maeda, J. -W. Zhao, Z. -Y. Wang, Z. -H. Peng, A. Reguitti, L. Tartaglia, A. V. Filippenko, Y. Pan, G. Valerin, B. Kumar, Z. Wang, M. Fraser, J. P. Anderson, S. Benetti, S. Bose, T. G. Brink, E. Cappellaro, T. -W. Chen, X. -L. Chen, N. Elias-Rosa, A. Esamdin, A. Gal-Yam, M. González-Bañuelos , et al. (41 additional authors not shown)

Abstract: We present a photometric and spectroscopic analysis of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of about -17.58 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands, similar to most SNe Ibn. The optical pseudobolometric light curve peaks at ($3.5\pm0.8) \times 10^{42}$ erg s$^{-1}$, with a total radiated energy of… ▽ More We present a photometric and spectroscopic analysis of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of about -17.58 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands, similar to most SNe Ibn. The optical pseudobolometric light curve peaks at ($3.5\pm0.8) \times 10^{42}$ erg s$^{-1}$, with a total radiated energy of $(5.0\pm0.4) \times 10^{48}$ erg. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni \Hei~lines and flash-ionisation emission lines of C {\sc iii}, N {\sc iii}, and He {\sc ii}. The P-Cygni \Hei~features gradually evolve and become emission-dominated in late-time spectra. The \Ha~line is detected throughout the entire spectral evolution, which indicates that the CSM is helium-rich with some residual amount of H. Our multiband light-curve modelling yields estimates of the ejecta mass of $M_{ej}$ = $0.98^{+0.30}_{-0.20} \, \msun$, with a kinetic energy of $E_{k} = 0.13^{+0.03}_{-0.02} \times 10^{51}$ erg, and a $^{56}Ni$ mass of $M_{\mathrm{Ni}} = 0.017 \, \msun$. The inferred CSM properties are characterised by a mass of $M_{\rm{CSM}} = 0.39^{+0.04}_{-0.04}$ \msun, an inner radius of $R_0$=$15.6^{+1.9}_{-2.0}$ AU, and a density $ρ_{CSM} = (1.32\pm0.22)\times10^{-11} \, \mathrm{g\,cm^{-3}}$. The multi-epoch spectra are well reproduced by the CMFGEN/ \texttt{he4p0} model, corresponding to a He-ZAMS mass of 4~M$_\odot$. These findings are consistent with a scenario of an SN powered by ejecta-CSM interaction, originating from a low-mass helium star that evolved within an interacting binary system where the CSM with some residual hydrogen may originate from the mass-transfer process. In addition, a channel of core-collapse explosion of a late-type Wolf-Rayet star with H, or an Ofpe/WN9 star with fallback accretion, cannot be entirely ruled out. △ Less

Submitted 6 November, 2025; originally announced November 2025.

Comments: 19 pages, 12 figures

Euclid Quick Data Release (Q1). The average far-infrared properties of Euclid-selected star-forming galaxies

Authors: Euclid Collaboration, R. Hill, A. Abghari, D. Scott, M. Bethermin, S. C. Chapman, D. L. Clements, S. Eales, A. Enia, B. Jego, A. Parmar, P. Tanouri, L. Wang, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera , et al. (280 additional authors not shown)

Abstract: The first Euclid Quick Data Release contains millions of galaxies with excellent optical and near-infrared (IR) coverage. To complement this dataset, we investigate the average far-IR properties of Euclid-selected main sequence (MS) galaxies using existing Herschel and SCUBA-2 data. We use 17.6deg$^2$ (2.4deg$^2$) of overlapping Herschel (SCUBA-2) data, containing 2.6 million (240000) MS galaxies.… ▽ More The first Euclid Quick Data Release contains millions of galaxies with excellent optical and near-infrared (IR) coverage. To complement this dataset, we investigate the average far-IR properties of Euclid-selected main sequence (MS) galaxies using existing Herschel and SCUBA-2 data. We use 17.6deg$^2$ (2.4deg$^2$) of overlapping Herschel (SCUBA-2) data, containing 2.6 million (240000) MS galaxies. We bin the Euclid catalogue by stellar mass and photometric redshift and perform a stacking analysis following SimStack, which takes into account galaxy clustering and bin-to-bin correlations. We detect stacked far-IR flux densities across a significant fraction of the bins. We fit modified blackbody spectral energy distributions in each bin and derive mean dust temperatures, dust masses, and star-formation rates (SFRs). We find similar mean SFRs compared to the Euclid catalogue, and we show that the average dust-to-stellar mass ratios decreased from z$\simeq$1 to the present day. Average dust temperatures are largely independent of stellar mass and are well-described by the function $T_2+(T_1-T_2){\rm e}^{-t/τ}$, where $t$ is the age of the Universe, $T_1=79.7\pm7.4$K, $T_2=23.2\pm0.1$K, and $τ=1.6\pm0.1$Gyr. We argue that since the dust temperatures are converging to a non-zero value below $z=1$, the dust is now primarily heated by the existing cooler and older stellar population, as opposed to hot young stars in star-forming regions at higher redshift. We show that since the dust temperatures are independent of stellar mass, the correlation between dust temperature and SFR depends on stellar mass. Lastly, we estimate the contribution of the Euclid catalogue to the cosmic IR background (CIB), finding that it accounts for >60% of the CIB at 250, 350, and 500$μ$m. Forthcoming Euclid data will extend these results to higher redshifts, lower stellar masses, and recover more of the CIB. △ Less

Submitted 5 November, 2025; v1 submitted 4 November, 2025; originally announced November 2025.

Comments: Submitted to A&A as part of the second Euclid Q1 paper splash. V2 fixed typo in title

Euclid: Quick Data Release (Q1) -- Secondary nuclei in early-type galaxies

Authors: M. Fabricius, R. Saglia, F. Balzer, L. R. Ecker, J. Thomas, R. Bender, J. Gracia-Carpio, M. Magliocchetti, O. Marggraf, A. Rawlings, J. G. Sorce, K. Voggel, L. Wang, A. van der Wel, B. Altieri, A. Amara, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, A. Balestra, S. Bardelli, A. Biviano, E. Branchini, M. Brescia , et al. (143 additional authors not shown)

Abstract: Massive early-type galaxies (ETGs) are believed to form primarily through mergers of less massive progenitors, leaving behind numerous traces of violent formation histories, such as stellar streams and shells. A particularly striking signature of these mergers is the formation of supermassive black hole (SMBH) binaries, which can create depleted stellar cores through interactions with stars on rad… ▽ More Massive early-type galaxies (ETGs) are believed to form primarily through mergers of less massive progenitors, leaving behind numerous traces of violent formation histories, such as stellar streams and shells. A particularly striking signature of these mergers is the formation of supermassive black hole (SMBH) binaries, which can create depleted stellar cores through interactions with stars on radial orbits - a process known as core scouring. The secondary SMBH in such systems may still carry a dense stellar envelope and thereby remain observable for some time as a secondary nucleus, while it is sinking towards the shared gravitational potential of the merged galaxy. We leverage Euclid's Q1 Early Release data to systematically search for secondary nuclei in ETGs. We present a preliminary sample of 666 candidate systems distributed over 504 hosts (some of which contain multiple secondary nuclei). The vast majority of these fall at separations of 3 kpc to 15 kpc, indicative of normal mergers. 44 fall at projected separations of less than 2 kpc. We argue those candidates at very close angular separations are unlikely to be a consequence of chance alignments. We show that their stellar masses are mostly too large for them to be globular clusters and that a significant subset are unresolved even at Euclid's spatial resolution, rendering them too small to be dwarf galaxies. These may represent the highest-density nuclei of a previously merged galaxy, currently sinking into the centre of the new, common gravitational potential and thus likely to host a secondary SMBH. We then demonstrate that convolutional neural networks offer a viable avenue to detect multiple nuclei in the thirty-times larger sky coverage of the future Euclid DR1. Finally, we argue that our method could detect the remnants of a recoil event from two merged SMBHs. △ Less

Submitted 4 November, 2025; originally announced November 2025.

Comments: 17 pages, 22 figures

Euclid: Quick Data Release (Q1)- The connection between galaxy close encounters and radio activity

Authors: M. Magliocchetti, A. La Marca, L. Bisigello, M. Bondi, F. Ricci, S. Fotopoulou, L. Wang, R. Scaramella, L. Pentericci, I. Prandoni, J. G. Sorce, H. J. A. Rottgering, M. J. Hardcastle, J. Petley, F. La Franca, K. Rubinur, Y. Toba, Y. Zhong, M. Mezcua, G. Zamorani, F. Shankar, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi , et al. (143 additional authors not shown)

Abstract: Using the large statistics provided by both Euclid and the LOFAR surveys, we present the first large-scale study of the connection between radio emission, its morphology, and the merging properties of the hosts of radio sources up to z=2. By dividing the radio sample into active galactic nuclei (AGN) and star-forming galaxies, we find that radio-emitting AGN show a clear preference to reside withi… ▽ More Using the large statistics provided by both Euclid and the LOFAR surveys, we present the first large-scale study of the connection between radio emission, its morphology, and the merging properties of the hosts of radio sources up to z=2. By dividing the radio sample into active galactic nuclei (AGN) and star-forming galaxies, we find that radio-emitting AGN show a clear preference to reside within galaxies undergoing a merging event. This is more significant for AGN that present extended and/or complex radio emission: indeed, about half of them are associated with merging systems, while only 15% are hosted by an isolated galaxy. The observed trend is primarily driven by AGN residing at z < 1, especially in the case of high - P144MHz > 10^24 W Hz-1 sr-1 - radio luminosities (60% in mergers versus 10% isolated regardless of radio appearance). The situation is reversed in the case of radio-emitting star-forming galaxies, which are preferentially associated with isolated systems. This is more significant as we move towards low radio-luminosity/star-formation objects (P144MHz < 10^23 W Hz-1 sr-1) for which we find 40% in isolated systems versus 20% in mergers. These values hold regardless of redshift. We interpret the above result for AGN with their need to accrete outer gas from local encounters in order to trigger (radio) activity, especially in the case of extended radio emission such as hot-spots and lobes. This is mostly observed at z < 1, since in the local Universe galaxies are more gas deprived than their higher-redshift counterparts. Internal gas reservoirs instead seem sufficient to trigger star formation within the majority of galaxies, which indeed prefer to be associated with isolated systems at all redshifts probed. (abridged) △ Less

Submitted 4 November, 2025; originally announced November 2025.

Comments: 22 pages, 16 figures, submitted to A&A

Direct Numerical Simulations of Oxygen-Flame-Driven Deflagration-to-Detonation Transition in Type Ia Supernovae

Authors: Xiaoyu Zhang, Lile Wang, Yang Gao, Yao Zhou

Abstract: We present direct numerical simulations demonstrating deflagration-to-detonation transition (DDT) driven by oxygen flames in Type Ia supernova progenitors. Using the Castro hydrodynamics code coupled with the ``aprox13'' 13-isotope nuclear network, we simulate combustion in isolated fuel regions where oxygen flames trail carbon flames. In a fiducial one-dimensional run at… ▽ More We present direct numerical simulations demonstrating deflagration-to-detonation transition (DDT) driven by oxygen flames in Type Ia supernova progenitors. Using the Castro hydrodynamics code coupled with the ``aprox13'' 13-isotope nuclear network, we simulate combustion in isolated fuel regions where oxygen flames trail carbon flames. In a fiducial one-dimensional run at $ρ_{0}=3.5\times10^{7}\ \mathrm{g\ cm^{-3}}$ we observe spontaneous DDT of the oxygen flame via the Zel'dovich gradient mechanism when the carbon-oxygen separation reaches $\sim 10\ \mathrm{km}$. The oxygen detonation then captures the carbon flame and triggers a stable carbon detonation. Systematic one-dimensional parameter scans show that successful carbon DDT requires upstream densities in the range $(3.1$--$3.6)\times10^{7}\ \mathrm{g\ cm^{-3}}$ and a minimum carbon-flame thickness of $\gtrsim 20\ \mathrm{m}$. Two-dimensional simulations confirm DDT and demonstrate that the multidimensional cellular structure of the oxygen detonation can promote carbon detonation at somewhat lower densities than in one dimension. These results provide direct numerical evidence that oxygen-flame-driven DDT is physically plausible in turbulent white-dwarf environments and underscore the importance of multidimensional effects for Type Ia supernova explosion modeling. △ Less

Submitted 30 October, 2025; originally announced October 2025.

Evidence of cosmic-ray acceleration up to sub-PeV energies in the supernova remnant IC 443

Authors: Zhen Cao, F. Aharonian, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, C. M. Cai, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, G. H. Chen, H. X. Chen, Liang Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen, S. H. Chen , et al. (291 additional authors not shown)

Abstract: Supernova remnants (SNRs) have been considered as the primary contributors to cosmic rays (CRs) in our Galaxy. However, the maximum energy of particles that can be accelerated by shocks of SNRs is uncertain observationally and theoretically, and the role of contribution to CRs around PeV energies by SNRs is unclear. In this study, we present observations of high-energy $γ$-ray emission from the SN… ▽ More Supernova remnants (SNRs) have been considered as the primary contributors to cosmic rays (CRs) in our Galaxy. However, the maximum energy of particles that can be accelerated by shocks of SNRs is uncertain observationally and theoretically, and the role of contribution to CRs around PeV energies by SNRs is unclear. In this study, we present observations of high-energy $γ$-ray emission from the SNR IC 443 using the Large High Altitude Air Shower Observatory (LHAASO). The morphological analysis reveals a pointlike source whose location and spectrum are consistent with those of the Fermi-LAT-detected compact source with $π^0$-decay signature, and a more extended source which is consistent with a newly discovered source, previously unrecognized by Fermi-LAT. The spectrum of the point source can be described by a power-law function with an index of $\sim3.0$, extending beyond $\sim 30$ TeV without apparent cutoff. Assuming a hadronic origin of the $γ$-ray emission, the $95\%$ lower limit of accelerated protons reaches about 300 TeV. The extended source might be coincident with IC 443, SNR G189.6+3.3 or the putative pulsar wind nebula CXOU J061705.3+222127, and can be explained by either a hadronic or leptonic model. The LHAASO results provide compelling evidence that CR protons up to sub-PeV energies can be accelerated by the SNR. △ Less

Submitted 29 October, 2025; originally announced October 2025.

Galactic bars and active galactic nucleus fuelling in the second half of cosmic history

Authors: A. La Marca, M. T. Nardone, L. Wang, B. Margalef-Bentabol, S. Kruk, S. C. Trager

Abstract: We investigate the role of galactic bars in fuelling and triggering Active Galactic Nucleus (AGN) in disc galaxies up to $z\sim 0.8$. We utilise a Deep Learning model, fine-tuned on Galaxy Zoo volunteer classifications, to identify (strongly and weakly) barred and unbarred disc galaxies in Hyper Suprime-Cam Subaru Strategic Program $i$-band images. We select AGN using three independent diagnostics… ▽ More We investigate the role of galactic bars in fuelling and triggering Active Galactic Nucleus (AGN) in disc galaxies up to $z\sim 0.8$. We utilise a Deep Learning model, fine-tuned on Galaxy Zoo volunteer classifications, to identify (strongly and weakly) barred and unbarred disc galaxies in Hyper Suprime-Cam Subaru Strategic Program $i$-band images. We select AGN using three independent diagnostics: mid-infrared colours, X-ray detections, and spectral energy distribution (SED) fitting. The SED analysis, performed using CIGALE, quantifies the relative AGN contribution to the total galaxy luminosity ($f_{\rm AGN}$) and the AGN luminosity ($L_{\rm disc}$). We assess the impact of bars by comparing AGN incidence and properties in barred galaxies against carefully constructed redshift-, stellar mass-, and colour-matched unbarred control samples. Our binary AGN classification experiment demonstrates that barred disc galaxies host a statistically detectable higher fraction of AGN compared to their unbarred counterparts, suggesting a contributing role for bars in the global AGN budget. The contribution of bars to AGN fuelling appears confined to systems where the AGN has a lower relative contribution to the host galaxy's emission ($f_{\rm AGN} < 0.75$). Crucially, we find a significant dearth of barred disc galaxies hosting AGN with $f_{\rm AGN} > 0.75$, independent of bar strength. Consistent with this, the fraction of barred galaxies among AGN hosts decreases with increasing $L_{\rm disc}$. Combined with previous results, we suggest that bars contribute to fuelling the population of low-to-moderate luminosity AGN, but major mergers are the principal mechanism for triggering the most powerful and dominant accretion events. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Comments: 16 pages (3 pages appendix), 19 figures. Re-submitted to the journal after a positive referee report

SN 2024iss: A Double-peaked Type IIb Supernova with Evidence of Circumstellar Interaction

Authors: Liyang Chen, Xiaofeng Wang, Qinyu Wu, Moira Andrews, Joseph Farah, Paolo Ochner, Andrea Reguitti, Thomas G. Brink, Jujia Zhang, Cuiying Song, Jialian Liu, Alexei V. Filippenko, David J. Sand, Irene Albanese, Kate D. Alexander, Jennifer Andrews, K. Azalee Bostroem, Yongzhi Cai, Collin Christy, Ali Esamdin, Andrea Farina, Noah Franz, D. Andrew Howell, Brian Hsu, Maokai Hu , et al. (32 additional authors not shown)

Abstract: We present optical, ultraviolet, and X-ray observations of supernova (SN) 2024iss, a Type IIb SN that shows a prominent double-peaked light curve. We modeled the first peak with a semianalytical shock-cooling model and the X-ray emission with a free-free model. We compare the envelope radius and mass-loss rate with other Type IIb SNe to explore the relationships between the progenitor envelope and… ▽ More We present optical, ultraviolet, and X-ray observations of supernova (SN) 2024iss, a Type IIb SN that shows a prominent double-peaked light curve. We modeled the first peak with a semianalytical shock-cooling model and the X-ray emission with a free-free model. We compare the envelope radius and mass-loss rate with other Type IIb SNe to explore the relationships between the progenitor envelope and the circumstellar material (CSM). The shock-cooling peak in the $V$-band light curve reached $M_V = -17.33\pm 0.26$mag, while the $^{56}$Ni-powered second peak attained $M_V = -17.43\pm 0.26$mag. Early spectra show an photospheric velocity of $\sim19,400\,km\,s^{-1}$ at 3.82days from the H$α$ P~Cygni profile. The Balmer lines persist at least +87 days after the explosion, characterizing hydrogen-rich ejecta. Modeling the first light-curve peak suggests an extended envelope with a mass of $0.11\pm0.04\,M_{\odot}$ and a radius of $244\pm43~R_{\odot}$. Fitting the second light-curve peak with an Arnett-like model indicates a typical $^{56}$Ni mass of $ 0.117\pm0.013~M_{\odot}$ and a relatively low ejecta mass of $1.272\pm0.343\,M_{\odot}$. X-ray observations reveal bright thermal bremsstrahlung emission and indicate a mass-loss rate of $1.6\times10^{-5}\ M_{\odot} \ \rm{yr}^{-1}$. SN 2024iss occupies a transitional position between the two subclasses of extended (eIIb) and compact (cIIb) Type IIb SNe. Its envelope radius and pre-explosion mass-loss rate appear to be correlated as theoretically predicted. The observational properties of SN 2024iss are compatible with a binary interaction scenario being the dominant mechanism for envelope stripping. Furthermore, the low column density of neutral hydrogen suggests a compact CSM with an outer radius of $\lesssim1.3\times10^{14}$ cm, indicating that the progenitor star experienced eruptive mass loss within $\sim4\,yr$ of its terminal explosion. △ Less

Submitted 27 October, 2025; originally announced October 2025.

Comments: 24 pages, 14 figures, submitted to A&A

Synergy between CSST and third-generation gravitational-wave detectors: Inferring cosmological parameters using cross-correlation of dark sirens and galaxies

Authors: Ya-Nan Du, Ji-Yu Song, Yichao Li, Shang-Jie Jin, Ling-Feng Wang, Jing-Fei Zhang, Xin Zhang

Abstract: Gravitational-wave (GW) events are generally believed to originate in galaxies and can thus serve, like galaxies, as tracers of the universe's large-scale structure. In GW observations, waveform analysis provides direct measurements of luminosity distances; however, the redshifts of GW sources cannot be determined due to the mass-redshift degeneracy. By cross-correlating GW events with galaxies, o… ▽ More Gravitational-wave (GW) events are generally believed to originate in galaxies and can thus serve, like galaxies, as tracers of the universe's large-scale structure. In GW observations, waveform analysis provides direct measurements of luminosity distances; however, the redshifts of GW sources cannot be determined due to the mass-redshift degeneracy. By cross-correlating GW events with galaxies, one can establish a correspondence between luminosity distance and redshift shells, enabling cosmological inference. In this work, we explore the scientific potential of cross-correlating GW sources detected by third-generation (3G) ground-based GW detectors with the photometric redshift survey of the China Space Station Survey Telescope (CSST). We find that the constraint precisions of the Hubble constant and the matter density parameter can reach $1.04\%$ and $2.04\%$, respectively. The GW clustering bias parameters $A_{\rm GW}$ and $γ$ can be constrained to $1.52\%$ and $4.67\%$, respectively. These results highlight the significant potential of the synergy between CSST and 3G ground-based GW detectors in constraining cosmological models and probing GW source formation channels using cross-correlation of dark sirens and galaxies. △ Less

Submitted 24 October, 2025; originally announced October 2025.

Comments: 15 pages, 7 figures

Observationally derived change in the star formation rate as mergers progress

Authors: W. J. Pearson, L. Wang, V. Rodriguez-Gomez, B. Margalef-Bentabol, L. E. Suelves

Abstract: Galaxy mergers can change the rate at which stars are formed. We can trace when these changes occur in simulations of galaxy mergers. However, for observed galaxies we do not know how the star formation rate (SFR) evolves along the merger sequence as it is difficult to probe the time before or after coalescence. We aim to derive how SFR changes in observed mergers throughout the merger sequence, f… ▽ More Galaxy mergers can change the rate at which stars are formed. We can trace when these changes occur in simulations of galaxy mergers. However, for observed galaxies we do not know how the star formation rate (SFR) evolves along the merger sequence as it is difficult to probe the time before or after coalescence. We aim to derive how SFR changes in observed mergers throughout the merger sequence, from a statistical perspective. Merger times were estimated for observed galaxy mergers in the Kilo Degree Survey (KiDS) using a convolutional neural network (CNN). The CNN was trained on mock KiDS images created using IllustrisTNG data. The SFRs were derived from spectral energy density fitting to KiDS and VIKINGs data. To determine the change in SFR for the merging galaxies, each merging galaxy was matched and compared to ten comparable non-merging galaxies; matching each galaxy in redshift, stellar mass, and local density. Mergers see an increase in the SFR for galaxies from 300~Myr before the merger until coalescence, continuing until at least 200~Myr after the merger event. After this, there is a possibility that SFR activity in the mergers begins to decrease, but we need more data to better constrain our merger times and SFRs to confirm this. We find that more galaxies with higher stellar mass (M$_{\star}$) have greater SFR enhancement as they merge compared to lower-M$_{\star}$ galaxies. There is no clear trend of changing SFR enhancement as local density changes, but the least dense environments have the least SFR enhancement. The increasing SFR enhancement is likely due to the closer proximity of galaxies and the presence of more close passes as the time before the merger approaches 0~Myr, with the SFR slowing 200~Myr after the merger event. △ Less

Submitted 28 October, 2025; v1 submitted 23 October, 2025; originally announced October 2025.

Comments: 18 pages, 14 figures, 2 tables, accepted for publication in A&A. Updated after language editor

Detecting Ca II Absorption Lines with a Fe II assisted Dual Neural Network

Authors: Lucas Wang, Jian Ge, Kevin Willis

Abstract: Ca II absorbers, characterized by dusty and metal-rich environments, provide unique insights into the interstellar medium of galaxies. However, their rarity and weak absorption features have hindered comprehensive studies. In this work, we present a novel dual CNN approach to detect Ca II absorption systems, analyzing over 100,000 quasar spectra from the Sloan Digital Sky Survey (SDSS) Data Releas… ▽ More Ca II absorbers, characterized by dusty and metal-rich environments, provide unique insights into the interstellar medium of galaxies. However, their rarity and weak absorption features have hindered comprehensive studies. In this work, we present a novel dual CNN approach to detect Ca II absorption systems, analyzing over 100,000 quasar spectra from the Sloan Digital Sky Survey (SDSS) Data Release 16. Our primary CNN identifies Ca II features, while a secondary CNN cross-verifies these detections using five Fe II absorption lines. This approach yielded 1,646 Ca II absorption systems, including 525 previously known absorbers and 1,121 new discoveries, nearly tripling the size of any previously reported catalog. Among our Ca II absorbers, 95 are found to show the 2175Å dust feature (2DA), corresponding to 22% of strong absorbers, 7% of weak absorbers, and $\sim$12% of the overall Ca II population at $0.8 < z_{\text{abs}} < 1.4$. Across the full redshift range of $0.36 < z_{\text{abs}} < 1.4$, $\sim$1.5% of Mg II absorbers host Ca II. △ Less

Submitted 13 October, 2025; originally announced October 2025.

Born Dry or Born Wet? A Palette of Water Growth Histories in TRAPPIST-1 Analogs and Compact Planetary Systems

Authors: Howard Chen, Matthew S. Clement, Le-Chris Wang, Jesse T. Gu

Abstract: It is still unclear whether exoplanets in compact multiplanet systems such as TRAPPIST-1 are able to accrete large quantities of volatiles, grow to sufficient mass, and maintain robust atmospheres and hydrospheres. Previous estimates of water content in M-dwarf systems have largely relied on population synthesis or atmosphere-interior evolution models, often treating impacts and atmospheric loss i… ▽ More It is still unclear whether exoplanets in compact multiplanet systems such as TRAPPIST-1 are able to accrete large quantities of volatiles, grow to sufficient mass, and maintain robust atmospheres and hydrospheres. Previous estimates of water content in M-dwarf systems have largely relied on population synthesis or atmosphere-interior evolution models, often treating impacts and atmospheric loss in isolation. In this work, we couple impact delivery, impact erosion, and mantle-atmosphere exchange within a model that tracks volatile evolution through stochastic collision histories. By explicitly including both planetesimal accretion and the prolonged luminous pre-main-sequence phase of M dwarfs, we find lower water inventories for the inner TRAPPIST-1 analogs (b-e), spanning only $10^{-4}$-$10^{-2} M_{\oplus,\rm ocn}$ across a wide range of disk structures and impact scenarios. By contrast, the outer planets (f-h analogs) frequently retain water inventories exceeding an Earth ocean mass. This systematic volatile gradient provides a physically motivated explanation for JWST's nondetections of atmospheres on TRAPPIST-1 b and c, implying an origin rooted in formation conditions rather than in post-formation escape. Our results suggest that many rocky planets in compact M-dwarf systems may form already depleted in volatile compounds, fundamentally limiting their capacity to sustain atmospheres or surface oceans. More broadly, our multistage framework for volatile tracking can help interpret future observations of compact systems and set more realistic initial conditions for exoplanet interior compositions and atmospheric models. △ Less

Submitted 14 October, 2025; originally announced October 2025.

Comments: 21 pages, 7 figures, 3 tables, published in the Astrophysical Journal Letters

Journal ref: Chen, H., Clement, M. S., Wang, L. C., & Gu, J. T. 2025, ApJL, 991, L11

An FPCA-Enhanced Ensemble Learning Framework for Photometric Identification of Type Ia Supernovae

Authors: Moonzarin Reza, Lifan Wang, Lei Hu

Abstract: Type Ia supernovae (SNe Ia) are essential tools for addressing key cosmic questions, including the Hubble tension and the nature of dark energy. Modern surveys are predominantly photometry-based, making the construction of a clean photometric SNe Ia sample crucial. In this study, we investigate whether functional principal component analysis (FPCA) scores derived from photometric light curves, com… ▽ More Type Ia supernovae (SNe Ia) are essential tools for addressing key cosmic questions, including the Hubble tension and the nature of dark energy. Modern surveys are predominantly photometry-based, making the construction of a clean photometric SNe Ia sample crucial. In this study, we investigate whether functional principal component analysis (FPCA) scores derived from photometric light curves, combined with ensemble learning, can reliably distinguish SNe Ia from other transients using the PLAsTiCC dataset. FPCA provides a data-driven, flexible characterization of light curves without relying on rigid theoretical model assumptions. Light curves are fitted by minimizing residuals with penalty terms from clean samples, making the method robust to outliers or poorly sampled bands. The first two FPCA scores and peak magnitudes across the five LSST bands are used as classification features. We implement two complementary binary classifiers: an ensemble boosting model (CatBoost) and a statistical probabilistic method based on Euclidean distances. CatBoost slightly outperforms the statistical method, achieving 98.5% accuracy and 97.8% precision. Performance remains robust (>90%) under typical photometric redshift uncertainties (σ = 0.1). On the spectroscopic DES Y5 sample, both methods reach approximately 90% accuracy and 95% precision, demonstrating strong out-of-domain generalization compared to state-of-the-art methods with limited cross-survey applicability. Applied to DECam DDF and DESIRT transients, the predictions strongly agree, and their intersection provides a high-confidence SNe Ia sample for cosmological analyses. Overall, this FPCA-based framework offers a powerful, flexible tool for classifying transients in upcoming large-scale surveys such as LSST and Roman. △ Less

Submitted 10 October, 2025; originally announced October 2025.

Comments: Submitted to The Astrophysical Journal (ApJ) 24 pages, 16 figures

The Astronomical Plate Digitization at SHAO

Authors: Yong Yu, Meiting Yang, Zhengjun Shang, Liangliang Wang, Jing Yang, Zhenghong Tang, Jianhai Zhao, Massinissa Hadjara

Abstract: The digitization of historical astronomical plates is essential for preserving century-long observational data. This work presents the development and application of the specialized digitizers at the Shanghai Astronomical Observatory (SHAO), including technical details, international collaborations, and scientific applications on the plates. The digitization of historical astronomical plates is essential for preserving century-long observational data. This work presents the development and application of the specialized digitizers at the Shanghai Astronomical Observatory (SHAO), including technical details, international collaborations, and scientific applications on the plates. △ Less

Submitted 8 October, 2025; originally announced October 2025.

Comments: 4 pages, 10 figures, conference

A Giant Peanut-shaped Ultra-High-Energy Gamma-Ray Emitter Off the Galactic Plane

Authors: Zhen Cao, Felix Aharonian, Yunxiang Bai, Yiwei Bao, Denis Bastieri, Xiaojun Bi, YuJiang Bi, Mr Bian WenYi, A. Butkevich, Chengmiao Cai, Wenyu Cao, Zhe Cao, Jin Chang, Jinfan Chang, Mr Aming Chen, Ensheng Chen, Mr Guo-Hai Chen, Mr Huaxi Chen, Liang Chen, Long Chen, Mingjun Chen, Mali Chen, Qihui Chen, Shi Chen, Suhong Chen , et al. (291 additional authors not shown)

Abstract: Ultra-high-energy (UHE), exceeding 100 TeV (10^12 electronvolts), γ-rays manifests extreme particle acceleration in astrophysical sources. Recent observations by γ-ray telescopes, particularly by the Large High Altitude Air Shower Observatory (LHAASO), have revealed a few tens of UHE sources, indicating numerous Galactic sources capable of accelerating particles to PeV (10^15 electronvolts) energi… ▽ More Ultra-high-energy (UHE), exceeding 100 TeV (10^12 electronvolts), γ-rays manifests extreme particle acceleration in astrophysical sources. Recent observations by γ-ray telescopes, particularly by the Large High Altitude Air Shower Observatory (LHAASO), have revealed a few tens of UHE sources, indicating numerous Galactic sources capable of accelerating particles to PeV (10^15 electronvolts) energies. However, discerning the dominant acceleration mechanisms (leptonic versus hadronic), the relative contributions of specific source classes, and the role of particle transport in shaping their observed emission are central goals of modern UHE astrophysics. Here we report the discovery of a giant UHE γ-ray emitter at -17.5° off the Galactic plane - a region where UHE γ-ray sources are rarely found. The emitter exhibits a distinctive asymmetric shape, resembling a giant "Peanut" spanning 0.45° \times 4.6°, indicative of anisotropic particle distribution over a large area. A highly aged millisecond pulsar (MSP) J0218+4232 is the sole candidate accelerator positionally coincident with the Peanut region. Its association with UHE γ-rays extending to 0.7 PeV, if confirmed, would provide the first evidence of a millisecond pulsar powering PeV particles. Such a finding challenges prevailing models, which posit that millisecond pulsars cannot sustain acceleration to PeV energies. The detection reveals fundamental gaps in understanding particle acceleration, cosmic-ray transport, and interstellar magnetic field effects, potentially revealing new PeV accelerator (PeVatron) classes. △ Less

Submitted 25 October, 2025; v1 submitted 8 October, 2025; originally announced October 2025.

On the Formation of GW231123 in Population III Star Clusters

Authors: Shuai Liu, Long Wang, Ataru Tanikawa, Weiwei Wu, Michiko S. Fujii

Abstract: GW231123 is a binary black hole merger whose primary component lies within or above the pair-instability mass gap, while the secondary component falls within this gap. The standard theory of stellar evolution is significantly challenged by this event. We investigate the formation of candidate progenitors of GW231123 in Population III (Pop III) star clusters. We find that they could form through st… ▽ More GW231123 is a binary black hole merger whose primary component lies within or above the pair-instability mass gap, while the secondary component falls within this gap. The standard theory of stellar evolution is significantly challenged by this event. We investigate the formation of candidate progenitors of GW231123 in Population III (Pop III) star clusters. We find that they could form through stellar mergers, binary black hole mergers, and mixed mergers. The mass distribution of these candidate progenitors covers the component masses of GW231123. Under our model assumptions, their predicted merger rate density spans the range of $0.001-0.26{\rm Gpc^{-3}yr^{-1}}$, encompassing that of GW231123. These findings suggest that GW231123 may originate from Pop III star clusters. Furthermore, such candidate progenitors are expected to be detectable by future gravitational wave detectors LISA/Taiji/TianQin/DECIGO/Cosmic Explorer/Einstein Telescope, which would provide valuable insights into the formation scenarios of events like GW231123. △ Less

Submitted 2 November, 2025; v1 submitted 7 October, 2025; originally announced October 2025.

Comments: 8 pages, 4 figures, and 1 table. Published in ApJL

Journal ref: ApJL, 993 (2025) L30

Intrinsically Quantum Effects of Axion Dark Matter are Undetectable

Authors: Yunjia Bao, Dhong Yeon Cheong, Nicholas L. Rodd, Joey Takach, Lian-Tao Wang, Kevin Zhou

Abstract: Is the usual treatment of axion dark matter as a classical field reliable? We show that the answer is subtle: the axion field could well be in a quantum state that has no complete classical description, but realistic detectors cannot tell the difference. To see this, we solve a fully quantum model of axion detection using quantum optics techniques. We show that intrinsically quantum effects are wa… ▽ More Is the usual treatment of axion dark matter as a classical field reliable? We show that the answer is subtle: the axion field could well be in a quantum state that has no complete classical description, but realistic detectors cannot tell the difference. To see this, we solve a fully quantum model of axion detection using quantum optics techniques. We show that intrinsically quantum effects are washed out by mode averaging or small amounts of noise, and significantly suppressed by the weakness of the axion coupling. Our work exemplifies that there should always be a classical analog for axion dark matter effects, extends to other wave (ultralight) dark-matter candidates, and gives a general method to compute the effects of exotic dark-matter states. △ Less

Submitted 6 October, 2025; originally announced October 2025.

Comments: 10 pages, 1 figure

DRAGON-III simulation: modelling million-body globular and nuclear star clusters

Authors: Kai Wu, Philip Cho, Rainer Spurzem, Long Wang, Francesco Flammini Dotti, Vahid Amiri

Abstract: As a continuation of DRAGON-II, we present the DRAGON-III project, which focuses on the simulations of million-body globular clusters and nuclear clusters over 10 Gyr. We report on its preliminary results on globular clusters. The first 100 Myr of the simulations have produced 41 pulsars, 191 X-ray binaries, 17 gravitational wave sources, and one black hole-black hole merger due to the loss of orb… ▽ More As a continuation of DRAGON-II, we present the DRAGON-III project, which focuses on the simulations of million-body globular clusters and nuclear clusters over 10 Gyr. We report on its preliminary results on globular clusters. The first 100 Myr of the simulations have produced 41 pulsars, 191 X-ray binaries, 17 gravitational wave sources, and one black hole-black hole merger due to the loss of orbital energy in the form of gravitational wave emission. The inclusion of initial soft binaries brings surprisingly interesting results, including one IMBH in a binary black hole, and compact object binaries resembling the Gaia-BH1 and the wide black hole-giant binary reported in Wang et al. (2024, Nat. Astro.). △ Less

Submitted 4 October, 2025; originally announced October 2025.

Comments: 4 pages, 1 figure, 1 table. Accepted for publication in IAU Conference proceedings of IAU Symposium 398 & MODEST-25: Compact Objects and Binaries in Dense Stellar Systems

Photometric Analysis of 30 Contact Binaries in M31

Authors: Xiang Gao, Kai Li, Li-Heng Wang, Hai-bo Yuan, Hong-rui Gu, Ya-Ni Guo

Abstract: M31, as the largest galaxy in the Local Group, is of significant importance for the study of stellar formation and evolution. Based on the data of 5,859 targets observed in M31 by Gu et al (2024), we selected 30 contact binaries by visual inspection for further study. Using the PHOEBE software and employing Bayesian optimization and Markov Chain Monte Carlo sampling, we determined the physical par… ▽ More M31, as the largest galaxy in the Local Group, is of significant importance for the study of stellar formation and evolution. Based on the data of 5,859 targets observed in M31 by Gu et al (2024), we selected 30 contact binaries by visual inspection for further study. Using the PHOEBE software and employing Bayesian optimization and Markov Chain Monte Carlo sampling, we determined the physical parameters of these 30 systems. The results show that 10 systems exhibit the O'Connell effect, which is well explained by introducing a dark spot on the primary star. 11 systems have mass ratios below 0.15, classifying them as extremely low mass ratio contact binaries, making them promising candidates for binary mergers. Six systems have primary star temperatures exceeding 10,000 K, classifying them as early-type contact binaries. The absolute physical parameters reveal that two contact binary systems contain massive stellar components, which may eventually evolve into compact binary star systems. To compare the effects of different galactic environments on the evolution of contact binaries, we constructed evolutionary diagrams for these 30 targets and for contact binaries in the Milky Way. The results show that, at the same mass, our targets have larger radii, higher luminosities, and lower orbital angular momenta than contact binaries in the Milky Way, indicating that they are at more advanced evolutionary stages. This may be attributed to the higher metallicity in M31 compared to the Milky Way. △ Less

Submitted 6 October, 2025; v1 submitted 3 October, 2025; originally announced October 2025.

Comments: 16pages, 5 figures, 3 tables, accepted by ApJ

SN 2025coe: A Multiple-Peaked Calcium-Strong Transient from A White-Dwarf Progenitor

Authors: Chun Chen, Ning-Chen Sun, Qiang Xi, Samaporn Tinyanont, David Aguado, Ismael Pérez-Fournon, Frédérick Poidevin, Justyn R. Maund, Amit Kumar, Junjie Jin, Yiming Mao, Beichuan Wang, Yu Zhang, Zhen Guo, Wenxiong Li, César Rojas-Bravo, Rong-Feng Shen, Lingzhi Wang, Ziyang Wang, Guoying Zhao, Jie Zheng, Yinan Zhu, David López Fernández-Nespral, Alicia López-Oramas, Zexi Niu , et al. (3 additional authors not shown)

Abstract: SN 2025coe is a calcium-strong transient located at an extremely large projected offset $\sim$39.3 kpc from the center of its host, the nearby early-type galaxy NGC 3277 at a distance of $\sim$25.5 Mpc. In this paper, we present multi-band photometric and spectroscopic observations spanning $\sim$100 days post-discovery. Its multi-band light curves display {multiple} distinct peaks: (1) an initial… ▽ More SN 2025coe is a calcium-strong transient located at an extremely large projected offset $\sim$39.3 kpc from the center of its host, the nearby early-type galaxy NGC 3277 at a distance of $\sim$25.5 Mpc. In this paper, we present multi-band photometric and spectroscopic observations spanning $\sim$100 days post-discovery. Its multi-band light curves display {multiple} distinct peaks: (1) an initial peak at $t \approx 1.6$ days attributed to shock cooling emission, (2) a secondary peak of $M_{R, \, peak} \approx$ $-$15.8 mag at $t \approx 10.2$ days powered by radioactive decay, and (3) a {possible} late-time bump at $t \approx 42.8$ days likely caused by ejecta-circumstellar material/clump interaction. Spectral evolution of SN 2025coe reveals a fast transition to the nebular phase within 2 months, where it exhibits an exceptionally high [Ca II]/[O I] ratio larger than 6. Modeling of the bolometric light curve suggests an ejecta mass of $M_{\rm ej} = 0.29^{+0.14}_{-0.15} \, M_{\odot}$, a $^{56}$Ni mass of $M_{\rm ^{56}Ni} = 2.4^{+0.06}_{-0.05} \times 10^{-2} M_{\odot}$, and a progenitor envelope with mass $M_e = 1.4^{+6.9}_{-1.2} \times 10^{-3} \, M_{\odot}$ and radius $R_e = 13.5^{+64.1}_{-11.1} \, R_{\odot}$. The tidal disruption of a hybrid HeCO white dwarf (WD) by a low-mass CO WD provides a natural explanation for the low ejecta mass, the small fraction of $^{56}$Ni, and the presence of an extended, low-mass envelope. △ Less

Submitted 2 December, 2025; v1 submitted 30 September, 2025; originally announced October 2025.

Comments: 12 pages, 9 figures, accepted for publication in ApJ

Hidden massive eclipsing binaries in red supergiant systems: The hierarchical triple system KQ Puppis and other candidates

Authors: D. Jadlovský, L. Molnár, A. Ercolino, M. Bernini-Peron, A. Mérand, J. Krtička, L. Wang, R. Z. Ádám, D. Baade, G. González-Torà, T. Granzer, J. Janík, J. Kolář, K. Kravchenko, N. Langer, L. M. Oskinova, D. Pauli, V. Ramachandran, A. C. Rubio, A. A. C. Sander, K. G. Strassmeier, M. Weber, M. Wittkowski, R. Brahm, V. Schaffenroth , et al. (2 additional authors not shown)

Abstract: The majority of massive stars are part of binary systems that may interact during their evolution. This has important consequences for systems in which one star develops into a Red supergiant (RSG); however, not many RSGs are known binaries. We aim to better constrain the properties of some of the known RSGs in binaries. We first focus on the VV Cephei type RSG KQ Pup (RSG+B-type companion, orbi… ▽ More The majority of massive stars are part of binary systems that may interact during their evolution. This has important consequences for systems in which one star develops into a Red supergiant (RSG); however, not many RSGs are known binaries. We aim to better constrain the properties of some of the known RSGs in binaries. We first focus on the VV Cephei type RSG KQ Pup (RSG+B-type companion, orbital period of 26 yr), where we have enough data to constrain the system's properties. We use archival photometry and UV spectroscopy, along with newly taken optical spectra and interferometric data. For KQ Pup, as well as for all other Galactic RSGs, we also analyzed the available TESS data. Using TESS photometry, we discovered eclipses with a period of $17.2596 \: \rm d$, associated with the hot B companion, making it a Ba+Bb pair. Meanwhile, the detection of the hydrogen Br$γ$ line with VLTI-GRAVITY enabled us to track the orbital motion of the KQ Pup Ba+Bb pair and thus to determine the astrometric orbit. The dynamical masses agree with independent estimates from asteroseismology and evolutionary models. The results give a mass of $ \sim 9 \: \rm M_{\odot} $ for the RSG and $ \sim 14 \: \rm M_{\odot} $ for the sum of the hot components Ba+Bb. The observed properties of the system are compatible with a coeval hierarchical triple-star, where we constrain the minimum mass of KQ Pup Bb as $ \gtrsim 1.2 \: \rm M_{\odot} $. The variability of Balmer lines and the detection of Br$γ$ represent a strong signature of Wind Roche Lobe Overflow, with enhanced signatures of disk-accretion to the Ba+Bb pair during the periastron. Meanwhile, TESS light curves show that about $\sim 10 \%$ of known Galactic binary RSGs may be eclipsing hierarchical triple systems, which suggests that a large fraction of other binary RSGs could also be triples. △ Less

Submitted 30 September, 2025; v1 submitted 29 September, 2025; originally announced September 2025.

Comments: submitted to A&A, comments welcome

Interstellar Dust-Catalyzed Molecular Hydrogen Formation Enabled by Nuclear Quantum Effects

Authors: Xiaolong Yang, Lile Wang, Di Li, Shenzhen Xu

Abstract: Molecular hydrogen (H$_2$) plays a critical role in astrophysical processes from galaxy evolution to the formation of planets. While the dominant formation channel in the interstellar medium is considered as dust-catalyzed H$_2$ formation, this process could become inefficient at low temperatures suppressed by the Boltzmann factor. This work demonstrates that quantum tunneling can dominate the for… ▽ More Molecular hydrogen (H$_2$) plays a critical role in astrophysical processes from galaxy evolution to the formation of planets. While the dominant formation channel in the interstellar medium is considered as dust-catalyzed H$_2$ formation, this process could become inefficient at low temperatures suppressed by the Boltzmann factor. This work demonstrates that quantum tunneling can dominate the formation of H$_2$, resolving the long-standing problem of formation efficiency. Path integral Monte Carlo simulations reveals that the quantum tunneling of hydrogen atoms maintains stable reaction rates at temperatures below 50 K on both graphitic and silicate grain surfaces. Kinetic Monte Carlo calculations further indicate that the actual H$_2$ formation efficiency is governed not by atomic diffusion, but rather by the energy barriers associated with chemisorption, desorption, and the association of two hydrogen atoms. These findings establish a robust physical basis for dust-catalyzed H$_2$ formation, offer quantitative reaction rates for refining astrophysical models, and provide a framework for interpreting observations of interstellar molecular materials. △ Less

Submitted 13 November, 2025; v1 submitted 29 September, 2025; originally announced September 2025.

Comments: 43 pages, 17 figures, submitted to PhRevLett