TITLE:   GCN CIRCULAR
NUMBER:  10888
SUBJECT: GRB 100625A: Swift-XRT Team refined analysis
DATE:    10/06/26 08:34:27 GMT
FROM:    Kim Page at U.of Leicester  <kpa@star.le.ac.uk>

K.L. Page (U. Leicester) and S. T. Holland (CRESST/USRA/GSFC) report on behalf 
of the Swift-XRT team:

We have analysed 16 ks of XRT data for GRB 100625A (Holland et al. GCN Circ. 
10884), from 61 s to 35.4 ks after the BAT trigger. The data are entirely in 
Photon Counting (PC) mode. The enhanced XRT position for this burst was given 
by Goad et al. (GCN. Circ 10886).

The light curve can be modelled with a power-law decay with a decay index 
of alpha=1.34 (+0.44, -0.26), with a small flare in the first orbit of 
data.

A spectrum formed from the PC mode data can be fitted with an absorbed 
power-law with a photon spectral index of 2.34 (+0.31, -0.23). The best-fitting 
absorption column is consistent with the Galactic value of 2.1 x 10^20 cm^-2 
(Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux 
conversion factor deduced from this spectrum is 3.2 x 10^-11 (3.6 x 10^-11) erg 
cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of 
1.34, the count rate at T+24 hours will be 1.1 x 10^-4 count s^-1, 
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.5 x 10^-15 
(3.9 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at 
http://www.swift.ac.uk/xrt_products/00425647.

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