TITLE: GCN CIRCULAR NUMBER: 42096 SUBJECT: GRB 251003A: Swift-XRT refined Analysis DATE: 25/10/03 16:16:36 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.8 ks of XRT data for GRB 251003A, from 59 s to 34.6 ks after the trigger. The data comprise 126 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+4.6 ks) can be modelled with a power-law decay with a decay index of alpha=0.6 (+0.4, -0.3).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.67 (+0.11, -0.10). The best-fitting absorption column is 1.4 (+3.0, -1.4) x 10^22 cm^-2, at a redshift of 4.412, in addition to the Galactic value of 4.4 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 2.8 x 10^-11 (7.5 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus: Galactic foreground: 4.4 x 10^21 cm^-2 Intrinsic column: 1.4 (+3.0, -1.4) x 10^22 cm^-2 at z=4.412 Photon index: 2.67 (+0.11, -0.10)
If the light curve continues to decay with a power-law decay index of 0.6, the count rate at T+24 hours will be 8.2 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x 10^-13 (6.1 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/01400964.
This circular is an official product of the Swift-XRT team.
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