Document detail
ID

oai:arXiv.org:2410.21617

Topic
Astrophysics - High Energy Astroph...
Author
Zhang, Wenda Yuan, Weimin Ling, Zhixing Chen, Yong Rea, Nanda Rau, Arne Cai, Zhiming Cheng, Huaqing Zelati, Francesco Coti Dai, Lixin Hu, Jingwei Jia, Shumei Jin, Chichuan Li, Dongyue O'Brien, Paul Shen, Rongfeng Shu, Xinwen Sun, Shengli Sun, Xiaojin Wang, Xiaofeng Yang, Lei Zhang, Bing Zhang, Chen Zhang, Shuang-Nan Zhang, Yonghe An, Jie Buckley, David Coleiro, Alexis Cordier, Bertrand Dou, Liming Eyles-Ferris, Rob Fan, Zhou Feng, Hua Fu, Shaoyu Fynbo, Johan P. U. Galbany, Lluis Jha, Saurabh W. Jiang, Shuaiqing Kong, Albert Kuulkers, Erik Lei, Weihua Li, Wenxiong Liu, Bifang Liu, Mingjun Liu, Xing Liu, Yuan Liu, Zhu Maitra, Chandreyee Marino, Alessio Monageng, Itumeleng Nandra, Kirpal Sanders, Jeremy Soria, Roberto Tao, Lian Wang, Junfeng Wang, Song Wang, Tinggui Wang, Zhongxiang Wu, Qingwen Wu, Xuefeng Xu, Dong Xu, Yanjun Xue, Suijian Xue, Yongquan Zhang, Zijian Zhu, Zipei Zou, Hu Bao, Congying Chen, Fansheng Chen, Houlei Chen, Tianxiang Chen, Wei Chen, Yehai Chen, Yifan Cui, Chenzhou Cui, Weiwei Dai, Yanfeng Fan, Dongwei Guan, Ju Han, Dawei Hou, Dongjie Hu, Haibo Huang, Maohai Huo, Jia Jia, Zhenqing Jiang, Bowen Jin, Ge Li, Chengkui Li, Junfei Li, Longhui Li, Maoshun Li, Wei Li, Zhengda Lian, Tianying Liu, Congzhan Liu, Heyang Liu, Huaqiu Lu, Fangjun Luo, Laidan Ma, Jia Mao, Xuan Pan, Haiwu Pan, Xin Song, Liming Sun, Hui Tan, Yunyin Tang, Qingjun Tao, Yihan Wang, Hao Wang, Juan Wang, Lei Wang, Wenxin Wang, Yilong Wang, Yusa Wu, Qinyu Xu, Haitao Xu, Jingjing Xu, Xinpeng Xu, Yunfei Xu, Zhao Xue, Changbin Xue, Yulong Yan, Ailiang Yang, Haonan Yang, Xiongtao Yang, Yanji Zhang, Juan Zhang, Mo Zhang, Wenjie Zhang, Zhen Zhang, Ziliang Zhao, Donghua Zhao, Haisheng Zhao, Xiaofan Zhao, Zijian Zhou, Hongyan Zhou, Yilin Zhu, Yuxuan Zhu, Zhencai
Category

sciences: astrophysics

Year

2024

listing date

11/6/2024

Keywords
transients detection intermediate found ep240408a x-ray
Metrics

Abstract

We report the discovery of a peculiar X-ray transient, EP240408a, by Einstein Probe (EP) and follow-up studies made with EP, Swift, NICER, GROND, ATCA and other ground-based multi-wavelength telescopes.

The new transient was first detected with Wide-field X-ray Telescope (WXT) on board EP on April 8th, 2024, manifested in an intense yet brief X-ray flare lasting for 12 seconds.

The flare reached a peak flux of 3.9x10^(-9) erg/cm2/s in 0.5-4 keV, about 300 times brighter than the underlying X-ray emission detected throughout the observation.

Rapid and more precise follow-up observations by EP/FXT, Swift and NICER confirmed the finding of this new transient.

Its X-ray spectrum is non-thermal in 0.5-10 keV, with a power-law photon index varying within 1.8-2.5.

The X-ray light curve shows a plateau lasting for about 4 days, followed by a steep decay till becoming undetectable about 10 days after the initial detection.

Based on its temporal property and constraints from previous EP observations, an unusual timescale in the range of 7-23 days is found for EP240408a, which is intermediate between the commonly found fast and long-term transients.

No counterparts have been found in optical and near-infrared, with the earliest observation at 17 hours after the initial X-ray detection, suggestive of intrinsically weak emission in these bands.

We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far, by comparison with, in particular, jetted tidal disruption events, gamma-ray bursts, X-ray binaries and fast blue optical transients.

The nature of EP240408a thus remains an enigma.

We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of about 10 days.

The detection and follow-ups of more of such objects are essential for revealing their origin.

;Comment: 25 pages, 11 figures

Zhang, Wenda,Yuan, Weimin,Ling, Zhixing,Chen, Yong,Rea, Nanda,Rau, Arne,Cai, Zhiming,Cheng, Huaqing,Zelati, Francesco Coti,Dai, Lixin,Hu, Jingwei,Jia, Shumei,Jin, Chichuan,Li, Dongyue,O'Brien, Paul,Shen, Rongfeng,Shu, Xinwen,Sun, Shengli,Sun, Xiaojin,Wang, Xiaofeng,Yang, Lei,Zhang, Bing,Zhang, Chen,Zhang, Shuang-Nan,Zhang, Yonghe,An, Jie,Buckley, David,Coleiro, Alexis,Cordier, Bertrand,Dou, Liming,Eyles-Ferris, Rob,Fan, Zhou,Feng, Hua,Fu, Shaoyu,Fynbo, Johan P. U.,Galbany, Lluis,Jha, Saurabh W.,Jiang, Shuaiqing,Kong, Albert,Kuulkers, Erik,Lei, Weihua,Li, Wenxiong,Liu, Bifang,Liu, Mingjun,Liu, Xing,Liu, Yuan,Liu, Zhu,Maitra, Chandreyee,Marino, Alessio,Monageng, Itumeleng,Nandra, Kirpal,Sanders, Jeremy,Soria, Roberto,Tao, Lian,Wang, Junfeng,Wang, Song,Wang, Tinggui,Wang, Zhongxiang,Wu, Qingwen,Wu, Xuefeng,Xu, Dong,Xu, Yanjun,Xue, Suijian,Xue, Yongquan,Zhang, Zijian,Zhu, Zipei,Zou, Hu,Bao, Congying,Chen, Fansheng,Chen, Houlei,Chen, Tianxiang,Chen, Wei,Chen, Yehai,Chen, Yifan,Cui, Chenzhou,Cui, Weiwei,Dai, Yanfeng,Fan, Dongwei,Guan, Ju,Han, Dawei,Hou, Dongjie,Hu, Haibo,Huang, Maohai,Huo, Jia,Jia, Zhenqing,Jiang, Bowen,Jin, Ge,Li, Chengkui,Li, Junfei,Li, Longhui,Li, Maoshun,Li, Wei,Li, Zhengda,Lian, Tianying,Liu, Congzhan,Liu, Heyang,Liu, Huaqiu,Lu, Fangjun,Luo, Laidan,Ma, Jia,Mao, Xuan,Pan, Haiwu,Pan, Xin,Song, Liming,Sun, Hui,Tan, Yunyin,Tang, Qingjun,Tao, Yihan,Wang, Hao,Wang, Juan,Wang, Lei,Wang, Wenxin,Wang, Yilong,Wang, Yusa,Wu, Qinyu,Xu, Haitao,Xu, Jingjing,Xu, Xinpeng,Xu, Yunfei,Xu, Zhao,Xue, Changbin,Xue, Yulong,Yan, Ailiang,Yang, Haonan,Yang, Xiongtao,Yang, Yanji,Zhang, Juan,Zhang, Mo,Zhang, Wenjie,Zhang, Zhen,Zhang, Ziliang,Zhao, Donghua,Zhao, Haisheng,Zhao, Xiaofan,Zhao, Zijian,Zhou, Hongyan,Zhou, Yilin,Zhu, Yuxuan,Zhu, Zhencai, 2024, Einstein Probe discovery of EP240408a: a peculiar X-ray transient with an intermediate timescale

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