TITLE: GCN CIRCULAR NUMBER: 37097 SUBJECT: EP240807a/GRB 240807A: EP-FXT detection of the X-ray emission DATE: 24/08/08 03:01:27 GMT FROM: EP Team at NAOC/CAS ep_ta@bao.ac.cn
J. W. Hu, S. Q. Jiang (NAOC, CAS), Y. C. Fu (BNU) , Z. X. Ling, W. D. Zhang, Y. Liu, C. C. Jin, C. Zhang, H. Q. Cheng, W. Chen, C. Z. Cui, D. W. Fan, H. B. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, M. J. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, X. Pan, H. Sun, W. X. Wang, Y. L. Wang, Q. Y. Wu, X. P. Xu, Y. F. Xu, H. N. Yang, W. Yuan, M. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), Y. Chen, S. M. Jia, W. W. Cui, D. W. Han, C. K. Li, L. M. Song, X. F. Zhao, 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
Following the detection of the fast X-ray transient EP240807a (trigger ID 11908397839; Fu et al., GCN 37088), which was temporally coincident with GRB 240807A (Fermi GBM team, GCN 37089), we performed an observation of EP240807a with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2024-08-07T13:23:29 UTC, about 7.7 hours after the EP-WXT detection. The exposure time is 4434 seconds. Within the error circle of the WXT source, an X-ray source was detected at R.A. = 300.9668 deg, DEC = -68.7861 deg, with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a photon index of 1.65(-0.38, +0.39) (with a fixed Galactic column density value of 5 x 10^20 cm^-2). The derived average unabsorbed 0.5-10 keV flux is 2.8(-0.8, +1.4) x 10^(-13) erg/s/cm^2. There is no cataloged X-ray source within the error circle, suggesting this source being associated with EP240807a.
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).
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