TITLE: GCN CIRCULAR NUMBER: 23604 SUBJECT: GRB 190103B: Swift-XRT refined Analysis DATE: 19/01/04 04:24:42 GMT FROM: Phil Evans at U of Leicester B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), A. Tohuvavohu (PSU) and A.Y. Lien report on behalf of the Swift-XRT team: We have analysed 7.8 ks of XRT data for GRB 190103B (Lien et al. GCN Circ. 23602), from 99 s to 18.1 ks after the BAT trigger. The data comprise 437 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 23603). The late-time light curve (from T0+4.2 ks) can be modelled with a power-law decay with a decay index of alpha=1.03 (+/-0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.38 (+/-0.06). The best-fitting absorption column is 4.27 (+0.28, -0.27) x 10^21 cm^-2, in excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.89 (+/-0.11) and a best-fitting absorption column of 3.9 (+0.6, -0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (6.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.9 (+0.6, -0.5) x 10^21 cm^-2 Galactic foreground: 1.4 x 10^20 cm^-2 Excess significance: 11.8 sigma Photon index: 1.89 (+/-0.11) If the light curve continues to decay with a power-law decay index of 1.03, the count rate at T+24 hours will be 0.027 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-12 (1.6 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/00881709. This circular is an official product of the Swift-XRT team.