TITLE: GCN CIRCULAR NUMBER: 8566 SUBJECT: GRB 081127: Swift-XRT refined analysis DATE: 08/11/27 17:42:56 GMT FROM: Jirong Mao at INAF-OAB J. Mao, C. Guidorzi (INAF-OAB) and R. Margutti (Univ. Bicocca & INAF-OAB) report on behalf of the Swift XRT team: We have analysed the first 4 orbits of Swift-XRT data obtained for GRB 081127 (Mao et al., GCN Circ. 8560), covering from 128 to 219 s in Windowed Timing (WT) and from 220 s to 19.5 ks in Photon Counting (PC) mode data, respectively. The net exposures are 90 s and 9.4 ks for the WT and PC modes data, respectively. The UVOT-enhanced XRT position was given by Beardmore et al. in GCN Circ. 8565. The light curve shows an inital steep decay of index 5.6 until 420 s, then it shows a shallow decay with index of 0.6. After 13.3 ks the lightcurve shows a decay with an index of about 2.0. The WT spectrum can be fit with an absorbed power-law model with a photon index of 4.2 +- 0.2 and an absorbing equivalent hydrogen column density is (2.8 +- 0.3)e21 cm^-2, which is larger than the Galactic one, 6.7e20 cm^-2 (Kalberla et al. 2005). The observed (unabsorbed) 0.3-10 keV flux is 3.7(4.5)e-10 erg cm^-2 s^-1. The PC spectrum can be fit with an absorbed power-law model with a photon index of 2.3 +- 0.3 with an absorbing equivalent hydrogen column density compatible with the Galactic value. If the light curve continues to decay with an index of 2.0, the count rate 24 hours after the burst will be 2.9e-4 c/s, corresponding to an absorbed flux of 9.9e-15 erg cm^-2 s^-1. This is an official product of the Swift-XRT team.