TITLE: GCN CIRCULAR NUMBER: 13101 SUBJECT: GRB 120324A: Swift-XRT refined Analysis DATE: 12/03/24 18:14:04 GMT FROM: Phil Evans at U of Leicester B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh (PSU), O.M. Littlejohns (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB) and B.-B. Zhang report on behalf of the Swift-XRT team: We have analysed 8.3 ks of XRT data for GRB 120324A (-B. Zhang et al. GCN Circ. 13090), from 81 s to 29.5 ks after the BAT trigger. The data comprise 160 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 13093). The late-time light curve (from T0+4.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.04 (+/-0.07). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.12 (+/-0.10). The best-fitting absorption column is 1.10 (+0.09, -0.08) x 10^22 cm^-2, in excess of the Galactic value of 4.5 x 10^21 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.07 (+/-0.14) and a best-fitting absorption column of 1.18 (+0.13, -0.12) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.7 x 10^-11 (1.3 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.18 (+0.13, -0.12) x 10^22 cm^-2 Galactic foreground: 4.5 x 10^21 cm^-2 Excess significance: 9.9 sigma Photon index: 2.07 (+/-0.14) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00518507. This circular is an official product of the Swift-XRT team.