Showing 1–50 of 97 results for author: Tang, J

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

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

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

Submitted 16 November, 2025; originally announced November 2025.

Comments: 24 pages, 17 figures, accepted by RAA

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

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

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

Submitted 16 November, 2025; originally announced November 2025.

Comments: 28 pages, 21 figures, accepted by RAA

Mock Observations for the CSST Mission: CPI-C -- Targets for High Contrast Imaging

Authors: Yi-Ming Zhu, Gang Zhao, Jiang-Pei Dou, Zhong-Hua Lv, Yi-Li Chen, Bo Ma, Zhao-Jun Yan, Jing Tang, Ran Li

Abstract: We introduce CPISM, a simulation program developed for the Cool Planet Imaging Coronagraph (CPI-C) on the China Space Station Telescope (CSST). CPISM supports high-contrast exoplanet imaging by simulating observational conditions and instrumental effects to optimize target selection and observation strategies. The modular design includes target modeling, imaging simulation, observational effects,… ▽ More We introduce CPISM, a simulation program developed for the Cool Planet Imaging Coronagraph (CPI-C) on the China Space Station Telescope (CSST). CPISM supports high-contrast exoplanet imaging by simulating observational conditions and instrumental effects to optimize target selection and observation strategies. The modular design includes target modeling, imaging simulation, observational effects, detector response, and data product generation modules, enabling flexible and realistic synthetic observations. Validation through simulations of a bright star shows strong agreement with theoretical expectations, confirming the program's accuracy. CPISM's modular design allows flexibility, accommodating different stellar and planetary models, and can simulate instrumental noise, cosmic rays, and other observational effects. This tool aids in data processing, signal-to-noise ratio analysis, and high-contrast photometry, contributing to future exoplanet discovery and characterization efforts. The program's outputs will enhance observation planning and scientific return for the CPI-C mission, providing critical insights into exoplanetary systems. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 21 pages, 11 figures, accepted by Research in Astronomy and Astrophysics

Mock Observations for the CSST Mission: HSTDM--Synthetic Data Generation

Authors: SiYuan Tan, WenYin Duan, YiLong Zhang, YiPing Ao, Yan Gong, ZhenHui Lin, Xuan Zhang, Yong Shi, Jing Tang, Jing Li, RuiQing Mao, Sheng-Cai Shi

Abstract: The High Sensitivity Terahertz Detection Module (HSTDM), a key component of the backend modules on board the China Space Station Telescope (CSST), will offer great opportunities for the discovery of Terahertz Astronomy, with implications that extend well beyond China to the global astronomical community. It is imperative that the raw data collected by HSTDM undergoes meticulous calibration and pro… ▽ More The High Sensitivity Terahertz Detection Module (HSTDM), a key component of the backend modules on board the China Space Station Telescope (CSST), will offer great opportunities for the discovery of Terahertz Astronomy, with implications that extend well beyond China to the global astronomical community. It is imperative that the raw data collected by HSTDM undergoes meticulous calibration and processing through the HSTDM data processing pipeline (HSTDM pipeline for short) to ensure the accuracy and effectiveness of the final science data to be archived for further research. This process necessitates that the HSTDM pipeline address instrumental artifacts and effects as well as the coordination of data flow of the scheduled observing sequences under all observing modes of HSTDM within the CSST automated processing environment. As the understanding of CSST HSTDM data processing develops during the pipeline development stage, it becomes essential to assess the accuracy, the robustness and the performance of the HSTDM pipeline under all observing modes of HSTDM so that components of the HSTDM pipeline be rationally added, removed, amended or extended within the modular framework. In this paper, we develop practical simulation methods to facilitate this need. The contribution of synthetic data generation of HSTDM observation includes two parts: 1. HSTDM instrumental effect simulation based on both real testing profiles and simulated models; 2. Observing data flow generation based on HSTDM observing mode scenario. The simulation methods have been implemented and shown to be practical in testing the HSTDM pipeline during the development stage. △ Less

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

Comments: 22 pages, 13 figures

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

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

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

Submitted 10 November, 2025; originally announced November 2025.

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

Mock Observations for the CSST Mission: Main Surveys-the Slitless Spectroscopy Simulation

Authors: Xin Zhang, Yue-dong Fang, Cheng-liang Wei, Guo-liang Li, Feng-shan Liu, Hang-xin Ji, Hao Tian, Nan Li, Xian-min Meng, Jian-jun Chen, Xia Wang, Rui Wang, Chao Liu, Zhong-wen Hu, Ran Li, Peng Wei, Jing Tang

Abstract: The China Space Station Telescope (CSST), slated to become China's largest space-based optical telescope in the coming decade, is designed to conduct wide-field sky surveys with high spatial resolution. Among its key observational modes, slitless spectral observation allows simultaneous imaging and spectral data acquisition over a wide field of view, offering significant advantages for astrophysic… ▽ More The China Space Station Telescope (CSST), slated to become China's largest space-based optical telescope in the coming decade, is designed to conduct wide-field sky surveys with high spatial resolution. Among its key observational modes, slitless spectral observation allows simultaneous imaging and spectral data acquisition over a wide field of view, offering significant advantages for astrophysical studies. Currently, the CSST is in the development phase and lacks real observational data. As a result, the development of its data processing pipeline and scientific pre-research must rely on the mock data generated through simulations. This work focuses on developing a simulation framework for the CSST slitless spectral imaging system, analyzing its spectral dispersing properties and structural design. Additionally, the detection performance of the slitless spectral system is assessed for various astrophysical targets. Simulation results demonstrate that nearly all 1st order spectra are accompanied by corresponding 0th order images, facilitating accurate source identification. Furthermore, the GI spectral band exhibits superior detection efficiency compared to the GV and GU bands, establishing it as the primary observational band for stellar and galactic studies. This work successfully develops a simulation framework for the CSST slitless spectroscopic equipment. △ Less

Submitted 16 November, 2025; v1 submitted 10 November, 2025; originally announced November 2025.

Study of Four nulling pulsars with FAST

Authors: Jingbo Wang, Jintao Xie, Jing Zou, Jianfei Tang

Abstract: We present an analysis of 4 nulling pulsars with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). For PSR J1649+2533, our results suggest mode changing rather than subpulse drifting as previously reported at lower frequencies. For PSR J1752+2359, we confirm its quasi-periodic switching between distinct emission states, but further show that the so-called "quasi-null" or "RRAT-like… ▽ More We present an analysis of 4 nulling pulsars with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). For PSR J1649+2533, our results suggest mode changing rather than subpulse drifting as previously reported at lower frequencies. For PSR J1752+2359, we confirm its quasi-periodic switching between distinct emission states, but further show that the so-called "quasi-null" or "RRAT-like" state actually consists of persistent low-level emission superposed with occasional bright pulses. For PSR J1819+1305, our data confirm the modulation reported earlier, while additional weaker features are also seen. For PSR J1916+1023, we detect both nulling and subpulse drifting, but find no clear evidence of direct interaction between them. These results provide new insights into the diverse manifestations of pulsar nulling, highlight the capability of FAST to detect subtle emission states, and add to the growing body of work on pulsar emission variability. △ Less

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

A Star's Death by a Thousand Cuts: The Runaway Periodic Eruptions of AT2023uqm

Authors: Yibo Wang, Tingui Wang, Shifeng Huang, Jiazheng Zhu, Ning Jiang, Wenbin Lu, Rongfeng Shen, Shiyan Zhong, Dong Lai, Yi Yang, Xinwen Shu, Tianyu Xia, Di Luo, Jianwei Lyu, Thomas Brink, Alex Filippenko, Weikang Zheng, Minxuan Cai, Zelin Xu, Mingxin Wu, Xiaer Zhang, Weiyu Wu, Lulu Fan, Ji-an Jiang, Xu Kong , et al. (15 additional authors not shown)

Abstract: Stars on bound orbits around a supermassive black hole may undergo repeated partial tidal disruption events (rpTDEs), producing periodic flares. While several candidates have been suggested, definitive confirmation of these events remains elusive. We report the discovery of AT2023uqm, a nuclear transient that has exhibited at least five periodic optical flares, making it only the second confirmed… ▽ More Stars on bound orbits around a supermassive black hole may undergo repeated partial tidal disruption events (rpTDEs), producing periodic flares. While several candidates have been suggested, definitive confirmation of these events remains elusive. We report the discovery of AT2023uqm, a nuclear transient that has exhibited at least five periodic optical flares, making it only the second confirmed case of periodicity after ASASSN-14ko. Uniquely, the flares from AT2023uqm show a nearly exponential increase in energy--a "runaway" phenomenon signaling the star's progressive destruction. This behavior is consistent with rpTDEs of low-mass, main-sequence stars or evolved giant stars. Multiwavelength observations and spectroscopic analysis of the two most recent flares reinforce its interpretation as an rpTDE. Intriguingly, each flare displays a similar double-peaked structure, potentially originating from a double-peaked mass fallback rate or two discrete collisions per orbit. The extreme ratio of peak separation to orbital period draws attention to the possibility of a giant star being disrupted, which could be distinguished from a low-mass main-sequence star by its future mass-loss evolution. Our analysis demonstrates the power of rpTDEs to probe the properties of disrupted stars and the physical processes of tidal disruption, though it is currently limited by our knowledge of these events. AT2023uqm emerges as the most compelling rpTDE thus far, serving as a crucial framework for modeling and understanding these phenomena. △ Less

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

Comments: Submitted. Comments are welcome

Investigating Production of TeV-scale Muons in Extensive Air Shower at 2400 Meters Underground

Authors: Xinshun Zhang, Shaomin Chen, Wei Dou, Haoyang Fu, Lei Guo, Ziyi Guo, XiangPan Ji, Jianmin Li, Jinjing Li, Bo Liang, Ye Liang, Qian Liu, Wentai Luo, Ming Qi, Wenhui Shao, Haozhe Sun, Jian Tang, Yuyi Wang, Zhe Wang, Changxu Wei, Jun Weng, Yiyang Wu, Benda Xu, Chuang Xu, Tong Xu , et al. (8 additional authors not shown)

Abstract: The China Jinping Underground Laboratory, characterized by a vertical rock overburden of 2,400 m, provides an exceptionally effective shield against cosmic muons with energies below 3 TeV. The surviving high-energy muons, produced as part of extensive air showers, open a unique observational window into primary cosmic rays with energies ranging from tens of TeV up to the PeV scale and beyond. This… ▽ More The China Jinping Underground Laboratory, characterized by a vertical rock overburden of 2,400 m, provides an exceptionally effective shield against cosmic muons with energies below 3 TeV. The surviving high-energy muons, produced as part of extensive air showers, open a unique observational window into primary cosmic rays with energies ranging from tens of TeV up to the PeV scale and beyond. This distinctive feature also enables detailed studies of the earliest stages of shower development. Using 1,338.6 live days of data collected with a one-ton prototype detector for the Jinping Neutrino Experiment, we measured the underground muon flux originating from air showers. The results show discrepancies of about 40%, corresponding to a significance of more than 5.5$σ$, relative to predictions from several leading hadronic interaction models. We interpret these findings from two complementary perspectives: (i) by adopting the expected cosmic ray spectra, we constrain the modeling of the initial hadronic interactions in air showers; and (ii) by assuming specific hadronic interaction models, we infer the mass composition of cosmic rays, and our data favor a lighter component in the corresponding energy range. Our study demonstrates the potential of deep underground laboratories to provide new experimental insights into cosmic rays. △ Less

Submitted 18 October, 2025; originally announced October 2025.

Comments: 7 pages; 5 figures

The Nearby Evolved Stars Survey III: First data release of JCMT CO-line observations

Authors: S. H. J. Wallström, P. Scicluna, S. Srinivasan, J. G. A. Wouterloot, I. McDonald, L. Decock, M. Wijshoff, R. Chen, D. Torres, L. Umans, B. Willebrords, F. Kemper, G. Rau, S. Feng, M. Jeste, T. Kaminski, D. Li, F. C. Liu, A. Trejo-Cruz, H. Chawner, S. Goldman, H. MacIsaac, J. Tang, S. T. Zeegers, T. Danilovich , et al. (15 additional authors not shown)

Abstract: Low- to intermediate-mass ($\sim$0.8$-$8 M$_\odot$) evolved stars contribute significantly to the chemical enrichment of the interstellar medium in the local Universe, making accurate mass-return estimates in their final stages crucial. The Nearby Evolved Stars Survey (NESS) is a large multi-telescope project targeting a volume-limited sample of $\sim$850 stars within 3 kpc in order to derive the… ▽ More Low- to intermediate-mass ($\sim$0.8$-$8 M$_\odot$) evolved stars contribute significantly to the chemical enrichment of the interstellar medium in the local Universe, making accurate mass-return estimates in their final stages crucial. The Nearby Evolved Stars Survey (NESS) is a large multi-telescope project targeting a volume-limited sample of $\sim$850 stars within 3 kpc in order to derive the dust and gas return rates in the Solar Neighbourhood, and to constrain the physics underlying these processes. We present an initial analysis of the CO-line observations, including detection statistics, carbon isotopic ratios, initial mass-loss rates, and gas-to-dust ratios. We describe a new data reduction pipeline to analyse the available NESS CO data from the JCMT, measuring line parameters and calculating empirical gas mass-loss rates. We present the first release of the available data on 485 sources, one of the largest homogeneous samples of CO data to date. Comparison with a large literature sample finds that high mass-loss rate and especially carbon-rich sources are over-represented in literature, while NESS is probing significantly more sources at low mass-loss rates, detecting 59 sources in CO for the first time and providing useful upper limits. CO line detection rates are 81% for the CO (2--1) line and 75% for CO (3--2). The majority (82%) of detected lines conform to the expected soft parabola shape, while eleven sources show a double wind. Calculated mass-loss rates show power-law relations with both the dust-production rates and expansion velocities up to $\sim 5 \times 10^{-6}$~\msunyr. Median gas-to-dust ratios of 250 and 680 are found for oxygen-rich and carbon-rich sources, respectively. Our analysis of CO observations in this first data release highlights the importance of our volume-limited approach in characterizing the local AGB population as a whole. △ Less

Submitted 16 October, 2025; originally announced October 2025.

Comments: 18 pages, 12 figures, accepted for publication in Astronomy & Astrophysics, data to be made available at https://evolvedstars.space

Revealing the Temporally Stable Bimodal Energy Distribution of FRB 20121102A with a Tripled Burst Set from AI Detections

Authors: Yidan Wang, Jing Han, Pei Wang, Di Li, Hanting Chen, Yuchuan Tian, Erbil Gugercinoglu, Jianing Tang, Zihan Zhang, Kaichao Wu, Xiaoli Zhang, Yuhao Zhu, Jinhuang Cao, Mingtai Chen, Jiapei Feng, Zhaoyu Huai, Zitao Lin, Jieming Luan, Hongbin Wang, Junjie Zhao, Chaowei Tsai, Weiwei Zhu, Yongkun Zhang, Yi Feng, Aiyuan Yang , et al. (12 additional authors not shown)

Abstract: Active repeating Fast Radio Bursts (FRBs), with their large number of bursts, burst energy distribution, and their potential energy evolution, offer critical insights into the FRBs emission mechanisms. Traditional pipelines search for bursts through conducting dedispersion trials and looking for signals above certain fluence thresholds, both of which could result in missing weak and narrow-band bu… ▽ More Active repeating Fast Radio Bursts (FRBs), with their large number of bursts, burst energy distribution, and their potential energy evolution, offer critical insights into the FRBs emission mechanisms. Traditional pipelines search for bursts through conducting dedispersion trials and looking for signals above certain fluence thresholds, both of which could result in missing weak and narrow-band bursts. In order to improve the completeness of the burst set, we develop an End-to-end DedispersE-agnostic Nonparametric AI model (EDEN), which directly detect bursts from dynamic spectrum and is the first detection pipeline that operates without attempting dedispersion. We apply EDEN to archival FAST L-band observations during the extreme active phase of the repeating source FRB 20121102A, resulting in the largest burst set for any FRB to date, which contains 5,927 individual bursts, tripling the original burst set. The much enhanced completeness enables a refined analysis of the temporal behavior of energy distribution, revealing that the bimodal energy distribution remains stable over time. It is rather an intrinsic feature of the emission mechanisms than a consequence of co-evolving with burst rate. △ Less

Submitted 8 October, 2025; originally announced October 2025.

Mineral Detection of Neutrinos and Dark Matter 2025 Proceedings

Authors: Shigenobu Hirose, Patrick Stengel, Natsue Abe, Daniel Ang, Lorenzo Apollonio, Gabriela R. Araujo, Yoshihiro Asahara, Laura Baudis, Pranshu Bhaumik, Nathaniel Bowden, Joseph Bramante, Lorenzo Caccianiga, Mason Camp, Qing Chang, Jordan Chapman, Reza Ebadi, Alexey Elykov, Anna Erickson, Valentin Fondement, Katherine Freese, Shota Futamura, Claudio Galelli, Andrew Gilpin, Takeshi Hanyu, Noriko Hasebe , et al. (48 additional authors not shown)

Abstract: The third ``Mineral Detection of Neutrinos and Dark Matter'' (MD$ν$DM'25) meeting was held May 20-23, 2025 in Yokohama, Japan, hosted by the Yokohama Institute for Earth Sciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC). These proceedings compile contributions from the workshop and update the progress of mineral detector research. MD$ν$DM'25 was the third such meeting, follo… ▽ More The third ``Mineral Detection of Neutrinos and Dark Matter'' (MD$ν$DM'25) meeting was held May 20-23, 2025 in Yokohama, Japan, hosted by the Yokohama Institute for Earth Sciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC). These proceedings compile contributions from the workshop and update the progress of mineral detector research. MD$ν$DM'25 was the third such meeting, following the first in October of 2022 held at the IFPU in Trieste, Italy and the second in January of 2024 hosted by the Center for Neutrino Physics at Virginia Tech in Arlington, USA. Mineral detectors record and retain damage induced by nuclear recoils in synthetic or natural mineral samples. The damage features can then be read out by a variety of nano- and micro-scale imaging techniques. Applications of mineral detectors on timescales relevant for laboratory experiments include reactor neutrino monitoring and dark matter detection, with the potential to measure the directions as well as the energies of the induced nuclear recoils. For natural mineral detectors which record nuclear recoils over geological timescales, reading out even small mineral samples could be sensitive to rare interactions induced by astrophysical neutrinos, cosmic rays, dark matter and heavy exotic particles. A series of mineral detectors of different ages could measure the time evolution of these fluxes, offering a unique window into the history of our solar system and the Milky Way. Mineral detector research is highly multidisciplinary, incorporating aspects of high energy physics, condensed matter physics, materials science, geoscience, and AI/ML for data analysis. Although realizing the scientific potential of mineral detectors poses many challenges, the MD$ν$DM community looks forward to the continued development of mineral detector experiments and the possible discoveries that mineral detectors could reveal. △ Less

Submitted 28 August, 2025; originally announced August 2025.

Comments: Summary and proceedings of the MDvDM'25 conference, May 20-23 2025 in Yokohama, Japan

Multiwavelength Observations of the Apparently Non-repeating FRB 20250316A

Authors: Ye Li, Hui Sun, Lei Qian, Dong-Yue Li, Yan-Long Hua, Li-Ping Xin, Cheng-Kui Li, Yi-Han Wang, Jia-Rui Niu, Tian-Rui Sun, Zhu-Heng Yao, Jin-Jun Geng, Chi-Chuan Jin, Nanda Rea, Yuan Liu, Zhi-Chen Pan, Tao An, Vadim Burwitz, Zhi-Ming Cai, Jin-Huang Cao, Yong Chen, Hua-Qing Cheng, Wei-Wei Cui, Hua Feng, Peter Friedrich , et al. (50 additional authors not shown)

Abstract: The physical origin of fast radio bursts (FRBs) remains uncertain. Although multiwavelength observations have been widely conducted, only Galactic FRB~20200428D is associated with an X-ray burst from the magnetar SGR J1935+2154. Here, we present multiwavelength follow-up observations of the nearby bright FRB~20250316A, including the Five-hundred-meter Aperture Spherical radio Telescope (FAST), Ein… ▽ More The physical origin of fast radio bursts (FRBs) remains uncertain. Although multiwavelength observations have been widely conducted, only Galactic FRB~20200428D is associated with an X-ray burst from the magnetar SGR J1935+2154. Here, we present multiwavelength follow-up observations of the nearby bright FRB~20250316A, including the Five-hundred-meter Aperture Spherical radio Telescope (FAST), Einstein Probe (EP) X-ray mission, Chandra X-ray Observatory, Wide Field Survey Telescope (WFST) and Space Variable Object Monitor/Visible Telescope (SVOM/VT). The 13.08-hour FAST follow-up campaign without pulse detection requires an energy distribution flatter than those of well-known repeating FRBs, suggesting that this burst is likely a one-off event. A prompt EP follow-up and multi-epoch observational campaign totaling $>$ 100 ks led to the detection of an X-ray source within the angular resolution of its Follow-up X-ray Telescope (FXT, $10^{\prime\prime}$). A subsequent Chandra observation revealed this source to be offset by $7^{\prime\prime}$ from the FRB position, and established a 0.5-10 keV flux upper limit of $7.6\times 10^{-15}$ $\rm erg\,cm^{-2}\,s^{-1}$ at the FRB position, corresponding to $\sim 10^{39}$ $\rm erg\,s^{-1}$ at the 40 Mpc distance of the host galaxy NGC~4141. These results set one of the most stringent limits on X-ray emission from a non-repeating FRB, disfavoring ultra-luminous X-ray sources (ULXs) as counterparts of apparently one-off FRBs and offering critical insights into afterglow models. Our study suggests that an arcsecond localization of both the FRB and its potential X-ray counterpart is essential for exploring the X-ray counterpart of an FRB. △ Less

Submitted 18 November, 2025; v1 submitted 19 August, 2025; originally announced August 2025.

Comments: Accepted for publication in The Astrophysical Journal

A Glimpse of Satellite Galaxies in the Milky Way with the 2.5-meter Wide Field Survey Telescope (WFST): Bootes III and Draco

Authors: Chao Yang, Zhizheng Pan, Min Fang, Xian Zhong Zheng, Binyang Liu, Guoliang Li, Tian-Rui Sun, Ji-An Jiang, Miaomiao Zhang, Zhen Wan, Shuang Liu, Han Qu, Ji Yang, Xu Kong, Wenhao Liu, Yiping Shu, Jiang Chang, Tinggui Wang, Lulu Fan, Yongquan Xue, Wentao Luo, Hongxin Zhang, Zheng Lou, Haibin Zhao, Bin Li , et al. (12 additional authors not shown)

Abstract: We carry out deep imaging of the Milky Way satellite galaxies, Bootes III and Draco, with WFST as one pilot observing program to demonstrate the capability of WFST. Combining catalogs with PS1 DR2 and Gaia DR3, we derive proper motions for candidate member stars in these two satellite galaxies over a 12-year time baseline, yielding uncertainties of ~1.8 mas/yr at 21 mag and ~3.0 mas/yr at 22 mag i… ▽ More We carry out deep imaging of the Milky Way satellite galaxies, Bootes III and Draco, with WFST as one pilot observing program to demonstrate the capability of WFST. Combining catalogs with PS1 DR2 and Gaia DR3, we derive proper motions for candidate member stars in these two satellite galaxies over a 12-year time baseline, yielding uncertainties of ~1.8 mas/yr at 21 mag and ~3.0 mas/yr at 22 mag in the r band. The proper motions derived from bright and faint stars are consistent, indicating no significant variation in proper motion across stellar luminosity as these galaxies undergo tidal interactions with the MW. Meanwhile, we suggest that Bootes III represents the bound remnant of the progenitor galaxy that gave rise to the Styx stream, as evidenced by its elongated density profile and overdensity in both spatial and kinematic space. This is the first paper to use WFST to measure the proper motions of faint stars in Milky Way satellite galaxies. More detailed analyses will be presented in forthcoming papers from the wide field survey (WFS) program. △ Less

Submitted 26 June, 2025; originally announced June 2025.

Comments: 17 pages, 12 figures, 3 tables. Accepted for publication in ApJ

Opening up New Parameter Space for Sterile Neutrino Dark Matter

Authors: P. S. Bhupal Dev, Bhaskar Dutta, Srubabati Goswami, Jianrong Paul Tang, Aaroodd Ujjayini Ramachandran

Abstract: Sterile neutrinos are compelling dark matter (DM) candidates, yet the minimal production mechanism solely based on active ($ν_a$)-sterile ($ν_s$) oscillations is excluded by astrophysical observations. Non-standard self-interactions in either active ($ν_a-ν_a$) or sterile ($ν_s-ν_s$) sector are known to alter the sterile neutrino DM production in the early Universe, which could alleviate the tensi… ▽ More Sterile neutrinos are compelling dark matter (DM) candidates, yet the minimal production mechanism solely based on active ($ν_a$)-sterile ($ν_s$) oscillations is excluded by astrophysical observations. Non-standard self-interactions in either active ($ν_a-ν_a$) or sterile ($ν_s-ν_s$) sector are known to alter the sterile neutrino DM production in the early Universe, which could alleviate the tension with astrophysical constraints to some extent. Here we propose a novel solution where scalar-mediated non-standard interactions between active and sterile neutrinos ($ν_a-ν_s$) generate new production channels for $ν_s$, independent of the active-sterile mixing and without the need for any fine-tuned resonance or primordial lepton asymmetry. This framework enables efficient sterile neutrino DM production even at vanishingly small mixing angles and opens up new viable regions of parameter space that can be tested with future $X$-ray and gamma-ray observations. △ Less

Submitted 7 November, 2025; v1 submitted 28 May, 2025; originally announced May 2025.

Comments: 12 pages, 7 figures. Added two more sections

Report number: MI-HET-858

Zangetsu: A Candidate of Isolated, Quiescent, and Backsplash Ultra-Diffuse Galaxy in the COSMOS Field

Authors: Leyao Wei, Song Huang, Jiaxuan Li, Zechang Sun, Mingyu Li, Jiaxin Tang

Abstract: Deep imaging surveys have changed our view of the low surface brightness (LSB) Universe. The "renaissance" of the low surface brightness dwarf galaxy population, as the prime example of such recent development, continues to challenge our understanding of galaxy formation. Here, We report the serendipitous discovery of Zangetsu, an isolated, quiescent, and distorted ultra-diffuse galaxy (UDG) candi… ▽ More Deep imaging surveys have changed our view of the low surface brightness (LSB) Universe. The "renaissance" of the low surface brightness dwarf galaxy population, as the prime example of such recent development, continues to challenge our understanding of galaxy formation. Here, We report the serendipitous discovery of Zangetsu, an isolated, quiescent, and distorted ultra-diffuse galaxy (UDG) candidate in the COSMOS field, using images from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Zangetsu exhibits an extremely low central surface brightness ($\mathrm{μ_{0,g}}=26.60\pm0.01$ mag arcsec$^{-2}$), a very shallow inner surface brightness profile ($\mathrm{n}_{\rm Sersic}=0.40\pm0.01$), and a large angular size ($\mathrm{R_e}\approx 10.44$ arcsec). Surprisingly, Zangetsu also has a quiescent stellar population ($\mathrm{g-i}=0.96$), an unusually elongated shape ($\mathrm{b/a}\sim 0.25$), and mild morphological asymmetry, making it a rare case among known UDGs. Surface brightness fluctuation analysis of HSC and Hubble Space Telescope (HST) images only provides a distance lower limit of $D>25.4$ Mpc (thus $\mathrm{R_e}>1.38$ kpc). However, Zangetsu remains an extreme outlier in the luminosity-size relation of known LSB galaxies, suggesting that it could be an exceptionally large and/or diffuse system. Classic internal or external UDG formation mechanisms alone struggle to explain such a system. A backsplash origin may account for its isolation and quiescent nature. This finding also raises the possibility that current works may overlook similarly extreme, elongated systems that could further our understanding of the LSB Universe. △ Less

Submitted 21 May, 2025; v1 submitted 20 May, 2025; originally announced May 2025.

Comments: 25 pages, 11 figures

DESI DR1 Lyα 1D power spectrum: The Fast Fourier Transform estimator measurement

Authors: Corentin Ravoux, Marie-Lynn Abdul-Karim, Jean-Marc Le Goff, Eric Armengaud, Jessica N. Aguilar, Steven Ahlen, Stephen Bailey, Davide Bianchi, Allyson Brodzeller, David Brooks, Jonás Chaves-Montero, Todd Claybaugh, Andrei Cuceu, Roger de Belsunce, Axel de la Macorra, Arjun Dey, Zhejie Ding, Peter Doel, Simone Ferraro, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztañaga, Naim Göksel Karaçaylı, Satya Gontcho A Gontcho, Gaston Gutierrez , et al. (42 additional authors not shown)

Abstract: We present the one-dimensional Lyman-$α$ forest power spectrum measurement derived from the data release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI). The measurement of the Lyman-$α$ forest power spectrum along the line of sight from high-redshift quasar spectra provides information on the shape of the linear matter power spectrum, neutrino masses, and the properties of dark matter.… ▽ More We present the one-dimensional Lyman-$α$ forest power spectrum measurement derived from the data release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI). The measurement of the Lyman-$α$ forest power spectrum along the line of sight from high-redshift quasar spectra provides information on the shape of the linear matter power spectrum, neutrino masses, and the properties of dark matter. In this work, we use a Fast Fourier Transform (FFT)-based estimator, which is validated on synthetic data in a companion paper. Compared to the FFT measurement performed on the DESI early data release, we improve the noise characterization with a cross-exposure estimator and test the robustness of our measurement using various data splits. We also refine the estimation of the uncertainties and now present an estimator for the covariance matrix of the measurement. Furthermore, we compare our results to previous high-resolution and eBOSS measurements. In another companion paper, we present the same DR1 measurement using the Quadratic Maximum Likelihood Estimator (QMLE). These two measurements are consistent with each other and constitute the most precise one-dimensional power spectrum measurement to date, while being in good agreement with results from the DESI early data release. △ Less

Submitted 21 November, 2025; v1 submitted 14 May, 2025; originally announced May 2025.

Comments: 38 pages, 16 figures

Journal ref: JCAP11(2025)079

DESI DR1 Ly$α$ 1D power spectrum: The optimal estimator measurement

Authors: N. G. Karaçaylı, P. Martini, J. Aguilar, S. Ahlen, E. Armengaud, S. Bailey, A. Bault, D. Bianchi, A. Brodzeller, D. Brooks, J. Chaves-Montero, T. Claybaugh, A. Cuceu, A. de la Macorra, A. Dey, B. Dey, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, J. Guy, C. Hahn , et al. (39 additional authors not shown)

Abstract: The one-dimensional power spectrum $P_{\mathrm{1D}}$ of Ly$α$ forest offers rich insights into cosmological and astrophysical parameters, including constraints on the sum of neutrino masses, warm dark matter models, and the thermal state of the intergalactic medium. We present the measurement of $P_{\mathrm{1D}}$ using the optimal quadratic maximum likelihood estimator applied to over 300,000 Ly… ▽ More The one-dimensional power spectrum $P_{\mathrm{1D}}$ of Ly$α$ forest offers rich insights into cosmological and astrophysical parameters, including constraints on the sum of neutrino masses, warm dark matter models, and the thermal state of the intergalactic medium. We present the measurement of $P_{\mathrm{1D}}$ using the optimal quadratic maximum likelihood estimator applied to over 300,000 Ly$α$ quasars from Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI) survey. This sample represents the largest to date for $P_{\mathrm{1D}}$ measurements and is larger than the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) by a factor of 1.7. We conduct a meticulous investigation of instrumental and analysis systematics and quantify their impact on $P_{\mathrm{1D}}$. This includes the development of a cross-exposure estimator that eliminates the need to model the pipeline noise and has strong potential for future $P_{\mathrm{1D}}$ measurements. We also present new insights into metal contamination through the 1D correlation function. Using a fitting function we measure the evolution of the Ly$α$ forest bias with high precision: $b_F(z) = (-0.218\pm0.002)\times((1 + z) / 4)^{2.96\pm0.06}$. In a companion validation paper, we substantially extend our previous suite of CCD image simulations to quantify the pipeline's exquisite performance accurately. In another companion paper, we present DR1 $P_{\mathrm{1D}}$ measurements using the Fast Fourier Transform (FFT) approach to power spectrum estimation. These two measurements produce a forest bias parameter that differs by 2.2 sigma. However, our model is simplistic, so this disagreement will be investigated in future work. △ Less

Submitted 26 August, 2025; v1 submitted 12 May, 2025; originally announced May 2025.

Comments: 41 pages, 15 figures

A pilot survey on globular clusters with the Wide Field Survey Telescope (WFST)

Authors: Zhen Wan, Lulu Fan, Xuzhi Li, Xu Kong, Tinggui Wang, Qingfeng Zhu, Ji-an Jiang, Minxuan Cai, Zelin Xu, Xianzhong Zheng, Jingquan Cheng, Feng Li, Ming Liang, Hao Liu, Wentao Luo, Jinlong Tang, Hairen Wang, Jian Wang, Yongquan Xue, Dazhi Yao, Hongfei Zhang, Wen Zhao

Abstract: We carry out an imaging survey of six globular clusters (GCs) with a limit magnitude to 22 mag at the 5 sigma level, down to the main sequence stars of the respective cluster, as one of the pilot observing program of the Wide Field Survey Telescope (WFST). This paper present the early results of this survey, where we investigate the tidal characters at the periphery of the clusters NGC 4147, NGC 5… ▽ More We carry out an imaging survey of six globular clusters (GCs) with a limit magnitude to 22 mag at the 5 sigma level, down to the main sequence stars of the respective cluster, as one of the pilot observing program of the Wide Field Survey Telescope (WFST). This paper present the early results of this survey, where we investigate the tidal characters at the periphery of the clusters NGC 4147, NGC 5024, NGC 5053, NGC 5272, NGC 5904 and NGC 6341. We present the estimated number density of cluster candidates and their spatial distribution. We confirm the presence of tidal arms in NGC 4147 and NGC 5904 and identify several intriguing potential tidal structures in NGC 4147, NGC 5024, NGC 5272, corroborated the elliptical morphology of the periphery of NGC 6341. WFST shows its ability to detect faint main-sequence stars of clusters beyond 15 kpc in helio-centric distance. Our findings underscore the WFST's capability for probing faint structural features in GCs, paving the way for future in-depth studies, especially for the search of the large scale tidal streams associated with the clusters with the future wide field survey. △ Less

Submitted 29 April, 2025; v1 submitted 7 March, 2025; originally announced March 2025.

Comments: 13 pages, 8 figures. accepted by MNRAS. Comments are welcome

The GeV $γ$-ray emission from the composite SNR CTB 87

Authors: Yuliang Xin, Jian Tang, Weixiong Ding, Xi Liu, Yunfeng Zhang, Xiaolei Guo

Abstract: We report the GeV $γ$-ray emission around the composite supernova remnant (SNR) CTB 87 with more than 16 yrs PASS 8 data recorded by the Fermi Large Area Telescope. Two separate point sources with the different GeV spectra are identified in this region: one has a soft $γ$-ray spectrum, likely due to interactions between the SNR shock and molecular clouds (MCs); and another source with a hard GeV… ▽ More We report the GeV $γ$-ray emission around the composite supernova remnant (SNR) CTB 87 with more than 16 yrs PASS 8 data recorded by the Fermi Large Area Telescope. Two separate point sources with the different GeV spectra are identified in this region: one has a soft $γ$-ray spectrum, likely due to interactions between the SNR shock and molecular clouds (MCs); and another source with a hard GeV $γ$-ray spectrum aligns with the TeV spectrum of VER J2016+371, suggesting it as the GeV counterpart. Considering the observations of CTB 87 in the radio and X-ray bands, VER J2016+371 is proposed to originate from the pulsar wind nebula (PWN) associated with PSR J2016+3711. A leptonic model with a broken power-law electron distribution could explain the multi-wavelength data of VER J2016+371, with fitted parameters matching typical $γ$-ray PWNe. Deeper searching for the SNR shock of CTB 87 in other bands and the future TeV observations by LHAASO and CTA are crucial to reveal the nature of CTB 87. △ Less

Submitted 6 February, 2025; originally announced February 2025.

Comments: 11 pages, 4 figures, 2 tables, accepted for publicaton in ApJ

Minute-cadence observations on Galactic plane with Wide Field Survey Telescope (WFST): Overview, methodology and early results

Authors: Jie Lin, Tinggui Wang, Minxuan Cai, Zhen Wan, Xuzhi Li, Lulu Fan, Qingfeng Zhu, Ji-an Jiang, Ning Jiang, Xu Kong, Zheyu Lin, Jiazheng Zhu, Zhengyan Liu, Jie Gao, Bin Li, Feng Li, Ming Liang, Hao Liu, Wei Liu, Wentao Luo, Jinlong Tang, Hairen Wang, Jian Wang, Yongquan Xue, Dazhi Yao , et al. (4 additional authors not shown)

Abstract: As the time-domain survey telescope of the highest survey power in the northern hemisphere currently, Wide Field Survey Telescope (WFST) is scheduled to hourly/daily/semi-weekly scan northern sky up to ~23 mag in four optical (ugri) bands. Unlike the observation cadences in the forthcoming regular survey missions, WFST performed "staring" observations toward Galactic plane in a cadence of… ▽ More As the time-domain survey telescope of the highest survey power in the northern hemisphere currently, Wide Field Survey Telescope (WFST) is scheduled to hourly/daily/semi-weekly scan northern sky up to ~23 mag in four optical (ugri) bands. Unlike the observation cadences in the forthcoming regular survey missions, WFST performed "staring" observations toward Galactic plane in a cadence of $\approx$1 minute for a total on-source time of about 13 hours, during the commissioning and pilot observation phases. Such an observation cadence is well applied in producing densely sampling light curves and hunting for stars exhibiting fast stellar variabilities. Here we introduce the primary methodologies in detecting variability, periodicity, and stellar flares among a half million sources from the minute-cadence observations, and present the WFST g-/r-band light curves generated from periodic variable stars and flaring stars. Benefit from high photometric precisions and deep detection limits of WFST, the observations have captured several rare variable stars, such as a variable hot white dwarf (WD) and an ellipsoidal WD binary candidate. By surveying the almost unexplored parameter spaces for variables, WFST will lead to new opportunities in discovering unique variable stars in the northern sky. △ Less

Submitted 16 March, 2025; v1 submitted 17 December, 2024; originally announced December 2024.

Comments: 20 pages, 12 figures, accepted by ApJS

Planets Around Solar Twins/Analogs (PASTA) I.: High precision stellar chemical abundance for 17 planet-hosting stars and the condensation temperature trend

Authors: Qinghui Sun, Sharon Xuesong Wang, Tianjun Gan, Chenyang Ji, Zitao Lin, Yuan-Sen Ting, Johanna Teske, Haining Li, Fan Liu, Xinyan Hua, Jiaxin Tang, Jie Yu, Jiayue Zhang, Mariona Badenas-Agusti, Andrew Vanderburg, George R. Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Jon M. Jenkins, Richard P. Schwarz, Tristan Guillot, Thiam-Guan Tan, Dennis M. Conti, Kevin I. Collins , et al. (8 additional authors not shown)

Abstract: The Sun is depleted in refractory elements compared to nearby solar twins, which may be linked to the formation of giant or terrestrial planets. Here we present high-resolution, high signal-to-noise spectroscopic data for 17 solar-like stars hosting planets, obtained with Magellan II/MIKE, to investigate whether this depletion is related to planet formation. We derive stellar parameters, including… ▽ More The Sun is depleted in refractory elements compared to nearby solar twins, which may be linked to the formation of giant or terrestrial planets. Here we present high-resolution, high signal-to-noise spectroscopic data for 17 solar-like stars hosting planets, obtained with Magellan II/MIKE, to investigate whether this depletion is related to planet formation. We derive stellar parameters, including stellar atmosphere, age, radius, mass, and chemical abundances for 22 elements from carbon to europium through line-by-line differential analysis. Our uncertainties range from 0.01 dex for Fe and Si to 0.08 dex for Sr, Y, and Eu. By comparing the solar abundances to those of the 17 stars, we investigate the differential abundance ([X/Fe]$_{\rm solar}$ - [X/Fe]$_{\rm star}$) versus condensation temperature ($T_c$) trend. In particular, we apply Galactic chemical evolution corrections to five solar twins within the full sample. Our results conform to previous studies that the Sun is relatively depleted in refractory compared to volatile elements. For both five solar twins and the rest of solar-like stars, we find that all stars hosting known gas giant planets exhibit negative $T_c$ trend slopes, suggesting that the Sun is relatively depleted in refractory elements compared to similar giant-planet-host stars. Additionally, we find no correlation between $T_c$ trend slopes and the total mass of detected terrestrial planets in each system, suggesting that terrestrial planet formation may not be the cause of refractory element depletion in the Sun. △ Less

Submitted 23 December, 2024; v1 submitted 20 November, 2024; originally announced November 2024.

Comments: 26 pages, 10 figures, 7 tables; accepted for publication in ApJ

Empirical color correction to MIST and PARSEC isochrones on Gaia BR-RP and G-RP with benchmark open clusters

Authors: Fan Wang, Min Fang, Xiaoting Fu, Yang Chen, Lu Li, Xiaoying Pang, Zhongmu Li, Jing Tang, Wenyuan Cui, Haijun Tian, Chao Liu

Abstract: Recent literature reports a color deviation between observed Gaia color-magnitude diagrams (CMDs) and theoretical model isochrone predictions, particularly in the very low-mass regime. To assess its impact on cluster age determination via isochrone fitting, we quantified the color deviations for three benchmark clusters, Hyades, Pleiades, and Praesepe, both for the Gaia color (BP-RP) and (G-RP). I… ▽ More Recent literature reports a color deviation between observed Gaia color-magnitude diagrams (CMDs) and theoretical model isochrone predictions, particularly in the very low-mass regime. To assess its impact on cluster age determination via isochrone fitting, we quantified the color deviations for three benchmark clusters, Hyades, Pleiades, and Praesepe, both for the Gaia color (BP-RP) and (G-RP). In general, the (G-RP) color deviations are smaller than the (BP-RP) ones. Empirical color correction functions based on these benchmarks are derived for the currently available MIST and PARSEC 1.2S isochrone models. Applying the correction functions to 31 additional open clusters and 3 moving groups results in a significantly improved alignment between the isochrones and observed CMDs. With our empirical corrections, isochrones provide age estimates consistent with literature values obtained through the spectral Lithium Depletion Boundary method, validating the effectiveness of our approach. The corresponding metallicities with PARSEC 1.2S also show a good agreement with the spectroscopic results. The empirical color correction function we present in this work offers a tool for a consistent age determination within the full mass range of stellar clusters using the isochrone fitting method. △ Less

Submitted 19 November, 2024; originally announced November 2024.

Comments: 27 pages. Accepted for publication in ApJ

The Variability Structure Function of the Highest-Luminosity Quasars on Short Timescales

Authors: Ji-Jia Tang, Christian Wolf, John Tonry

Abstract: The stochastic photometric variability of quasars is known to follow a random-walk phenomenology on emission timescales of months to years. Some high-cadence restframe optical monitoring in the past has hinted at a suppression of variability amplitudes on shorter timescales of a few days or weeks, opening the question of what drives the suppression and how it might scale with quasar properties. He… ▽ More The stochastic photometric variability of quasars is known to follow a random-walk phenomenology on emission timescales of months to years. Some high-cadence restframe optical monitoring in the past has hinted at a suppression of variability amplitudes on shorter timescales of a few days or weeks, opening the question of what drives the suppression and how it might scale with quasar properties. Here, we study a few thousand of the highest-luminosity quasars in the sky, mostly in the luminosity range of $L_{\rm bol}=[46.4, 47.3]$ and redshift range of $z=[0.7, 2.4]$. We use a dataset from the NASA/ATLAS facility with nightly cadence, weather permitting, which has been used before to quantify strong regularity in longer-term restframe-UV variability. As we focus on a careful treatment of short timescales across the sample, we find that a linear function is sufficient to describe the UV variability structure function. Although the result can not rule out the existence of breaks in some groups completely, a simpler model is usually favoured under this circumstance. In conclusion, the data is consistent with a single-slope random walk across restframe timescales of $Δt=[10, 250]$ days. △ Less

Submitted 11 November, 2024; originally announced November 2024.

Comments: 9 pages, 5 figures, Accepted for publication in MNRAS

Timescales of Quasar Accretion Discs from Low to High Black Hole Masses and a Turnover at the High Mass End

Authors: C. Wolf, S. Lai, J. -J. Tang, J. Tonry

Abstract: Characteristic time scales in the stochastic UV-optical variability of quasars may depend on the mass of their black holes, $M_{\rm BH}$, as much as physical timescales in their accretion discs do. We calculate emission-weighted mean radii, $R_{\rm mean}$, and orbital timescales, $t_{\rm mean}$, of standard thin disc models for emission wavelengths $λ$ from 1000 to 10000 AA, $M_{\rm BH}$ from… ▽ More Characteristic time scales in the stochastic UV-optical variability of quasars may depend on the mass of their black holes, $M_{\rm BH}$, as much as physical timescales in their accretion discs do. We calculate emission-weighted mean radii, $R_{\rm mean}$, and orbital timescales, $t_{\rm mean}$, of standard thin disc models for emission wavelengths $λ$ from 1000 to 10000 AA, $M_{\rm BH}$ from $10^6$ to $10^{11}$ solar masses, and Eddington ratios from 0.01 to 1. At low $M_{\rm BH}$, we find the textbook behaviour of $t_{\rm mean}\propto M_{\rm BH}^{-1/2}$ alongside $R_{\rm mean} \approx \mathrm{const}$, but toward higher masses the growing event horizon imposes $R_{\rm mean} \propto M_{\rm BH}$ and thus a turnover into $t_{\rm mean}\propto M_{\rm BH}$. For quasars of $\log L_{\rm bol}=47$, the turnover mass, where $t_{\rm mean}$ starts rising is $M_{\rm BH}\approx 9.5$, which means that the turnover in $t_{\rm mean}$ is well within the range of high-luminosity quasar samples, whose variability time scales might thus show little mass dependence. We fit smoothly broken power laws to the results and provide analytic convenience functions for $R_{\rm mean}(λ,M_{\rm BH},L_{3000})$ and $t_{\rm mean}(λ,M_{\rm BH},L_{3000})$. △ Less

Submitted 29 October, 2025; v1 submitted 4 November, 2024; originally announced November 2024.

Comments: 11 pages, 6 figures, submitted to MNRAS

GRB 240529A: A Tale of Two Shocks

Authors: Tian-Rui Sun, Jin-Jun Geng, Jing-Zhi Yan, You-Dong Hu, Xue-Feng Wu, Alberto J. Castro-Tirado, Chao Yang, Yi-Ding Ping, Chen-Ran Hu, Fan Xu, Hao-Xuan Gao, Ji-An Jiang, Yan-Tian Zhu, Yongquan Xue, Ignacio Pérez-García, Si-Yu Wu, Emilio Fernández-García, María D. Caballero-García, Rubén Sánchez-Ramírez, Sergiy Guziy, Ignacio Olivares, Carlos Jesus Pérez del Pulgar, A. Castellón, Sebastián Castillo, Ding-Rong Xiong , et al. (44 additional authors not shown)

Abstract: Thanks to the rapidly increasing time-domain facilities, we are entering a golden era of research on gamma-ray bursts (GRBs). In this Letter, we report our observations of GRB 240529A with the Burst Optical Observer and Transient Exploring System, the 1.5-meter telescope at Observatorio Sierra Nevada, the 2.5-meter Wide Field Survey Telescope of China, the Large Binocular Telescope, and the Telesc… ▽ More Thanks to the rapidly increasing time-domain facilities, we are entering a golden era of research on gamma-ray bursts (GRBs). In this Letter, we report our observations of GRB 240529A with the Burst Optical Observer and Transient Exploring System, the 1.5-meter telescope at Observatorio Sierra Nevada, the 2.5-meter Wide Field Survey Telescope of China, the Large Binocular Telescope, and the Telescopio Nazionale Galileo. The prompt emission of GRB 240529A shows two comparable energetic episodes separated by a quiescence time of roughly 400 s. Combining all available data on the GRB Coordinates Network, we reveal the simultaneous apparent X-ray plateau and optical re-brightening around $10^3-10^4$ s after the burst. Rather than the energy injection from the magnetar as widely invoked for similar GRBs, the multi-wavelength emissions could be better explained as two shocks launched from the central engine separately. The optical peak time and our numerical modeling suggest that the initial bulk Lorentz factor of the later shock is roughly 50, which indicates that the later jet should be accretion-driven and have a higher mass loading than a typical one. The quiescence time between the two prompt emission episodes may be caused by the transition between different accretion states of a central magnetar or black hole, or the fall-back accretion process. A sample of similar bursts with multiple emission episodes in the prompt phase and sufficient follow-up could help to probe the underlying physics of GRB central engines. △ Less

Submitted 26 September, 2024; originally announced September 2024.

Comments: Resubmitted to ApJL after addressing the referee's comments; comments are welcome

Optical Extinctions of Inter-Arm Molecular Clouds in M31: A Pilot Study for the Upcoming CSST Observations

Authors: Cailing Chen, Zheng Zheng, Chao-Wei Tsai, Sihan Jiao, Jing Tang, Jingwen Wu, Di Li, Yun Zheng, Linjing Feng, Yujiao Yang, Yuan Liang

Abstract: Recent sub-millimeter dust thermal emission observations have unveiled a significant number of inter-arm massive molecular clouds in M31.However,the effectiveness of this technique is limited to its sensitivity,making it challenging to study more distant galaxies.This study introduces an alternative approach,utilizing optical extinctions derived from space-based telescopes,with a focus on the fort… ▽ More Recent sub-millimeter dust thermal emission observations have unveiled a significant number of inter-arm massive molecular clouds in M31.However,the effectiveness of this technique is limited to its sensitivity,making it challenging to study more distant galaxies.This study introduces an alternative approach,utilizing optical extinctions derived from space-based telescopes,with a focus on the forthcoming China Space Station Telescope(CSST).We first demonstrate the capability of this method by constructing dust extinction maps for 17 inter-arm massive molecular clouds in M31 using the Panchromatic Hubble Andromeda Treasury(PHAT) data.Our analysis reveals that inter-arm massive molecular clouds with an optical extinction(AV) greater than 1.6 mag exhibit a notable AV excess,facilitating their identification.The majority of these inter-arm massive molecular clouds show an AV around 1 mag,aligning with measurements from our JCMT data.Further validation using a mock CSST RGB star catalog confirms the method's effectiveness.We show that the derived AV values using CSST z and y photometries align more closely with the input values.Molecular clouds with AV>1.6 mag can also be identified using the CSST mock data.We thus claim that future CSST observation could provide an effective way for the detection of inter-arm massive molecular clouds with significant optical extinction in nearby galaxies. △ Less

Submitted 30 May, 2024; originally announced May 2024.

Comments: 15 pages,9 figures

Mineral Detection of Neutrinos and Dark Matter 2024. Proceedings

Authors: Sebastian Baum, Patrick Huber, Patrick Stengel, Natsue Abe, Daniel G. Ang, Lorenzo Apollonio, Gabriela R. Araujo, Levente Balogh, Pranshu Bhaumik Yilda Boukhtouchen, Joseph Bramante, Lorenzo Caccianiga, Andrew Calabrese-Day, Qing Chang, Juan I. Collar, Reza Ebadi, Alexey Elykov, Katherine Freese, Audrey Fung, Claudio Galelli, Arianna E. Gleason, Mariano Guerrero Perez, Janina Hakenmüller, Takeshi Hanyu, Noriko Hasebe, Shigenobu Hirose , et al. (35 additional authors not shown)

Abstract: The second "Mineral Detection of Neutrinos and Dark Matter" (MDvDM'24) meeting was held January 8-11, 2024 in Arlington, VA, USA, hosted by Virginia Tech's Center for Neutrino Physics. This document collects contributions from this workshop, providing an overview of activities in the field. MDvDM'24 was the second topical workshop dedicated to the emerging field of mineral detection of neutrinos a… ▽ More The second "Mineral Detection of Neutrinos and Dark Matter" (MDvDM'24) meeting was held January 8-11, 2024 in Arlington, VA, USA, hosted by Virginia Tech's Center for Neutrino Physics. This document collects contributions from this workshop, providing an overview of activities in the field. MDvDM'24 was the second topical workshop dedicated to the emerging field of mineral detection of neutrinos and dark matter, following a meeting hosted by IFPU in Trieste, Italy in October 2022. Mineral detectors have been proposed for a wide variety of applications, including searching for dark matter, measuring various fluxes of astrophysical neutrinos over gigayear timescales, monitoring nuclear reactors, and nuclear disarmament protocols; both as paleo-detectors using natural minerals that could have recorded the traces of nuclear recoils for timescales as long as a billion years and as detectors recording nuclear recoil events on laboratory timescales using natural or artificial minerals. Contributions to this proceedings discuss the vast physics potential, the progress in experimental studies, and the numerous challenges lying ahead on the path towards mineral detection. These include a better understanding of the formation and annealing of recoil defects in crystals; identifying the best classes of minerals and, for paleo-detectors, understanding their geology; modeling and control of the relevant backgrounds; developing, combining, and scaling up imaging and data analysis techniques; and many others. During the last years, MDvDM has grown rapidly and gained attention. Small-scale experimental efforts focused on establishing various microscopic readout techniques are underway at institutions in North America, Europe and Asia. We are looking ahead to an exciting future full of challenges to overcome, surprises to be encountered, and discoveries lying ahead of us. △ Less

Submitted 2 May, 2024; originally announced May 2024.

Comments: Summary and proceedings of the MDvDM'24 conference, Jan 8-11 2024

AT2023lli: A Tidal Disruption Event with Prominent Optical Early Bump and Delayed Episodic X-ray Emission

Authors: Shifeng Huang, Ning Jiang, Jiazheng Zhu, Yibo Wang, Tinggui Wang, Shan-Qin Wang, Wen-Pei Gan, En-Wei Liang, Yu-Jing Qin, Zheyu Lin, Lin-Na Xu, Min-Xuan Cai, Ji-An Jiang, Xu Kong, Jiaxun Li, Long Li, Jian-Guo Wang, Ze-Lin Xu, Yongquan Xue, Ye-Fei Yuan, Jingquan Cheng, Lulu Fan, Jie Gao, Lei Hu, Weida Hu , et al. (20 additional authors not shown)

Abstract: High-cadence, multiwavelength observations have continuously revealed the diversity of tidal disruption events (TDEs), thus greatly advancing our knowledge and understanding of TDEs. In this work, we conducted an intensive optical-UV and X-ray follow-up campaign of TDE AT2023lli, and found a remarkable month-long bump in its UV/optical light curve nearly two months prior to maximum brightness. The… ▽ More High-cadence, multiwavelength observations have continuously revealed the diversity of tidal disruption events (TDEs), thus greatly advancing our knowledge and understanding of TDEs. In this work, we conducted an intensive optical-UV and X-ray follow-up campaign of TDE AT2023lli, and found a remarkable month-long bump in its UV/optical light curve nearly two months prior to maximum brightness. The bump represents the longest separation time from the main peak among known TDEs to date. The main UV/optical outburst declines as $t^{-4.10}$, making it one of the fastest decaying optically selected TDEs. Furthermore, we detected sporadic X-ray emission 30 days after the UV/optical peak, accompanied by a reduction in the period of inactivity. It is proposed that the UV/optical bump could be caused by the self-intersection of the stream debris, whereas the primary peak is generated by the reprocessed emission of the accretion process. In addition, our results suggest that episodic X-ray radiation during the initial phase of decline may be due to the patched obscurer surrounding the accretion disk, a phenomenon associated with the inhomogeneous reprocessing process. The double TDE scenario, in which two stars are disrupted in sequence, is also a possible explanation for producing the observed early bump and main peak. We anticipate that the multicolor light curves of TDEs, especially in the very early stages, and the underlying physics can be better understood in the near future with the assistance of dedicated surveys such as the deep high-cadence survey of the 2.5-meter Wide Field Survey Telescope (WFST). △ Less

Submitted 26 March, 2024; v1 submitted 3 March, 2024; originally announced March 2024.

Comments: 14 pages, 8 figures,accepted for publication by ApJL

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Authors: Angel Abusleme, Thomas Adam, Shakeel Ahmad, Rizwan Ahmed, Sebastiano Aiello, Muhammad Akram, Abid Aleem, Fengpeng An, Qi An, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, João Pedro Athayde Marcondes de André, Didier Auguste, Weidong Bai, Nikita Balashov, Wander Baldini, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Bellato, Marco Beretta, Antonio Bergnoli , et al. (606 additional authors not shown)

Abstract: The core-collapse supernova (CCSN) is considered one of the most energetic astrophysical events in the universe. The early and prompt detection of neutrinos before (pre-SN) and during the supernova (SN) burst presents a unique opportunity for multi-messenger observations of CCSN events. In this study, we describe the monitoring concept and present the sensitivity of the system to pre-SN and SN neu… ▽ More The core-collapse supernova (CCSN) is considered one of the most energetic astrophysical events in the universe. The early and prompt detection of neutrinos before (pre-SN) and during the supernova (SN) burst presents a unique opportunity for multi-messenger observations of CCSN events. In this study, we describe the monitoring concept and present the sensitivity of the system to pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton liquid scintillator detector currently under construction in South China. The real-time monitoring system is designed to ensure both prompt alert speed and comprehensive coverage of progenitor stars. It incorporates prompt monitors on the electronic board as well as online monitors at the data acquisition stage. Assuming a false alert rate of 1 per year, this monitoring system exhibits sensitivity to pre-SN neutrinos up to a distance of approximately 1.6 (0.9) kiloparsecs and SN neutrinos up to about 370 (360) kiloparsecs for a progenitor mass of 30 solar masses, considering both normal and inverted mass ordering scenarios. The pointing ability of the CCSN is evaluated by analyzing the accumulated event anisotropy of inverse beta decay interactions from pre-SN or SN neutrinos. This, along with the early alert, can play a crucial role in facilitating follow-up multi-messenger observations of the next galactic or nearby extragalactic CCSN. △ Less

Submitted 4 December, 2023; v1 submitted 13 September, 2023; originally announced September 2023.

Comments: 24 pages, 9 figures, accepted for the publication at JCAP

Laboratory and astronomical discovery of the cyanovinyl radical H2CCCN

Authors: C. Cabezas, J. Tang, M. Agúndez, K. Seiki, Y. Sumiyoshi, Y. Ohshima, B. Tercero, N. Marcelino, R. Fuentetaja, P. de Vicente, Y. Endo, J. Cernicharo

Abstract: We report the first laboratory and interstellar detection of the alpha-cyano vinyl radical (H2CCCN). This species was produced in the laboratory by an electric discharge of a gas mixture of vinyl cyanide, CH2CHCN, and Ne, and its rotational spectrum was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating in the frequency region of 8-40 GHz. The ob… ▽ More We report the first laboratory and interstellar detection of the alpha-cyano vinyl radical (H2CCCN). This species was produced in the laboratory by an electric discharge of a gas mixture of vinyl cyanide, CH2CHCN, and Ne, and its rotational spectrum was characterized using a Balle-Flygare narrowband-type Fourier-transform microwave spectrometer operating in the frequency region of 8-40 GHz. The observed spectrum shows a complex structure due to tunneling splittings between two torsional sublevels of the ground vibronic state, 0+ and 0-, derived from a large-amplitude inversion motion. In addition, the presence of two equivalent hydrogen nuclei makes necessary to discern between ortho- and para-H2CCCN. A least squares analysis reproduces the observed transition frequencies with a standard deviation of ca. 3 kHz. Using the laboratory predictions, this radical is detected in the cold dark cloud TMC-1 using the Yebes 40m telescope and the QUIJOTE line survey. The 404-303 and 505-404 rotational transitions, composed of several hyperfine components, were observed in the 31.0-50.4 GHz range. Adopting a rotational temperature of 6K we derive a column density of (1.4+/-0.2)e11 cm-2 and (1.1+/-0.2)e11 cm-2 for ortho-H2CCCN and para-H2CCCN, respectively. The reactions C + CH3CN, and perhaps also N + CH2CCH, emerge as the most likely routes to H2CCCN in TMC-1. △ Less

Submitted 18 July, 2023; originally announced July 2023.

Comments: Accepted for publication in A&A Letters on 18/07/2023

Journal ref: A&A 676, L5 (2023)

JUNO sensitivity to the annihilation of MeV dark matter in the galactic halo

Authors: JUNO Collaboration, Angel Abusleme, Thomas Adam, Shakeel Ahmad, Rizwan Ahmed, Sebastiano Aiello, Muhammad Akram, Abid Aleem, Tsagkarakis Alexandros, Fengpeng An, Qi An, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, João Pedro Athayde Marcondes de André, Didier Auguste, Weidong Bai, Nikita Balashov, Wander Baldini, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Bellato , et al. (581 additional authors not shown)

Abstract: We discuss JUNO sensitivity to the annihilation of MeV dark matter in the galactic halo via detecting inverse beta decay reactions of electron anti-neutrinos resulting from the annihilation. We study possible backgrounds to the signature, including the reactor neutrinos, diffuse supernova neutrino background, charged- and neutral-current interactions of atmospheric neutrinos, backgrounds from muon… ▽ More We discuss JUNO sensitivity to the annihilation of MeV dark matter in the galactic halo via detecting inverse beta decay reactions of electron anti-neutrinos resulting from the annihilation. We study possible backgrounds to the signature, including the reactor neutrinos, diffuse supernova neutrino background, charged- and neutral-current interactions of atmospheric neutrinos, backgrounds from muon-induced fast neutrons and cosmogenic isotopes. A fiducial volume cut, as well as the pulse shape discrimination and the muon veto are applied to suppress the above backgrounds. It is shown that JUNO sensitivity to the thermally averaged dark matter annihilation rate in 10 years of exposure would be significantly better than the present-day best limit set by Super-Kamiokande and would be comparable to that expected by Hyper-Kamiokande. △ Less

Submitted 13 September, 2023; v1 submitted 15 June, 2023; originally announced June 2023.

Comments: 25 pages, 9 figures, matches the publised version

Journal ref: JCAP 09 (2023) 001

Probing Quasar Viewing Angle with the Variability Structure Function

Authors: Ji-Jia Tang, Christian Wolf, John Tonry, Samuel Lai, Suk Yee Yong, Zachary Steyn

Abstract: Given the anisotropic emission from quasar accretion discs, their viewing angle affects estimates of the quasar luminosity, black-hole mass and Eddington ratio. Discs appear overluminous when viewed pole-on and underluminous when viewed at high inclination. In radio-quiet quasars, the viewing angle is usually unknown, although spectroscopic indicators have been proposed. Here, we use a recently di… ▽ More Given the anisotropic emission from quasar accretion discs, their viewing angle affects estimates of the quasar luminosity, black-hole mass and Eddington ratio. Discs appear overluminous when viewed pole-on and underluminous when viewed at high inclination. In radio-quiet quasars, the viewing angle is usually unknown, although spectroscopic indicators have been proposed. Here, we use a recently discovered universality in the variability structure function (SF) of quasar light curves (LCs), where all quasars show the same SF when clocks run in units of orbital timescale. As an offset from the mean relation can be caused by incorrect orbital timescales and thus incorrect luminosities, we correlate these offsets with suggested inclination indicators. We derive SFs from NASA/ATLAS LCs spanning $\sim 6$ years of observation, using a sample of 183 luminous quasars with measured H$β$ lines as well as 753 quasars with CIV and MgII lines. Starting from the proposed orientation indicators, we expect quasars with narrower H$β$ lines and with more blueshifted CIV lines to be viewed more pole-on and thus appear overluminous. In contrast, our SF analysis finds that presumed pole-on discs appear underluminous, consistently for both line indicators. We discuss possible explanations for the behaviour of quasars with highly blueshifted CIV lines irrespective of inclination angle, including dusty outflows that might render the accretion disc underluminous and flatter disc temperature profiles with longer orbital timescales than in thin-disc models but reach no satisfying conclusion. △ Less

Submitted 8 June, 2023; originally announced June 2023.

Comments: 15 pages, 10 figures, Accepted for publication in MNRAS

The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite

Authors: Z. X. Ling, X. J. Sun, C. Zhang, S. L. Sun, G. Jin, S. N. Zhang, X. F. Zhang, J. B. Chang, F. S. Chen, Y. F. Chen, Z. W. Cheng, W. Fu, Y. X. Han, H. Li, J. F. Li, Y. Li, Z. D. Li, P. R. Liu, Y. H. Lv, X. H. Ma, Y. J. Tang, C. B. Wang, R. J. Xie, Y. L. Xue, A. L. Yan , et al. (101 additional authors not shown)

Abstract: The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (Fo… ▽ More The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available. △ Less

Submitted 24 May, 2023; originally announced May 2023.

Comments: Accepted by RAA

A fast tunable driver of light source for the TRIDENT Pathfinder experiment

Authors: Jiannan Tang, Weihao Wu, Liang Li, Peng Miao, Zhengyang Sun, Mingxin Wang, Donglian Xu

Abstract: TRIDENT (The tRopIcal DEep-sea Neutrino Telescope) is a proposed next-generation neutrino telescope to be constructed in the South China Sea. In September 2021, the TRIDENT Pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted to evaluate the in-situ optical properties of seawater. The T-REX experiment deployed three digital optical modules at a depth of 3420 meters, including a… ▽ More TRIDENT (The tRopIcal DEep-sea Neutrino Telescope) is a proposed next-generation neutrino telescope to be constructed in the South China Sea. In September 2021, the TRIDENT Pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted to evaluate the in-situ optical properties of seawater. The T-REX experiment deployed three digital optical modules at a depth of 3420 meters, including a light emitter module (LEM) and two light receiver modules (LRMs) equipped with photomultiplier tubes (PMTs) and cameras to detect light signals. The LEM emits light in pulsing and steady modes. It features a fast tunable driver to activate light-emitting diodes (LEDs) that emit nanosecond-width light pulses with tunable intensity. The PMTs in the LRM receive single photo-electron (SPE) signals with an average photon number of approximately 0.3 per 1-microsecond time window, which is used to measure the arrival time distribution of the SPE signals. The fast tunable driver can be remotely controlled in real-time by the data acquisition system onboard the research vessel, allowing for convenient adjustments to the driver's parameters and facilitating the acquisition of high-quality experimental data. This paper describes the requirements, design scheme, and test results of the fast tunable driver, highlighting its successful implementation in the T-REX experiment and its potential for future deep-sea experiments. △ Less

Submitted 13 July, 2023; v1 submitted 3 May, 2023; originally announced May 2023.

The Light Source of the TRIDENT Pathfinder Experiment

Authors: Wenlian Li, Xiaohui Liu, Wei Tian, Fuyudi Zhang, Shishen Xian, Mingxin Wang, Jiannan Tang, Fan Hu, Ziping Ye, Peng Miao, Zhengyang Sun, Donglian Xu

Abstract: In September 2021, a site scouting mission known as the TRIDENT pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted in the South China Sea with the goal of envisaging a next-generation multi-cubic-kilometer neutrino telescope. One of the main tasks is to measure the in-situ optical properties of seawater at depths between $2800~\mathrm{m}$ and $3500~\mathrm{m}$, where the neutr… ▽ More In September 2021, a site scouting mission known as the TRIDENT pathfinder experiment (TRIDENT EXplorer, T-REX for short) was conducted in the South China Sea with the goal of envisaging a next-generation multi-cubic-kilometer neutrino telescope. One of the main tasks is to measure the in-situ optical properties of seawater at depths between $2800~\mathrm{m}$ and $3500~\mathrm{m}$, where the neutrino telescope will be instrumented. To achieve this, we have developed a light emitter module equipped with a clock synchronization system to serve as the light source, which could be operated in pulsing and steady modes. Two light receiver modules housing both photomultiplier tubes (PMTs) and cameras are employed to detect the photons emitted by the light source. This paper presents the instrumentation of the light source in T-REX, including its design, calibration, and performance. △ Less

Submitted 29 January, 2025; v1 submitted 27 April, 2023; originally announced April 2023.

Reproducing some observed galactic rotation curves without dark matter or modified Newtonian dynamics

Authors: Jau Tang, Qiang Tang

Abstract: Dark matter has been a long-standing and important issue in physics, but direct evidence of its existence is lacking. This work aims to elucidate the mystery and show that the dark matter hypothesis is unnecessary. We can nicely reproduce the observed rotation curves using only conventional Newtonian dynamics based on experimental surface brightness profiles of several galaxies. Our success is bas… ▽ More Dark matter has been a long-standing and important issue in physics, but direct evidence of its existence is lacking. This work aims to elucidate the mystery and show that the dark matter hypothesis is unnecessary. We can nicely reproduce the observed rotation curves using only conventional Newtonian dynamics based on experimental surface brightness profiles of several galaxies. Our success is based on realizing that the mass radial distribution follows a stretched exponential decay with a small exponent over a few hundred kiloparsecs. Our quantitative analysis indicates that for these four example galaxies, there is no need to invoke the hypothetical dark matter presently unknown to humans or the modified Newtonian dynamics (MOND) paradigm. △ Less

Submitted 5 March, 2023; originally announced March 2023.

Cluster Population Demographics in NGC 628 Derived from Stochastic Population Synthesis Models

Authors: Jianling Tang, Kathryn Grasha, Mark R. Krumholz

Abstract: The physical properties of star cluster populations offer valuable insights into their birth, evolution, and disruption. However, individual stars in clusters beyond the nearest neighbours of the Milky Way are unresolved, forcing analyses of star cluster demographics to rely on integrated light, a process fraught with uncertainty. Here we infer the demographics of the cluster population in the ben… ▽ More The physical properties of star cluster populations offer valuable insights into their birth, evolution, and disruption. However, individual stars in clusters beyond the nearest neighbours of the Milky Way are unresolved, forcing analyses of star cluster demographics to rely on integrated light, a process fraught with uncertainty. Here we infer the demographics of the cluster population in the benchmark galaxy NGC 628 using data from the Legacy Extra-galactic UV Survey (LEGUS) coupled to a novel Bayesian forward-modelling technique. Our method analyzes all 1178 clusters in the LEGUS catalogue, $\sim4$ times more than prior studies severely affected by completeness cuts. Our results indicate that the cluster mass function is either significantly steeper than the commonly-observed slope of $-2$ or is truncated at $\approx 10^{4.5}$ M$_\odot$; the latter possibility is consistent with proposed relations between truncation mass and star formation surface density. We find that cluster disruption is relatively mild for the first $\approx 200$ Myr of cluster evolution; no evidence for mass-dependent disruption is found. We find suggestive but not incontrovertible evidence that inner galaxy clusters may be more prone to disruption and outer galaxy clusters have a more truncated mass function, but confirming or refuting these findings will require larger samples from future observations of outer galaxy clusters. Finally, we find that current stellar track and atmosphere models, along with common forms for cluster mass and age distributions, cannot fully capture all features in the multidimensional photometric distribution of star clusters. While our forward-modelling approach outperforms earlier backward-modeling approaches, some systematic differences persist between observed and modelled photometric distributions. △ Less

Submitted 22 July, 2024; v1 submitted 14 January, 2023; originally announced January 2023.

Comments: 20 pages, 20 figures, 3 tables, accepted for publication in MNRAS on July 22nd 2024

Universality in the Random Walk Structure Function of Luminous Quasi-Stellar Objects

Authors: Ji-Jia Tang, Christian Wolf, John Tonry

Abstract: Rapidly growing black holes are surrounded by accretion disks that make them the brightest objects in the Universe. Their brightness is known to be variable, but the causes of this are not implied by simple disk models and still debated. Due to the small size of accretion disks and their great distance, there are no resolved images addressing the puzzle. In this work, we study the dependence of th… ▽ More Rapidly growing black holes are surrounded by accretion disks that make them the brightest objects in the Universe. Their brightness is known to be variable, but the causes of this are not implied by simple disk models and still debated. Due to the small size of accretion disks and their great distance, there are no resolved images addressing the puzzle. In this work, we study the dependence of their variability on luminosity, wavelength and orbital/thermal timescale. We use over 5,000 of the most luminous such objects with light curves of almost nightly cadence from $>5$ years of observations by the NASA/ATLAS project, which provides 2 billion magnitude pairs for a structure function analysis. When time is expressed in units of orbital or thermal time scale in thin-disk models, we find a universal structure function, independent of luminosity and wavelength, supporting the model of magneto-rotational instabilities as a main cause. Over a $>1$~dex range in time, the fractional variability amplitude follows $\log (A/A_0) \simeq 1/2 \times \log (Δt/t_{\rm th})$. Deviations from the universality may hold clues on the structure and orientation of disks. △ Less

Submitted 3 January, 2023; originally announced January 2023.

Comments: 21 pages, 5 figures

Measurement of the $^{159}$Tb(n, $γ$) cross section at the CSNS Back-n facility

Authors: S. Zhang, G. Li, W. Jiang, D. X. Wang, J. Ren, E. T. Li, M. Huang, J. Y. Tang, X. C. Ruan, H. W. Wang, Z. H. Li, Y. S. Chen, L. X. Liu, X. X. Li, Q. W. Fan, R. R. Fan, X. R. Hu, J. C. Wang, X. Li, 1D. D. Niu, N. Song, M. Gu

Abstract: The stellar (n, $γ$) cross section data for the mass numbers around A $\approx$ 160 are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occur in the thermally pulsing asymptotic giant branch (TP--AGB). The new measurement of (n, $γ$) cross sections for $^{159}$Tb was performed using the C$_6$D$_6$ detector system at the back streaming white neu… ▽ More The stellar (n, $γ$) cross section data for the mass numbers around A $\approx$ 160 are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occur in the thermally pulsing asymptotic giant branch (TP--AGB). The new measurement of (n, $γ$) cross sections for $^{159}$Tb was performed using the C$_6$D$_6$ detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source (CSNS) with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels were reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) were derived from the measured $^{159}$Tb (n, $γ$) cross sections at $kT$ = 5 $\sim$ 100 keV and are in good agreement with the recommended data of KADoNiS-v0.3 and JEFF-3.3, while KADoNiS-v1.0 and ENDF-VIII.0 significantly overestimate the present MACS up to 40$\%$ and 20$\%$, respectively. A sensitive test of the s-process nucleosynthesis was also performed with the stellar evolution code MESA. Significant changes in abundances around A $\approx$ 160 were observed between the ENDF/B-VIII.0 and present measured rate of $^{159}$Tb(n, $γ$)$^{160}$Tb in the MESA simulation. △ Less

Submitted 4 December, 2022; originally announced December 2022.

Comments: 13 pages, 7 figures

First wide field-of-view X-ray observations by a lobster eye focusing telescope in orbit

Authors: C. Zhang, Z. X. Ling, X. J. Sun, S. L. Sun, Y. Liu, Z. D. Li, Y. L. Xue, Y. F. Chen, Y. F. Dai, Z. Q. Jia, H. Y. Liu, X. F. Zhang, Y. H. Zhang, S. N. Zhang, F. S. Chen, Z. W. Cheng, W. Fu, Y. X. Han, H. Li, J. F. Li, Y. Li, P. R. Liu, X. H. Ma, Y. J. Tang, C. B. Wang , et al. (53 additional authors not shown)

Abstract: As a novel X-ray focusing technology, lobster eye micro-pore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel (1979), the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we repor… ▽ More As a novel X-ray focusing technology, lobster eye micro-pore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel (1979), the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy ($LEIA$), a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in July 2022, has a mostly un-vignetted field of view of $18.6^\circ \times 18.6^\circ $. Its spatial resolution is in the range of 4$-$7 arcmin in FWHM and the focal spot effective area is 2$-$3 cm$^2$, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1 and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5$-$4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster eye MPO. △ Less

Submitted 17 November, 2022; originally announced November 2022.

Comments: 11 pages, 4 figures. Accepted for publication in Astrophysical Journal Letter

Three low-mass companions around aged stars discovered by TESS

Authors: Zitao Lin, Tianjun Gan, Sharon X. Wang, Avi Shporer, Markus Rabus, George Zhou, Angelica Psaridi, François Bouchy, Allyson Bieryla, David W. Latham, Shude Mao, Keivan G. Stassun, Coel Hellier, Steve B. Howell, Carl Ziegler, Douglas A. Caldwell, Catherine A. Clark, Karen A. Collins, Jason L. Curtis, Jacqueline K. Faherty, Crystal L. Gnilka, Samuel K. Grunblatt, Jon M. Jenkins, Marshall C. Johnson, Nicholas Law , et al. (20 additional authors not shown)

Abstract: We report the discovery of three transiting low-mass companions to aged stars: a brown dwarf (TOI-2336b) and two objects near the hydrogen burning mass limit (TOI-1608b and TOI-2521b). These three systems were first identified using data from the Transiting Exoplanet Survey Satellite (TESS). TOI-2336b has a radius of $1.05\pm 0.04\ R_J$, a mass of $69.9\pm 2.3\ M_J$ and an orbital period of 7.71 d… ▽ More We report the discovery of three transiting low-mass companions to aged stars: a brown dwarf (TOI-2336b) and two objects near the hydrogen burning mass limit (TOI-1608b and TOI-2521b). These three systems were first identified using data from the Transiting Exoplanet Survey Satellite (TESS). TOI-2336b has a radius of $1.05\pm 0.04\ R_J$, a mass of $69.9\pm 2.3\ M_J$ and an orbital period of 7.71 days. TOI-1608b has a radius of $1.21\pm 0.06\ R_J$, a mass of $90.7\pm 3.7\ M_J$ and an orbital period of 2.47 days. TOI-2521b has a radius of $1.01\pm 0.04\ R_J$, a mass of $77.5\pm 3.3\ M_J$ and an orbital period of 5.56 days. We found all these low-mass companions are inflated. We fitted a relation between radius, mass and incident flux using the sample of known transiting brown dwarfs and low-mass M dwarfs. We found a positive correlation between the flux and the radius for brown dwarfs and for low-mass stars that is weaker than the correlation observed for giant planets. We also found that TOI-1608 and TOI-2521 are very likely to be spin-orbit synchronized, leading to the unusually rapid rotation of the primary stars considering their evolutionary stages. Our estimates indicate that both systems have much shorter spin-orbit synchronization timescales compared to their ages. These systems provide valuable insights into the evolution of stellar systems with brown dwarf and low-mass stellar companions influenced by tidal effects. △ Less

Submitted 15 August, 2023; v1 submitted 25 October, 2022; originally announced October 2022.

Comments: 23 pages, 15 figures; Published in MNRAS

Model Independent Approach of the JUNO $^8$B Solar Neutrino Program

Authors: JUNO Collaboration, Jie Zhao, Baobiao Yue, Haoqi Lu, Yufeng Li, Jiajie Ling, Zeyuan Yu, Angel Abusleme, Thomas Adam, Shakeel Ahmad, Rizwan Ahmed, Sebastiano Aiello, Muhammad Akram, Abid Aleem, Tsagkarakis Alexandros, Fengpeng An, Qi An, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, João Pedro Athayde Marcondes de André, Didier Auguste, Weidong Bai , et al. (579 additional authors not shown)

Abstract: The physics potential of detecting $^8$B solar neutrinos will be exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model independent manner by using three distinct channels of the charged-current (CC), neutral-current (NC) and elastic scattering (ES) interactions. Due to the largest-ever mass of $^{13}$C nuclei in the liquid-scintillator detectors and the {expected} low backg… ▽ More The physics potential of detecting $^8$B solar neutrinos will be exploited at the Jiangmen Underground Neutrino Observatory (JUNO), in a model independent manner by using three distinct channels of the charged-current (CC), neutral-current (NC) and elastic scattering (ES) interactions. Due to the largest-ever mass of $^{13}$C nuclei in the liquid-scintillator detectors and the {expected} low background level, $^8$B solar neutrinos would be observable in the CC and NC interactions on $^{13}$C for the first time. By virtue of optimized event selections and muon veto strategies, backgrounds from the accidental coincidence, muon-induced isotopes, and external backgrounds can be greatly suppressed. Excellent signal-to-background ratios can be achieved in the CC, NC and ES channels to guarantee the $^8$B solar neutrino observation. From the sensitivity studies performed in this work, we show that JUNO, with ten years of data, can reach the {1$σ$} precision levels of 5%, 8% and 20% for the $^8$B neutrino flux, $\sin^2θ_{12}$, and $Δm^2_{21}$, respectively. It would be unique and helpful to probe the details of both solar physics and neutrino physics. In addition, when combined with SNO, the world-best precision of 3% is expected for the $^8$B neutrino flux measurement. △ Less

Submitted 6 March, 2024; v1 submitted 15 October, 2022; originally announced October 2022.

Comments: 19 pages, 7 figures, accepted version to appear in The Astrophysical Journal. Yufeng Li and Jiajie Ling are corresponding authors

Journal ref: Astrophysical Journal 965 (2024) 122

A multi-cubic-kilometre neutrino telescope in the western Pacific Ocean

Authors: Z. P. Ye, F. Hu, W. Tian, Q. C. Chang, Y. L. Chang, Z. S. Cheng, J. Gao, T. Ge, G. H. Gong, J. Guo, X. X. Guo, X. G. He, J. T. Huang, K. Jiang, P. K. Jiang, Y. P. Jing, H. L. Li, J. L. Li, L. Li, W. L. Li, Z. Li, N. Y. Liao, Q. Lin, F. Liu, J. L. Liu , et al. (33 additional authors not shown)

Abstract: Next-generation neutrino telescopes with significantly improved sensitivity are required to pinpoint the sources of the diffuse astrophysical neutrino flux detected by IceCube and uncover the century-old puzzle of cosmic ray origins. A detector near the equator will provide a unique viewpoint of the neutrino sky, complementing IceCube and other neutrino telescopes in the Northern Hemisphere. Here… ▽ More Next-generation neutrino telescopes with significantly improved sensitivity are required to pinpoint the sources of the diffuse astrophysical neutrino flux detected by IceCube and uncover the century-old puzzle of cosmic ray origins. A detector near the equator will provide a unique viewpoint of the neutrino sky, complementing IceCube and other neutrino telescopes in the Northern Hemisphere. Here we present results from an expedition to the north-eastern region of the South China Sea, in the western Pacific Ocean. A favorable neutrino telescope site was found on an abyssal plain at a depth of $\sim$ 3.5km. At depths below 3km, the sea current speed, water absorption and scattering lengths for Cherenkov light, were measured to be $v_{\mathrm{c}}<$10cm/s, $λ_{\mathrm{abs} }\simeq$ 27m and $λ_{\mathrm{sca} }\simeq$ 63m, respectively. Accounting for these measurements, we present the design and expected performance of a next-generation neutrino telescope, TRopIcal DEep-sea Neutrino Telescope (TRIDENT). With its advanced photon-detection technology and large dimensions, TRIDENT expects to observe the IceCube steady source candidate NGC 1068 with 5$σ$ significance within 1 year of operation. This level of sensitivity will open a new arena for diagnosing the origin of cosmic rays and probing fundamental physics over astronomical baselines. △ Less

Submitted 13 May, 2024; v1 submitted 10 July, 2022; originally announced July 2022.

Comments: 34 pages,12 figures. Correspondence should be addressed to D. L. Xu: donglianxu@sjtu.edu.cn

Prospects for Detecting the Diffuse Supernova Neutrino Background with JUNO

Authors: JUNO Collaboration, Angel Abusleme, Thomas Adam, Shakeel Ahmad, Rizwan Ahmed, Sebastiano Aiello, Muhammad Akram, Fengpeng An, Qi An, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, Burin Asavapibhop, João Pedro Athayde Marcondes de André, Didier Auguste, Nikita Balashov, Wander Baldini, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Bellato, Antonio Bergnoli, Thilo Birkenfeld, Sylvie Blin , et al. (577 additional authors not shown)

Abstract: We present the detection potential for the diffuse supernova neutrino background (DSNB) at the Jiangmen Underground Neutrino Observatory (JUNO), using the inverse-beta-decay (IBD) detection channel on free protons. We employ the latest information on the DSNB flux predictions, and investigate in detail the background and its reduction for the DSNB search at JUNO. The atmospheric neutrino induced n… ▽ More We present the detection potential for the diffuse supernova neutrino background (DSNB) at the Jiangmen Underground Neutrino Observatory (JUNO), using the inverse-beta-decay (IBD) detection channel on free protons. We employ the latest information on the DSNB flux predictions, and investigate in detail the background and its reduction for the DSNB search at JUNO. The atmospheric neutrino induced neutral current (NC) background turns out to be the most critical background, whose uncertainty is carefully evaluated from both the spread of model predictions and an envisaged \textit{in situ} measurement. We also make a careful study on the background suppression with the pulse shape discrimination (PSD) and triple coincidence (TC) cuts. With latest DSNB signal predictions, more realistic background evaluation and PSD efficiency optimization, and additional TC cut, JUNO can reach the significance of 3$σ$ for 3 years of data taking, and achieve better than 5$σ$ after 10 years for a reference DSNB model. In the pessimistic scenario of non-observation, JUNO would strongly improve the limits and exclude a significant region of the model parameter space. △ Less

Submitted 13 October, 2022; v1 submitted 18 May, 2022; originally announced May 2022.

Comments: 29 pages, 11 figures, final published version in JCAP

Journal ref: JCAP 10 (2022) 033

The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey

Authors: Jing Tang, Chao-Wei Tsai, Di Li

Abstract: The Five-hundred-meter Aperture Spherical radio Telescope (FAST) completed its commissioning and began the Commensal Radio Astronomy FasT Survey (CRAFTS), a multi-year survey to cover 60% of the sky, in 2020. We present predictions for the number of radio-flaring ultracool dwarfs (UCDs) that are likely to be detected by CRAFTS. Based on the observed flaring UCDs from a number of unbiased, targeted… ▽ More The Five-hundred-meter Aperture Spherical radio Telescope (FAST) completed its commissioning and began the Commensal Radio Astronomy FasT Survey (CRAFTS), a multi-year survey to cover 60% of the sky, in 2020. We present predictions for the number of radio-flaring ultracool dwarfs (UCDs) that are likely to be detected by CRAFTS. Based on the observed flaring UCDs from a number of unbiased, targeted radio surveys in the literature, we derive a detection rate of $\ge$3%. Assuming a flat radio spectrum $νL _ν\propto ν^{β+1} $ with $β$ = -1.0 for UCD flares, we construct a flare luminosity function $d N/d L \propto L^{-1.96 \pm 0.45}$ (here $L=νL_ν$). CRAFTS is found to be sensitive enough for flares from UCDs up to $\sim$180 pc. Considering the Galactic thin disk, we carry out a 3D Monte Carlo simulation of the UCD population, which is then fed to mock CRAFTS observations. We estimate that $\sim$170 flaring UCDs would be detected through transient searches in circular polarization. Though only marginally sensitive to the scale height of UCDs, the results are very sensitive to the assumed spectral index $β$. For $β$ from 0 to -2.5, the number of expected detections increases dramatically from $\sim$20 to $\sim$3460. We also contemplate the strategies for following up candidates of flaring UCDs, and discuss the implications of survey results for improving our knowledge of UCD behavior at $L$ band and dynamos. △ Less

Submitted 2 May, 2022; originally announced May 2022.

Comments: 22 pages, 8 figures, 1 table

Performance of the X-Calibur Hard X-Ray Polarimetry Mission during its 2018/19 Long-Duration Balloon Flight

Authors: Quincy Abarr, Banafsheh Beheshtipour, Matthias Beilicke, Richard Bose, Dana Braun, Gianluigi de Geronimo, Paul Dowkontt, Manel Errando, Thomas Gadson, Victor Guarino, Scott Heatwole, Md. Arman Hossen, Nirmal K. Iyer, Fabian Kislat, Mózsi Kiss, Takao Kitaguchi, Henric Krawczynski, R. James Lanzi, Shaorui Li, Lindsey Lisalda, Takashi Okajima, Mark Pearce, Zachary Peterson, Logan Press, Brian Rauch , et al. (6 additional authors not shown)

Abstract: X-Calibur is a balloon-borne telescope that measures the polarization of high-energy X-rays in the 15--50keV energy range. The instrument makes use of the fact that X-rays scatter preferentially perpendicular to the polarization direction. A beryllium scattering element surrounded by pixellated CZT detectors is located at the focal point of the InFOCμS hard X-ray mirror. The instrument was launche… ▽ More X-Calibur is a balloon-borne telescope that measures the polarization of high-energy X-rays in the 15--50keV energy range. The instrument makes use of the fact that X-rays scatter preferentially perpendicular to the polarization direction. A beryllium scattering element surrounded by pixellated CZT detectors is located at the focal point of the InFOCμS hard X-ray mirror. The instrument was launched for a long-duration balloon (LDB) flight from McMurdo (Antarctica) on December 29, 2018, and obtained the first constraints of the hard X-ray polarization of an accretion-powered pulsar. Here, we describe the characterization and calibration of the instrument on the ground and its performance during the flight, as well as simulations of particle backgrounds and a comparison to measured rates. The pointing system and polarimeter achieved the excellent projected performance. The energy detection threshold for the anticoincidence system was found to be higher than expected and it exhibited unanticipated dead time. Both issues will be remedied for future flights. Overall, the mission performance was nominal, and results will inform the design of the follow-up mission XL-Calibur, which is scheduled to be launched in summer 2022. △ Less

Submitted 20 April, 2022; originally announced April 2022.

Comments: 19 pages, 31 figures, submitted to Astropart. Phys

An Early Transition to Magnetic Supercriticality in Star Formation

Authors: Tao-Chung Ching, Di Li, Carl Heiles, Zhi-Yun Li, Lei Qian, Youling Yue, Jing Tang, Sihan Jiao

Abstract: Magnetic fields play an important role in the evolution of interstellar medium and star formation. As the only direct probe of interstellar field strength, credible Zeeman measurements remain sparse due to the lack of suitable Zeeman probes, particularly for cold, molecular gas. Here we report the detection of a magnetic field of $+$3.8 $\pm$ 0.3 $μ$G through the HI narrow self-absorption (HINSA)… ▽ More Magnetic fields play an important role in the evolution of interstellar medium and star formation. As the only direct probe of interstellar field strength, credible Zeeman measurements remain sparse due to the lack of suitable Zeeman probes, particularly for cold, molecular gas. Here we report the detection of a magnetic field of $+$3.8 $\pm$ 0.3 $μ$G through the HI narrow self-absorption (HINSA) toward L1544, a well-studied prototypical prestellar core in an early transition between starless and protostellar phases characterized by high central number density and low central temperature. A combined analysis of the Zeeman measurements of quasar HI absorption, HI emission, OH emission, and HINSA reveals a coherent magnetic field from the atomic cold neutral medium (CNM) to the molecular envelope. The molecular envelope traced by HINSA is found to be magnetically supercritical, with a field strength comparable to that of the surrounding diffuse, magnetically subcritical CNM despite a large increase in density. The reduction of the magnetic flux relative to the mass, necessary for star formation, thus seems to have already happened during the transition from the diffuse CNM to the molecular gas traced by HINSA, earlier than envisioned in the classical picture where magnetically supercritical cores capable of collapsing into stars form out of magnetically subcritical envelopes. △ Less

Submitted 23 December, 2021; originally announced December 2021.

Comments: 3 figures, 1 table, Nature accepted

The Nearby Evolved Stars Survey II: Constructing a volume-limited sample and first results from the James Clerk Maxwell Telescope

Authors: P. Scicluna, F. Kemper, I. McDonald, S. Srinivasan, A. Trejo, S. H. J. Wallström, J. G. A. Wouterloot, J. Cami, J. Greaves, Jinhua He, D. T. Hoai, Hyosun Kim, O. C. Jones, H. Shinnaga, C. J. R. Clark, T. Dharmawardena, W. Holland, H. Imai, J. Th. van Loon, K. M. Menten, R. Wesson, H. Chawner, S. Feng, S. Goldman, F. C. Liu , et al. (67 additional authors not shown)

Abstract: The Nearby Evolved Stars Survey (NESS) is a volume-complete sample of $\sim$850 Galactic evolved stars within 3\,kpc at (sub-)mm wavelengths, observed in the CO $J = $ (2$-$1) and (3$-$2) rotational lines, and the sub-mm continuum, using the James Clark Maxwell Telescope and Atacama Pathfinder Experiment. NESS consists of five tiers, based on distances and dust-production rate (DPR). We define a n… ▽ More The Nearby Evolved Stars Survey (NESS) is a volume-complete sample of $\sim$850 Galactic evolved stars within 3\,kpc at (sub-)mm wavelengths, observed in the CO $J = $ (2$-$1) and (3$-$2) rotational lines, and the sub-mm continuum, using the James Clark Maxwell Telescope and Atacama Pathfinder Experiment. NESS consists of five tiers, based on distances and dust-production rate (DPR). We define a new metric for estimating the distances to evolved stars and compare its results to \emph{Gaia} EDR3. Replicating other studies, the most-evolved, highly enshrouded objects in the Galactic Plane dominate the dust returned by our sources, and we initially estimate a total DPR of $4.7\times 10^{-5}$ M$_\odot$ yr$^{-1}$ from our sample. Our sub-mm fluxes are systematically higher and spectral indices are typically shallower than dust models typically predict. The 450/850 $μ$m spectral indices are consistent with the blackbody Rayleigh--Jeans regime, suggesting a large fraction of evolved stars have unexpectedly large envelopes of cold dust. △ Less

Submitted 24 October, 2021; originally announced October 2021.

Comments: 20 pages, 13 figures, 5 tables, accepted for publications in MNRAS

Revised Best Estimates for the Age and Mass of the Methuselah Star HD 140283 using MESA and Interferometry and Implications for 1D Convection

Authors: J. Tang, M. Joyce

Abstract: In light of recently revised observational measurements of the radius and spectroscopic parameters of the extremely old and metal-poor Gaia benchmark star HD 140283 -- also known as the Methuselah star due to prior suggestions that its age is in tension with the age of the Universe -- we present new, best estimates for the star's mass and age from stellar modeling. These are derived using 1D stell… ▽ More In light of recently revised observational measurements of the radius and spectroscopic parameters of the extremely old and metal-poor Gaia benchmark star HD 140283 -- also known as the Methuselah star due to prior suggestions that its age is in tension with the age of the Universe -- we present new, best estimates for the star's mass and age from stellar modeling. These are derived using 1D stellar evolutionary tracks computed with MESA and the most up-to-date measurements from CHARA interferometry. Excluding modeling variance from the uncertainties, we report a mass of $0.809 \pm 0.001 M_{\odot}$ and an age of $12.01 \pm 0.05$ Gyr ($1 σ$). When dominant sources of modeling uncertainty are taken into account, we report $0.81 \pm 0.05 M_{\odot}$ and $12 \pm 0.5$ Gyr, respectively. These results are consistent with recent literature, and the best-fitting age is not in conflict with the currently accepted age of the universe ($13.5$ Gyr; arXiv:1303.5089 [astro-ph.CO]). △ Less

Submitted 20 May, 2021; originally announced May 2021.

Journal ref: Res. Notes AAS 5(2021) 117