Einstein Probe 对 EP240408a 的发现：一个具有中等时标的特殊 X 射线暂现源
高能天体物理现象
2024-10-30 v1
摘要
我们报告了由 Einstein Probe (EP) 发现的一个特殊 X 射线暂现源 EP240408a，以及由 EP、Swift、NICER、GROND、ATCA和其他地基多波长望远镜进行的后续观测。这个新暂现源于2024年4月8日首次被EP搭载的广角X射线望远镜（WXT）探测到，表现为持续12秒的强烈而短暂的X射线耀发。该耀发在0.5-4 keV波段达到峰值通量3.9x10^(-9) erg/cm2/s，比整个观测期间探测到的底层X射线辐射亮约300倍。EP/FXT、Swift和NICER的快速且更精确的后续观测证实了对这一新暂现源的发现。其X射线谱在0.5-10 keV波段是非热辐射的，幂律光子指数在1.8-2.5范围内变化。其X射线光变曲线显示了一个持续约4天的平台期，随后陡峭衰减，直到初次探测后约10天变得无法探测。基于其时间特性和先前EP观测的约束，发现EP240408a具有7-23天范围内的不寻常时标，介于常见的快速和长期暂现源之间。在光学和近红外波段未发现对应体，最早的观测在初次X射线探测后17小时进行，表明其在这些波段内禀辐射微弱。我们证明，通过与喷流潮汐撕裂事件、伽马射线暴、X射线双星和快速蓝色光学暂现源等的比较，EP240408a的显著特性与目前已知的任何暂现源类型都不一致。因此，EP240408a的本质仍然是个谜。我们建议EP240408a可能代表一种具有约10天中等时标的新型暂现源。探测和后续观测更多此类天体对于揭示其起源至关重要。
引用
@article{arxiv.2410.21617,
title = {Einstein Probe discovery of EP240408a: a peculiar X-ray transient with an intermediate timescale},
author = {Wenda Zhang and Weimin Yuan and Zhixing Ling and Yong Chen and Nanda Rea and Arne Rau and Zhiming Cai and Huaqing Cheng and Francesco Coti Zelati and Lixin Dai and Jingwei Hu and Shumei Jia and Chichuan Jin and Dongyue Li and Paul O'Brien and Rongfeng Shen and Xinwen Shu and Shengli Sun and Xiaojin Sun and Xiaofeng Wang and Lei Yang and Bing Zhang and Chen Zhang and Shuang-Nan Zhang and Yonghe Zhang and Jie An and David Buckley and Alexis Coleiro and Bertrand Cordier and Liming Dou and Rob Eyles-Ferris and Zhou Fan and Hua Feng and Shaoyu Fu and Johan P. U. Fynbo and Lluis Galbany and Saurabh W. Jha and Shuaiqing Jiang and Albert Kong and Erik Kuulkers and Weihua Lei and Wenxiong Li and Bifang Liu and Mingjun Liu and Xing Liu and Yuan Liu and Zhu Liu and Chandreyee Maitra and Alessio Marino and Itumeleng Monageng and Kirpal Nandra and Jeremy Sanders and Roberto Soria and Lian Tao and Junfeng Wang and Song Wang and Tinggui Wang and Zhongxiang Wang and Qingwen Wu and Xuefeng Wu and Dong Xu and Yanjun Xu and Suijian Xue and Yongquan Xue and Zijian Zhang and Zipei Zhu and Hu Zou and Congying Bao and Fansheng Chen and Houlei Chen and Tianxiang Chen and Wei Chen and Yehai Chen and Yifan Chen and Chenzhou Cui and Weiwei Cui and Yanfeng Dai and Dongwei Fan and Ju Guan and Dawei Han and Dongjie Hou and Haibo Hu and Maohai Huang and Jia Huo and Zhenqing Jia and Bowen Jiang and Ge Jin and Chengkui Li and Junfei Li and Longhui Li and Maoshun Li and Wei Li and Zhengda Li and Tianying Lian and Congzhan Liu and Heyang Liu and Huaqiu Liu and Fangjun Lu and Laidan Luo and Jia Ma and Xuan Mao and Haiwu Pan and Xin Pan and Liming Song and Hui Sun and Yunyin Tan and Qingjun Tang and Yihan Tao and Hao Wang and Juan Wang and Lei Wang and Wenxin Wang and Yilong Wang and Yusa Wang and Qinyu Wu and Haitao Xu and Jingjing Xu and Xinpeng Xu and Yunfei Xu and Zhao Xu and Changbin Xue and Yulong Xue and Ailiang Yan and Haonan Yang and Xiongtao Yang and Yanji Yang and Juan Zhang and Mo Zhang and Wenjie Zhang and Zhen Zhang and Zhen Zhang and Ziliang Zhang and Donghua Zhao and Haisheng Zhao and Xiaofan Zhao and Zijian Zhao and Hongyan Zhou and Yilin Zhou and Yuxuan Zhu and Zhencai Zhu},
journal= {arXiv preprint arXiv:2410.21617},
year = {2024}
}
备注
25 pages, 11 figures