TITLE: GCN CIRCULAR NUMBER: 40705 SUBJECT: GRB 250610B: Swift-XRT refined Analysis DATE: 25/06/12 15:11:21 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: We have analysed 5.0 ks of XRT data for GRB 250610B, from 2.9 ks to 105.7 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. Using 2013 s of PC mode data and 2 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 200.17991, +31.10477 which is equivalent to: RA (J2000): 13h 20m 43.18s Dec(J2000): +31d 06' 17.2" with an uncertainty of 2.8 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=0.68 (+0.12, -0.10). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.86 (+0.33, -0.25). The best-fitting absorption column is 3.1 (+7.7, -2.0) x 10^20 cm^-2, consistent with the Galactic value of 1.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.1 (+7.7, -2.0) x 10^20 cm^-2 Galactic foreground: 1.1 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.86 (+0.33, -0.25) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019863. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40705. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...