TITLE: GCN CIRCULAR NUMBER: 37059 SUBJECT: GRB 240805B: Swift-XRT refined Analysis DATE: 24/08/06 02:27:11 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J. D. Gropp (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 8.2 ks of XRT data for GRB 240805B, from 71 s to 30.3 ks after the BAT trigger. The data comprise 4.5 ks in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+5.6 ks) can be modelled with a power-law decay with a decay index of alpha=1.55 (+/-0.26).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.77 (+/-0.06). The best-fitting absorption column is 1.19 (+0.21, -0.20) x 10^21 cm^-2, in excess of the Galactic value of 7.6 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.9 (+0.4, -0.3) and a best-fitting absorption column of 1.5 (+1.4, -0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus: Total column: 1.5 (+1.4, -0.7) x 10^21 cm^-2 Galactic foreground: 7.6 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.9 (+0.4, -0.3)
If the light curve continues to decay with a power-law decay index of 1.55, the count rate at T+24 hours will be 3.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (1.6 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/01246989.
This circular is an official product of the Swift-XRT team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/37059. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...