TITLE: GCN CIRCULAR NUMBER: 16106 SUBJECT: GRB 140413A: Swift-XRT refined Analysis DATE: 14/04/14 11:39:30 GMT FROM: Luca Izzo at ICRA L. Izzo (URoma/ICRA) and V. D'Elia (ASDC) report on behalf of the Swift-XRT team: We have analysed 13 ks of XRT data for GRB 140413A, from 2.2 ks to 83.3 ks after the BAT trigger. The data comprise 2.1 ks in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. Using 3951 s of PC mode data and 4 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 = 65.45475, -51.18310 which is equivalent to: RA (J2000): 04h 21m 49.14s Dec(J2000): -51d 10' 59.2" with an uncertainty of 1.6 arcsec (radius, 90% confidence). The late-time light curve (from T0+38.1 ks) can be modelled with a power-law decay with a decay index of alpha=1.7 (+/-0.4). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.989 (+0.025, -0.024). The best-fitting absorption column is 4.04 (+/-0.13) x 10^21 cm^-2, in excess of the Galactic value of 1.4 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 3.9 x 10^-11 (6.0 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 4.04 (+/-0.13) x 10^21 cm^-2 Galactic foreground: 1.4 x 10^20 cm^-2 Excess significance: 49.9 sigma Photon index: 1.989 (+0.025, -0.024) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00595616. This circular is an official product of the Swift-XRT team.