Showing 1–50 of 273 results for author: Liu, G

An Extended WZDR Model with Interacting Scalar Field Dark Matter and Stepped Dark Radiation

Authors: Gang Liu

Abstract: In this paper, we explore the interaction between scalar field dark matter and stepped dark radiation as an extension of the WZDR model. The supersymmetry-based WZDR framework has demonstrated considerable potential in alleviating the Hubble tension. Previous investigations have examined the interaction between stepped dark radiation and cold dark matter, with the aim of simultaneously addressing… ▽ More In this paper, we explore the interaction between scalar field dark matter and stepped dark radiation as an extension of the WZDR model. The supersymmetry-based WZDR framework has demonstrated considerable potential in alleviating the Hubble tension. Previous investigations have examined the interaction between stepped dark radiation and cold dark matter, with the aim of simultaneously addressing both the Hubble and $S_8$ tensions. Given the suppressive effect of scalar field dark matter on small-scale structure growth, we replace cold dark matter with scalar field dark matter in the present work and introduce its interaction with stepped dark radiation via pure momentum coupling, thereby formulating a novel coupling model. We impose constraints on the model parameters using a variety of cosmological datasets, including the Cosmic Microwave Background, Baryon Acoustic Oscillations, Type Ia Supernovae, $H_0$ measurements from SH0ES, $S_8$ data from the Dark Energy Survey Year 3, and data from the Atacama Cosmology Telescope. Our analysis reveals that the performance of the new model is nearly identical to that of the original WZDR model, with only a marginal improvement. When using the full data combination, the best-fit values for $H_0$ in the coupled model and WZDR model are 70.89 km/s/Mpc and 70.68 km/s/Mpc, respectively. For the $S_8$ parameter, the new model results in a decrease from 0.8136 in the original model to 0.8113. Furthermore, the coupling signal remains weak, with the constraint on the coupling parameter being $\log_{10}(ξ)<4.56$. While the coupling model offers some improvement, it does not fully resolve the cosmological tensions, indicating that further investigation is required to address these issues. △ Less

Submitted 7 December, 2025; originally announced December 2025.

Comments: 12 pages, 6 figures

The First Scientific Flight and Observations of the 50-mm Balloon-Borne White-Light Coronagraph

Authors: Kaifeng Kang, Min Huang, Yang Liu, Jun Lin, Tengfei Song, Xuefei Zhang, Dayang Liu, Tao Zhang, Yan Li, Jingxing Wang, Mingzhe Sun, Mingyu Zhao, Guangqian Liu, Xianyong Bai, Lidong Xia, Yu Liu

Abstract: A 50-mm balloon-borne white-light coronagraph (BBWLC) to observe whitelight solar corona over the altitude range from 1.08 to 1.50 solar radii has recently been indigenously developed by Yunnan Observatories in collaboration with Shangdong University (in Weihai) and Changchun Institute of Optics, Fine Mechanics and Physics, which will significantly improve the ability of China to detect and measur… ▽ More A 50-mm balloon-borne white-light coronagraph (BBWLC) to observe whitelight solar corona over the altitude range from 1.08 to 1.50 solar radii has recently been indigenously developed by Yunnan Observatories in collaboration with Shangdong University (in Weihai) and Changchun Institute of Optics, Fine Mechanics and Physics, which will significantly improve the ability of China to detect and measure inner corona. On 2022 October 4, its first scientific flight took place at the Dachaidan area in Qinghai province of China. We describe briefly the BBWLC mission including its optical design, mechanical structure, pointing system, the first flight and results associated with the data processing approach. Preliminary analysis of the data shows that BBWLC imaged the Kcorona with three streamer structures on the west limb of the Sun. To further confirm the coronal signals obtained by BBWLC, comparisonswere made with observations of the Kcoronagraph of the High Altitude Observatory and the Atmospheric ImagingAssembly on board the Solar Dynamics Observatory. We conclude that BBWLC eventually observed the white-light corona in its first scientific flight. △ Less

Submitted 27 November, 2025; originally announced November 2025.

Comments: 17 pages, 10 figures,

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… ▽ More 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. △ Less

Submitted 5 December, 2025; v1 submitted 24 November, 2025; originally announced November 2025.

Comments: 6 pages (main) + 7 pages (appendix) + refs; 8 figures

Report number: P2500248

A catalog of new blue stragglers in open clusters with Gaia DR3

Authors: Songmei Qin, Jing Zhong, Friedrich Anders, Lola Balaguer-Núñez, Chunyan Li, Yueyue Jiang, Guimei Liu, Tong Tang, Li Chen

Abstract: The high-precision {\it Gaia} data release 3 (DR3) enables the discovery of numerous open clusters in the Milky Way, providing an excellent opportunity to search for blue straggler stars in open clusters and investigate their formation and evolution in these environments. Using the member stars from literature open cluster catalogs, we visually inspected the color-magnitude diagram (CMD) of each c… ▽ More The high-precision {\it Gaia} data release 3 (DR3) enables the discovery of numerous open clusters in the Milky Way, providing an excellent opportunity to search for blue straggler stars in open clusters and investigate their formation and evolution in these environments. Using the member stars from literature open cluster catalogs, we visually inspected the color-magnitude diagram (CMD) of each cluster and selected cluster candidates that potentially host blue stragglers. We then reassessed cluster memberships using the {\tt pyUPMASK} algorithm with {\it Gaia} DR3 and performed isochrone fitting to derive physical parameters for each cluster, including age, distance modulus, mean reddening, and metallicity. Finally, we empirically identified straggler stars based on their positions relative to the best-fitting isochrone, zero-age main sequence (ZAMS), and equal-mass binary sequence on the CMD. In total, we identified 272 new straggler stars in 99 open clusters, comprising 153 blue stragglers, 98 probable blue stragglers, and 21 yellow stragglers. Compared to the reported blue straggler catalogs based on earlier {\it Gaia} data, our results increase the number of open clusters with stragglers in the Milky Way by 22.2\%, and the total number of blue stragglers by 11.2\%. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Comments: 24 pages, 15 figures

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… ▽ More 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. △ Less

Submitted 11 December, 2025; v1 submitted 30 October, 2025; originally announced October 2025.

Comments: 9 pages, 1 figure (+1 figure in appendix)

Report number: P2500252

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… ▽ More 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. △ Less

Submitted 30 October, 2025; originally announced October 2025.

Comments: Data available from Zenodo (https://zenodo.org/records/17343574) or the Gravitational-Wave Open Science Center (https://gwosc.org)

Report number: LIGO-P2500402

Journal ref: Astrophys. J. Letters, 993, L21 (2025)

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… ▽ More 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. △ Less

Submitted 7 November, 2025; v1 submitted 30 October, 2025; originally announced October 2025.

Comments: Main paper: 45 pages, 20 figures

Report number: LIGO-PP2500150

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… ▽ More 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 $C_\ell^{1/2} < (0.63 - 17) \times 10^{-10} \,\mathrm{sr}^{-1}$. △ Less

Submitted 20 October, 2025; originally announced October 2025.

Comments: Main paper: 11 pages and 4 figures; Total with appendices: 39 pages and 12 figures

Report number: LIGO-P250038

Scientific Objectives of the Xue-shan-mu-chang 15-meter Submillimeter Telescope

Authors: XSMT Project Collaboration Group, Yiping Ao, Jin Chang, Zhiwei Chen, Xiangqun Cui, Kaiyi Du, Fujun Du, Yan Gong, Zhanwen Han, Gregory Herczeg, Luis C. Ho, Jie Hu, Yipeng Jing, Sihan Jiao, Binggang Ju, Jing Li, Xiaohu Li, Xiangdong Li, Lingrui Lin, Zhenhui Lin, Daizhong Liu, Dong Liu, Guoxi Liu, Zheng Lou, Dengrong Lu , et al. (26 additional authors not shown)

Abstract: Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China,… ▽ More Submillimeter astronomy is poised to revolutionize our understanding of the Universe by revealing cosmic phenomena hidden from optical and near-infrared observations, particularly those associated with interstellar dust, molecular gas, and star formation. The Xue-shan-mu-chang 15-meter submillimeter telescope (XSMT-15m), to be constructed at a premier high-altitude site (4813 m) in Qinghai, China, marks a major milestone for Chinese astronomy, establishing the China mainland's first independently developed, world-class submillimeter facility. Equipped with state-of-the-art instruments, XSMT-15m will address a diverse range of frontier scientific questions spanning extragalactic astronomy, Galactic structure, time-domain astrophysics, and astrochemistry. In synergy with current and forthcoming observatories, XSMT-15m will illuminate the formation and evolution of galaxies, unravel the physical and chemical processes shaping the interstellar medium, and explore transient phenomena in the submillimeter regime. These capabilities will advance our understanding across extragalactic astronomy, Galactic ecology, astrochemistry, and time-domain astrophysics, inaugurating a new era for submillimeter research in China and the northern hemisphere. △ Less

Submitted 17 September, 2025; originally announced September 2025.

Comments: Accepted by Science China Physics, Mechanics & Astronomy

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-… ▽ More 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. △ Less

Submitted 9 September, 2025; originally announced September 2025.

Comments: 6 pages, 5 figures (plus supplement)

Report number: LIGO-P2500421

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… ▽ More 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. △ Less

Submitted 14 September, 2025; v1 submitted 8 September, 2025; originally announced September 2025.

Comments: 33 pages, 4 figures

Report number: LIGO-P2500256

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… ▽ More 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. △ Less

Submitted 7 October, 2025; v1 submitted 4 September, 2025; originally announced September 2025.

Comments: As part of the Astrophysical Journal Letters Focus Issue on the Gravitational Wave Transient Catalog

Report number: LIGO-P2400152

A magnetic white dwarf formed through a binary merger within 35 million years

Authors: Huahui Yan, Jiamao Lin, Rizhong Zheng, Li Wang, Genghao Liu, Liangliang Ren, Zhen Guo, Siyi Xu, Zhangliang Chen, Chun Chen, Bo Ma, Yong Shao, Zhenwei Li, Xianfei Zhang, Christoffer Fremling, Jan J. Eldridge, Hongwei Ge, Chengyuan Li

Abstract: White dwarfs (WDs) represent the final evolutionary stage of most stars, typically originating from progenitor stars with masses below approximately 8 $M_{\odot}$ to 10 $M_{\odot}$. Formation through single-star evolution generally requires at least 25 Myr, with the youngest WDs often near the Chandrasekhar limit of 1.4 $M_{\odot}$. In contrast, WDs formed via binary channels, such as mergers or m… ▽ More White dwarfs (WDs) represent the final evolutionary stage of most stars, typically originating from progenitor stars with masses below approximately 8 $M_{\odot}$ to 10 $M_{\odot}$. Formation through single-star evolution generally requires at least 25 Myr, with the youngest WDs often near the Chandrasekhar limit of 1.4 $M_{\odot}$. In contrast, WDs formed via binary channels, such as mergers or mass transfer, can develop smaller masses in a shorter timescale and may exhibit unique characteristics, including strong surface magnetic fields and rapid rotation. Accurately determining the ages of these WDs is essential for understanding their formation. A valuable method involves studying WDs in star clusters, where member stars share the same age and chemical composition, allowing for precise constraints on the formation times and metallicities of the WDs' progenitors. Here we report a WD found in the open cluster RSG 5, which is only 35 Myr old. The WD's mass is lower than 1.05 $M_{\odot}$, indicating it may not have formed through single-star evolution. The WD possesses an exceptionally strong surface magnetic field ($\ge 200$ MG), a short rotational period ($\sim 6.5$ min), and, most notably, a co-rotating half-ring of ionized circumstellar debris. This distinctive feature provides evidence for a binary merger origin, a scenario further substantiated by our stellar evolution models. △ Less

Submitted 31 August, 2025; originally announced September 2025.

Comments: 16 pages, 9 figures, accepted for publication in ApJ Letters

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… ▽ More 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, $Ω_{\rm BBH}(25{\rm Hz})=0.8^{+1.1}_{-0.5}\times 10^{-9}$. △ Less

Submitted 28 August, 2025; originally announced August 2025.

Comments: 31 pages, 7 figures

Report number: LIGO-P2500349

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… ▽ More 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) △ Less

Submitted 17 September, 2025; v1 submitted 25 August, 2025; originally announced August 2025.

Comments: As part of the Astrophysical Journal Letters Focus Issue on the Gravitational Wave Transient Catalog

Report number: LIGO-P2400004

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… ▽ More 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. △ Less

Submitted 8 September, 2025; v1 submitted 25 August, 2025; originally announced August 2025.

Comments: As part of the Astrophysical Journal Letters Focus Issue on the Gravitational Wave Transient Catalog

Report number: LIGO-P2400386

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… ▽ More 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. △ Less

Submitted 25 August, 2025; originally announced August 2025.

Comments: As part of the Astrophysical Journal Letters Focus Issue on the Gravitational Wave Transient Catalog

Report number: LIGO-P2400300

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… ▽ More 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 △ Less

Submitted 23 September, 2025; v1 submitted 25 August, 2025; originally announced August 2025.

Comments: As part of the Astrophysical Journal Letters Focus Issue on the Gravitational Wave Transient Catalog. Update following peer review

Report number: LIGO-P2400293

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… ▽ More 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. △ Less

Submitted 4 November, 2025; v1 submitted 25 August, 2025; originally announced August 2025.

Comments: 26 pages. The version updates Table 3, updates the author list, removes one figure, and updates some text for clarity and grammar

Report number: LIGO-P2500167

Binary clusters in the Galactic disk I: Systematic identification and classification using Gaia DR3

Authors: Guimei Liu, Yu Zhang, Jing Zhong, Songmei Qin, Yueyue Jiang, Li Chen

Abstract: Aims. We aim to identify and classify BCs using high-precision astrometric and kinematic data, and to investigate their physical properties, mutual gravitational interactions, and formation rates. Methods. We used a comprehensive star cluster catalog that contains 4,084 high-quality clusters. Based on spatial and kinematic proximity, we identified 400 cluster pairs involving 686 unique clusters. T… ▽ More Aims. We aim to identify and classify BCs using high-precision astrometric and kinematic data, and to investigate their physical properties, mutual gravitational interactions, and formation rates. Methods. We used a comprehensive star cluster catalog that contains 4,084 high-quality clusters. Based on spatial and kinematic proximity, we identified 400 cluster pairs involving 686 unique clusters. These pairs were classified into three types: primordial BCs, systems formed through tidal capture or resonant trapping, and hyperbolic encounter pairs. For each system, we calculated the tidal factor to quantify the strength of mutual tidal interaction. Additionally, we constructed multi-cluster systems by identifying transitive connections among cluster pairs. Results. Among the 400 identified cluster pairs, nearly 60.8% (243 pairs) are probably primordial BCs, exhibiting both similar ages and motions. This supports a scenario where they formed together in the same giant molecular cloud. We find that 82.5% of the cluster pairs have strong mutual tidal forces. In addition, 278 star clusters are identified as members of 82 multi-cluster systems, including 27 newly reported groups. Cross-matching with the literature confirms the recovery of previously reported systems and leads to the discovery of 268 new cluster pairs. In our sample, about 16.8% of star clusters are involved in some type of interaction with another cluster, and 9.94% of star clusters are likely born in primordial BCs. Conclusions. Our results provide a comprehensive, homogeneously identified sample of Galactic BCs. The high fraction of primordial BCs and their mutual tidal interaction suggest that cluster formation in pairs is a main outcome of star formation. This work offers new observational constraints on the formation and dynamical evolution of multiple star cluster systems. △ Less

Submitted 12 August, 2025; originally announced August 2025.

Comments: Accepted for publications in A&A. 11 pages, 8 figures

Journal ref: A&A 702, A48 (2025)

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… ▽ More 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. △ Less

Submitted 5 August, 2025; originally announced August 2025.

Report number: JGW-P2516701

Revealing the Origins of Galactic Globular Clusters via Their Mg-Al Abundances

Authors: Shihui Lin, Baitian Tang, Genghao Liu, JosÉ G. Fernández-Trincado, Douglas Geisler, Guy Worthey, Dante Minnitit

Abstract: Many Galactic globular clusters (GCs) originated in diverse host galaxies before being subsequently incorporated into the Milky Way through hierarchical galaxy assembly. Identifying their origins is crucial for revealing galaxy properties at early times. Traditional classification methods relying on dynamical properties face inherent uncertainties stemming from the evolving Galactic potential and… ▽ More Many Galactic globular clusters (GCs) originated in diverse host galaxies before being subsequently incorporated into the Milky Way through hierarchical galaxy assembly. Identifying their origins is crucial for revealing galaxy properties at early times. Traditional classification methods relying on dynamical properties face inherent uncertainties stemming from the evolving Galactic potential and complex merger histories. Chemically driven classification confronts a distinct obstacle: multiple populations - abundance variations in light elements of GC members. In this Letter, we identify primordial populations exhibiting lower [Al/Fe] as reliable tracers of their birth environments' chemical evolution. A clear chemical dichotomy emerges between in-situ and accreted GC populations at [Fe/H] > -1.5, particularly in the [Mg/Fe]-[Al/Fe] plane, indicating that their progenitor galaxies have experienced fundamentally different enrichment histories. While our chemically driven classification demonstrates general consistency with dynamically driven classifications, notable discrepancies emerge: NGC 288 and M4 are reclassified as in-situ, and Terzan 9 as accreted. This chemically driven GC classification provides promising application for Galactic archaeology. △ Less

Submitted 14 August, 2025; v1 submitted 1 August, 2025; originally announced August 2025.

Comments: 10 pages, 4 figures, 2 tables, accepted for ApJL

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… ▽ More 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. △ Less

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

Comments: 27 pages, 10 figures

Report number: DCC: P2500026-v8

Journal ref: ApJL 993 L25 (2025)

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… ▽ More 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. △ Less

Submitted 26 June, 2025; originally announced June 2025.

Comments: To appear in Progress of Theoretical and Experimental Physics (PTEP), accepted June 2025

Journal ref: Prog Theor Exp Phys (2025)

Dense Matter in Neutron Stars with eXTP

Authors: Ang Li, Anna L. Watts, Guobao Zhang, Sebastien Guillot, Yanjun Xu, Andrea Santangelo, Silvia Zane, Hua Feng, Shuang-Nan Zhang, Mingyu Ge, Liqiang Qi, Tuomo Salmi, Bas Dorsman, Zhiqiang Miao, Zhonghao Tu, Yuri Cavecchi, Xia Zhou, Xiaoping Zheng, Weihua Wang, Quan Cheng, Xuezhi Liu, Yining Wei, Wei Wang, Yujing Xu, Shanshan Weng , et al. (60 additional authors not shown)

Abstract: In this White Paper, we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission to constrain the equation of state of dense matter in neutron stars, exploring regimes not directly accessible to terrestrial experiments. By observing a diverse population of neutron stars - including isolated objects, X-ray bursters, and accreting systems - eXTP's unique combination of timin… ▽ More In this White Paper, we present the potential of the enhanced X-ray Timing and Polarimetry (eXTP) mission to constrain the equation of state of dense matter in neutron stars, exploring regimes not directly accessible to terrestrial experiments. By observing a diverse population of neutron stars - including isolated objects, X-ray bursters, and accreting systems - eXTP's unique combination of timing, spectroscopy, and polarimetry enables high-precision measurements of compactness, spin, surface temperature, polarimetric signals, and timing irregularity. These multifaceted observations, combined with advances in theoretical modeling, pave the way toward a comprehensive description of the properties and phases of dense matter from the crust to the core of neutron stars. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is planned to be launched in early 2030. △ Less

Submitted 8 September, 2025; v1 submitted 9 June, 2025; originally announced June 2025.

Comments: accepted for publication in the SCIENCE CHINA Physics, Mechanics & Astronomy

Journal ref: SCIENCE CHINA Physics, Mechanics & Astronomy 68, 119503 (2025)

The Parameter Dependence of $\mathbf{n_{s}}$ and $\mathbf{r}$ of the Scalar Power Spectrum during Single-Field Slow-Roll Inflation: A Comparative Study of Inflationary Potentials

Authors: Guanqiao Liu

Abstract: Inflation in cosmology is a specific stage preceding the Big Bang, aimed at solving both old background problems and new perturbation issues. Single-field inflation is a candidate to illustrate the picture of the initial universe, and various potential functions lead to different scenarios during the inflationary stage. This paper introduces two essential parameters: the spectral index and the ten… ▽ More Inflation in cosmology is a specific stage preceding the Big Bang, aimed at solving both old background problems and new perturbation issues. Single-field inflation is a candidate to illustrate the picture of the initial universe, and various potential functions lead to different scenarios during the inflationary stage. This paper introduces two essential parameters: the spectral index and the tensor-to-scalar ratio detected from the initial power spectrum, derived from the action of the scalar field and using approximation that the potential is flat. A brief overview of the origins of Starobinsky Inflation, Chaotic Inflation, Small Field Inflation, and Natural Inflation is also presented, along with their mathematical representations. Finally, the results derived from various inflation models regarding the index and ratio are tested using the Planck data, and the deviations in each model are analyzed. △ Less

Submitted 20 May, 2025; v1 submitted 16 May, 2025; originally announced May 2025.

Insights into the 3D layered structure of nearby open clusters through N-body simulations

Authors: Kaixiang Lang, Yu Zhang, Hubiao Niu, Jayanand Maurya, Jinzhong Liu, Guimei Liu

Abstract: Context. Open clusters (OCs) are important for understanding star formation, dynamics, and evolution. Previous studies have indicated a relationship between cluster structure and member star properties, but the formation mechanism of the layered structure of OCs remains unclear. Aims. We study the three-dimensional spatial distribution of 279 nearby OCs to understand the formation mechanism of the… ▽ More Context. Open clusters (OCs) are important for understanding star formation, dynamics, and evolution. Previous studies have indicated a relationship between cluster structure and member star properties, but the formation mechanism of the layered structure of OCs remains unclear. Aims. We study the three-dimensional spatial distribution of 279 nearby OCs to understand the formation mechanism of the layered structure. Methods. We analyzed the spatial distribution of member stars within each OC and correlated the presence of a layered structure with the number of member stars. Additionally, we performd N-body simulations to model the evolution of OCSN 125. We assessd the correlation between the binary fraction, the most massive star, and the radius of the layered structure in each simulated OC. Results. Our analysis reveals that OCs with fewer member stars tend to lack a layered structure. The results from N-body simulations indicate that the presence of a layered structure is strongly influenced by dynamical factors, particularly the most massive star and the binary fraction. Massive stars drive mass loss through supernova explosions and stellar winds, which weaken the spatial layering. Furthermore, clusters with higher binary fractions exhibit a weaker layered structure, likely due to energy equipartition, dynamical friction, and perturbations caused by binary systems. These factors contribute to delaying core collapse and slowing the emergence of a layered structure. Conclusions. Our findings suggest that dynamical interactions, including the effects of the most massive stars and binary fraction, play a critical role in the formation and disruption of the layered structure in OCs. △ Less

Submitted 15 May, 2025; v1 submitted 12 May, 2025; originally announced May 2025.

Comments: 10 pages, 6 figures; Accepted by A&A

Fine-scale opposite-polarity magnetic fields in a solar plage revealed by integral field spectropolarimetry

Authors: G. Liu, I. Milić, J. S. Castellanos Duran, J. M. Borrero, M. van Noort, C. Kuckein

Abstract: Plages are small concentrations of strong, nearly vertical magnetic fields in the solar photosphere that expand with height. A high spatial and spectral resolution that can resolve their fine structure is required to characterize them, and spectropolarimetric capabilities are needed to infer their magnetic fields. We constrain the 3D fine structure of the magnetic field in the photosphere of a sol… ▽ More Plages are small concentrations of strong, nearly vertical magnetic fields in the solar photosphere that expand with height. A high spatial and spectral resolution that can resolve their fine structure is required to characterize them, and spectropolarimetric capabilities are needed to infer their magnetic fields. We constrain the 3D fine structure of the magnetic field in the photosphere of a solar plage from a unique spectropolarimetric dataset with a very high spatial and spectral resolution and a fast temporal cadence. We analyzed spectropolarimetric observations of a solar plage in the two magnetically sensitive spectral lines of neutral iron around 630 nm. The observations were obtained with MiHI, which is an integral field unit attached to the Swedish Solar Telescope. MiHI obtained diffraction-limited, high-cadence observations with high spectral fidelity. These observations were interpreted using the spectropolarimetric inversion with magnetohydrostatic constraints, which allowed us to recover the magnetic and thermodynamic structure of the plage on a geometrical scale. The inversion results reveal that the magnetic field can reach up to 2 kG and that it expands significantly from the deep to the mid-photosphere. Weaker (200 G), and very small (subarcsecond) vertical magnetic loops lie beneath this canopy, rooted in the photosphere. This novel picture of a solar plage, in which weak opposite-polarity field patches surround the main polarity, provides new insight into convection in strongly magnetized plasma. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Comments: Accepted for publication in Astronomy & Astrophysics

Pulsation Properties of Blazhko and Non-Blazhko RRab Stars

Authors: Peng Zong, Jian-Ning Fu, Jie Su, Bing-Kai Zhang, Gao-Chao Liu, Weichao Sun, Jiaxin Wang, Bo Zhang, Xueying Hu, Zhongrui Bai, Weikai Zong

Abstract: In this study, we conduct a comparative analysis of the properties of Blazhko and non-Blazhko RRab stars. We identified 1054 non-Blazhko and 785 Blazhko RRab stars in the photometric data observed by K2 mission, which, combined with those 37 stars observed in the original Kepler field, constituted our study sample. Using the Fourier Decomposition method, we calculated the pulsation parameters, inc… ▽ More In this study, we conduct a comparative analysis of the properties of Blazhko and non-Blazhko RRab stars. We identified 1054 non-Blazhko and 785 Blazhko RRab stars in the photometric data observed by K2 mission, which, combined with those 37 stars observed in the original Kepler field, constituted our study sample. Using the Fourier Decomposition method, we calculated the pulsation parameters, including phase differences and amplitude ratios, for these RRab stars, revealing significant discrepancies in the pulsation parameters between Blazhko and non-Blazhko RRab stars. However, distinguishing between Blazhko and Non-Blazhko RRab stars based on Fourier parameters remains challenging due to the significant overlap in their distributions. By cross-matching our sample with the LRS of LAMOST DR12, we identified 147 Blazhko and 111 non-Blazhko RRab stars, which exhibit similar metallicity distributions. Furthermore, cross-matching with Gaia DR3 data yielded 766 Blazhko and 950 non-Blazhko RRab stars, showing differences in color indices but not in absolute magnitudes. Our findings suggested the Blazhko effect is linked to pulsation parameters and colors, rather than metallicities or absolute magnitude. △ Less

Submitted 18 March, 2025; originally announced March 2025.

Formation and evolution of new primordial open cluster groups: Feedback-driven star formation

Authors: Guimei Liu, Yu Zhang, Jing Zhong, Li Chen, Xiangcun Meng, Kai Wu

Abstract: The formation mechanisms of open cluster (OCs) groups remain unclear due to limited sample sizes and data precision. Recent advancements in Gaia astrometric data provide an unprecedented opportunity to study OC groups in greater detail. This study aims to extend the sample of OC groups and investigate their formation and evolution mechanisms, with a focus on the role of stellar feedback in trigger… ▽ More The formation mechanisms of open cluster (OCs) groups remain unclear due to limited sample sizes and data precision. Recent advancements in Gaia astrometric data provide an unprecedented opportunity to study OC groups in greater detail. This study aims to extend the sample of OC groups and investigate their formation and evolution mechanisms, with a focus on the role of stellar feedback in triggering star formation. We identify four new OC groups based on Gaia data, whose member OCs are spatially proximate and kinematically coherent. Their age spreads are consistent with the timescale of continuous star formation, suggesting that their member OCs formed sequentially from the same molecular cloud. N-body simulation results further reveal that these groups will gradually disperse, evolving into independent OCs. By analyzing the correlation between OC ages and their separation from potential SN explosion sites, we predict SN explosion regions around the birthplaces of OC groups. The strong correlation between OC ages and predicted SN explosion sites supports a supernova-triggered star formation scenario. Additionally, we trace pulsar (PSR) orbits to examine their association with these regions. We detected three PSRs near Group 1 and 26 PSRs near Group 2, whose birthplaces align with the predicted SN explosions regions. The presence of PSRs associated with OC groups provides additional observational evidence for SN explosions in this region, further supporting a supernova-triggered star formation scenario for G1 and G2. We propose that multiple SN explosions in a short period triggered the formation of Group 1 and Group 2, reinforcing the hierarchical star formation model. These results highlight the multi-scale interactions driving star and OC formation and provide new insights into the role of stellar feedback in shaping OC groups. △ Less

Submitted 18 March, 2025; originally announced March 2025.

Comments: 13 pages, 6 figures, accepted for publication in A&A

Photometric-Metallicity and Distance Estimates for $\sim$70,000 RR Lyrae Stars from the Zwicky Transient Facility

Authors: Shunxuan He, Yang Huang, XinYi Li, Huawei Zhang, Gaochao Liu, Timothy C. Beers, Hong Wu, Zhou Fan

Abstract: Utilizing Zwicky Transient Facility (ZTF) data and existing RR Lyrae stars (RRLs) catalogs, this study achieves the first calibration of the $P - φ_{31} - R_{21} - \text{[Fe/H]}$ and $P-φ_{31}-A_{2}-A_{1}-\text{[Fe/H]}$ relations in the ZTF photometric system for RRab and RRc stars. We also re-calibrate the period-absolute magnitude-metallicity (PMZ) and period-Wesenheit-metallicity (PWZ) relation… ▽ More Utilizing Zwicky Transient Facility (ZTF) data and existing RR Lyrae stars (RRLs) catalogs, this study achieves the first calibration of the $P - φ_{31} - R_{21} - \text{[Fe/H]}$ and $P-φ_{31}-A_{2}-A_{1}-\text{[Fe/H]}$ relations in the ZTF photometric system for RRab and RRc stars. We also re-calibrate the period-absolute magnitude-metallicity (PMZ) and period-Wesenheit-metallicity (PWZ) relations in the ZTF $gri$-bands for RRab and RRc stars. Based on nearly 4100 stars with precise measurements of $P$, $φ_{31}$, $A_{2}$, and $A_{1}$, and available spectroscopic-metallicity estimates, the photometric-metallicity relations exhibit strong internal consistency across different bands, supporting the use of a weighted averaging method for the final estimates. The photometric-metallicity estimates of globular clusters based on RR Lyrae members also show excellent agreement with high-resolution spectroscopic measurements, with typical scatter of 0.15 dex for RRab stars and 0.14 dex for RRc stars, respectively. Using hundreds of local RRLs with newly derived photometric metallicities and precise Gaia Data Release 3 parallaxes, we establish the PMZ and PWZ relations in multiple bands. Validation with globular cluster RR Lyrae members reveals typical distance errors of 3.1% and 3.0% for the PMZ relations, and 3.1% and 2.6% for the PWZ relations for RRab and RRc stars, respectively. Compared to PMZ relations, the PWZ relations are tighter and almost unbiased, making them the recommended choice for distance calculations. We present a catalog of 73,795 RRLs with precise photometric metallicities; over 95% of them have accurate distance measurements. Compared to Gaia DR3, approximately 25,000 RRLs have precise photometric metallicities and distances derived for the first time. △ Less

Submitted 5 March, 2025; originally announced March 2025.

Comments: 29 pages, 31 figures and 7 tables, accepted by ApJS, the RRL parameter catalogs are available at https://zenodo.org/records/14561442

The distance of quasar outflows from the central source: The first consistent values from emission and absorption determinations

Authors: Mayank Sharma, Nahum Arav, Qinyuan Zhao, Maryam Dehghanian, Doyee Byun, Gwen Walker, Luming Sun, Lu Shen, Yulong Gao, Guilin Liu, Junfeng Wang

Abstract: Measuring the distance of quasar outflows from the central source ($R$) is essential for determining their importance for AGN feedback. There are two methods to measure $R$: 1) A direct determination using spatially resolved Integral Field Spectroscopy (IFS) of the outflow in emission. 2) An indirect method which uses the absorption troughs from ionic excited states. The column density ratio betwe… ▽ More Measuring the distance of quasar outflows from the central source ($R$) is essential for determining their importance for AGN feedback. There are two methods to measure $R$: 1) A direct determination using spatially resolved Integral Field Spectroscopy (IFS) of the outflow in emission. 2) An indirect method which uses the absorption troughs from ionic excited states. The column density ratio between the excited and resonance states yields the outflow number density. Combined with a knowledge of the outflow's ionization parameter, $R$ can be determined. Generally, the IFS method probes $R$ range of several kpc or more, while the absorption method usually yields $R$ values of less than 1 kpc. There is no inconsistency between the two methods as the determinations come from different objects. Here we report the results of applying both methods to the same quasar outflow, where we derive consistent determinations of $R$ $\approx$ 5 kpc. This is the first time where the indirect absorption $R$ determination is verified by a direct spatially resolved IFS observation. In addition, the velocities (and energetics) from the IFS and absorption data are also found to be consistent. Therefore, these are two manifestations of the same outflow. In this paper we concentrate on the absorption $R$ determination for the outflow seen in quasar 3C 191 using VLT/X-shooter observations. We also reanalyze an older absorption determination for the outflow based on Keck/HIRES data and find that revised measurement to be consistent with ours. Our companion paper details the IFS analysis of the same object. △ Less

Submitted 26 February, 2025; originally announced February 2025.

Comments: 18 pages, 11 figures. Accepted for publication in ApJ along with the companion paper

Galactic-scale emission-line outflow from the radio-loud quasar 3C 191

Authors: Qinyuan Zhao, Luming Sun, Lu Shen, Guilin Liu, Junfeng Wang, Mayank Sharma, Nahum Arav, Yulong Gao, Chris Benn

Abstract: Quasar feedback is routinely invoked as an indispensable ingredient in galaxy formation models. Galactic outflows are a crucial agent of quasar feedback that frequently manifest themselves in absorption and emission lines. Measuring the size and energetics of outflows based on absorption lines remains a challenge, and integral-field spectroscopy (IFS) mapping in emission lines is complementary. We… ▽ More Quasar feedback is routinely invoked as an indispensable ingredient in galaxy formation models. Galactic outflows are a crucial agent of quasar feedback that frequently manifest themselves in absorption and emission lines. Measuring the size and energetics of outflows based on absorption lines remains a challenge, and integral-field spectroscopy (IFS) mapping in emission lines is complementary. We present a VLT/SINFONI IFS mapping of quasar 3C 191 at $z \sim 2$, in which the outflow has been analyzed in absorption line spectroscopy. Three components are found based on the morphology and kinetics of [OIII]-emitting gas: a unshifted component which consistent with the systemic redshift and the location of the nucleus, a blueshifted in the north, and a redshifted in the south. The latter two components have velocities $\sim$ 600 km s$^{-1}$ and projected extents of 5 and 11 kpc, respectively, suggesting a biconical outflow structure. The blueshifted component's velocity is consistent with that derived from absorption lines. Using the electron density measured by the absorption lines and the luminosity and velocity of [OIII] outflow, we derive the mass outflow rate to be $\dot{M} \sim $ 9.5-13.4 M$_\odot$ yr$^{-1}$ and kinetic luminosity $\dot{E}_{\rm kin}$ ~ 2.5-3.7 $\times 10^{42}$ erg s$^{-1}$, consistent with absorption line analyses with VLT/Xshooter spectrum. The kinetic luminosity is only 0.01% of the bolometric luminosity, rendering a relatively weak outflow compared to typical expectation for effective feedback. △ Less

Submitted 26 February, 2025; originally announced February 2025.

Comments: 18gapes, 10 figures, Accepted for publication in ApJS

Search for continuous gravitational waves from known pulsars in 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, R. Abbott, I. Abouelfettouh, F. Acernese, K. Ackley, S. Adhicary, N. Adhikari, R. X. Adhikari, V. K. Adkins, D. Agarwal, M. Agathos, M. Aghaei Abchouyeh, O. D. Aguiar, I. Aguilar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, R. A. Alfaidi, A. Al-Jodah, C. Alléné , et al. (1794 additional authors not shown)

Abstract: Continuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of General Relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO--Virgo--KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent ana… ▽ More Continuous gravitational waves (CWs) emission from neutron stars carries information about their internal structure and equation of state, and it can provide tests of General Relativity. We present a search for CWs from a set of 45 known pulsars in the first part of the fourth LIGO--Virgo--KAGRA observing run, known as O4a. We conducted a targeted search for each pulsar using three independent analysis methods considering the single-harmonic and the dual-harmonic emission models. We find no evidence of a CW signal in O4a data for both models and set upper limits on the signal amplitude and on the ellipticity, which quantifies the asymmetry in the neutron star mass distribution. For the single-harmonic emission model, 29 targets have the upper limit on the amplitude below the theoretical spin-down limit. The lowest upper limit on the amplitude is $6.4\!\times\!10^{-27}$ for the young energetic pulsar J0537-6910, while the lowest constraint on the ellipticity is $8.8\!\times\!10^{-9}$ for the bright nearby millisecond pulsar J0437-4715. Additionally, for a subset of 16 targets we performed a narrowband search that is more robust regarding the emission model, with no evidence of a signal. We also found no evidence of non-standard polarizations as predicted by the Brans-Dicke theory. △ Less

Submitted 26 September, 2025; v1 submitted 2 January, 2025; originally announced January 2025.

Comments: main paper: 12 pages, 6 figures, 4 tables

Report number: LIGO-P2400315

Journal ref: Astrophys.J. 983 (2025) 2, 99

Identifying the Galactic Substructures in 5D Space Using All-sky RR Lyrae Stars in Gaia DR3

Authors: Shenglan Sun, Fei Wang, Huawei Zhang, Xiang-Xiang Xue, Yang Huang, Ruizhi Zhang, Hans-Walter Rix, Xinyi Li, Gaochao Liu, Lan Zhang, Chengqun Yang, Shuo Zhang

Abstract: Motivated by the vast gap between photometric and spectroscopic data volumes, there is great potential in using 5D kinematic information to identify and study substructures of the Milky Way. We identify substructures in the Galactic halo using 46,575 RR Lyrae stars (RRLs) from Gaia DR3 with the photometric metallicities and distances newly estimated by Li et al. (2023). Assuming a Gaussian prior d… ▽ More Motivated by the vast gap between photometric and spectroscopic data volumes, there is great potential in using 5D kinematic information to identify and study substructures of the Milky Way. We identify substructures in the Galactic halo using 46,575 RR Lyrae stars (RRLs) from Gaia DR3 with the photometric metallicities and distances newly estimated by Li et al. (2023). Assuming a Gaussian prior distribution of radial velocity, we calculate the orbital distribution characterized by the integrals of motion for each RRL based on its 3D positions, proper motions and corresponding errors, and then apply the friends-of-friends algorithm to identify groups moving along similar orbits. We have identified several known substructures, including Sagittarius (Sgr) Stream, Hercules-Aquila Cloud (HAC), Virgo Overdensity (VOD), Gaia-Enceladus-Sausage (GES), Orphan-Chenab stream, Cetus-Palca, Helmi Streams, Sequoia, Wukong and Large Magellanic Cloud (LMC) leading arm, along with 18 unknown groups. Our findings indicate that HAC and VOD have kinematic and chemical properties remarkably similar to GES, with most HAC and VOD members exhibiting eccentricity as high as GES, suggesting that they may share a common origin with GES. The ability to identify the low mass and spatially dispersed substructures further demonstrates the potential of our method, which breaks the limit of spectroscopic survey and is competent to probe the substructures in the whole Galaxy. Finally, we have also identified 18 unknown groups with good spatial clustering and proper motion consistency, suggesting more excavation of Milky Way substructures in the future with only 5D data. △ Less

Submitted 20 November, 2024; originally announced November 2024.

Comments: 23 pages, 19 figures, 4 tables, accepted for publication in ApJ, version before language edition

CHANG-ES XXXV: Cosmic Ray Transport and Magnetic Field Structure of NGC 3556 at 3 GHz

Authors: Jianghui Xu, Yang Yang, Jiang-Tao Li, Guilin Liu, Judith Irwin, Ralf-Jürgen Dettmar, Michael Stein, Theresa Wiegert, Q. Daniel Wang, Jayanne English

Abstract: Radio halos of edge-on galaxies are crucial for investigating cosmic ray propagation and magnetic field structures in galactic environments. We present VLA C-configuration S-band (2--4 GHz) observations of the spiral galaxy NGC 3556, a target from the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES). We estimate the thermal contribution to the radio emission from a combination of the… ▽ More Radio halos of edge-on galaxies are crucial for investigating cosmic ray propagation and magnetic field structures in galactic environments. We present VLA C-configuration S-band (2--4 GHz) observations of the spiral galaxy NGC 3556, a target from the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES). We estimate the thermal contribution to the radio emission from a combination of the H$α$ and mid-IR data, and employ Rotation Measure Synthesis to reveal the magnetic field structures. In our data, NGC 3556 exhibits a box-like radio halo extending nearly 7 kpc from the galactic plane. The scale height of the total S-band intensity in the halo is $1.68\pm 0.29$ kpc, while that of the non-thermal intensity is $1.93\pm 0.28$ kpc. Fitting the data to a 1-D cosmic-ray transport model, we find advection to describe the cosmic-ray propagation within the halo better than diffusion, with advection speeds of $245 \pm 15$ km s$^{-1}$ and $205 \pm 25$ km s$^{-1}$ above and below the disk, respectively. The magnetic field is detected patchily across the galaxy, displaying a toroidal configuration in the rotation measure map. The mean equipartition magnetic field strength is approximately $8.3\ μ$G in the disk and $4.5\ μ$G in the halo. In addition, a bubble-like structure extends nearly 3~kpc into the southern halo, aligned with the polarized intensity and H$α$ image, suggestive of superwinds generated by recent star formation feedback in the nuclear region. △ Less

Submitted 19 November, 2024; originally announced November 2024.

Comments: 17 pages, 10 figures, 4 tables, accepted for publication in ApJ

Ultra High Energy Cosmic Rays in light of the Lorentz Invariance Violation Effects within the Proton Sector

Authors: Guo-Li Liu, Xinbo Su, Fei Wang

Abstract: Tiny Lorentz Invariance Violation (LIV) effects, potentially arising from quantum gravity-induced spacetime structures, may also manifest in the proton sector, offering a plausible pathway to test Planck-scale physics through high-energy cosmic phenomena. Our analysis reveals that even minuscule LIV effects in the proton sector can significantly elevate the photon threshold energy for photopion pr… ▽ More Tiny Lorentz Invariance Violation (LIV) effects, potentially arising from quantum gravity-induced spacetime structures, may also manifest in the proton sector, offering a plausible pathway to test Planck-scale physics through high-energy cosmic phenomena. Our analysis reveals that even minuscule LIV effects in the proton sector can significantly elevate the photon threshold energy for photopion production to $\cal {O}$(0.1 to $10^3$ eV), orders of magnitude higher than in Lorentz-symmetric scenarios. Consequently, protons in ultra-high-energy cosmic rays (UHECRs) can propagate for very long distances without significant energy loss via photopion interactions with cosmic microwave background (CMB) photons. This suppression of attenuation may provide a plausible explanation for the observed cosmic-ray events exceeding the Greisen-Zatsepin-Kuzmin (GZK) cutoff energy. We further demonstrate that when both leading-order and next-to-leading-order LIV effects are considered, higher-order LIV contributions induce discontinuous transitions in the GZK cutoff energy spectrum. Observations of proton-dominated UHECRs beyond the GZK threshold could provide constraints the LIV energy scale. Offering insights into the ultraviolet regime of LIV theories near the Planck scale, UHECRs may serve as a sensitive probe of LIV and provide a means to test quantum gravity predictions by constraining deviations from Lorentz symmetry in extreme-energy regimes. △ Less

Submitted 26 May, 2025; v1 submitted 6 November, 2024; originally announced November 2024.

Comments: 22 pages, 3 figures, Matches published version in EPJC

Unveiling the Binary Nature of NGC 2323

Authors: Songmei Qin, Jing Zhong, Tong Tang, Yueyue Jiang, Long Wang, Kai Wu, Friedrich Anders, Lola Balaguer-Núñez, Guimei Liu, Chunyan Li, Jinliang Hou, Li Chen

Abstract: As a well-known open cluster, NGC 2323 (also called M50) has been widely investigated for over a hundred years and has always been considered a classical single cluster. In this work, with the help of Gaia DR3, we study the binary structure nature of this cluster. Although indistinguishable in the spatial space, the small but undeniable difference in the proper motion indicates that they may be tw… ▽ More As a well-known open cluster, NGC 2323 (also called M50) has been widely investigated for over a hundred years and has always been considered a classical single cluster. In this work, with the help of Gaia DR3, we study the binary structure nature of this cluster. Although indistinguishable in the spatial space, the small but undeniable difference in the proper motion indicates that they may be two individual clusters. After investigating the properties of the two clusters, it is found that they have very close positions (three-dimensional $Δ$pos = 12.3 pc, $σ_{Δ\mathrm{pos}} = 3.4$ pc) and similar tangential velocities (two-dimensional $Δ$V = 2.2 km s$^{-1}$, $σ_{Δ\mathrm{V}} = 0.02$ km s$^{-1}$), indicating the existence of their physical association. Moreover, the best isochrone fitting ages of the two clusters are the same (158 Myr), further proving their possibly common origin. To comprehensively understand the formation and evolution of this binary cluster, we employ the PETAR $N$-body code to trace back their birthplace and deduce their dynamical evolutionary fate. With observational mean cluster properties, the simulations suggest that they may form together, and then orbit each other as a binary cluster for over 200 Myr. After that, because of their gradual mass loss, the two clusters will eventually separate and evolve into two independent clusters. Meanwhile, the numerical $N$-body simulation suggests that the less massive cluster is unlikely to be the cluster tidal tails created by the differential rotation of the Milky Way. △ Less

Submitted 6 November, 2024; originally announced November 2024.

Comments: 14 pages, 8 figures

Journal ref: A&A 693, A317 (2025)

First results from the JWST Early Release Science Program Q3D: AGN photoionization and shock4 ionization in a red quasar at z = 0.45

Authors: Swetha Sankar, Nadia L. Zakamska, David S. N. Rupke, Weizhe Liu, Dominika Wylezalek, Sylvain Veilleux, Caroline Bertemes, Nadiia Diachenko, Yu-Ching Chen, Yuzo Ishikawa, Andrey Vayner, Nicole P. H. Nesvadba, Guilin Liu, Andy D. Goulding, Dieter Lutz

Abstract: Red quasars, often associated with potent [OIII] outflows on both galactic and circumgalactic scales, may play a pivotal role in galactic evolution and black hole feedback. In this work, we explore the [FeII] emission in one such quasar at redshift z = 0.4352, F2M J110648.32+480712.3, using the integral field unit (IFU) mode of the Near Infrared Spectrograph (NIRSpec) aboard the James Webb Space T… ▽ More Red quasars, often associated with potent [OIII] outflows on both galactic and circumgalactic scales, may play a pivotal role in galactic evolution and black hole feedback. In this work, we explore the [FeII] emission in one such quasar at redshift z = 0.4352, F2M J110648.32+480712.3, using the integral field unit (IFU) mode of the Near Infrared Spectrograph (NIRSpec) aboard the James Webb Space Telescope (JWST). Our observations reveal clumpy [FeII] gas located to the south of the quasar. By comparing the kinematics of [FeII] and [OIII], we find that the clumpy [FeII] gas in the southeast and southwest aligns with the outflow, exhibiting similar median velocities up to v_50 ~ 1200 km/s and high velocity widths W_80 > 1000 km/s. In contrast, the [FeII] gas to the south shows kinematics inconsistent with the outflow, with W_80 ~ 500 km/s, significantly smaller than the [OIII] at the same location, suggesting that the [FeII] may be confined within the host galaxy. Utilizing standard emission-line diagnostic ratios, we map the ionization sources of the gas. According to the MAPPINGS III shock models for [FeII]/Pabeta, the regions to the southwest and southeast of the quasar are primarily photoionized. Conversely, the [FeII] emission to the south is likely excited by shocks generated by the back-pressure of the outflow on the galaxy disk, a direct signature of the impact of the quasar on its host. △ Less

Submitted 29 October, 2024; originally announced October 2024.

Rapid cooling of the Cassiopeia A neutron star due to superfluid quantum criticality

Authors: Hao-Fu Zhu, Guo-Zhu Liu, Xufen Wu

Abstract: The rapid cooling of the neutron star in Cassiopeia A is speculated to arise from an enhanced neutrino emission caused by the onset of $^3P_2$-wave neutron superfluidity in the core. However, the neutrino emissivity due to Cooper-pair breaking and formation is too small to yield the observed cooling rate. Here, we show that such a rapid cooling can be explained once the non-Fermi liquid behavior o… ▽ More The rapid cooling of the neutron star in Cassiopeia A is speculated to arise from an enhanced neutrino emission caused by the onset of $^3P_2$-wave neutron superfluidity in the core. However, the neutrino emissivity due to Cooper-pair breaking and formation is too small to yield the observed cooling rate. Here, we show that such a rapid cooling can be explained once the non-Fermi liquid behavior of the non-superfluid neutron liquid induced by superfluid quantum criticality is included into the theoretical description of neutron star cooling, without assuming the existence of additional energy loss processes. Our results indicate that the neutron star in Cassiopeia A remains in the thermal relaxation stage, which is greatly prolonged by the non-Fermi liquid behavior. The good agreement between our theoretical results and recent observational cooling data points to the pivotal role played by superfluid quantum criticality in neutron stars. △ Less

Submitted 29 October, 2024; originally announced October 2024.

Comments: 6 pages, 4 figures

Search for gravitational waves emitted from SN 2023ixf

Authors: The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration, A. G. Abac, R. Abbott, I. Abouelfettouh, F. Acernese, K. Ackley, S. Adhicary, N. Adhikari, R. X. Adhikari, V. K. Adkins, D. Agarwal, M. Agathos, M. Aghaei Abchouyeh, O. D. Aguiar, I. Aguilar, L. Aiello, A. Ain, T. Akutsu, S. Albanesi, R. A. Alfaidi, A. Al-Jodah, C. Alléné, A. Allocca , et al. (1758 additional authors not shown)

Abstract: We present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been… ▽ More We present the results of a search for gravitational-wave transients associated with core-collapse supernova SN 2023ixf, which was observed in the galaxy Messier 101 via optical emission on 2023 May 19th, during the LIGO-Virgo-KAGRA 15th Engineering Run. We define a five-day on-source window during which an accompanying gravitational-wave signal may have occurred. No gravitational waves have been identified in data when at least two gravitational-wave observatories were operating, which covered $\sim 14\%$ of this five-day window. We report the search detection efficiency for various possible gravitational-wave emission models. Considering the distance to M101 (6.7 Mpc), we derive constraints on the gravitational-wave emission mechanism of core-collapse supernovae across a broad frequency spectrum, ranging from 50 Hz to 2 kHz where we assume the gravitational-wave emission occurred when coincident data are available in the on-source window. Considering an ellipsoid model for a rotating proto-neutron star, our search is sensitive to gravitational-wave energy $1 \times 10^{-4} M_{\odot} c^2$ and luminosity $2.6 \times 10^{-4} M_{\odot} c^2/s$ for a source emitting at 82 Hz. These constraints are around an order of magnitude more stringent than those obtained so far with gravitational-wave data. The constraint on the ellipticity of the proto-neutron star that is formed is as low as 1.08, at frequencies above 1200 Hz, surpassing past results. △ Less

Submitted 11 March, 2025; v1 submitted 21 October, 2024; originally announced October 2024.

Comments: Main paper: 6 pages, 4 figures and 1 table. Total with appendices: 20 pages, 4 figures, and 1 table

Report number: LIGO-P2400125

Journal ref: ApJ 985 183 (2025)

Resolving turbulence drivers in two luminous obscured quasars with JWST/NIRSpec IFU

Authors: Mandy C. Chen, Hsiao-Wen Chen, Michael Rauch, Andrey Vayner, Weizhe Liu, David S. N. Rupke, Jenny E. Greene, Nadia L. Zakamska, Dominika Wylezalek, Guilin Liu, Sylvain Veilleux, Nicole P. H. Nesvadba, Caroline Bertemes

Abstract: In this Letter, we investigate the turbulence and energy injection in the extended nebulae surrounding two luminous obscured quasars, WISEA J100211.29$+$013706.7 ($z=1.5933$) and SDSS J165202.64$+$172852.3 ($z=2.9489$). Utilizing high-resolution data from the NIRSpec IFU onboard the James Webb Space Telescope, we analyze the velocity fields of line-emitting gas in and around these quasars and cons… ▽ More In this Letter, we investigate the turbulence and energy injection in the extended nebulae surrounding two luminous obscured quasars, WISEA J100211.29$+$013706.7 ($z=1.5933$) and SDSS J165202.64$+$172852.3 ($z=2.9489$). Utilizing high-resolution data from the NIRSpec IFU onboard the James Webb Space Telescope, we analyze the velocity fields of line-emitting gas in and around these quasars and construct the second-order velocity structure functions (VSFs) to quantify turbulent motions across different spatial scales. Our findings reveal a notable flattening in the VSFs from $\approx\!3$ kpc up to a scale of 10--20 kpc, suggesting that energy injection predominantly occurs at a scale $\lesssim$10 kpc, likely powered by quasar outflows and jet-driven bubbles. The extended spatial range of flat VSFs may also indicate the presence of multiple energy injection sources at these scales. For J1652, the turbulent energy in the host interstellar medium (ISM) is significantly higher than in tidally stripped gas, consistent with the expectation of active galactic nucleus (AGN) activities stirring up the host ISM. Compared to the VSFs observed on spatial scales of 10--50 kpc around lower-redshift UV-bright quasars, these obscured quasars exhibit higher turbulent energies in their immediate surroundings, implying different turbulence drivers between the ISM and halo-scale gas. Future studies with an expanded sample are essential to elucidate further the extent and the pivotal role of AGNs in shaping the gas kinematics of host galaxies and beyond. △ Less

Submitted 6 January, 2025; v1 submitted 18 October, 2024; originally announced October 2024.

Comments: 10 pages, 4 figures; ApJL accepted version; comments welcome!

First results from the JWST Early Release Science Program Q3D: The Fast Outflow in a Red Quasar at z=0.44

Authors: Weizhe Liu, Sylvain Veilleux, Swetha Sankar, David S. N. Rupke, Nadia L. Zakamska, Dominika Wylezalek, Andrey Vayner, Caroline Bertemes, Yu-Ching Chen, Yuzo Ishikawa, Jenny E. Greene, Timothy Heckman, Guilin Liu, Hsiao-Wen Chen, Dieter Lutz, Sean D. Johnson, Nicole P. H. Nesvadba, Patrick Ogle, Nadiia Diachenko, Andy D. Goulding, Kevin N. Hainline, Fred Hamann, Hui Xian Grace Lim, Nora Lützgendorf, Vincenzo Mainieri , et al. (4 additional authors not shown)

Abstract: Quasar feedback may play a key role in the evolution of massive galaxies. The dust-reddened quasar, F2M110648.35$+$480712 at $z = 0.4352$ is one of the few cases at its redshift that exhibits powerful quasar feedback through bipolar outflows. Our new observation with the integral field unit mode of Near-infrared Spectrograph onboard JWST opens a new window to examine this spectacular outflow throu… ▽ More Quasar feedback may play a key role in the evolution of massive galaxies. The dust-reddened quasar, F2M110648.35$+$480712 at $z = 0.4352$ is one of the few cases at its redshift that exhibits powerful quasar feedback through bipolar outflows. Our new observation with the integral field unit mode of Near-infrared Spectrograph onboard JWST opens a new window to examine this spectacular outflow through Pa$α$ emission line with $\sim$3$\times$ better spatial resolution than previous work. The morphology and kinematics of the Pa$α$ nebula confirm the existence of a bipolar outflow extending on a scale of $\sim$17$\times$14 kpc and with a velocity reaching $\sim$1100 km s$^{-1}$. The higher spatial resolution of our new observation leads to more reliable measurements of outflow kinematics. Considering only the spatially resolved outflow and assuming an electron density of 100 cm$^{-2}$, the mass, momentum and kinetic energy outflow rates are $\sim$50-210 M$_{\odot}$ yr$^{-1}$, $\sim$0.3-1.7$\times$10$^{36}$ dynes ($\sim$14-78\% of the quasar photon momentum flux) and $\sim$0.16-1.27$\times$10$^{44}$ erg s$^{-1}$ ($\sim$0.02-0.20\% of the quasar bolometric luminosity), respectively. The local instantaneous outflow rates generally decrease radially. We infer that the quasar is powerful enough to drive the outflow, while stellar processes cannot be overlooked as a contributing energy source. The mass outflow rate is $\sim$0.4-1.5 times the star formation rate, and the ratio of kinetic energy outflow rate to the quasar bolometric luminosity is comparable to the minimum value required for negative quasar feedback in simulations. This outflow may help regulate the star formation activity within the system to some extent. △ Less

Submitted 18 October, 2024; originally announced October 2024.

Comments: 14 pages, 6 figures, 1 table, ApJ in review

Could the inter-band lag of active galactic nucleus vary randomly?

Authors: Zhen-Bo Su, Zhen-Yi Cai, Jun-Xian Wang, Tinggui Wang, Yongquan Xue, Min-Xuan Cai, Lulu Fan, Hengxiao Guo, Zhicheng He, Zizhao He, Xu-Fan Hu, Ji-an Jiang, Ning Jiang, Wen-Yong Kang, Lei Lei, Guilin Liu, Teng Liu, Zhengyan Liu, Zhenfeng Sheng, Mouyuan Sun, Wen Zhao

Abstract: The inter-band lags among the optical broad-band continua of active galactic nuclei (AGNs) have been intensively explored over the past decade. However, the nature of the lags remains under debate. Here utilizing two distinct scenarios for AGN variability, i.e., the thermal fluctuation of accretion disk and the reprocessing of both the accretion disk and clouds in the broad line region, we show th… ▽ More The inter-band lags among the optical broad-band continua of active galactic nuclei (AGNs) have been intensively explored over the past decade. However, the nature of the lags remains under debate. Here utilizing two distinct scenarios for AGN variability, i.e., the thermal fluctuation of accretion disk and the reprocessing of both the accretion disk and clouds in the broad line region, we show that, owing to the random nature of AGN variability, the inter-band lags of an individual AGN would vary from one campaign with a finite baseline to another. Specifically, the thermal fluctuation scenario implies larger variations in the lags than the reprocessing scenario. Moreover, the former predicts a positive correlation between the lag and variation amplitude, while the latter does not result in such a correlation. For both scenarios, averaging the lags of an individual AGN measured with repeated and non-overlapping campaigns would give rise to a stable lag, which is larger for a longer baseline and gets saturation for a sufficiently long baseline. However, obtaining the stable lag for an individual AGN is very time-consuming. Alternatively, it can be equivalently inferred by averaging the lags of a sample of AGNs with similar physical properties, thus can be properly compared with predictions of AGN models. In addition, discussed are several new observational tests suggested by our simulations as well as the role of the deep high-cadence surveys of the Wide Field Survey Telescope in enriching our knowledge of the lags. △ Less

Submitted 13 October, 2024; originally announced October 2024.

Comments: 16 pages, 10 figures. Accepted for publication in Astrophysical Journal, comments are welcome!

A search using GEO600 for gravitational waves coincident with fast radio bursts from SGR 1935+2154

Authors: The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration, A. G. Abac, R. Abbott, I. Abouelfettouh, F. Acernese, K. Ackley, S. Adhicary, N. Adhikari, R. X. Adhikari, V. K. Adkins, D. Agarwal, M. Agathos, M. Aghaei Abchouyeh, O. D. Aguiar, I. Aguilar, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, R. A. Alfaidi, A. Al-Jodah, C. Alléné , et al. (1758 additional authors not shown)

Abstract: The magnetar SGR 1935+2154 is the only known Galactic source of fast radio bursts (FRBs). FRBs from SGR 1935+2154 were first detected by CHIME/FRB and STARE2 in 2020 April, after the conclusion of the LIGO, Virgo, and KAGRA Collaborations' O3 observing run. Here we analyze four periods of gravitational wave (GW) data from the GEO600 detector coincident with four periods of FRB activity detected by… ▽ More The magnetar SGR 1935+2154 is the only known Galactic source of fast radio bursts (FRBs). FRBs from SGR 1935+2154 were first detected by CHIME/FRB and STARE2 in 2020 April, after the conclusion of the LIGO, Virgo, and KAGRA Collaborations' O3 observing run. Here we analyze four periods of gravitational wave (GW) data from the GEO600 detector coincident with four periods of FRB activity detected by CHIME/FRB, as well as X-ray glitches and X-ray bursts detected by NICER and NuSTAR close to the time of one of the FRBs. We do not detect any significant GW emission from any of the events. Instead, using a short-duration GW search (for bursts $\leq$ 1 s) we derive 50\% (90\%) upper limits of $10^{48}$ ($10^{49}$) erg for GWs at 300 Hz and $10^{49}$ ($10^{50}$) erg at 2 kHz, and constrain the GW-to-radio energy ratio to $\leq 10^{14} - 10^{16}$. We also derive upper limits from a long-duration search for bursts with durations between 1 and 10 s. These represent the strictest upper limits on concurrent GW emission from FRBs. △ Less

Submitted 21 May, 2025; v1 submitted 11 October, 2024; originally announced October 2024.

Comments: 15 pages of text including references, 4 figures, 5 tables

Report number: LIGO-P2400192

Journal ref: ApJ 977 255 (2024)

CTC and CT5TEA: an advanced multi-channel digitizer and trigger ASIC for imaging atmospheric Cherenkov telescopes

Authors: Benjamin Schwab, Adrian Zink, Davide Depaoli, Jim Hinton, Gang Liu, Akira Okumura, Duncan Ross, Johannes Schäfer, Harm Schoorlemmer, Hiro Tajima, Justin Vandenbroucke, Richard White, Jason John Watson, Justus Zorn, Stefan Funk

Abstract: We have developed a new set of Application-Specific Integrated Circuits (ASICs) of the TARGET family (CTC and CT5TEA), designed for the readout of signals from photosensors in cameras of Imaging Atmospheric Cherenkov Telescopes (IACTs) for ground-based gamma-ray astronomy. We present the performance and design details. Both ASICs feature 16 channels, with CTC being a Switched-Capacitor Array (SCA)… ▽ More We have developed a new set of Application-Specific Integrated Circuits (ASICs) of the TARGET family (CTC and CT5TEA), designed for the readout of signals from photosensors in cameras of Imaging Atmospheric Cherenkov Telescopes (IACTs) for ground-based gamma-ray astronomy. We present the performance and design details. Both ASICs feature 16 channels, with CTC being a Switched-Capacitor Array (SCA) sampler at 0.5 to 1 GSa/s with a 16,384 sample deep storage buffer, including the functionality to digitize full waveforms at arbitrary times. CT5TEA is its companion trigger ASIC (though may be used on its own), which provides trigger information for the analog sum of four (and 16) adjacent channels. Since sampling and triggering takes place in two separate ASICs, the noise due to interference from the SCA is suppressed, and allows a minimal trigger threshold of $\leq$ 2.5 mV (0.74 photo electrons (p.e.)) with a trigger noise of $\leq$ 0.5 mV (0.15 p.e.). For CTC, a maximal input voltage range from $-$0.5 V up to 1.7 V is achieved with an effective bit range of $>$ 11.6 bits and a baseline noise of 0.7 mV. The cross-talk improved to $\leq$ 1% over the whole $-$3 dB bandwidth of 220 MHz and even down to 0.2% for 1.5 V pulses of 10 ns width. Not only is the performance presented, but a temperature-stable calibration routine for pulse mode operation is introduced and validated. The resolution is found to be $\sim$ 2.5% at 33.7 mV (10 p.e.) and $\leq$ 0.3% at 337 mV (100 p.e.) with an integrated non-linearity of $<$ 1.6 mV. Developed for the Small-Sized Telescope (SST) and Schwarzschild-Couder Telescope (SCT) cameras of the Cherenkov Telescope Array Observatory (CTAO), CTC and CT5TEA are deployed for both prototypes and shall be integrated into the final versions. △ Less

Submitted 10 September, 2024; originally announced September 2024.

Comments: 18 pages, 26 figures, 1 table

Detection of gamma-ray burst Amati relation based on Hubble data set and Pantheon+ samples

Authors: Yufen Han, Jiaze Gao, Gang Liu, Lixin Xu

Abstract: Using gamma-ray bursts as standard candles for cosmological parameter constraints rely on their empirical luminosity relations and low-redshift calibration. In this paper, we examine the Amati relation and its potential corrections based on the A118 sample of higher-quality gamma-ray bursts, using both Hubble data set and Pantheon+ samples as calibration samples in the redshift range of z < 1.965.… ▽ More Using gamma-ray bursts as standard candles for cosmological parameter constraints rely on their empirical luminosity relations and low-redshift calibration. In this paper, we examine the Amati relation and its potential corrections based on the A118 sample of higher-quality gamma-ray bursts, using both Hubble data set and Pantheon+ samples as calibration samples in the redshift range of z < 1.965. In calibrating gamma-ray bursts using these two datasets, we employ Gaussian processes to obtain corresponding Hubble diagrams to avoid the dependence on cosmological models in the calibration process. We first divided the low-redshift sample of GRBs into two bins and examined the Amati relation and its potential modifications. We found that under both calibrations, the Amati relation did not show evidence of redshift evolution (68% confidence level). For the other two Amati relations that include redshift evolution terms, the central values of the redshift evolution coefficients deviated from 0, but due to the limitations of the sample size and the increase in the number of parameters, most of the redshift evolution coefficients were not able to be excluded from 0 at the 1 sigma level. Therefore, to assess their situation across the entire redshift range, we employed MCMC to globally fit three types of Amati relations. By computing AIC and BIC, we found that for the GRB A118 sample, the standard Amati relation remains the most fitting empirical luminosity formula, and no potential redshift evolution trend was observed for two different low-redshift calibrating sources. △ Less

Submitted 3 September, 2024; v1 submitted 24 August, 2024; originally announced August 2024.

The Transition from Galaxy-wide Gas Inflow to Outflow in Quasar Host Galaxies

Authors: Zhicheng He, Zhifu Chen, Guilin Liu, Tinggui Wang, Luis C. Ho, Junxian Wang, Weihao Bian, Zheng Cai, Guobin Mou, Qiusheng Gu, Zhiwen Wang

Abstract: Galactic-wide outflows driven by active galactic nuclei (AGNs) is a routinely invoked feedback mechanism in galaxy evolution models. Hitherto, the interplay among the interstellar gas on galactic scales, the propagation of AGN outflows and the fundamental AGN parameters during evolution remains elusive. Powerful nuclear outflows are found to favorably exist at early AGN stages usually associated w… ▽ More Galactic-wide outflows driven by active galactic nuclei (AGNs) is a routinely invoked feedback mechanism in galaxy evolution models. Hitherto, the interplay among the interstellar gas on galactic scales, the propagation of AGN outflows and the fundamental AGN parameters during evolution remains elusive. Powerful nuclear outflows are found to favorably exist at early AGN stages usually associated with high accretion rates and weak narrow emission lines. In a sample of quasars emitting Mg II narrow absorption lines (NALs) from the Sloan Digital Sky Survey, we discover an unprecedented phenomenon where galaxy-scale inflow-dominated transforming into outflow-dominated gas accompanied by an increasing strength of the narrow [O III] line, at a confidence level of 6.7σ. The fact that nuclear outflows diminish while galaxy-wide outflows intensifies as AGNs evolve implies that early-stage outflows interact with interstellar medium on galactic scales and trigger the gradual transformation into galaxy-wide outflows, providing observational links to the hypothetical multi-stage propagation of AGN outflows that globally regulates galaxy evolution. △ Less

Submitted 8 August, 2024; originally announced August 2024.

Comments: Accepted by SCIENCE CHINA Physics, Mechanics & Astronomy; 15 pages, 4 figures and 6 appendix figures

Journal ref: Science China Physics, Mechanics & Astronomy, 67, 129512, (2024)

Superfluid quantum criticality and the thermal evolution of neutron stars

Authors: Hao-Fu Zhu, Guo-Zhu Liu, Jing-Rong Wang, Xufen Wu

Abstract: The neutron star starts to cool down shortly after its birth by emitting neutrinos. As it becomes cold enough, the Cooper pairs of neutrons are formed, triggering a superfluid transition. Previous studies on neutron superfluidity focused on finite-temperature transitions, with little attention paid to the potentially important quantum critical phenomena associated with superfluidity. Here, we prov… ▽ More The neutron star starts to cool down shortly after its birth by emitting neutrinos. As it becomes cold enough, the Cooper pairs of neutrons are formed, triggering a superfluid transition. Previous studies on neutron superfluidity focused on finite-temperature transitions, with little attention paid to the potentially important quantum critical phenomena associated with superfluidity. Here, we provide the first theoretical analysis of superfluid quantum criticality, concentrating on its impact on neutron star cooling. Extensive calculations found that superfluidity occurs within a finite range of neutron star density $ρ$. The density serves as a nonthermal parameter for a superfluid quantum phase transition. In a broad quantum critical region, gapless neutrons are strongly coupled to the quantum critical fluctuations of the superfluid order parameter. We handle this coupling using both perturbation theory and renormalization group methods and find that it leads to non-Fermi liquid behavior, which yields a logarithmic $T\ln(1/T)$ correction to the neutron specific heat $c_{\mathrm{n}}\propto T$ and also dramatically alters the neutrino emissivity. Quantum critical phenomena emerge much earlier than the onset of superfluidity and persist throughout almost the entire lifetime of a neutron star. At low temperatures, these phenomena coexist with superfluidity in the neutron star interior but occupy different layers. We incorporate superfluid quantum criticality into the theoretical description of neutron star cooling and show that it substantially prolongs the thermal relaxation time. By varying the strength of superfluid fluctuations and other quantities, we obtain an excellent fit to the observed cooling data of a number of neutron stars. Our results indicate an intriguing correlation between superfluid quantum criticality and the thermal evolution of neutron stars. △ Less

Submitted 9 September, 2025; v1 submitted 7 August, 2024; originally announced August 2024.

Comments: 32 pages, 6 figures

Journal ref: Phys. Rev. D 112, 043014 (2025)

A new code for low-resolution spectral identification of white dwarf binary candidates

Authors: Genghao Liu, Baitian Tang, Liangliang Ren, Chengyuan Li, Sihao Cheng, Weikai Zong, Jianning Fu, Bo Ma, Cheng Xu, Yiming Hu

Abstract: Close white dwarf binaries (CWDBs) are considered to be progenitors of several exotic astronomical phenomena (e.g., type Ia supernovae, cataclysmic variables). These violent events are broadly used in studies of general relativity and cosmology. However, obtaining precise stellar parameter measurements for both components of CWDBs is a challenging task given their low luminosities, swift time vari… ▽ More Close white dwarf binaries (CWDBs) are considered to be progenitors of several exotic astronomical phenomena (e.g., type Ia supernovae, cataclysmic variables). These violent events are broadly used in studies of general relativity and cosmology. However, obtaining precise stellar parameter measurements for both components of CWDBs is a challenging task given their low luminosities, swift time variation, and complex orbits. High-resolution spectra (R$> 20 000$) are preferred but expensive, resulting in a sample size that is insufficient for robust population study. To release the full potential of the less expensive low-resolution spectroscopic surveys, and thus greatly expand the CWDB sample size, it is necessary to develop a robust pipeline for spectra decomposition and analysis. We used an artificial neural network (ANN) to build spectrum generators for DA/DB white dwarfs and main-sequence stars. The best-fit stellar parameters were obtained by finding the least $χ^2$ solution to these feature lines and the continuum simultaneously. We demonstrate the reliability of our code with two well-studied CWDBs, WD 1534+503 and PG 1224+309. We also estimate the stellar parameters of 14 newly identified CWDB candidates, most of which are fitted with double component models for the first time. Our estimates agree with previous results for the common stars and follow the statistical distribution in the literature. The application of our code to a large volume of white dwarf binary candidates will offer important statistic samples to stellar evolution studies and future gravitational wave monitoring. △ Less

Submitted 6 August, 2024; originally announced August 2024.

Comments: 14pages, 12 figures, 2 tables.Accepted by A&A

Journal ref: A&A 690, A29 (2024)