TITLE: GCN CIRCULAR NUMBER: 23633 SUBJECT: GRB 190106A: Swift-XRT refined Analysis DATE: 19/01/07 13:45:03 GMT FROM: Phil Evans at U of Leicester K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU) and V. Yurkov report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team: We have analysed 5.7 ks of XRT data for GRB 190106A (Yurkov et al. GCN Circ. 23614), from 85 s to 44.7 ks after the BAT trigger. The data comprise 254 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 23619). The late-time light curve (from T0+11.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.02 (+/-0.11). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.06 (+0.06, -0.05). The best-fitting absorption column is 1.9 (+/-1.1) x 10^21 cm^-2, at a redshift of 1.86, in addition to the Galactic value of 1.0 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.95 (+0.09, -0.06) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.0 x 10^21 cm^-2 Intrinsic column: 1.0 (+1.6, -0.0) x 10^21 cm^-2 at z=1.86 Photon index: 1.95 (+0.09, -0.06) If the light curve continues to decay with a power-law decay index of 1.02, the count rate at T+24 hours will be 0.096 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.4 x 10^-12 (4.2 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/00882252. This circular is an official product of the Swift-XRT team.