TITLE: GCN CIRCULAR NUMBER: 41862 SUBJECT: GRB 250916A: Swift-XRT observations DATE: 25/09/18 07:58:29 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 250916A, collecting 1.6 ks of Photon Counting (PC) mode data between T0+101.9 ks and T0+107.2 ks. One uncatalogued X-ray source has been detected within the estimated 3-sigma GOTO error region (0.8 arcsec) given in GCN Circ. 41847, it is below the RASS limit and shows no definitive signs of fading. However, given its coincident location with the fading optical source, it is indeed likely to be the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 26.5708 = 01h 46m 16.99s Dec (J2000.0): +36.1652 = +36d 09' 54.6" Error: 3.7 arcsec (radius, 90% conf. [Enhanced position]) Count-rate: 0.0274 +/- 0.0049 ct s^-1 Distance: 2 arcsec from GOTO position. Flux: (9.2 +/- 1.6)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) An uncatalogued source was also detected, however this was too far from the GRB position to be the afterglow. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021859. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...