TITLE: GCN CIRCULAR NUMBER: 16475 SUBJECT: GRB 140628A: Swift-XRT refined Analysis DATE: 14/06/29 06:59:22 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, M.G. Bernardini, A. Melandri (INAF/OAB), P.A. Evans (U. Leicester) and E. Sonbas (NASA/GSFC/Adiyaman Univ.) report on behalf of the Swift-XRT team: We have analysed 8.2 ks of XRT data for GRB 140628A (Sonbas et al. GCN Circ. 16467), from 231 s to 23.2 ks after the BAT trigger. The data comprise 47 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. Using 5310 s of PC mode data and 10 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 40.66617, -0.38489 which is equivalent to: RA (J2000): 02h 42m 39.88s Dec(J2000): -00d 23' 05.6" with an uncertainty of 1.5 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.21 (+0.03, -0.04). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.88 (+0.19, -0.18). The best-fitting absorption column is 8.9 (+5.3, -4.7) x 10^20 cm^-2, in excess of the Galactic value of 3.2 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 8.9 (+5.3, -4.7) x 10^20 cm^-2 Galactic foreground: 3.2 x 10^20 cm^-2 Excess significance: 2.0 sigma Photon index: 1.88 (+0.19, -0.18) If the light curve continues to decay with a power-law decay index of 1.21, the count rate at T+24 hours will be 4.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x 10^-13 (1.9 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/00602803. This circular is an official product of the Swift-XRT team.