TITLE: GCN CIRCULAR NUMBER: 35291 SUBJECT: GRB 231205B: Swift-XRT refined Analysis DATE: 23/12/06 15:26:36 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> S. Dichiara (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.5 ks of XRT data for GRB 231205B, from 224 s to 68.4 ks after the BAT trigger. The data comprise 3 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with an initial power-law decay with an index of alpha=0.27 (+0.04, -0.05), followed by a break at T+6137 s to an alpha of 1.32 (+/-0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.06 (+/-0.10). The best-fitting absorption column is 4.5 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (6.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.5 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 1.5 x 10^21 cm^-2 Excess significance: 9.6 sigma Photon index: 2.06 (+/-0.10) If the light curve continues to decay with a power-law decay index of 1.32, the count rate at T+24 hours will be 0.063 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x 10^-12 (3.9 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01200812. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/35291. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...