TITLE: GCN CIRCULAR NUMBER: 18237 SUBJECT: GRB 150902A: Swift-XRT observations DATE: 15/09/04 14:55:37 GMT FROM: Boris Sbarufatti at INAF-OAB/IASFPA L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), A. Maselli (INAF-IASFPA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 150902A (Arimoto et al. GCN Circ. 18228), collecting 4.9 ks of Photon Counting (PC) mode data between T0+59.6 ks and T0+78.6 ks. Two uncatalogued X-ray sources have been detected inside or close to the Fermi/LAT error region, however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 1: RA (J2000.0): 214.9797 = 14:19:55.13 Dec (J2000.0): -69.3535 = -69:21:12.6 Error: 4.4 arcsec (radius, 90% conf.) Count-rate: 0.0116 +/- 0.0022 ct s^-1 Flux: (5.16 +/- 0.98)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 2: RA (J2000.0): 215.2707 = 14:21:4.97 Dec (J2000.0): -69.4918 = -69:29:30.3 Error: 8.2 arcsec (radius, 90% conf.) Count-rate: (5.1 +/- 1.5)e-3 ct s^-1 Flux: (2.07 +/- 0.62)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020549. This circular is an official product of the Swift-XRT team.