GCN Circular 37541

Z. J. Zhang (HKU), Y. F. Liang (PMO, CAS), H. Y. Liu, W. Chen, T. Zhao , Z. X. Ling, J. W. Hu, W. M. Yuan, C. C. Jin, Y. Liu, C. Zhang, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), X. F. Zhao, Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, J. Zhang, S. N. Zhang (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team

We report on the detection of an X-ray transient designated EP240918a by the Einstein Probe (EP) mission. The transient event triggered the Wide-field X-ray Telescope (WXT) on-board processing unit at 2024-09-18T11:24:37 (UTC). An autonomous observation was performed by the Follow-up X-ray Telescope (FXT) about two minutes later. Afterwards, the FXT on-board processing unit was also triggered, showing that an uncatalogued source was detected at R.A. = 289.3937, DEC = 46.1281 (J2000) with an uncertainty of about 20 arcsec (radius, 90% C.L. statistical and systematic).  

More information on this source will be updated when the full telemetry data is received. Further follow-up observations are encouraged to identify the nature of this X-ray transient.  

Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).