TITLE: GCN CIRCULAR NUMBER: 14904 SUBJECT: GRB 130615A: Swift-XRT refined Analysis DATE: 13/06/15 22:00:05 GMT FROM: Phil Evans at U of Leicester P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh (PSU), B.P. Gompertz (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC), A. Maselli (INAF-IASFPA) and E. Sonbas report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 130615A (Sonbas et al. GCN Circ. 14897), from 180 s to 28.9 ks after the BAT trigger. The data comprise 459 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 14900). The late-time light curve (from T0+5.3 ks) can be modelled with a power-law decay with a decay index of alpha=0.5 (+/-0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.05 (+/-0.03). The best-fitting absorption column is 1.93 (+/-0.09) x 10^21 cm^-2, in excess of the Galactic value of 8.3 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.06 (+0.27, -0.09) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 0 (+4.4, -0) x 10^20 cm^-2 Galactic foreground: 8.3 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 2.06 (+0.27, -0.09) If the light curve continues to decay with a power-law decay index of 0.5, the count rate at T+24 hours will be 4.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x 10^-13 (2.2 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00558271. This circular is an official product of the Swift-XRT team.