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| Format: | Preprint |
| Published: |
2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2604.14341 |
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| _version_ | 1866914476993806336 |
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| author | Fu, Shao-Yu Dai, Cui-Yuan Wang, Ai-Ling Xu, Dong An, Tao Geng, Jin-Jun Lei, Wei-Hua Wang, Xiang-Yu Jiang, Shuai-Qing Zhu, Zi-Pei Liu, Xing An, Jie He, Lin-Bo Jin, Jun-Jie Zhang, Yu Zhang, Jinlei Fan, Zhou Gao, Xing Iskandar, Abdusamatjan Yaqup, Shahidin Zhong, Tu-Hong Esamdin, Ali Bai, Chun-Hai Zhang, Yu Gao, He Wu, Xue-Feng Malesani, Daniele Bjørn Izzo, Luca Eyles-Ferris, R. A. J. Saccardi, A. Schneider, B. Palmerio, J. Tanvir, N. R. Pozanenko, Alexei Pankov, Nicolai Moskvitin, A. S. Spiridonova, O. I. Maslennikova, O. A. Volnova, A. Klunko, E. Rumyantsev, V. Volvach, A. Volvach, L. Komesh, Toktarkhan Abdikamalov, Ernazar Berdikhan, Dilda Maksut, Zhanat Zou, Yuan-Chuan Wu, Hong-Zhou Yu, Yun-Wei Shen, Rong-Feng Wang, Yi-Han Sun, Hui Zhang, Bin-Bin Liu, Liang-Duan Li, Ye D'Elia, Valerio Salvaterra, Ruben De Pasquale, Massimiliano Zhang, Bing Yuan, Wei-Min |
| author_facet | Fu, Shao-Yu Dai, Cui-Yuan Wang, Ai-Ling Xu, Dong An, Tao Geng, Jin-Jun Lei, Wei-Hua Wang, Xiang-Yu Jiang, Shuai-Qing Zhu, Zi-Pei Liu, Xing An, Jie He, Lin-Bo Jin, Jun-Jie Zhang, Yu Zhang, Jinlei Fan, Zhou Gao, Xing Iskandar, Abdusamatjan Yaqup, Shahidin Zhong, Tu-Hong Esamdin, Ali Bai, Chun-Hai Zhang, Yu Gao, He Wu, Xue-Feng Malesani, Daniele Bjørn Izzo, Luca Eyles-Ferris, R. A. J. Saccardi, A. Schneider, B. Palmerio, J. Tanvir, N. R. Pozanenko, Alexei Pankov, Nicolai Moskvitin, A. S. Spiridonova, O. I. Maslennikova, O. A. Volnova, A. Klunko, E. Rumyantsev, V. Volvach, A. Volvach, L. Komesh, Toktarkhan Abdikamalov, Ernazar Berdikhan, Dilda Maksut, Zhanat Zou, Yuan-Chuan Wu, Hong-Zhou Yu, Yun-Wei Shen, Rong-Feng Wang, Yi-Han Sun, Hui Zhang, Bin-Bin Liu, Liang-Duan Li, Ye D'Elia, Valerio Salvaterra, Ruben De Pasquale, Massimiliano Zhang, Bing Yuan, Wei-Min |
| contents | Extragalactic Fast X-ray Transients (EFXTs) represent an emerging class of high-energy phenomena characterized by X-ray outbursts lasting from tens to hundreds of seconds. However, for more than half of the EFXTs, their physical origins remain elusive. In this Letter, we report the discovery of EP250302a, a luminous EFXT detected by the Einstein Probe (EP) at a redshift of $z = 1.131$. The multi-wavelength light curves of EP250302a reveal remarkable temporal features that distinguish it from the previously known EP-detected EFXT population, most notably a needle-like X-ray flare accompanied by smooth optical rebrightening during the afterglow phase. We suggest that the distinct X-ray and optical behaviors constitute the first observed instance of late-time violent collision of two relativistic shells in an EFXT. Drawing on insights from GRB studies, such a collision process strongly indicates the reactivation of a central engine, making EP250302a-like transients a unique laboratory for probing the late-time activity and jet physics of EFXT central engines. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_14341 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | A fast X-ray transient with chromatic flares: signatures of violent collisions induced by late-time central engine reactivation Fu, Shao-Yu Dai, Cui-Yuan Wang, Ai-Ling Xu, Dong An, Tao Geng, Jin-Jun Lei, Wei-Hua Wang, Xiang-Yu Jiang, Shuai-Qing Zhu, Zi-Pei Liu, Xing An, Jie He, Lin-Bo Jin, Jun-Jie Zhang, Yu Zhang, Jinlei Fan, Zhou Gao, Xing Iskandar, Abdusamatjan Yaqup, Shahidin Zhong, Tu-Hong Esamdin, Ali Bai, Chun-Hai Zhang, Yu Gao, He Wu, Xue-Feng Malesani, Daniele Bjørn Izzo, Luca Eyles-Ferris, R. A. J. Saccardi, A. Schneider, B. Palmerio, J. Tanvir, N. R. Pozanenko, Alexei Pankov, Nicolai Moskvitin, A. S. Spiridonova, O. I. Maslennikova, O. A. Volnova, A. Klunko, E. Rumyantsev, V. Volvach, A. Volvach, L. Komesh, Toktarkhan Abdikamalov, Ernazar Berdikhan, Dilda Maksut, Zhanat Zou, Yuan-Chuan Wu, Hong-Zhou Yu, Yun-Wei Shen, Rong-Feng Wang, Yi-Han Sun, Hui Zhang, Bin-Bin Liu, Liang-Duan Li, Ye D'Elia, Valerio Salvaterra, Ruben De Pasquale, Massimiliano Zhang, Bing Yuan, Wei-Min High Energy Astrophysical Phenomena Extragalactic Fast X-ray Transients (EFXTs) represent an emerging class of high-energy phenomena characterized by X-ray outbursts lasting from tens to hundreds of seconds. However, for more than half of the EFXTs, their physical origins remain elusive. In this Letter, we report the discovery of EP250302a, a luminous EFXT detected by the Einstein Probe (EP) at a redshift of $z = 1.131$. The multi-wavelength light curves of EP250302a reveal remarkable temporal features that distinguish it from the previously known EP-detected EFXT population, most notably a needle-like X-ray flare accompanied by smooth optical rebrightening during the afterglow phase. We suggest that the distinct X-ray and optical behaviors constitute the first observed instance of late-time violent collision of two relativistic shells in an EFXT. Drawing on insights from GRB studies, such a collision process strongly indicates the reactivation of a central engine, making EP250302a-like transients a unique laboratory for probing the late-time activity and jet physics of EFXT central engines. |
| title | A fast X-ray transient with chromatic flares: signatures of violent collisions induced by late-time central engine reactivation |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2604.14341 |