TITLE: GCN CIRCULAR NUMBER: 42936 SUBJECT: GRB 251201B: Swift-XRT refined Analysis DATE: 25/12/02 03:23:04 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Salvaggio (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 251201B, from 86 s to 23.3 ks after the trigger. The data comprise 362 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+6.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.6 (+/-0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.40 (+/-0.04). The best-fitting absorption column is 2.30 (+/-0.12) x 10^21 cm^-2, in excess of the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.93 (+0.16, -0.15) and a best-fitting absorption column of 10.0 (+4.5, -4.0) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 10.0 (+4.5, -4.0) x 10^20 cm^-2 Galactic foreground: 1.8 x 10^20 cm^-2 Excess significance: 3.4 sigma Photon index: 1.93 (+0.16, -0.15) If the light curve continues to decay with a power-law decay index of 1.6, the count rate at T+24 hours will be 3.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (1.5 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01418729. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42936. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...