A fast X-ray transient from a weak relativistic jet associated with a type Ic-BL supernova
Sun, H.; Li, W. -X.; Liu, L. -D.; Gao, H.; Wang, X. -F.; Yuan, W.; Zhang, B.; Filippenko, A. V.; Xu, D.; An, T.; Ai, S.; Brink, T. G.; Liu, Y.; Liu, Y. -Q.; Wang, C. -Y.; Wu, Q. -Y.; Wu, X. -F.; Yang, Y.; Zhang, B. -B.; Zheng, W. -K.; Ahumada, T.; Dai, Z. -G.; Delaunay, J.; Elias-Rosa, N.; Benetti, S.; Fu, S. -Y.; Howell, D. A.; Huang, Y. -F.; Kasliwal, M. M.; Karambelkar, V.; Stein, R.; Lei, W. -H.; Lian, T. -Y.; Peng, Z. -K.; Ridnaia, A. V.; Svinkin, D. S.; Wang, X. -Y.; Wang, A. -L.; Wei, D. -M.; An, J.; Andrews, M.; Bai, J. -M; Dai, C. -Y.; Ehgamberdiev, S. A.; Fan, Z.; Farah, J.; Feng, H. -C.; Fynbo, J. P. U.; Guo, W. -J.; Guo, Z.; Hu, M. -K.; Hu, J. -W.; Jiang, S. -Q.; Jin, J. -J.; Li, A.; Li, J. -D.; Li, R. -Z.; Liang, Y. -F.; Ling, Z. -X.; Liu, X.; Mao, J. -R.; McCully, C.; Mirzaqulov, D.; Newsome, M.; Padilla Gonzalez, E.; Pan, X.; Terreran, G.; Tinyanont, S.; Wang, B. -T.; Wang, L. -Z.; Wen, X. -D.; Xiang, D. -F.; Xue, S. -J.; Yang, J.; Zhu, Z. -P.; Cai, Z. -M.; Castro-Tirado, A. J.; Chen, F. -S.; Chen, H. -L.; Chen, T. -X.; Chen, W.; Chen, Y. -H.; Chen, Y. -F.; Chen, Y.; Cheng, H. -Q.; Cordier, B.; Cui, C. -Z.; Cui, W. -W.; Dai, Y. -F.; Fan, D. -W.; Feng, H.; Guan, J.; Han, D. -W.; Hou, D. -J.; Hu, H. -B.; Huang, M. -H.; Huo, J.; Jia, S. -M.; Jia, Z. -Q.; Jiang, B. -W.; Jin, C. -C.; Jin, G.; Kuulkers, E.; Li, C. -K.; Li, D. -Y.; Li, J. -F.; Li, L. -H.; Li, M. -S.; Li, W.; Li, Z. -D.; Liu, C. -Z; Liu, H. -Y.; Liu, H. -Q.; Liu, M. -J.; Lu, F. -J.; Luo, L. -D.; Ma, J.; Mao, X.; Nandra, K.; O'Brien, P.; Pan, H. -W.; Rau, A.; Rea, N.; Sanders, J.; Song, L. -M.; Sun, S. -L.; Sun, X. -J.; Tan, Y. -Y.; Tang, Q. -J.; Tao, Y. -H.; Wang, H.; Wang, J.; Wang, L.; Wang, W. -X.; Wang, Y. -L.; Wang, Y. -S.; Xiong, D. -R.; Xu, H. -T.; Xu, J. -J.; Xu, X. -P.; Xu, Y. -F.; Xu, Z.; Xue, C. -B.; Xue, Y. -L.; Yan, A. -L.; Yang, H. -N.; Yang, X. -T.; Yang, Y. -J.; Zhang, C.; Zhang, J.; Zhang, M.; Zhang, S. -N.; Zhang, W. -D.; Zhang, W. -J.; Zhang, Y. -H.; Zhang, Z.; Zhang, Z.; Zhang, Z. -L.; Zhao, D. -H.; Zhao, H. -S.; Zhao, X. -F.; Zhao, Z. -J.; Zhou, Y. -L.; Zhu, Y. -X.; Zhu, Z. -C. June 2025, Nature Astronomy, Published online
Massive stars end their lives as core-collapse supernovae, among which some extremes are broad-lined type Ic supernovae from Wolf–Rayet stars associated with long-duration gamma-ray bursts (LGRBs) with powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. However, there exists a population of extragalactic fast X-ray transients with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Here we report the discovery of the bright X-ray transient EP240414a detected by the Einstein Probe, which is associated with the type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterized by a very soft energy spectrum peaking at <1.3 keV, which makes it different from known LGRBs, X-ray flashes or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a population of explosions of Wolf–Rayet stars characterized by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors.
