TITLE: GCN CIRCULAR NUMBER: 43172 SUBJECT: EP251220a: EP-FXT follow-up observation DATE: 25/12/21 15:05:25 GMT FROM: EP Team at NAOC/CAS <ep_ta@bao.ac.cn> Q. C. Liu (THU), Y. Wang (PMO), H.Y. Liu, H. W. Pan (NAO,CAS) on behalf of the Einstein Probe team: EP-FXT performed a follow-up observation of EP251220a (detected by EP-WXT, GCN 43162; and followed by MASTER-Net observations, COLIBRI telescope and GOTO; GCN 43163, GCN 43167, GCN 41369, GCN 43170) about 19 hours after the WXT detection, with an exposure time of 2.6 ks. The FXT telemetry data show that an uncatalogued source was detected within the WXT error circle at R.A. = 17.3189, DEC = 19.0923 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT X-ray spectrum of this uncatalogued source can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 4.8x 10^20 cm^-2 and a photon index of 1.7 (+0.5/-0.5). The derived unabsorbed 0.5-10 keV flux is approximately 3.6 (+2.4/-1.2) x 10^-13 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/43172. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...