GRB 241113A: Swift-XRT refined Analysis

We have analysed 7.7 ks of XRT data for GRB 241113A, from 60 s to 34.4 ks after the BAT trigger. The data comprise 75 s in Windowed Timing (WT) mode (the first 10 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with an initial power-law decay with an index of alpha=1.90 (+/-0.24), followed by a break at T+165 s to an alpha of 0.92 (+0.04, -0.05). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.32 (+0.33, -0.30). The best-fitting absorption column is 2.2 (+1.1, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 2.0 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 3.2 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.2 (+1.1, -0.9) x 10^21 cm^-2 Galactic foreground: 2.0 x 10^20 cm^-2 Excess significance: 3.7 sigma Photon index: 2.32 (+0.33, -0.30) If the light curve continues to decay with a power-law decay index of 0.92, the count rate at T+24 hours will be 8.0 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x 10^-13 (4.1 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/01267501. This circular is an official product of the Swift-XRT team.