TITLE: GCN CIRCULAR NUMBER: 14061 SUBJECT: GRB 121211A: Swift-XRT refined Analysis DATE: 12/12/12 02:01:06 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), M.C. Stroh (PSU) and V. Mangano report on behalf of the Swift-XRT team: We have analysed 12 ks of XRT data for GRB 121211A (Mangano et al. GCN Circ. 14057), from 95 s to 29.5 ks after the BAT trigger. The data comprise 203 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 14060). The late-time light curve (from T0+3.9 ks) can be modelled with a power-law decay with a decay index of alpha=0.77 (+/-0.07). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.15 (+/-0.04). The best-fitting absorption column is 2.85 (+/-0.13) x 10^21 cm^-2, in excess of the Galactic value of 9.5 x 10^19 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.11 (+0.15, -0.14) and a best-fitting absorption column of 1.4 (+0.4, -0.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (5.0 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+0.4, -0.3) x 10^21 cm^-2 Galactic foreground: 9.5 x 10^19 cm^-2 Excess significance: 6.4 sigma Photon index: 2.11 (+0.15, -0.14) If the light curve continues to decay with a power-law decay index of 0.76, the count rate at T+24 hours will be 0.025 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.9 x 10^-13 (1.3 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/00541200. This circular is an official product of the Swift-XRT team.