TITLE: GCN CIRCULAR NUMBER: 9298 SUBJECT: GRB 090429B: Swift XRT refined analysis DATE: 09/04/29 20:14:12 GMT FROM: Antonia Rowlinson at U.of Leicester A. Rowlinson (U. Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift-XRT team: We have analysed 8.9 ks of XRT data for GRB 090429B (Ukwatta et al. GCN Circ. 9281), from 104 s to 29.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 9288). The light curve initially shows a slow rise, which can be fitted with a power-law of index 0.89 (+0.36, -0.46). At around T+642 s the light curve breaks to a power-law decay, with index 1.20 (+0.11, -0.10). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.00 (+0.15, -0.24). The best-fitting absorption column is 10.0 (+4.2, -5.3) x 10^20, in excess of the Galactic value of 1.2 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 3.8 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 1.20, the count rate at T+24 hours will be 0.0014 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.3 x 10^-14 (6.9 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/00350854. This circular is an official product of the Swift-XRT team.