TITLE: GCN CIRCULAR NUMBER: 29790 SUBJECT: GRB 210410A: Swift-XRT refined Analysis DATE: 21/04/11 04:35:55 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team: We have analysed 4.4 ks of XRT data for GRB 210410A, from 61 s to 52.6 ks after the BAT trigger. The data comprise 115 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 702 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 269.75437, +45.36192 which is equivalent to: RA (J2000): 17h 59m 01.05s Dec(J2000): +45d 21' 42.9" with an uncertainty of 2.4 arcsec (radius, 90% confidence). The late-time light curve (from T0+4.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.5 (+0.5, -0.4). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.33 (+/-0.11). The best-fitting absorption column is 1.4 (+0.5, -0.4) x 10^21 cm^-2, in excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.47 (+0.18, -0.16) and a best-fitting absorption column of 7.2 (+6.0, -3.2) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.5 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 7.2 (+6.0, -3.2) x 10^20 cm^-2 Galactic foreground: 4.0 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.47 (+0.18, -0.16) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01042113. This circular is an official product of the Swift-XRT team.