TITLE: GCN CIRCULAR NUMBER: 42162 SUBJECT: GRB 251007A: Swift-XRT refined Analysis DATE: 25/10/08 08:34:11 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.5 ks of XRT data for GRB 251007A, from 58 s to 39.2 ks after the trigger. The data comprise 362 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+11.9 ks) can be modelled with a power-law decay with a decay index of alpha=1.46 (+/-0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.92 (+/-0.04). The best-fitting absorption column is 1.79 (+0.15, -0.14) x 10^21 cm^-2, in excess of the Galactic value of 4.0 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.82 (+/-0.12) and a best-fitting absorption column of 1.6 (+/-0.4) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus: Total column: 1.6 (+/-0.4) x 10^21 cm^-2 Galactic foreground: 4.0 x 10^20 cm^-2 Excess significance: 5.1 sigma Photon index: 1.82 (+/-0.12)
If the light curve continues to decay with a power-law decay index of 1.46, the count rate at T+24 hours will be 0.052 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x 10^-12 (2.5 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/01402466.
This circular is an official product of the Swift-XRT team.
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