TITLE: GCN CIRCULAR NUMBER: 35810 SUBJECT: GRB 240225B: Swift-XRT observations DATE: 24/02/26 22:22:37 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) and A. A. Breeveld (UCL-MSSL) reports on behalf of the Swift-XRT and the Swift-UVOT team: Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 240225B in a series of observations tiled on the sky. The total exposure time is 1.8 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 693 s. The data were collected between T0+29.1 ks and T0+30.9 ks, and are entirely in Photon Counting (PC) mode. Two uncatalogued X-ray sources are detected, of which one ("Source 1") is above the RASS 3-sigma upper limit at this position. The position of this source is RA, Dec=128.3629, +27.0746 which is equivalent to: RA (J2000): 08:33:27.11 Dec(J2000): +27:04:28.5 with an uncertainty of 4.4 arcsec (radius, 90% confidence). This position is 25.3 arcmin from the MAXI position. At the present time the light curve of Source 1 shows no signs of fading and we can not confirm this source as the GRB afterglow. The results of the full analysis of the tiled XRT observations are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00124. Source 1 was out of the field of view for UVOT so we can't say anything about optical properties. This circular is an official product of the Swift team. View this GCN Circular online at https://gcn.nasa.gov/circulars/35810. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...