TITLE: GCN CIRCULAR NUMBER: 14577 SUBJECT: GRB 130505A: Swift-XRT refined Analysis DATE: 13/05/05 20:36:04 GMT FROM: Phil Evans at U of Leicester D.N. Burrows (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea (PSU), M.C. Stroh (PSU) and J.K. Cannizzo report on behalf of the Swift-XRT team: We have analysed 11 ks of XRT data for GRB 130505A (Cannizzo et al. GCN Circ. 14563), from 102 s to 29.4 ks after the BAT trigger. The data comprise 503 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 14569). The late-time light curve (from T0+3.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.06 (+0.03, -0.04). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.86 (+/-0.03). The best-fitting absorption column is 10.0 (+/-0.7) x 10^20 cm^-2, in excess of the Galactic value of 3.6 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.92 (+/-0.07) and a best-fitting absorption column of 8.8 (+1.6, -1.5) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 8.8 (+1.6, -1.5) x 10^20 cm^-2 Galactic foreground: 3.6 x 10^20 cm^-2 Excess significance: 5.6 sigma Photon index: 1.92 (+/-0.07) If the light curve continues to decay with a power-law decay index of 1.06, the count rate at T+24 hours will be 0.27 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.0 x 10^-11 (1.3 x 10^-11) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00555163. This circular is an official product of the Swift-XRT team.