GCN Circular 10866
J. Mao (INAF-OAB) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift-XRT team: We have analysed 6.6 ks of XRT data for GRB 100619A (Cannizzo et al. GCN Circ. 10863), from 80 s to 13.2 ks after the BAT trigger. The data comprise 492 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve initially shows a flare feature at the time 90s, then it has a power-law decay with an index 0.88, after that, the light curve shows a clear flare feature with the peak at 1000s. Then, the light cure has a power-law decay with an index of alpha=0.85 (+/-0.02). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.41 (+/-0.03). The best-fitting absorption column is 3.4 (+/-0.1) x 1021 cm^-2, in excess of the Galactic value of 2.0 x 1020 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.16 (+0.20, -0.19) and a best-fitting absorption column of 3.7 (+/-0.6) x 1021 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.7 x 10^-11 (9.6 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.85, the count rate at T+24 hours will be 0.015 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-12 (1.4 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/00424998. This circular is an official product of the Swift-XRT team.