TITLE: GCN CIRCULAR NUMBER: 7694 SUBJECT: GRB 080506: Swift XRT refined analysis DATE: 08/05/07 17:49:36 GMT FROM: Boris Sbarufatti at INAF-IASF-Pa B. Sbarufatti, V. Mangano, V. La Parola (INAF-IASF PA) and W. H. Baumgartner (GSFC/UMBC) The Swift-XRT began observing GRB 080506 (trigger=311159, Baumgartner et al., GCN Circ. 7685) in Window Timing mode, 146 s after the BAT trigger. The enhanced XRT position was given in Osborne et al. (GCN Circ. 7687). The lightcurve is quite complex. It shows two initial bright flares centered at 182+/-2 s and 254+/-2 s, with folding times of 22+/-1 s and 88+/-2 s, respectively. Flaring activity is detected until times > T+10 ks. The decay slope after 10 ks from the trigger time is -0.6+/-0.2. The spectrum of the first flare can be fit by a power-law model, with a photon index of 1.46 ± 0.06 and column density consistent with the average Galactic column density in this direction of 1.66e21 cm-2 (Kalberla et al 2005). The observed (unabsorbed) 0.3-10 keV flux is 1.5e-9 (1.8e-9) erg cm-2 s-1. The spectrum of the second flare can be fit by a power-law model, with a photon index of 2.3 ± 0.1 and column density consistent with the average Galactic column density in this direction. The observed (unabsorbed) 0.3-10 keV flux is 3.2e-10 (5.2e-9) erg cm-2 s-1. The PC mode spectrum, covering times > T+1000 s, is fit by a power law model with photon index 2.0 ± 0.2 and no evidence for any additional column density with respect to the Galactic one. The corresponding observed (unabsorbed) 0.3-10 keV fluxes are 2.3e-12 (3.5e-12 ) erg cm-2 s-1, respectively. If the burst continues to decay at the same rate, we predict an XRT count rate of 9.8 e-3 counts/s and 6.4 e-3 counts/s at T+24 hours and T+48 hours, respectively. This corresponds to observed 0.3-10 keV fluxes of approximately 5.4e-13 and 3.6e-13 erg cm-2 s-1. This circular is an official product of the Swift-XRT team.