[vsnet-grb-info 28518] GRB 210807C: Swift-XRT refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30621
SUBJECT: GRB 210807C: Swift-XRT refined Analysis
DATE:    21/08/09 06:57:14 GMT
FROM:    Phil Evans at U of Leicester  <pae9 at leicester.ac.uk>

P.A. Evans (U. Leicester) and A. Y. Lien (GSFC/UMBC) reports on behalf
of the Swift-XRT team:

We have analysed 5.8 ks of XRT data for GRB 210807C (Lien et al. GCN
Circ. 30610), from 183 s to 56.8 ks after the  BAT trigger. The data
comprise 203 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 30615).

The light curve can be modelled with a power-law decay with a decay
index of alpha=3.11 (+2.96, -0.22), followed by a break at T0+420.7
(+18.1, -165.2) s to a decay of 1.32 (+0.09, -0.07).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.28 (+0.15, -0.14). The
best-fitting absorption column is  4.9 (+/-0.4) x 10^22 cm^-2, in
excess of the Galactic value of 8.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.5 (+/-0.6) and a
best-fitting absorption column of 6.0 (+1.8, -1.5) x 10^22 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 7.6 x 10^-11 (4.1 x 10^-10) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.0 (+1.8, -1.5) x 10^22 cm^-2
Galactic foreground: 8.5 x 10^21 cm^-2
Excess significance: 5.5 sigma
Photon index:	     2.5 (+/-0.6)


The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01064421.

This circular is an official product of the Swift-XRT team.