GCN Circular 14555
A. Melandri (INAF-OAB) and S. Immler (NASA/CRESST/GSFC) report on behalf of the Swift-XRT team: We have analysed 8.3 ks of XRT data for the Fermi/LAT-detected burst: GRB 130502B (Kocevski et al. GCN Circ. 14532), from 55.1 ks to 101.8 ks after the Fermi/LAT trigger. The object dectected in the first 3.4 ks of XRT data (Melandri & Immler GCN Circ. 14540) is now clearly fading. The light curve can be modelled with a power-law decay with a decay index of alpha=1.52 (+/-0.25). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.89 (+/-0.20). The best- fitting absorption column is 1.73 (+0.78, -0.71) x 10^21 cm^-2, in addition to the Galactic value of 1.1 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (6.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.1 x 10^21 cm^-2 Intrinsic column: 1.73 (+0.78, -0.71) x 10^20 cm^-2 Photon index: 1.89 (+0.21, -0.20) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020266. This circular is an official product of the Swift-XRT team.