TITLE: GCN CIRCULAR NUMBER: 13115 SUBJECT: GRB 120326A: Swift-XRT refined Analysis DATE: 12/03/26 13:32:06 GMT FROM: Phil Evans at U of Leicester J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and M.H. Siegel report on behalf of the Swift-XRT team: We have analysed 12 ks of XRT data for GRB 120326A (Siegel et al. GCN Circ. 13105), from 65 s to 34.6 ks after the BAT trigger. The data comprise 100 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN. Circ 13110). The late-time light curve (from T0+3.7 ks) can be modelled with an initial power-law decay with an index of alpha=0.20 (+0.15, -0.11), followed by a break at T+16.6 ks to an alpha of -1.47 (+0.76, -0.03). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 4.4 (+0.4, -0.3). The best-fitting absorption column is 3.4 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 5.2 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.89 (+/-0.10) and a best-fitting absorption column of 9.1 (+2.3, -2.2) 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 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 9.1 (+2.3, -2.2) x 10^20 cm^-2 Galactic foreground: 5.2 x 10^20 cm^-2 Excess significance: 2.9 sigma Photon index: 1.89 (+/-0.10) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00518626. This circular is an official product of the Swift-XRT team.