GCN Circular 10764
G. Stratta (ASDC), V. D'Elia (ASDC) and C. B. Markwardt (CRESST/GSFC/UMD) report on behalf of the Swift-XRT team: We have analysed 24.9 ks of XRT data for GRB 100514A (Markwardt et al. GCN Circ. 10759), from 91 s to 25.0 ks after the BAT trigger. The data comprise 82 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 10762). The light curve can be modelled with a broken power-law decay with decay indices of alpha_1 = 5.15 +/- 0.15, alpha_2 = 0.55 +/- 0.20 and a break at t = 560+/-60 sec after the trigger. A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 3.96 (+0.18, -0.17). The best-fitting absorption column is 2.9 (+/-0.3) x 10^21 cm^-2, in excess of the Galactic value of 7.7 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 2.1 x 10^-11 (2.0 x 10^-10) erg cm^-2 count^-1. The spectrum softens in the PC mode data to a photon spectral index of 2.74 (+0.46, -0.44) with a best-fitting column of 5.4 (+6.5, -2.9) x 10^20 cm^-2 in excess of the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is now 2.9 x 10^-11 (5.5 x 10^-11) erg cm^-2 count^-1. Uncertainties are given at 90% confidence level. If the light curve continues to decay with a power-law decay index of 0.55, the count rate at T+24 hours will be 1.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.2 x 10^-14 (9.9 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00421962. This circular is an official product of the Swift-XRT team.