[vsnet-grb-info 2322] GRB051021B: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4160
SUBJECT: GRB051021B: Swift XRT refined analysis
DATE:    05/10/24 23:02:36 GMT
FROM:    Judith Racusin at PSU  <racusin at astro.psu.edu>

J. Racusin, C. Pagani, D. Morris, A. Retter, D. Burrows (PSU), N. Gehrels 
(GSFC) on behalf of the Swift XRT team:

We have analyzed the first 13 orbits of data from GRB051021B (Retter et 
al., GCN 4126).  XRT observations began in Window Timing mode 87 seconds 
after the BAT trigger and continued for 32 seconds before switching to 
Photon Counting mode.

The XRT light curve shows an initial decline with a decay slope of 
1.9+/-0.1 , followed by a break at ~T+2500s to a shallower decay slope of 
0.6+/-0.1.

A preliminary spectral fit using an absorbed power-law to the Photon 
Counting mode data yields a photon index of 1.64+/-0.12 in the 0.85-10 keV 
band, fixing nH to the Galactic value of 7.7E21 cm-2.

The observed 0.85-10 keV flux for the Photon Counting mode data in the 
first orbit is 7.3E-12 ergs cm-2 s-1 corresponding to an unabsorbed flux 
of 9.0E-12 ergs cm-2 s-1.