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Observational Properties of $β$ Cephei Stars: 88 new samples discovered Based on TESS and Gaia Data
Authors:
Xiang-dong Shi,
Sheng-bang Qian,
Li-ying Zhu,
Lin-jia Li,
Er-gang Zhao,
David Mkrtichian,
Farkhodjon Khamrakulov,
Wen-xu Lin
Abstract:
We present a systematic investigation of $β$ Cephei (BCEP) stars by integrating photometric data from the Transiting Exoplanet Survey Satellite (TESS) with astrometric parameters from Gaia Data Release 3. Utilizing TESS's short-cadence (SC) and full-frame image (FFI) photometry, along with Gaia parallaxes and temperatures derived from the Extended Stellar Parametrizer for Hot Stars (ESP-HS) pipeli…
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We present a systematic investigation of $β$ Cephei (BCEP) stars by integrating photometric data from the Transiting Exoplanet Survey Satellite (TESS) with astrometric parameters from Gaia Data Release 3. Utilizing TESS's short-cadence (SC) and full-frame image (FFI) photometry, along with Gaia parallaxes and temperatures derived from the Extended Stellar Parametrizer for Hot Stars (ESP-HS) pipeline, we identify 88 new BCEP stars and candidates--85 from SC data and 3 from SPOC-processed FFI observations. These targets exhibit visual magnitudes ranging from 8.0 to 12.0 mag, parallaxes between 0.11 and 1.74 mas, effective temperatures of 18,000 to 30,000 K, and luminosities from 1,500--38,000 $L_\odot$, consistent with previously cataloged BCEP populations, thereby demonstrating the robustness of our classification criteria. Key findings include: (1) a significant detection disparity between SC and FFI datasets, with 30\% of SC targets exceeding 18,000 K compared to only 0.7\% in FFI, reflecting observational biases toward high-luminosity, hotter stars in SC data; (2) four samples near the red edge of the theoretical instability strip, exhibiting sparse pulsation modes that are important samples for testing pulsation models under low-mass, low-temperature conditions; and (3) spatial clustering within the Galactic disk ($|b| < 20^\circ$), with two high-latitude outliers likely representing runaway stars ejected from disk environments. Our analysis underscores the critical role of space-based photometry in detecting low-amplitude pulsators and the transformative potential of multi-survey integration in the era of time-domain astronomy. These results provide new samples to constrain stellar pulsation theories of massive stars and to study Galactic dynamics.
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Submitted 13 December, 2025;
originally announced December 2025.
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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…
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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.
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Submitted 12 December, 2025;
originally announced December 2025.
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Multiple outflows and delayed ejections revealed by early imaging of novae
Authors:
Elias Aydi,
John D. Monnier,
Antoine Mérand,
Gail H. Schaefer,
Laura Chomiuk,
Magdalena Otulakowska-Hypka,
Jhih-Ling Fan,
Kwan Lok Li,
Kirill V. Sokolovsky,
Ricardo Salinas,
Michael Tucker,
Benjamin Shappee,
Richard Rudy,
Kim L. Page,
N. Paul M. Kuin,
David A. H. Buckley,
Peter Craig,
Luca Izzo,
Justin Linford,
Brian D. Metzger,
Koji Mukai,
Marina Orio,
Ken J. Shen,
Jay Strader,
Jennifer L. Sokoloski
, et al. (17 additional authors not shown)
Abstract:
Novae are thermonuclear eruptions on accreting white dwarfs in interacting binaries. Although most of the accreted envelope is expelled, the mechanism -- impulsive ejection, multiple outflows or prolonged winds, or a common-envelope interaction -- remains uncertain. GeV $γ$-ray detections from $>20$ Galactic novae establish these eruptions as nearby laboratories for shock physics and particle acce…
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Novae are thermonuclear eruptions on accreting white dwarfs in interacting binaries. Although most of the accreted envelope is expelled, the mechanism -- impulsive ejection, multiple outflows or prolonged winds, or a common-envelope interaction -- remains uncertain. GeV $γ$-ray detections from $>20$ Galactic novae establish these eruptions as nearby laboratories for shock physics and particle acceleration, underscoring the need to determine how novae eject their envelopes. Here we report on near-infrared interferometry, supported with multiwavelength observations, of two $γ$-ray detected novae. The images of the very fast 2021 nova V1674~Her, taken just 2--3 days after discovery, reveal the presence of two perpendicular outflows. The interaction between these outflows likely drives the observed $γ$-ray emission. Conversely, the images of the very slow 2021 nova V1405~Cas suggest a delay in the ejection of the bulk of the accreted envelope of more than 50 days after the start of eruption, as the nova slowly rises to visible peak and during which the envelope engulfed the system in a common envelope phase. These unprecedented images offer direct observational evidence that the mechanisms driving mass ejection from the surfaces of accreting white dwarfs are not as simple as previously thought, revealing multiple outflows and delayed ejections.
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Submitted 4 December, 2025;
originally announced December 2025.
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Large Language Models for Limited Noisy Data: A Gravitational Wave Identification Study
Authors:
Yixuan Li,
Yuhao Lu,
Yang Liu,
Liang Li,
R. Ruffini,
Di Li,
Rong-Gen Cai,
Xiaoyan Zhu,
Wenbin Lin,
Yu Wang
Abstract:
This work investigates whether large language models (LLMs) offer advantages over traditional neural networks for astronomical data processing, in regimes with non-Gaussian, non-stationary noise and limited labeled samples. Gravitational wave observations provide an suitable test case, using only 90 LIGO events, finetuned LLMs achieve 97.4\% accuracy for identifying signals. Further experiments sh…
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This work investigates whether large language models (LLMs) offer advantages over traditional neural networks for astronomical data processing, in regimes with non-Gaussian, non-stationary noise and limited labeled samples. Gravitational wave observations provide an suitable test case, using only 90 LIGO events, finetuned LLMs achieve 97.4\% accuracy for identifying signals. Further experiments show that, in contrast to traditional networks that rely on large simulated datasets, additional simulated samples do not improve LLM performance, while scaling studies reveal predictable gains with increasing model size and dataset size. These results indicate that LLMs can extract discriminative structure directly from observational data and provide an efficient assessment for gravitational wave identification. The same strategy may extend to other astronomical domains with similar noise properties, such as radio or pulsar observations.
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Submitted 3 December, 2025;
originally announced December 2025.
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Constraining the Properties of GRB Accreting Magnetar with $R/I$ Evolutionary Effects Using \emph{Swift}/XRT Data
Authors:
Lin Lan,
He Gao,
Litao Zhao,
Shunke Ai,
Jie Lin,
Long Li,
Lang Xie,
Li-Ping Xin,
Jian-Yan Wei
Abstract:
A newly born millisecond magnetar has been proposed as one possible central engine of some long gamma-ray bursts (LGRBs) with X-ray plateau. In this work, we used a universal correlation between initial spin period ($P_0$) and surface magnetic field ($B_p$) of newborn magnetar based on an LGRB sample in \cite{Lan2025} to explore the propeller properties of accreting magnetar with $R/I$ evolutionar…
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A newly born millisecond magnetar has been proposed as one possible central engine of some long gamma-ray bursts (LGRBs) with X-ray plateau. In this work, we used a universal correlation between initial spin period ($P_0$) and surface magnetic field ($B_p$) of newborn magnetar based on an LGRB sample in \cite{Lan2025} to explore the propeller properties of accreting magnetar with $R/I$ evolutionary effects. We found that $B_p-P_0$ relation is approximately consistent with $B_p\propto P_{\rm eq}^{7/6}$. Here, $P_{\rm eq}$ is equilibrium spin period in magnetic propeller model. The $B_p-P_0$ relation indicates that $P_0$ may not be true initial spin period of newborn magnetar, but had reached an equilibrium spin period via fallback accretion in propeller model. The magnetar accretion rate in our LGRBs is in range of $\dot{M}\sim10^{-5}-10^{-2} M_{\odot} \rm s^{-1}$ by incorporating $R/I$ evolutionary effects, and using the transition relation between gravitational mass $M_g$ and baryonic mass $M_b$ in different equation of states. Such accretion rates ensure that the accreting magnetars in our sample survive until reaching the equilibrium spin period, and the accretion rate is one order of magnitude lower compared to the statistical results in \cite{Stratta2018} and \cite{Linweili2020}, which used constant $R/I/M_g$ scenario. We suggested that adopting a constant $R/I/M_g$ scenario for modeling propeller regime in accreting magnetar results in a higher mass accretion rate, which may impair our understanding of the physical nature and its surroundings of accreting magnetar, and low-metallicity progenitors can provide enough material to satisfy the accretion requirements of newborn accreting magnetar in LGRBs.
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Submitted 27 November, 2025;
originally announced November 2025.
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Search for planetary-mass ultra-compact binaries using data from the first part of the LIGO--Virgo--KAGRA fourth observing run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1743 additional authors not shown)
Abstract:
We present a search for gravitational waves from inspiraling, planetary-mass ultra-compact binaries using data from the first part of the fourth observing run of LIGO, Virgo and KAGRA. Finding no evidence of such systems, we determine the maximum distance reach for such objects and their merger rate densities, independently of how they could have formed. Then, we identify classes of primordial bla…
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We present a search for gravitational waves from inspiraling, planetary-mass ultra-compact binaries using data from the first part of the fourth observing run of LIGO, Virgo and KAGRA. Finding no evidence of such systems, we determine the maximum distance reach for such objects and their merger rate densities, independently of how they could have formed. Then, we identify classes of primordial black-hole mass distributions for which these rate limits can be translated into relevant constraints on the mass distribution of primordial black holes, assuming that they compose all of dark matter, in the mass range $[10^{-6},10^{-3}]M_\odot$. Our constraints are consistent with existing microlensing results in the planetary-mass range, and provide a complementary probe to sub-solar mass objects.
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Submitted 5 December, 2025; v1 submitted 24 November, 2025;
originally announced November 2025.
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A Catalog of Galactic Atomic Hydrogen Position-Position-Velocity Filaments
Authors:
M. E. Putman,
D. A. Kim,
S. E. Clark,
L. Li,
C. Holm-Hansen,
J. E. G. Peek
Abstract:
We present a catalog of 3D Galactic HI filaments over 1/3 of the sky using Galactic Arecibo L-band Feed Array HI (GALFA-HI) data. The 3D filaments are defined to be linear HI features that are continuous in position-position-velocity (PPV) and are found with fil3d, an algorithm that expands on the 2D FilFinder. The catalog contains 3333 HI filaments between +/- 50 km/s at a range of Galactic posit…
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We present a catalog of 3D Galactic HI filaments over 1/3 of the sky using Galactic Arecibo L-band Feed Array HI (GALFA-HI) data. The 3D filaments are defined to be linear HI features that are continuous in position-position-velocity (PPV) and are found with fil3d, an algorithm that expands on the 2D FilFinder. The catalog contains 3333 HI filaments between +/- 50 km/s at a range of Galactic positions. 1542 of the PPV filaments are identified as local at the distance of the wall of the Local Bubble, and 209 are likely at the disk-halo interface of our Galaxy. The catalog and properties of the PPV filaments are obtained after an unsharp mask (USM) is applied to the data. The widths of the filaments are consistently ~12' (0.34 pc at 100 pc), and constrained by the 4' resolution. The local filaments have median properties of N_HI = $6 \times 10^{18}$ cm$^{-2}$, M_HI = 0.17 M_sun, FWHM = 3.2 km/s, and length of 6.4 pc. The disk-halo population has similar column densities, but the median FWHM = 7.7 km/s, consistent with them being higher z-height, warmer structures. The L $\propto$ M$^{0.5}$ relationship found for the HI filaments and their bundling on the sky are consistent with a hierarchical structure, and is likely related to turbulence playing a role in their formation.
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Submitted 23 November, 2025;
originally announced November 2025.
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Modeling the Multi-Wavelength Afterglow of Short Gamma-Ray Bursts with a Plateau Phase
Authors:
Chen Deng,
Yong-Feng Huang,
Abdusattar Kurban,
Jin-Jun Geng,
Fan Xu,
Xiao-Fei Dong,
Hao-Xuan Gao,
En-Wei Liang,
Liang Li
Abstract:
Short gamma-ray bursts (GRBs) exhibiting a plateau phase provide valuable insights into the post-merger activity of their central engines. Although the physical origin of the plateau remains uncertain, the magnetar energy injection model offers a compelling explanation that reproduces the observed temporal and luminosity features. However, previous studies relying solely on X-ray data have suffere…
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Short gamma-ray bursts (GRBs) exhibiting a plateau phase provide valuable insights into the post-merger activity of their central engines. Although the physical origin of the plateau remains uncertain, the magnetar energy injection model offers a compelling explanation that reproduces the observed temporal and luminosity features. However, previous studies relying solely on X-ray data have suffered from strong parameter degeneracies when constraining the magnetar parameters. Here we perform broadband afterglow modeling on seven short GRBs with plateau features by combining X-ray, optical, and radio observations within the framework of the magnetar energy injection model. Key model parameters are derived by using the Markov Chain Monte Carlo method. It is found that the energy injection substantially modifies the afterglow dynamics in most events. Compared with X-ray--only analyses, our broadband modeling yields systematically a lower magnetic field strength and a shorter spin period for the central magnetar, corresponding to a higher injection luminosity. The study clearly shows that incorporating multi-wavelength data effectively alleviates the degeneracy between the magnetar parameters and X-ray radiative efficiency. In addition, the distribution of our short GRBs differs markedly from long GRBs when they are plotted on the initial Lorentz factor versus gamma-ray energy plane. This offset, consistent with the observed harder spectrum of short GRBs, may serve as a useful diagnostic for investigating the progenitor as larger samples are available.
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Submitted 14 November, 2025;
originally announced November 2025.
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A Census of Pulsars in Possible Association with Galactic Open Clusters
Authors:
Lu Zhou,
Zhi-Qiang You,
Lu Li,
Xiao-Jin Liu,
Xing-Jiang Zhu,
Zong-Hong Zhu
Abstract:
Among the $\sim 4000$ known pulsars in our Galaxy, $\lesssim 10\%$ are found in globular clusters, but none has been confirmed in any open clusters yet, although they outnumber globular clusters by about 20 times. In this work, we make use of the Gaia DR3 catalog of Galactic open clusters and conduct a pulsar census, in order to identify pulsars that are either 1) current members of open clusters,…
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Among the $\sim 4000$ known pulsars in our Galaxy, $\lesssim 10\%$ are found in globular clusters, but none has been confirmed in any open clusters yet, although they outnumber globular clusters by about 20 times. In this work, we make use of the Gaia DR3 catalog of Galactic open clusters and conduct a pulsar census, in order to identify pulsars that are either 1) current members of open clusters, or 2) escaped from open clusters to the field. Among 164 pulsars with independent distance measurements and 3530 open clusters, we find that 4 pulsars are likely residing in open clusters. In particular, we find compelling evidence that the binary pulsar J1302$-$6350 (B1259$-$63) is a member of the open cluster UBC~525; based on Gaia data, we update its distance to be $2.26\pm 0.07$~kpc and measure the mass of its companion Be star LS 2883 to be $16.8 M_\odot$. For 145 pulsars with both distance and proper motion measurements and 2967 open clusters with full kinematic parameters, we trace the past trajectories of both pulsars and open clusters in the Galactic gravitational potential, and find pulsars that were within 3 times the radius of a cluster. This results in 19 pulsars that were likely born in open clusters. We discuss implications for the formation history of PSR J1302$-$6350 and highlight the scientific potential of searching for pulsars in open clusters.
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Submitted 10 November, 2025;
originally announced November 2025.
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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…
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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.
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Submitted 6 November, 2025;
originally announced November 2025.
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Direct multi-model dark-matter search with gravitational-wave interferometers using data from the first part of the fourth LIGO-Virgo-KAGRA observing run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1745 additional authors not shown)
Abstract:
Gravitational-wave detectors can probe the existence of dark matter with exquisite sensitivity. Here, we perform a search for three kinds of dark matter -- dilatons (spin-0), dark photons (spin-1) and tensor bosons (spin-2) -- using three independent methods on the first part of the most recent data from the fourth observing run of LIGO--Virgo--KAGRA. Each form of dark matter could have interacted…
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Gravitational-wave detectors can probe the existence of dark matter with exquisite sensitivity. Here, we perform a search for three kinds of dark matter -- dilatons (spin-0), dark photons (spin-1) and tensor bosons (spin-2) -- using three independent methods on the first part of the most recent data from the fourth observing run of LIGO--Virgo--KAGRA. Each form of dark matter could have interacted with different standard-model particles in the instruments, causing unique differential strains on the interferometers. While we do not find any evidence for a signal, we place the most stringent upper limits to-date on each of these models. For scalars with masses between $[4\times 10^{-14},1.5\times 10^{-13}]$ eV that couple to photons or electrons, our constraints improve upon those from the third observing run by one order of magnitude, with the tightest limit of $\sim 10^{-20}\,\text{GeV}^{-1}$ at a mass of $\sim2\times 10^{-13}\text{ eV}$. For vectors with masses between $[7\times 10^{-13},8.47\times 10^{-12}]$ eV that couple to baryons, our constraints supersede those from MICROSCOPE and Eöt-Wash by one to two orders of magnitude, reaching a minimum of $\sim 5\times 10^{-24}$ at a mass of $\sim 10^{-12}$ eV. For tensors with masses of $[4\times 10^{-14},8.47\times 10^{-12}]$ eV (the full mass range analyzed) that couple via a Yukawa interaction, our constraints surpass those from fifth-force experiments by four to five orders of magnitude, achieving a limit as low as $\sim 8\times 10^{-9}$ at $\sim2\times 10^{-13}$ eV. Our results show that gravitational-wave interferometers have become frontiers for new physics and laboratories for direct multi-model dark-matter detection.
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Submitted 11 December, 2025; v1 submitted 30 October, 2025;
originally announced October 2025.
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GW241011 and GW241110: Exploring Binary Formation and Fundamental Physics with Asymmetric, High-Spin Black Hole Coalescence
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1761 additional authors not shown)
Abstract:
We report the observation of gravitational waves from two binary black hole coalescences during the fourth observing run of the LIGO--Virgo--KAGRA detector network, GW241011 and GW241110. The sources of these two signals are characterized by rapid and precisely measured primary spins, non-negligible spin--orbit misalignment, and unequal mass ratios between their constituent black holes. These prop…
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We report the observation of gravitational waves from two binary black hole coalescences during the fourth observing run of the LIGO--Virgo--KAGRA detector network, GW241011 and GW241110. The sources of these two signals are characterized by rapid and precisely measured primary spins, non-negligible spin--orbit misalignment, and unequal mass ratios between their constituent black holes. These properties are characteristic of binaries in which the more massive object was itself formed from a previous binary black hole merger, and suggest that the sources of GW241011 and GW241110 may have formed in dense stellar environments in which repeated mergers can take place. As the third loudest gravitational-wave event published to date, with a median network signal-to-noise ratio of $36.0$, GW241011 furthermore yields stringent constraints on the Kerr nature of black holes, the multipolar structure of gravitational-wave generation, and the existence of ultralight bosons within the mass range $10^{-13}$--$10^{-12}$ eV.
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Submitted 30 October, 2025;
originally announced October 2025.
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Cosmological and High Energy Physics implications from gravitational-wave background searches in LIGO-Virgo-KAGRA's O1-O4a runs
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1747 additional authors not shown)
Abstract:
We search for gravitational-wave background signals produced by various early Universe processes in the Advanced LIGO O4a dataset, combined with the data from the earlier O1, O2, and O3 (LIGO-Virgo) runs. The absence of detectable signals enables powerful constraints on fundamental physics. We derive gravitational-wave background energy density upper limits from the O1-O4a data to constrain parame…
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We search for gravitational-wave background signals produced by various early Universe processes in the Advanced LIGO O4a dataset, combined with the data from the earlier O1, O2, and O3 (LIGO-Virgo) runs. The absence of detectable signals enables powerful constraints on fundamental physics. We derive gravitational-wave background energy density upper limits from the O1-O4a data to constrain parameters associated with various possible processes in the early Universe: first-order phase transitions, cosmic strings, domain walls, stiff equation of state, axion inflation, second-order scalar perturbations, primordial black hole binaries, and parity violation. In our analyses, the presence of an astrophysical background produced by compact (black hole and neutron star) binary coalescences throughout the Universe is also considered. We address the implications for various cosmological and high energy physics models based on the obtained parameter constraints. We conclude that LIGO-Virgo data already yield significant constraints on numerous early Universe scenarios.
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Submitted 7 November, 2025; v1 submitted 30 October, 2025;
originally announced October 2025.
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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…
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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.
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Submitted 29 October, 2025;
originally announced October 2025.
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Validating Open Cluster Candidates with Photometric Bayesian Evidence
Authors:
Lu Li,
Zhaozhou Li,
Zhengyi Shao
Abstract:
The thousands of open cluster (OC) candidates identified by the Gaia mission are significantly contaminated by false positives from field star fluctuations, posing a major validation challenge. Based on the Mixture Model for OCs (MiMO), we present a Bayesian framework for validating OC candidates in the color--magnitude diagram. The method compares the Bayesian evidence of two competing models: a…
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The thousands of open cluster (OC) candidates identified by the Gaia mission are significantly contaminated by false positives from field star fluctuations, posing a major validation challenge. Based on the Mixture Model for OCs (MiMO), we present a Bayesian framework for validating OC candidates in the color--magnitude diagram. The method compares the Bayesian evidence of two competing models: a single stellar population with field contamination versus a pure field population. Their ratio, the Bayes factor (BF), quantifies the statistical support for cluster existence. Tests on confirmed clusters and random fields show that a threshold of BF > 100 effectively distinguishes genuine clusters from chance field overdensities. This approach provides a robust, quantitative tool for OC validation and catalog refinement. The framework is extendable to multi-dimensional validation incorporating kinematics and is broadly applicable to other resolved stellar systems, including candidate moving groups, stellar streams, and dwarf satellites.
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Submitted 27 October, 2025;
originally announced October 2025.
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The MiMO Catalog: Physical Parameters and Stellar Mass Functions of 1,232 Open Clusters from Gaia DR3
Authors:
Lu Li,
Zhengyi Shao,
Zhaozhou Li,
Xiaoting Fu
Abstract:
We present a homogeneous catalog of 1,232 open clusters with precisely determined ages, metallicities, distances, extinctions, and stellar mass function (MF) slopes, derived from Gaia DR3 data. The parameters are inferred using the Mixture Model for Open clusters (MiMO), a novel Bayesian framework for modeling clusters in the color-magnitude diagram. By explicitly accounting for field-star contami…
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We present a homogeneous catalog of 1,232 open clusters with precisely determined ages, metallicities, distances, extinctions, and stellar mass function (MF) slopes, derived from Gaia DR3 data. The parameters are inferred using the Mixture Model for Open clusters (MiMO), a novel Bayesian framework for modeling clusters in the color-magnitude diagram. By explicitly accounting for field-star contamination as a model component, MiMO removes the conventional need for stringent membership preselection, allowing for a more complete inclusion of member stars and thereby enhancing both precision and robustness. Our results broadly agree with existing catalogs but offer improved precision. For each cluster, we provide the best-fit age, metallicity, distance, extinction, and MF slope, along with their full likelihood chains and photometric membership probabilities for individual stars. We further identify an ``MF Prime'' subsample of 163 clusters with high-quality data, for which the MF estimates are considered most reliable. The catalog and an open-source implementation of MiMO are made publicly available to the community.
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Submitted 27 October, 2025;
originally announced October 2025.
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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…
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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.
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Submitted 27 October, 2025;
originally announced October 2025.
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SN2017ckj: A linearly declining Type IIb supernova with a relatively massive hydrogen envelope
Authors:
L. -H. Li,
S. Benetti,
Y. -Z. Cai,
B. Wang,
A. Pastorello,
N. Elias-Rosa,
A. Reguitti,
L. Borsato,
E. Cappellaro,
A. Fiore,
M. Fraser,
M. Gromadzki,
J. Harmanen,
J. Isern,
T. Kangas,
E. Kankare,
P. Lundqvist,
S. Mattila,
P. Ochner,
Z. -H. Peng,
T. M. Reynolds,
I. Salmaso,
S. Srivastav,
M. D. Stritzinger,
L. Tomasella
, et al. (4 additional authors not shown)
Abstract:
We present optical observations of the Type IIb supernova (SN) 2017ckj, covering approximately 180 days after the explosion. Its early-time multi-band light curves display no clear evidence of a shock-cooling tail, resembling the behavior of SN2008ax. The $V$-band light curve exhibits a short rise time of about 5 days and reaches an absolute fitted peak magnitude of…
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We present optical observations of the Type IIb supernova (SN) 2017ckj, covering approximately 180 days after the explosion. Its early-time multi-band light curves display no clear evidence of a shock-cooling tail, resembling the behavior of SN2008ax. The $V$-band light curve exhibits a short rise time of about 5 days and reaches an absolute fitted peak magnitude of $M_{\rm V}=-18.49\pm0.18\mathrm{mag}$. The late-time multi-band light curves reveal a linear decline. We modelled the bolometric light curve of SN2017ckj to constrain the progenitor and the explosion parameters. We estimated a total mass of $\rm ^{56}Ni$ synthesized by SN2017ckj of $M_{\rm Ni} = 0.21^{+0.05}_{-0.03}\ M_\odot$, with a massive H-rich envelope of $M_{\rm env} = 0.4^{+0.1}_{-0.1}\ M_\odot$. Both the $\rm ^{56}Ni$ mass and the envelope mass of SN2017ckj are higher than those of typical SNe IIb, in agreement with its peculiar light curve evolution. The early-time spectra of SN2017ckj are dominated by a blue continuum, accompanied by narrow $\rm H_α$ and \Heii emission lines. The earliest spectrum exhibits flash ionization features, from which we estimated a progenitor mass-loss rate of $\sim 3\times10^{-4}M_\odot \mathrm{yr}^{-1}$. At later epochs, the spectra develop broad P-Cygni profiles and become increasingly similar to those of SNe IIb, especially SN2018gk. The late-time spectrum at around 139 days does not show a distinct decline in the strength of $\rm H_α$ emission profile, also indicating a relatively massive envelope of its progenitor. Aside from the $\rm H_α$ feature, the nebular spectrum exhibits prominent emission lines of \Oi, \Caii, [\Caii], and \Mgi], which are consistent with the prototypical SN1993J.
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Submitted 16 December, 2025; v1 submitted 27 October, 2025;
originally announced October 2025.
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The Velocity Map Asymmetry of Ionized Gas in MaNGA II. Correlation between Velocity Map Morphology, Star Formation, and Metallicity in Regular Disk Galaxies
Authors:
Shuai Feng,
Shiyin Shen,
Yanmei Chen,
Y. Sophia Dai,
Jun Yin,
Wenyuan Cui,
Mengting Ju,
Linlin Li
Abstract:
The morphology of ionized gas velocity maps provides a direct probe of the internal gas kinematics of galaxies. Using integral field spectroscopy from SDSS-IV MaNGA, we analyze a sample of 528 low-inclination, regular disk galaxies to investigate the correlations between velocity map morphology, star formation rate, and gas-phase metallicity. We quantify velocity map morphology using harmonic expa…
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The morphology of ionized gas velocity maps provides a direct probe of the internal gas kinematics of galaxies. Using integral field spectroscopy from SDSS-IV MaNGA, we analyze a sample of 528 low-inclination, regular disk galaxies to investigate the correlations between velocity map morphology, star formation rate, and gas-phase metallicity. We quantify velocity map morphology using harmonic expansion and adopt two complementary diagnostics: the global kinematic asymmetry, which traces non-axisymmetric perturbations, and the first-order term ratio, which captures axisymmetric radial motions. We find that galaxies with higher kinematic asymmetry are more likely to deviate from the scaling relations, typically lying either above or below the star formation main sequence and systematically below the mass-metallicity relation. In contrast, the first-order term ratio shows only a correlation with gas-phase metallicity in the low-mass range and no significant dependence on star formation rate. Moreover, galaxies below the mass-metallicity relation generally exhibit higher HI gas fractions. These results suggest that external gas accretion is the primary driver of the observed phenomena: inflowing metal-poor gas increases velocity map asymmetry in disk galaxies, dilutes the metallicity, and triggers enhanced star formation. Feedback-driven outflows, bar- and spiral-driven inflows, and galaxy mergers may also contribute, but likely play a secondary role.
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Submitted 27 October, 2025;
originally announced October 2025.
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Sympathetic Eruption of Two Filaments and Associated Solar Coronal Jet
Authors:
Jiayan Yang,
Leping Li,
Huadong Chen,
Yi Bi,
Bo Yang,
Junchao Hong,
Yan Dong
Abstract:
Combining the high-quality observations from the {\it Solar Dynamics Observatory} (SDO), the Global Oscillation Network Group (GONG), and the Chinese H$α$ Solar Explorer (CHASE), we report a solar coronal jet triggered by the sympathetic eruption of two filaments on 2024 January 11. Initially, the western segment of an active region filament erupted. The erupting plasma propagated eastward, approx…
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Combining the high-quality observations from the {\it Solar Dynamics Observatory} (SDO), the Global Oscillation Network Group (GONG), and the Chinese H$α$ Solar Explorer (CHASE), we report a solar coronal jet triggered by the sympathetic eruption of two filaments on 2024 January 11. Initially, the western segment of an active region filament erupted. The erupting plasma propagated eastward, approximately along the filament's axis. This eruption perturbed the magnetic field of a second filament situated near its eastern footpoint, the second filament then erupted sympathetically about one hour later. The eruption of the second filament is a failed one, with the majority of the filament material falling back after the initial lifting. Although no GOES flare accompanied these filament eruptions, distinct brightenings were observed following each eruption. The second eruption produced a large coronal jet, which propagated along a bent trajectory with an apparent deflection angle of approximately 90 degrees. No clear evidence of magnetic reconnection was detected at the deflection site, thus we suspect that the jet may have traveled along an S-shaped trans-equatorial loop and shown a curved trajectory. This event exhibits multiple phenomena: partial filament eruption, failed filament eruption, sympathetic filament eruption, jet initiation by filament eruption, and apparently deflected jet propagation. Collectively, these observations highlight the complexity and diversity of solar activity.
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Submitted 21 October, 2025;
originally announced October 2025.
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Directional Search for Persistent Gravitational Waves: Results from the First Part of LIGO-Virgo-KAGRA's Fourth Observing Run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1743 additional authors not shown)
Abstract:
The angular distribution of gravitational-wave power from persistent sources may exhibit anisotropies arising from the large-scale structure of the Universe. This motivates directional searches for astrophysical and cosmological gravitational-wave backgrounds, as well as continuous-wave emitters. We present results of such a search using data from the first observing run through the first portion…
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The angular distribution of gravitational-wave power from persistent sources may exhibit anisotropies arising from the large-scale structure of the Universe. This motivates directional searches for astrophysical and cosmological gravitational-wave backgrounds, as well as continuous-wave emitters. We present results of such a search using data from the first observing run through the first portion of the fourth observing run of the LIGO-Virgo-KAGRA Collaborations. We apply gravitational-wave radiometer techniques to generate skymaps and search for both narrowband and broadband persistent gravitational-wave sources. Additionally, we use spherical harmonic decomposition to probe spatially extended sources. No evidence of persistent gravitational-wave signals is found, and we set the most stringent constraints to date on such emissions. For narrowband point sources, our sensitivity estimate to effective strain amplitude lies in the range $(0.03 - 8.4) \times 10^{-24}$ across all sky and frequency range $(20 - 160)$ Hz. For targeted sources -- Scorpius X-1, SN 1987A, the Galactic Center, Terzan 5, and NGC 6397 -- we constrain the strain amplitude with best limits ranging from $\sim 1.1 \times 10^{-25}$ to $6.5 \times 10^{-24}$. For persistent broadband sources, we constrain the gravitational-wave flux $F_{α, \hat{n}}^{95\%, \mathrm{UL}}(25\, \mathrm{Hz}) < (0.008 - 5.5) \times 10^{-8}\, \mathrm{erg\, cm^{-2}\, s^{-1}\, Hz^{-1}}$, depending on the sky direction $\hat{n}$ and spectral index $α=0,\,2/3,\,3$. Finally, for extended sources, we place upper limits on the strain angular power spectrum $C_\ell^{1/2} < (0.63 - 17) \times 10^{-10} \,\mathrm{sr}^{-1}$.
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Submitted 20 October, 2025;
originally announced October 2025.
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Generalized Distributions of Host Dispersion Measures in the Fast Radio Burst Cosmology
Authors:
Jing-Yi Jia,
Da-Chun Qiang,
Lin-Yu Li,
Hao Wei
Abstract:
As is well known, Hubble tension is one of the most serious challenges in cosmology to date. So, it is of interest to measure the Hubble constant by using some new probes independent of cosmic microwave background (CMB) and type Ia supernovae (SNIa). One of the promising probes is the fast radio bursts (FRBs), which could be useful in cosmology. In the literature, the methodology proposed by Macqu…
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As is well known, Hubble tension is one of the most serious challenges in cosmology to date. So, it is of interest to measure the Hubble constant by using some new probes independent of cosmic microwave background (CMB) and type Ia supernovae (SNIa). One of the promising probes is the fast radio bursts (FRBs), which could be useful in cosmology. In the literature, the methodology proposed by Macquart {\it et al.} has been widely used, in which both $\rm DM_{IGM}$ and $\rm DM_{host}$ are described by probability distribution functions. Recently, it was found that in order to obtain a Hubble constant $H_0$ consistent with the ones of Planck 2018 and SH0ES by using the current ${\cal O}(100)$ localized FRBs, an unusually large $f_{\rm IGM}$ fairly close to its upper bound $1$ is required, if the narrow prior bounded by $0.5$ for the parameter $F$ in the distribution of $\rm DM_{IGM}$ was used. In fact, a small $F$ is the key to make $H_0$ larger. In the present work, we consider a loose prior for the parameter $F$, and find an unusually low $H_0$ by using 125 localized FRBs. We show that the model with loose $F$ prior is strongly preferred over the one with narrow $F$ prior in all terms of the Bayesian evidence and the information criteria AIC, BIC. So, the great Hubble tension between FRBs, Planck 2018 and SH0ES should be taken seriously. Instead of modifying $σ_Δ=Fz^{-0.5}$ in the distribution of $\rm DM_{IGM}$, here we try to find a new way out by generalizing the distribution of $\rm DM_{host}$ with varying location and scale parameters $\ell$ and $e^μ$, respectively. We find that $H_0$ can be consistent with the ones of Planck 2018 and SH0ES in all cases. All the Bayesian evidence and the information criteria AIC, BIC for the generalized distributions of $\rm DM_{host}$ are overwhelmingly strong.
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Submitted 10 October, 2025;
originally announced October 2025.
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Explanation of the Mass Distribution of Binary Black Hole Mergers
Authors:
Lei Li,
Guoliang Lv,
Chunhua Zhu,
Sufen Guo,
Hongwei Ge,
Weimin Gu,
Zhuowen Li,
Xiaolong He
Abstract:
Gravitational wave detectors are observing an increasing number of binary black hole (BBH) mergers, revealing a bimodal mass distribution of BBHs, which hints at diverse formation histories for these systems. Using the rapid binary population synthesis code MOBSE, we simulate a series of population synthesis models that include chemically homogeneous evolution (CHE). By considering metallicity-spe…
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Gravitational wave detectors are observing an increasing number of binary black hole (BBH) mergers, revealing a bimodal mass distribution of BBHs, which hints at diverse formation histories for these systems. Using the rapid binary population synthesis code MOBSE, we simulate a series of population synthesis models that include chemically homogeneous evolution (CHE). By considering metallicity-specific star formation and selection effects, we compare the intrinsic merger rates and detection rates of each model with observations. We find that the observed peaks in the mass distribution of merging BBHs at the low-mass end (10\msun) and the high-mass end (35\msun) are contributed by the common envelope channel or stable mass transfer channel (depending on the stability criteria for mass transfer) and the CHE channel, respectively, in our model. The merger rates and detection rates predicted by our model exhibit significant sensitivity to the choice of physical parameters. Different models predict merger rates ranging from 15.4 to $96.7\,\rm{Gpc^{-3}yr^{-1}}$ at redshift $z$ = 0.2, and detection rates ranging from 22.2 to 148.3$\mathrm{yr^{-1}}$ under the assumption of a detectable redshift range of $z \le$ 1.0.
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Submitted 9 October, 2025;
originally announced October 2025.
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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…
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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.
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Submitted 25 October, 2025; v1 submitted 8 October, 2025;
originally announced October 2025.
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The influence of rotation and metallicity on the explodability of massive stars
Authors:
Renyu Luo,
Chunhua Zhu,
Guoliang Lü,
Helei Liu,
Sufen Guo,
Lei Li,
Zhuowen Li
Abstract:
During the late stages of massive stellar evolution, failed supernovae (FSN) may form through core-collapse processes. The traditional evaluation criterion $ξ_{2.5}$ $=$ 0.45, primarily established using non-rotating progenitor models, suffers from significant inaccuracies when applied to rotating pre-supernova systems. The effects of metallicity and rotation on the explodability landscapes of mas…
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During the late stages of massive stellar evolution, failed supernovae (FSN) may form through core-collapse processes. The traditional evaluation criterion $ξ_{2.5}$ $=$ 0.45, primarily established using non-rotating progenitor models, suffers from significant inaccuracies when applied to rotating pre-supernova systems. The effects of metallicity and rotation on the explodability landscapes of massive stars lack robust quantification. We aim to investigate how rotation and metallicity influence the explodability of massive stars. We investigate how rotation and metallicity affect stellar explodability using MESA simulations with initial rotational velocities of $0$, $300$, and $600~\mathrm{km,s^{-1}}$ at three metallicities ($Z_{\odot}$, $1/10,Z_{\odot}$, $1/50,Z_{\odot}$). Core-collapse phases are simulated with GR1D to determine critical heating efficiencies. Our results yield revised $ξ_{2.5}$ criteria: 0.45 for non-rotating models; 0.48 for $300~\mathrm{km,s^{-1}}$; 0.47 for $600~\mathrm{km,s^{-1}}$ at solar metallicity; and 0.59 for low-metallicity models. Chemically homogeneous evolution in rapidly rotating low-metallicity stars significantly raises the compactness limit for successful explosions and narrows the zero-age main sequence mass range for failed supernovae. Rotation substantially affects the explodability of low-metallicity massive stars, underscoring the importance of incorporating rotational effects in models of core-collapse supernova progenitors.
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Submitted 7 October, 2025;
originally announced October 2025.
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Investigation of hadronic cross sections of cosmic ray carbon and oxygen on BGO from 200 GeV to 10 TeV energy at the DAMPE experiment
Authors:
F. Alemanno,
Q. An,
P. Azzarello,
F. C. T. Barbato,
P. Bernardini,
X. J. Bi,
H. Boutin,
I. Cagnoli,
M. S. Cai,
E. Casilli,
E. Catanzani,
J. Chang,
D. Y. Chen,
J. L. Chen,
Z. F. Chen,
Z. X. Chen,
P. Coppin,
M. Y. Cui,
T. S. Cui,
Y. X. Cui,
I. De Mitri,
F. de Palma,
A. Di Giovanni,
T. K. Dong,
Z. X. Dong
, et al. (122 additional authors not shown)
Abstract:
The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, f…
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The Dark Matter Particle Explorer (DAMPE) has made significant progress in measuring the fluxes of cosmic rays. These new measurements are pivotal in advancing our understanding of the origins and propagation mechanisms of cosmic rays. The bismuth germanium oxide (BGO) calorimeter plays a crucial role in these measurements, particularly in the precise determination of cosmic ray fluxes. However, for a calorimetric experiment like DAMPE, uncertainties in hadronic models persist as a major barrier in achieving more accurate measurements of fluxes of cosmic ray nuclei. This study centers on the measurement of the inelastic hadronic cross sections of carbon and oxygen nuclei interacting with BGO crystals target over an extensive energy range, spanning from 200 GeV to 10 TeV. For carbon nuclei interacting with the BGO target, the measurements of the cross sections have achieved a total relative uncertainty of less than 10% below 8 TeV for carbon, and below 3 TeV for oxygen. For oxygen nuclei, the same level of precision was attained below 3 TeV. Additionally, we compare the experimental results with Geant4 and FLUKA simulations to validate the accuracy and consistency of these simulation tools. Through comprehensive analysis of the inelastic hadronic interaction cross sections, this research provides validation for the hadronic interaction models used in DAMPE's cosmic-ray flux measurements.
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Submitted 21 September, 2025;
originally announced September 2025.
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Revealing Event Rate of Repeating Fast Radio Bursts
Authors:
Q. Pan,
X. Y. Du,
Z. B. Zhang,
Y. F. Huang,
L. B. Li,
G. A. Li
Abstract:
How the event rate of fast radio bursts (FRBs) evolves with redshift is a hot topic to explore their cosmological origin and the circum-burst environment. Particularly, it is urgent to know what the difference of event rates between repeating and non-repeating FRBs is. For the first time, we calculate the event rates of repeating FRBs detected by diverse telescopes at frequencies higher/lower than…
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How the event rate of fast radio bursts (FRBs) evolves with redshift is a hot topic to explore their cosmological origin and the circum-burst environment. Particularly, it is urgent to know what the difference of event rates between repeating and non-repeating FRBs is. For the first time, we calculate the event rates of repeating FRBs detected by diverse telescopes at frequencies higher/lower than 1 GHz in this work. Luminosity and redshift are found to be positively correlated with a power law form for both high- and low-frequency FRBs, showing an obvious evolution of luminosity with redshift. Furthermore, we compare the differential luminosity and local event rate distributions of high- and low-luminosity FRBs at different frequencies. It is found that the event rates of these sub-samples of repeating FRBs similarly exceed the star formation rate at lower redshift than 1. Interestingly, we confirm with bootstrap method that the event rates of low-frequency FRBs exhibit different evolution patterns and are higher than that of high-frequency ones.
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Submitted 15 September, 2025;
originally announced September 2025.
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Cosmic $τ$ensions Indirectly Correlate with Reionization Optical Depth
Authors:
Itamar J. Allali,
Lingfeng Li,
Praniti Singh,
JiJi Fan
Abstract:
The reionization optical depth $τ_{\rm reio}$ has interesting connections to existing cosmological anomalies. As first studied in the context of the Hubble tension in our previous paper, a larger $τ_{\rm reio}$, which could be achieved by removing the Planck low-$\ell$ polarization data, could boost $H_0$ slightly, resulting in a mild reduction of the tension between the early- and late-universe d…
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The reionization optical depth $τ_{\rm reio}$ has interesting connections to existing cosmological anomalies. As first studied in the context of the Hubble tension in our previous paper, a larger $τ_{\rm reio}$, which could be achieved by removing the Planck low-$\ell$ polarization data, could boost $H_0$ slightly, resulting in a mild reduction of the tension between the early- and late-universe determinations of $H_0$. It has been shown later that a larger $τ_{\rm reio}$ could also relieve other anomalies including: the tension between BAO and CMB data, the neutrino mass tension, and the latest DESI plus supernovae data's tension with the standard cosmological constant scenario. In this paper, we systematically analyze the correlations between $τ_{\rm reio}$ and relevant cosmological parameters in the existing cosmic observation anomalies. In addition to Pearson correlation coefficients extracted directly from the covariance matrix, we also study partial correlation coefficients which measure intrinsic relationships between pairs of parameters removing the influence of other parameters. We show that $τ_{\rm reio}$ has weak intrinsic correlations with the parameters responsible for the tensions and anomalies discussed. The large direct Pearson correlations that allow larger $τ_{\rm reio}$ inferences to alleviate the cosmological tensions each arise from complicated networks through multiple parameters. As a result, the relationships between $τ_{\rm reio}$ and each anomaly are not independent of each other. We also employ our method of computing correlations to clarify the impact of large scale polarization data, and comment also on the effects of CMB observations from ACT and SPT.
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Submitted 11 September, 2025;
originally announced September 2025.
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GW250114: testing Hawking's area law and the Kerr nature of black holes
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1763 additional authors not shown)
Abstract:
The gravitational-wave signal GW250114 was observed by the two LIGO detectors with a network matched-filter signal-to-noise ratio of 80. The signal was emitted by the coalescence of two black holes with near-equal masses $m_1 = 33.6^{+1.2}_{-0.8}\,M_\odot$ and $m_2 = 32.2^{+0.8}_{-1.3}\,M_\odot$, and small spins $χ_{1,2} \leq 0.26$ (90% credibility) and negligible eccentricity $e \leq 0.03$. Post-…
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The gravitational-wave signal GW250114 was observed by the two LIGO detectors with a network matched-filter signal-to-noise ratio of 80. The signal was emitted by the coalescence of two black holes with near-equal masses $m_1 = 33.6^{+1.2}_{-0.8}\,M_\odot$ and $m_2 = 32.2^{+0.8}_{-1.3}\,M_\odot$, and small spins $χ_{1,2} \leq 0.26$ (90% credibility) and negligible eccentricity $e \leq 0.03$. Post-merger data excluding the peak region are consistent with the dominant quadrupolar $(\ell = |m| = 2)$ mode of a Kerr black hole and its first overtone. We constrain the modes' frequencies to $\pm 30\%$ of the Kerr spectrum, providing a test of the remnant's Kerr nature. We also examine Hawking's area law, also known as the second law of black hole mechanics, which states that the total area of the black hole event horizons cannot decrease with time. A range of analyses that exclude up to 5 of the strongest merger cycles confirm that the remnant area is larger than the sum of the initial areas to high credibility.
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Submitted 9 September, 2025;
originally announced September 2025.
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Directed searches for gravitational waves from ultralight vector boson clouds around merger remnant and galactic black holes during the first part of the fourth LIGO-Virgo-KAGRA observing run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1747 additional authors not shown)
Abstract:
We present the first directed searches for long-transient and continuous gravitational waves from ultralight vector boson clouds around known black holes (BHs). We use LIGO data from the first part of the fourth LIGO-Virgo-KAGRA observing run. The searches target two distinct types of BHs and use two new semicoherent methods: hidden Markov model (HMM) tracking for the remnant BHs of the mergers GW…
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We present the first directed searches for long-transient and continuous gravitational waves from ultralight vector boson clouds around known black holes (BHs). We use LIGO data from the first part of the fourth LIGO-Virgo-KAGRA observing run. The searches target two distinct types of BHs and use two new semicoherent methods: hidden Markov model (HMM) tracking for the remnant BHs of the mergers GW230814_230901 and GW231123_135430 (referred to as GW230814 and GW231123 in this study), and a dedicated method using the Band Sampled Data (BSD) framework for the galactic BH in the Cygnus X-1 binary system. Without finding evidence of a signal from vector bosons in the data, we estimate the mass range that can be constrained. For the HMM searches targeting the remnants from GW231123 and GW230814, we disfavor vector boson masses in the ranges $[0.94, 1.08]$ and $[2.75, 3.28] \times 10^{-13}$ eV, respectively, at 30% confidence, assuming a 1% false alarm probability. Although these searches are only marginally sensitive to signals from merger remnants at relatively large distances, future observations are expected to yield more stringent constraints with high confidence. For the BSD search targeting the BH in Cygnus X-1, we exclude vector boson masses in the range $[0.85, 1.59] \times 10^{-13}$ eV at 95% confidence, assuming an initial BH spin larger than 0.5.
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Submitted 14 September, 2025; v1 submitted 8 September, 2025;
originally announced September 2025.
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GWTC-4.0: Constraints on the Cosmic Expansion Rate and Modified Gravitational-wave Propagation
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1750 additional authors not shown)
Abstract:
We analyze data from 142 of the 218 gravitational-wave (GW) sources in the fourth LIGO-Virgo-KAGRA Collaboration (LVK) Gravitational-Wave Transient Catalog (GWTC-4.0) to estimate the Hubble constant $H_0$ jointly with the population properties of merging compact binaries. We measure the luminosity distance and redshifted masses of GW sources directly; in contrast, we infer GW source redshifts stat…
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We analyze data from 142 of the 218 gravitational-wave (GW) sources in the fourth LIGO-Virgo-KAGRA Collaboration (LVK) Gravitational-Wave Transient Catalog (GWTC-4.0) to estimate the Hubble constant $H_0$ jointly with the population properties of merging compact binaries. We measure the luminosity distance and redshifted masses of GW sources directly; in contrast, we infer GW source redshifts statistically through i) location of features in the compact object mass spectrum and merger rate evolution, and ii) identifying potential host galaxies in the GW localization volume. Probing the relationship between source luminosity distances and redshifts obtained in this way yields constraints on cosmological parameters. We also constrain parameterized deviations from general relativity which affect GW propagation, specifically those modifying the dependence of a GW signal on the source luminosity distance. Assuming our fiducial model for the source-frame mass distribution and using GW candidates detected up to the end of the fourth observing run (O4a), together with the GLADE+ all-sky galaxy catalog, we estimate $H_0 = 76.6^{+13.0}_{-9.5} (76.6^{+25.2}_{-14.0})$ km s$^{-1}$ Mpc$^{-1}$. This value is reported as a median with 68.3% (90%) symmetric credible interval, and includes combination with the $H_0$ measurement from GW170817 and its electromagnetic counterpart. Using a parametrization of modified GW propagation in terms of the magnitude parameter $Ξ_0$, we estimate $Ξ_0 = 1.2^{+0.8}_{-0.4} (1.2^{+2.4}_{-0.5})$, where $Ξ_0 = 1$ recovers the behavior of general relativity.
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Submitted 7 October, 2025; v1 submitted 4 September, 2025;
originally announced September 2025.
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Upper Limits on the Isotropic Gravitational-Wave Background from the first part of LIGO, Virgo, and KAGRA's fourth Observing Run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1751 additional authors not shown)
Abstract:
We present results from the search for an isotropic gravitational-wave background using Advanced LIGO and Advanced Virgo data from O1 through O4a, the first part of the fourth observing run. This background is the accumulated signal from unresolved sources throughout cosmic history and encodes information about the merger history of compact binaries throughout the Universe, as well as exotic physi…
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We present results from the search for an isotropic gravitational-wave background using Advanced LIGO and Advanced Virgo data from O1 through O4a, the first part of the fourth observing run. This background is the accumulated signal from unresolved sources throughout cosmic history and encodes information about the merger history of compact binaries throughout the Universe, as well as exotic physics and potentially primordial processes from the early cosmos. Our cross-correlation analysis reveals no statistically significant background signal, enabling us to constrain several theoretical scenarios. For compact binary coalescences which approximately follow a 2/3 power-law spectrum, we constrain the fractional energy density to $Ω_{\rm GW}(25{\rm Hz})\leq 2.0\times 10^{-9}$ (95% cred.), a factor of 1.7 improvement over previous results. Scale-invariant backgrounds are constrained to $Ω_{\rm GW}(25{\rm Hz})\leq 2.8\times 10^{-9}$, representing a 2.1x sensitivity gain. We also place new limits on gravity theories predicting non-standard polarization modes and confirm that terrestrial magnetic noise sources remain below detection threshold. Combining these spectral limits with population models for GWTC-4, the latest gravitational-wave event catalog, we find our constraints remain above predicted merger backgrounds but are approaching detectability. The joint analysis combining the background limits shown here with the GWTC-4 catalog enables improved inference of the binary black hole merger rate evolution across cosmic time. Employing GWTC-4 inference results and standard modeling choices, we estimate that the total background arising from compact binary coalescences is $Ω_{\rm CBC}(25{\rm Hz})={0.9^{+1.1}_{-0.5}\times 10^{-9}}$ at 90% confidence, where the largest contribution is due to binary black holes only, $Ω_{\rm BBH}(25{\rm Hz})=0.8^{+1.1}_{-0.5}\times 10^{-9}$.
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Submitted 28 August, 2025;
originally announced August 2025.
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GWTC-4.0: Population Properties of Merging Compact Binaries
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
D. Agarwal,
M. Agathos,
M. Aghaei Abchouyeh,
O. D. Aguiar,
S. Ahmadzadeh,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu,
S. Albanesi,
R. A. Alfaidi
, et al. (1783 additional authors not shown)
Abstract:
We detail the population properties of merging compact objects using 158 mergers from the cumulative Gravitational-Wave Transient Catalog 4.0, which includes three types of binary mergers: binary neutron star, neutron star--black hole binary, and binary black hole mergers. We resolve multiple over- and under-densities in the black hole mass distribution: features persist at primary masses of…
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We detail the population properties of merging compact objects using 158 mergers from the cumulative Gravitational-Wave Transient Catalog 4.0, which includes three types of binary mergers: binary neutron star, neutron star--black hole binary, and binary black hole mergers. We resolve multiple over- and under-densities in the black hole mass distribution: features persist at primary masses of $10\,M_\odot$ and $35\,M_\odot$ with a possible third feature at $\sim 20\,M_\odot$. These are departures from an otherwise power-law-like continuum that steepens above $35\,M_\odot$. Binary black holes with primary masses near $10\,M_\odot$ are more likely to have less massive secondaries, with a mass ratio distribution peaking at $q = 0.74^{+0.13}_{-0.13}$, potentially a signature of stable mass transfer during binary evolution. Black hole spins are inferred to be non-extremal, with 90\% of black holes having $χ< 0.57$, and preferentially aligned with binary orbits, implying many merging binaries form in isolation. However, we find a significant fraction, 0.24-0.42, of binaries have negative effective inspiral spins, suggesting many could be formed dynamically in gas-free environments. We find evidence for correlation between effective inspiral spin and mass ratio, though it is unclear if this is driven by variation in the mode of the distribution or the width. (Abridged)
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Submitted 17 September, 2025; v1 submitted 25 August, 2025;
originally announced August 2025.
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GWTC-4.0: Updating the Gravitational-Wave Transient Catalog with Observations from the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1748 additional authors not shown)
Abstract:
Version 4.0 of the Gravitational-Wave Transient Catalog (GWTC-4.0) adds new candidates detected by the LIGO, Virgo, and KAGRA observatories through the first part of the fourth observing run (O4a: 2023 May 24 15:00:00 to 2024 January 16 16:00:00 UTC) and a preceding engineering run. In this new data, we find 128 new compact binary coalescence candidates that are identified by at least one of our s…
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Version 4.0 of the Gravitational-Wave Transient Catalog (GWTC-4.0) adds new candidates detected by the LIGO, Virgo, and KAGRA observatories through the first part of the fourth observing run (O4a: 2023 May 24 15:00:00 to 2024 January 16 16:00:00 UTC) and a preceding engineering run. In this new data, we find 128 new compact binary coalescence candidates that are identified by at least one of our search algorithms with a probability of astrophysical origin $p_{\rm astro} \geq 0.5$ and that are not vetoed during event validation. We also provide detailed source property measurements for 86 of these that have a false alarm rate $< 1 \rm{yr}^{-1}$. Based on the inferred component masses, these new candidates are consistent with signals from binary black holes and neutron star-black hole binaries (GW230518_125908 and GW230529_181500). Median inferred component masses of binary black holes in the catalog now range from $5.79\,M_\odot$ (GW230627_015337) to $137\,M_\odot$ (GW231123_135430), while GW231123_135430 was probably produced by the most massive binary observed in the catalog. For the first time we have discovered binary black hole signals with network signal-to-noise ratio exceeding 30, GW230814_230901 and GW231226_01520, enabling high-fidelity studies of the waveforms and astrophysical properties of these systems. Combined with the 90 candidates included in GWTC-3.0, the catalog now contains 218 candidates with $p_{\rm astro} \geq 0.5$ and not otherwise vetoed, doubling the size of the catalog and further opening our view of the gravitational-wave Universe.
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Submitted 8 September, 2025; v1 submitted 25 August, 2025;
originally announced August 2025.
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GWTC-4.0: Methods for Identifying and Characterizing Gravitational-wave Transients
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
D. Agarwal,
M. Agathos,
M. Aghaei Abchouyeh,
O. D. Aguiar,
S. Ahmadzadeh,
L. Aiello,
A. Ain,
P. Ajith,
S. Akcay,
T. Akutsu,
S. Albanesi,
R. A. Alfaidi
, et al. (1787 additional authors not shown)
Abstract:
The Gravitational-Wave Transient Catalog (GWTC) is a collection of candidate gravitational-wave transient signals identified and characterized by the LIGO-Virgo-KAGRA Collaboration. Producing the contents of the GWTC from detector data requires complex analysis methods. These comprise techniques to model the signal; identify the transients in the data; evaluate the quality of the data and mitigate…
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The Gravitational-Wave Transient Catalog (GWTC) is a collection of candidate gravitational-wave transient signals identified and characterized by the LIGO-Virgo-KAGRA Collaboration. Producing the contents of the GWTC from detector data requires complex analysis methods. These comprise techniques to model the signal; identify the transients in the data; evaluate the quality of the data and mitigate possible instrumental issues; infer the parameters of each transient; compare the data with the waveform models for compact binary coalescences; and handle the large amount of results associated with all these different analyses. In this paper, we describe the methods employed to produce the catalog's fourth release, GWTC-4.0, focusing on the analysis of the first part of the fourth observing run of Advanced LIGO, Advanced Virgo and KAGRA.
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Submitted 25 August, 2025;
originally announced August 2025.
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GWTC-4.0: An Introduction to Version 4.0 of the Gravitational-Wave Transient Catalog
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
D. Agarwal,
M. Agathos,
M. Aghaei Abchouyeh,
O. D. Aguiar,
S. Ahmadzadeh,
L. Aiello,
A. Ain,
P. Ajith,
S. Akcay,
T. Akutsu,
S. Albanesi,
R. A. Alfaidi
, et al. (1786 additional authors not shown)
Abstract:
The Gravitational-Wave Transient Catalog (GWTC) is a collection of short-duration (transient) gravitational wave signals identified by the LIGO-Virgo-KAGRA Collaboration in gravitational-wave data produced by the eponymous detectors. The catalog provides information about the identified candidates, such as the arrival time and amplitude of the signal and properties of the signal's source as inferr…
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The Gravitational-Wave Transient Catalog (GWTC) is a collection of short-duration (transient) gravitational wave signals identified by the LIGO-Virgo-KAGRA Collaboration in gravitational-wave data produced by the eponymous detectors. The catalog provides information about the identified candidates, such as the arrival time and amplitude of the signal and properties of the signal's source as inferred from the observational data. GWTC is the data release of this dataset and version 4.0 extends the catalog to include observations made during the first part of the fourth LIGO-Virgo-KAGRA observing run up until 2024 January 31. This paper marks an introduction to a collection of articles related to this version of the catalog, GWTC-4.0. The collection of articles accompanying the catalog provides documentation of the methods used to analyze the data, summaries of the catalog of events, observational measurements drawn from the population, and detailed discussions of selected candidates
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Submitted 23 September, 2025; v1 submitted 25 August, 2025;
originally announced August 2025.
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Open Data from LIGO, Virgo, and KAGRA through the First Part of the Fourth Observing Run
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1746 additional authors not shown)
Abstract:
LIGO, Virgo, and KAGRA form a network of gravitational-wave observatories. Data and analysis results from this network are made publicly available through the Gravitational Wave Open Science Center. This paper describes open data from this network, including the addition of data from the first part of the fourth observing run (O4a) and selected periods from the preceding engineering run, collected…
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LIGO, Virgo, and KAGRA form a network of gravitational-wave observatories. Data and analysis results from this network are made publicly available through the Gravitational Wave Open Science Center. This paper describes open data from this network, including the addition of data from the first part of the fourth observing run (O4a) and selected periods from the preceding engineering run, collected from May 2023 to January 2024. The public data set includes calibrated strain time series for each instrument, data from additional channels used for noise subtraction and detector characterization, and analysis data products from version 4.0 of the Gravitational-Wave Transient Catalog.
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Submitted 4 November, 2025; v1 submitted 25 August, 2025;
originally announced August 2025.
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Decadal upgrade strategy for KAGRA toward post-O5 gravitational-wave astronomy
Authors:
KAGRA Collaboration,
T. Akutsu,
M. Ando,
M. Aoumi,
A. Araya,
Y. Aso,
L. Baiotti,
R. Bajpai,
K. Cannon,
A. H. -Y. Chen,
D. Chen,
H. Chen,
A. Chiba,
C. Chou,
M. Eisenmann,
K. Endo,
T. Fujimori,
S. Garg,
D. Haba,
S. Haino,
R. Harada,
H. Hayakawa,
K. Hayama,
S. Fujii,
Y. Himemoto
, et al. (129 additional authors not shown)
Abstract:
The KAGRA Collaboration has investigated a ten-year upgrade strategy for the KAGRA gravitational wave detector, considering a total of 14 upgrade options that vary in mirror mass, quantum noise reduction techniques, and the quality of cryogenic suspensions. We evaluated the scientific potential of these configurations with a focus on key targets such as parameter estimation of compact binary coale…
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The KAGRA Collaboration has investigated a ten-year upgrade strategy for the KAGRA gravitational wave detector, considering a total of 14 upgrade options that vary in mirror mass, quantum noise reduction techniques, and the quality of cryogenic suspensions. We evaluated the scientific potential of these configurations with a focus on key targets such as parameter estimation of compact binary coalescences, binary neutron star post-merger signals, and continuous gravitational waves. Rather than aiming to improve all science cases uniformly, we prioritized those most sensitive to the detector configuration. Technical feasibility was assessed based on required hardware developments, associated R\&D efforts, cost, and risk. Our study finds that a high-frequency upgrade plan that enhances sensitivity over a broad frequency range above ~200 Hz offers the best balance between scientific return and technical feasibility. Such an upgrade would enable sky localization of binary neutron star mergers at 100 Mpc to better than 0.5 deg$^2$ in a LIGO-Virgo-KAGRA network, and improve the measurement precision of tidal deformability parameter by approximately 10% at median, compared to a network without KAGRA.
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Submitted 5 August, 2025;
originally announced August 2025.
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SN 2024gy: Multi-epoch Spectroscopic Features Suggestive of Delayed Detonation in a Type Ia Supernova
Authors:
Liping Li,
Zhenyu Wang,
Jialian Liu,
Yu Pan,
Alexei V. Filippenko,
Jujia Zhang,
Xiaofeng Wang,
Brajesh Kumar,
Yi Yang,
Thomas G. Brink,
WeiKang Zheng,
Xiangcun Meng,
Lingzhi Wang,
Zeyi Zhao,
Qian Zhai,
Yongzhi Cai,
Giuliano Pignata,
Xinlei Chen,
Xingzhu Zou,
Jiewei Zhao,
Xiangkun Liu,
Xiaowei Liu,
Xinzhong Er,
A. Reguitti,
R. Michael Rich
, et al. (6 additional authors not shown)
Abstract:
We present photometric and spectroscopic observations of SN 2024gy, a Type Ia supernova (SN Ia) exhibiting high-velocity features (HVFs) in its early-time spectra. This SN reaches a peak $B$-band magnitude of $-19.25 \pm 0.29$ mag and subsequently declines by $Δm_{15}(B) \approx 1.12$ mag, consistent with the luminosity-width relation characteristic of normal SNe Ia. Based on the peak thermal lumi…
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We present photometric and spectroscopic observations of SN 2024gy, a Type Ia supernova (SN Ia) exhibiting high-velocity features (HVFs) in its early-time spectra. This SN reaches a peak $B$-band magnitude of $-19.25 \pm 0.29$ mag and subsequently declines by $Δm_{15}(B) \approx 1.12$ mag, consistent with the luminosity-width relation characteristic of normal SNe Ia. Based on the peak thermal luminosity of $(1.2 \pm 0.3) \times 10^{43}$ erg s$^{-1}$, we estimate that $0.57 \pm 0.14~\rm M_{\odot}$ of $^{56}$Ni was synthesized during the explosion. Our dense early spectral monitoring revealed significant velocity disparities within the ejecta. Notably, absorption features from the Ca II near-infrared triplet were observed at velocities exceeding 25,000 km s$^{-1}$, while the Si II $λ$6355 line velocity at the same epoch was significantly lower at $\sim$ 16,000 km s$^{-1}$. This velocity disparity likely reflects distinct ionization states of intermediate-mass elements in the outermost layers. The prominent Ca II HVFs may originate from ionization suppression within the highest-velocity ejecta, potentially indicative of minimal hydrogen mixing in a delayed-detonation explosion scenario. Additionally, the Ni/Fe ratio derived from the nebular spectrum of SN 2024gy provides further support for this model.
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Submitted 30 October, 2025; v1 submitted 2 August, 2025;
originally announced August 2025.
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Image of a time-dependent rotating regular black hole
Authors:
Sen Guo,
En-Wei Liang,
Yu-Xiang Huang,
Yu Liang,
Qing-Quan Jiang,
Kai Lin,
Li-Fang Li
Abstract:
In this study, we develop a modeling framework based on spatio-temporal generalized random fields to simulate the time-evolving accretion flows and their associated imaging signatures around rotating regular black holes. We extend the Matérn field formalism to the spatio-temporal domain and introduce a locally anisotropic tensor structure \(Λ(\mathbf{x})\), which encodes direction-dependent correl…
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In this study, we develop a modeling framework based on spatio-temporal generalized random fields to simulate the time-evolving accretion flows and their associated imaging signatures around rotating regular black holes. We extend the Matérn field formalism to the spatio-temporal domain and introduce a locally anisotropic tensor structure \(Λ(\mathbf{x})\), which encodes direction-dependent correlation scales motivated by Keplerian velocity fields, thereby generating physically informed perturbation structures. Coupled with a computationally efficient light ray-tracing scheme, this framework produces a sequence of time-resolved images of regular black hole shadow and accretion structures. By incorporating light-travel time effects, we identify significant temporal smearing of features within strongly lensed regions and rapidly varying sources, thus enhancing the physical realism of the modeling. Comparison with existing general relativistic magnetohydrodynamic simulations demonstrates that our stochastic generative model maintains statistical consistency while offering substantial computational efficiency. Moreover, the simulated results reproduce the dynamic positional shift of the bright ring structure observed in M87$^{*}$, providing theoretical support for interpreting its time-variable images.
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Submitted 29 July, 2025;
originally announced July 2025.
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SVOM GRB 250314A at z $\simeq$ 7.3: an exploding star in the era of reionization
Authors:
B. Cordier,
J. Y. Wei,
N. R. Tanvir,
S. D. Vergani,
D. B. Malesani,
J. P. U. Fynbo,
A. de Ugarte Postigo,
A. Saccardi,
F. Daigne,
J. -L. Atteia,
O. Godet,
D. Gotz,
Y. L. Qiu,
S. Schanne,
L. P. Xin,
B. Zhang,
S. N. Zhang,
A. J. Nayana,
L. Piro,
B. Schneider,
A. J. Levan,
A. L. Thakur,
Z. P. Zhu,
G. Corcoran,
N. A. Rakotondrainibe
, et al. (81 additional authors not shown)
Abstract:
Most long Gamma-ray bursts originate from a rare type of massive stellar explosion. Their afterglows, while rapidly fading, can be initially extremely luminous at optical/near-infrared wavelengths, making them detectable at large cosmological distances. Here we report the detection and observations of GRB 250314A by the SVOM satellite and the subsequent follow-up campaign with the near-infrared af…
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Most long Gamma-ray bursts originate from a rare type of massive stellar explosion. Their afterglows, while rapidly fading, can be initially extremely luminous at optical/near-infrared wavelengths, making them detectable at large cosmological distances. Here we report the detection and observations of GRB 250314A by the SVOM satellite and the subsequent follow-up campaign with the near-infrared afterglow discovery and the spectroscopic measurements of its redshift z $\simeq$ 7.3 . This burst happened when the Universe was only $\sim$ 5% of its current age. We discuss the signature of these rare events within the context of the SVOM operating model, and the ways to optimize their identification with adapted ground follow-up observation strategies.
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Submitted 24 July, 2025;
originally announced July 2025.
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Results of 15-Year Pulsar Timing of PSR J0007+7303 with Fermi-LAT
Authors:
Zhi-xiang Yu,
Shi-jun Dang,
Wei-hua Wang,
Lin Li,
Wei Li,
Jian-ping Yuan,
Fei-fei Kou,
Jun-tao Bai,
Mingyu Ge,
Xia Zhou,
Lun-hua Shang,
Zu-rong Zhou,
Yu-bin Wang,
Yan-qing Cai,
Ru-shuang Zhao,
Qing-ying Li,
Xiang-dong Zeng,
Na Wang
Abstract:
The study of pulsar glitches provides a unique window into the internal structure and dynamic processes of neutron stars. PSR J0007+7303, a very bright gamma-ray pulsar, is the first pulsar discovered by the Fermi-LAT telescope. In this paper, we present the 15 years of timing results of this pulsar using the Fermi-LAT data. We identified nine glitches, five of which are newly discovered. Among th…
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The study of pulsar glitches provides a unique window into the internal structure and dynamic processes of neutron stars. PSR J0007+7303, a very bright gamma-ray pulsar, is the first pulsar discovered by the Fermi-LAT telescope. In this paper, we present the 15 years of timing results of this pulsar using the Fermi-LAT data. We identified nine glitches, five of which are newly discovered. Among these, two are small glitches, occurring between the three previously reported ones, while the other four are large glitches. The glitches exhibit fractional frequency changes ranging from 15 x 10^-9 to 1238 x 10^-9, with intervals of approximately 1-2 years between events. Uniquely, this pulsar shows no exponential recovery behavior following any glitch, setting it apart from most glitching pulsars. Furthermore, no significant changes were observed in the gamma-ray pulse profile, flux, or phase-averaged spectra before and after glitches, indicating the stability of the pulsar's emission properties despite internal changes. A parametric analysis of the glitches yielded a fractional moment of inertia of the crustal superfluid involved in glitches as 1.06 percent, which matches extremely well with previous statistical work if the non-dissipative entrainment effect is not considered and strongly supports the internal origin of these glitches. These results highlight the distinct glitch behavior of PSR J0007+7303 and offer valuable insights into the crust-superfluid interaction in neutron stars. The physical origin of no exponential recovery is also discussed.
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Submitted 24 July, 2025;
originally announced July 2025.
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The Event Rate and Luminosity Function of Fermi/GBM Gamma-Ray Bursts
Authors:
Yang Liu,
Zhi-Bin Zhang,
Xiao-Fei Dong,
Long-Biao Li,
Xiu-Yun Du
Abstract:
Luminosity function and event rate of Gamma-Ray Bursts (GRBs) are easily biased by the instrument and selection effects. We select 115 Fermi/GBM GRBs with good spectra fitted by a smoothly broken power-law function. The $τ$-statistic method is used to describe how the luminosity evolves with redshift. The non-parametric Lynden-Bell's c$^{-}$ method has been applied to get the cumulative luminosity…
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Luminosity function and event rate of Gamma-Ray Bursts (GRBs) are easily biased by the instrument and selection effects. We select 115 Fermi/GBM GRBs with good spectra fitted by a smoothly broken power-law function. The $τ$-statistic method is used to describe how the luminosity evolves with redshift. The non-parametric Lynden-Bell's c$^{-}$ method has been applied to get the cumulative luminosity function and event rate which is compared with the star formation history. How the selection and instrument effects bias the deduced event rate has been carefully studied. We find that the event rate always exceeds the star formation rate (SFR) at lower redshift and matches with each other at higher redshift, which is independent of energy bands and consistent with previous findings of other satellites. Furthermore, it is found that sample completeness does not affect the deduced event rate too much as mentioned for the Swift lGRBs in Dong et al.. A triple power-law function has been used to fit the cumulative flux distribution and categorize the total sample into three subsamples of bright, medium and faint GRBs. We find that the event rates of bright GRBs, unlike medium and faint ones, comply with the SFR ideally, which indicates that these bright GRBs with higher luminosity are possibly produced from the core-collapse of massive stars.
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Submitted 22 July, 2025;
originally announced July 2025.
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Lunar Orbital VLBI Experiment: motivation, scientific purposes and status
Authors:
Xiaoyu Hong,
Weiren Wu,
Qinghui Liu,
Dengyun Yu,
Chi Wang,
Tao Shuai,
Weiye Zhong,
Renjie Zhu,
Yonghui Xie,
Lihua Zhang,
Liang Xiong,
Yuhua Tang,
Yongliao Zou,
Haitao Li,
Guangli Wang,
Jianfeng Xie,
Changbin Xue,
Hao Geng,
Juan Zhang,
Xiaojing Wu,
Yong Huang,
Weimin Zheng,
Lei Liu,
Fang Wu,
Xiuzhong Zhang
, et al. (25 additional authors not shown)
Abstract:
The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang'E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 2024 March 20, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequ…
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The Lunar Orbital VLBI Experiment (LOVEX) is a scientific component of the Chinese Lunar Exploration Project (CLEP) Chang'E-7. The spaceborne component of LOVEX is implemented onboard the relay satellite QueQiao-2, which was launched on 2024 March 20, and later placed into an elliptical selenocentric orbit. The LOVEX-specific payload consists of an X-band cryogenic receiver, a hydrogen maser frequency standard, and VLBI data formatting and acquisition electronics. Several components of the QueQiao-2 nominal onboard instrumentation, such as the 4.2-meter antenna, the data storage device, and the downlink communication system, contribute to the overall spaceborne VLBI instrumentation. This allows us to form a space radio telescope capable of co-observing with Earth-based radio telescopes in VLBI mode. In this space VLBI system, the length of the baseline extends up to approximately 380,000 km. This paper presents the LOVEX scientific objectives, architecture, instrumentation, pre-launch tests, in-flight verification and calibration, and the first in-flight detections of interferometric response (''fringes'') achieved through observations of the quasar AO 0235+164 and the Chang'E-6 orbital module, positioned at the Sun-Earth Lagrange point L2. These initial results demonstrate the successful performance of LOVEX, verifying its capability for both astronomical and spacecraft tracking observations at ultra-long VLBI baselines.
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Submitted 22 July, 2025;
originally announced July 2025.
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Einstein Probe Discovery of EP J182730.0-095633: A New Black Hole X-ray Binary Candidate in Faint Outburst?
Authors:
Huaqing Cheng,
Qingchang Zhao,
L. Tao,
H. Feng,
F. Coti Zelati,
H. W. Pan,
A. L. Wang,
Y. N. Wang,
M. Y. Ge,
A. Rau,
A. Marino,
L. Zhang,
W. J. Zhang,
F. Carotenuto,
L. Ji,
C. C. Jin,
D. Y. Li,
B. F. Liu,
Y. Liu,
E. L. Qiao,
N. Rea,
R. Soria,
S. Wang,
Z. Yan,
W. Yuan
, et al. (56 additional authors not shown)
Abstract:
Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts exhibiting peak X-ray luminosities $L_{\rm X}\lesssim10^{36}~{\rm erg~s^{-1}}$, likely due to the previous lack of sensitive, wide-field monitoring instruments in…
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Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts exhibiting peak X-ray luminosities $L_{\rm X}\lesssim10^{36}~{\rm erg~s^{-1}}$, likely due to the previous lack of sensitive, wide-field monitoring instruments in the X-ray band. In this Letter, we present the discovery of an intriguing X-ray transient, EP J182730.0-095633, via the Einstein Probe (EP) and subsequent multi-wavelength follow-up studies. This transient, located on the Galactic plane, experienced a faint and brief X-ray outburst lasting about 20 days. Its X-ray spectrum is non-thermal and consistent with a power-law model with a nearly constant photon index of $Γ\sim2$ throughout the outburst. A long-lasting millihertz quasi-periodic oscillation (QPO) signal was detected in its X-ray light curve, centered around a frequency of $\sim0.04$ Hz. A transient near-infrared source was identified as its counterpart, although no optical emission was detectable, likely due to significant extinction. A radio counterpart was also observed, displaying an inverted radio spectrum with $α\sim0.45$. The X-ray spectral and temporal characteristics, along with the multi-wavelength properties, indicate that the source is a faint low-mass X-ray binary, with the compact object likely being a black hole. This work demonstrates the potential of the EP in discovering new X-ray binaries by capturing faint-level X-ray outbursts.
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Submitted 17 July, 2025;
originally announced July 2025.
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Constrain magnetar parameters by taking into account the evolutionary effects of radius and moment of inertia with \emph{Swift}/XRT data
Authors:
Lin Lan,
He Gao,
Shunke Ai,
Wen-Jin Xie,
Yong Yuan,
Long Li,
Li-Ping Xin,
Jian-Yan Wei
Abstract:
A newly born millisecond magnetar has been proposed as one possible central engine of some GRBs with X-ray plateau emission. In this work, we systematically analyzed the Swift/XRT data of long GRBs with plateau emission that were detected before 2023 December, and estimated the physical parameters by considering the $R/I$ evolutionary effects. We found that neglecting the $R/I$ evolutionary effect…
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A newly born millisecond magnetar has been proposed as one possible central engine of some GRBs with X-ray plateau emission. In this work, we systematically analyzed the Swift/XRT data of long GRBs with plateau emission that were detected before 2023 December, and estimated the physical parameters by considering the $R/I$ evolutionary effects. We found that neglecting the $R/I$ evolutionary effects can lead to systematic overestimation or underestimation of magnetar parameters such as $B_p$, $P_0$, and $ε$ from 20\% to 50\%. We also found that some tight correlations, which can be approximately expressed as $ε\propto P_0^{1.57\pm0.22}$, $ε\propto B_p^{0.97\pm0.13}$, $B_p\propto P_0^{1.30\pm0.16}$, $E_{\rm wind}\propto E_{\rm jet,iso}^{0.83\pm0.07}(E_{\rm jet}^{0.76\pm0.06})$, $P_0\propto E_{\rm jet,iso}^{-0.29\pm0.03}(E_{\rm jet}^{-0.26\pm0.02})$, $B_p\propto E_{\rm jet,iso}^{-0.58\pm0.06}(E_{\rm jet}^{-0.55\pm0.05})$, and $ε\propto E_{\rm jet,iso}^{-0.55\pm0.07}(E_{\rm jet}^{-0.52\pm0.06})$ for our selected EoSs. The universal correlations suggest that a nascent magnetar with the faster $P_0$, lower $B_p$, and lower $ε$ are more inclined to power a more energetic GRB jet, and the $ε$ and $P_0$ of newborn magnetar are likely to originate from the magnetically induced distortion and correspond to the equilibrium spin period as a result of interaction between the magnetar and its accretion disk, respectively. Finally, we found that the GW signals from the remnants of those GW-dominated GRBs with redshift measurements cannot reach aLIGO sensitivity threshold, and only two cases (GRBs 150323A and 170607A) can reach ET sensitivity threshold. Future GW observations could not only offer the first smoking gun that a protomagnetar can serve as the central engine of GRBs but also play a crucial role in precisely constraining the neutron star EoS.
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Submitted 2 September, 2025; v1 submitted 15 July, 2025;
originally announced July 2025.
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GW231123: a Binary Black Hole Merger with Total Mass 190-265 $M_{\odot}$
Authors:
The LIGO Scientific Collaboration,
the Virgo Collaboration,
the KAGRA Collaboration,
A. G. Abac,
I. Abouelfettouh,
F. Acernese,
K. Ackley,
C. Adamcewicz,
S. Adhicary,
D. Adhikari,
N. Adhikari,
R. X. Adhikari,
V. K. Adkins,
S. Afroz,
A. Agapito,
D. Agarwal,
M. Agathos,
N. Aggarwal,
S. Aggarwal,
O. D. Aguiar,
I. -L. Ahrend,
L. Aiello,
A. Ain,
P. Ajith,
T. Akutsu
, et al. (1749 additional authors not shown)
Abstract:
On 2023 November 23 the two LIGO observatories both detected GW231123, a gravitational-wave signal consistent with the merger of two black holes with masses $137^{+23}_{-18}\, M_\odot$ and $101^{+22}_{-50}\, M_\odot$ (90\% credible intervals), at luminosity distance 0.7-4.1 Gpc and redshift of $0.40^{+0.27}_{-0.25}$, and a network signal-to-noise ratio of $\sim$20.7. Both black holes exhibit high…
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On 2023 November 23 the two LIGO observatories both detected GW231123, a gravitational-wave signal consistent with the merger of two black holes with masses $137^{+23}_{-18}\, M_\odot$ and $101^{+22}_{-50}\, M_\odot$ (90\% credible intervals), at luminosity distance 0.7-4.1 Gpc and redshift of $0.40^{+0.27}_{-0.25}$, and a network signal-to-noise ratio of $\sim$20.7. Both black holes exhibit high spins, $0.9^{+0.10}_{-0.19}$ and $0.80^{+0.20}_{-0.52}$ respectively. A massive black hole remnant is supported by an independent ringdown analysis. Some properties of GW231123 are subject to large systematic uncertainties, as indicated by differences in inferred parameters between signal models. The primary black hole lies within or above the theorized mass gap where black holes between 60-130 $M_\odot$ should be rare due to pair instability mechanisms, while the secondary spans the gap. The observation of GW231123 therefore suggests the formation of black holes from channels beyond standard stellar collapse, and that intermediate-mass black holes of mass $\sim$200 $M_\odot$ form through gravitational-wave driven mergers.
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Submitted 10 November, 2025; v1 submitted 10 July, 2025;
originally announced July 2025.
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Twin peaks: SN 2021uvy and SN 2022hgk in the landscape of double-peaked stripped envelope supernovae
Authors:
Yashvi Sharma,
Jesper Sollerman,
William Meynardie,
Christoffer Fremling,
Kaustav K. Das,
Gene Yun,
Shrinivas R. Kulkarni,
Steve Schulze,
Jacob Wise,
Seán. J. Brennan,
Thomas G. Brink,
Michael W. Coughlin,
Richard Dekany,
Matthew J. Graham,
K. R. Hinds,
Viraj Karambelkar,
Mansi M. Kasliwal,
Maggie L. Li,
Kira Nolan,
Daniel A. Perley,
Josiah N. Purdum,
Sam Rose,
Ben Rusholme,
Tawny Sit,
Anastasios Tzanidakis
, et al. (3 additional authors not shown)
Abstract:
In recent years, a class of stripped-envelope supernovae (SESNe) showing two distinct light-curve peaks has emerged, where the first peak cannot be attributed to shock cooling emission. Such peculiar SNe are often studied individually, explained by a combination of powering mechanisms, but are rarely discussed broadly as a group. In this paper, we attempt to form a picture of the landscape of doub…
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In recent years, a class of stripped-envelope supernovae (SESNe) showing two distinct light-curve peaks has emerged, where the first peak cannot be attributed to shock cooling emission. Such peculiar SNe are often studied individually, explained by a combination of powering mechanisms, but are rarely discussed broadly as a group. In this paper, we attempt to form a picture of the landscape of double-peaked SESNe and their powering mechanisms by adding two more objects -- SN 2021uvy and SN 2022hgk. SN 2021uvy is a broad, luminous SN Ib with an unusually long first peak rise and constant color evolution with rising photospheric temperature during the second peak. Though its first peak resembles SN 2019stc, their second peaks differ, making SN 2021uvy unique. SN 2022hgk shows photometric similarity to SN 2019cad and spectroscopic similarity to SN 2005bf, both proposed to be powered by a double-nickel distribution in their ejecta. We analyze their light curves and colors, compare them with a sample of double-peaked SESNe from the ZTF archive, and analyze the light curve parameters of the sample. We observe a correlation (p-value~0.025) between the peak absolute magnitudes of the first and second peaks. No single definitive powering mechanism applies to the whole sample, as it shows variety in the photometric and spectroscopic properties. However, sub-groups of similarity exist that can be explained by mechanisms like the double-nickel distribution, magnetar central engine, interaction, and fallback accretion. We also map out the duration between the peaks ($Δt^{21}$) vs the difference between peak absolute magnitudes ($ΔM^{21}$) as a phase-space that could potentially delineate the most promising powering mechanisms for the double-peaked SESNe.
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Submitted 4 July, 2025;
originally announced July 2025.
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Identification of Noise-Associated Glitches in KAGRA O3GK with Hveto
Authors:
T. Akutsu,
M. Ando,
M. Aoumi,
A. Araya,
Y. Aso,
L. Baiotti,
R. Bajpai,
K. Cannon,
A. H. -Y. Chen,
D. Chen,
H. Chen,
A. Chiba,
C. Chou,
M. Eisenmann,
K. Endo,
T. Fujimori,
S. Garg,
D. Haba,
S. Haino,
R. Harada,
H. Hayakawa,
K. Hayama,
S. Fujii,
Y. Himemoto,
N. Hirata
, et al. (127 additional authors not shown)
Abstract:
Transient noise ("glitches") in gravitational wave detectors can mimic or obscure true signals, significantly reducing detection sensitivity. Identifying and excluding glitch-contaminated data segments is therefore crucial for enhancing the performance of gravitational-wave searches. We perform a noise analysis of the KAGRA data obtained during the O3GK observation. Our analysis is performed with…
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Transient noise ("glitches") in gravitational wave detectors can mimic or obscure true signals, significantly reducing detection sensitivity. Identifying and excluding glitch-contaminated data segments is therefore crucial for enhancing the performance of gravitational-wave searches. We perform a noise analysis of the KAGRA data obtained during the O3GK observation. Our analysis is performed with hierarchical veto (Hveto) which identifies noises based on the statistical time correlation between the main channel and the auxiliary channels. A total of 2,531 noises were vetoed by 28 auxiliary channels with the configuration (i.e., signal-to-noise threshold set to 8) that we chose for Hveto. We identify vetoed events as glitches on the spectrogram via visual examination after plotting them with Q-transformation. By referring to the Gravity Spy project, we categorize 2,354 glitches into six types: blip, helix, scratchy, and scattered light, which correspond to those listed in Gravity Spy, and dot and line, which are not found in the Gravity Spy classification and are thus named based on their spectrogram morphology in KAGRA data. The remaining 177 glitches are determined not to belong to any of these six types. We show how the KAGRA glitch types are related to each subsystem of KAGRA. To investigate the possible correlation between the main channel and the round winner - an auxiliary channel statistically associated with the main channel for vetoing purposes - we visually examine the similarity or difference in the glitch pattern on the spectrogram. We compare the qualitative correlation found through visual examination with coherence, which is known to provide quantitative measurement for the correlation between the main channel and each auxiliary channel. Our comprehensive noise analysis will help improve the data quality of KAGRA by applying it to future KAGRA observation data.
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Submitted 26 June, 2025;
originally announced June 2025.
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In-flight calibration of the Lobster Eye Imager for Astronomy
Authors:
Huaqing Cheng,
Hai-Wu Pan,
Yuan Liu,
Jingwei Hu,
Haonan Yang,
Donghua Zhao,
Zhixing Ling,
He-Yang Liu,
Yifan Chen,
Xiaojin Sun,
Longhui Li,
Ge Jin,
Chen Zhang,
Shuang-Nan Zhang,
Weimin Yuan
Abstract:
The Lobster Eye Imager for Astronomy (LEIA), as a pathfinder of the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe (EP) satellite, is the first lobster-eye focusing X-ray telescope with a considerably large field-of-view (FoV) ever flown. During the two and half years of operations, a series of calibration observations were performed, to fully characterize its performance and calibrat…
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The Lobster Eye Imager for Astronomy (LEIA), as a pathfinder of the Wide-field X-ray Telescope (WXT) onboard the Einstein Probe (EP) satellite, is the first lobster-eye focusing X-ray telescope with a considerably large field-of-view (FoV) ever flown. During the two and half years of operations, a series of calibration observations were performed, to fully characterize its performance and calibrate the instrumental properties. In this paper, we present the results of the in-flight calibration campaign of LEIA, focusing on the properties of the PSF, source positional accuracy, effective area, energy response and the instrumental background. The calibration sources used are the Crab nebula, Sco X-1 and Cassiopeia A supernova remnant. Specifically, it is found that the spatial resolution remains almost unchanged compared to the pre-launch values, ranging from 3.6'-9.3' with a median of 5.9'. The post-calibration source positional accuracy is found to be ~2' (at the 90% C.L.). The Crab spectra can be well reproduced by the absorbed power-law model with the best-fit parameters in large agreement with the literature values, indicating that the in-orbit effective area is overall consistent with the model predictions and ground measurements. The effective area exhibits a systematic of $\lesssim10\%$ (at the 68% C.L.), and a mild deterioration of ~15% at the lower energy end after one year of operation. The Cas A spectral analysis shows that the energy scale and spectral resolution of the detectors are generally consistent with ground values. The instrumental background is found to be largely consistent among the four detectors, with strong modulations by the geomagnetic activity and the spectrum qualitatively consistent with our previous simulations. These instrumental performances well meet the design requirements. This work paves the way for the in-orbit calibration of the EP-WXT.
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Submitted 25 June, 2025;
originally announced June 2025.