GRB 241030A: Swift-XRT refined Analysis

We have analysed 11 ks of XRT data for GRB 241030A, from 63 s to 45.7 ks after the BAT trigger. The data comprise 859 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+4.5 ks) can be modelled with an initial power-law decay with an index of alpha=0.87 (+0.17, -0.57), followed by a break at T+10.4 ks to an alpha of 1.58 (+/-0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.720 (+0.016, -0.011). The best-fitting absorption column is consistent with the Galactic value of 1.8 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.95 (+0.08, -0.06) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 1.8 x 10^21 cm^-2 Intrinsic column: 1.8 (+1.8, -0.0) x 10^21 cm^-2 at z=1.411 Photon index: 1.95 (+0.08, -0.06) If the light curve continues to decay with a power-law decay index of 1.58, the count rate at T+24 hours will be 0.034 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-12 (1.6 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01263718. This circular is an official product of the Swift-XRT team.