TITLE: GCN CIRCULAR NUMBER: 43320 SUBJECT: GRB 260104A: Swift-XRT refined Analysis DATE: 26/01/04 14:58:50 GMT FROM: Phil Evans at U of Leicester <pae9@star.le.ac.uk> J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 260104A, from 101 s to 28.3 ks after the trigger. The data comprise 10 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+5.1 ks) can be modelled with a power-law decay with a decay index of alpha=1.22 (+0.26, -0.23). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.78 (+0.16, -0.10). The best-fitting absorption column is 3.55 (+3.69, -0.15) x 10^20 cm^-2, consistent with the Galactic value of 3.4 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 3.7 x 10^-11 (4.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.55 (+3.69, -0.15) x 10^20 cm^-2 Galactic foreground: 3.4 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.78 (+0.16, -0.10) If the light curve continues to decay with a power-law decay index of 1.22, the count rate at T+24 hours will be 4.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (1.8 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/01430212. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43320. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...