GCN Circular 7605
P.A. Evans, K.L. Page, A.P. Beardmore, R.L.C. Starling (U. Leicester) and F.E. Marshall (NASA/GSFC) report on behalf of the Swift-XRT team: We have analysed 5.2 ks of Swift XRT data for GRB 080413A (Beardmore et al. GCN Circ. 7594), from T0+67 s to T0+21000 s. The first 186 s of data were obtained in Windowed Timing (WT mode); the remainder in Photon Counting mode. The best XRT position for this object is the UVOT-enhanced position given in Osborne et al. (GCN Circ. 7596). The X-ray light curve is well fitted by a power-law decay, with an initial decay slope of 2.87 (+/- 0.19) up to T0+175 (+23/-16) s, at which point the decay shallows to a slope of 1.10 (+0.06/-0.07). A spectrum obtained from all of the WT mode data can be modelled with an absorbed power-law with a photon index gamma=3.12 (+0.16/-0.15). A redshifted absorbing column of 1.53 (+0.43/-0.38) x 10^22 cm^-2, at a redshift of z=2.433 (Thoene et al. GCN Circ 7602) is necessary in addition to the Galactic column of 8.71 x 10^20 cm^-2 (Kalberla et al. 2005). The observed (unabsorbed) 0.3-10 keV flux in this spectrum is 4.1 x 10^-10 (1.71 x 10^-9) erg cm^-2 s^-1. If the source continues to decay at the present rate, we predict a count rate of 3.51 x 10^-3 count/sec at T0+24 hours, which correponds to a 0.3-10 keV observed (unabsorbed) flux of 9.54 x 10^-14 (2.72 x 10^-13) erg cms^-2 s^-1. This circular is an official product of the Swift-XRT team.