TITLE: GCN CIRCULAR NUMBER: 41733 SUBJECT: GRB 250905A: Swift-XRT refined Analysis DATE: 25/09/06 02:25:05 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 4.7 ks of XRT data for GRB 250905A, from 140 s to 27.9 ks after the trigger. The data comprise 26 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=5.2 (+0.4, -0.3). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.8, -0.6). The best-fitting absorption column is 1.8 (+3.2, -1.2) x 10^21 cm^-2, consistent with the Galactic value of 5.5 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 4.1 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.8 (+3.2, -1.2) x 10^21 cm^-2 Galactic foreground: 5.5 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.9 (+0.8, -0.6) If the light curve continues to decay with a power-law decay index of 5.2, the count rate at T+24 hours will be 2.5 x 10^-14 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-24 (1.3 x 10^-24) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01347265. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41733. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...