[vsnet-grb-info 6305] GRB 080702A: Swift-XRT Team refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7925
SUBJECT: GRB 080702A: Swift-XRT Team refined analysis
DATE:    08/07/02 21:03:07 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page (U. Leicester) & M. De Pasquale (UCL-MSSL) report on behalf of 
the Swift-XRT team:

We have analysed the first 3 orbits of Swift-XRT data obtained for GRB 
080702A (De Pasquale et al., GCN Circ. 7920), covering 5.2 ks of Photon 
Counting mode data, between ~75 and 12.6 ks after the trigger. The 
UVOT-enhanced XRT position was given by Goad et al. in GCN Circ. 7923.

The light-curve can be modelled by a broken power-law, with a flat decay 
of alpha = 0.5 +/- 0.3 until around the end of the first orbit of data. At 
this point, the decay steepens to 1.6 +0.9/-0.3. The afterglow is already 
faint by the end of the third orbit.

A spectrum extracted from the first orbit of data can be modelled with an 
absorbed power-law, with Gamma = 2.05 +0.71/-0.64 and NH = (6.2 
+5.4/-3.6)x10^21 cm^-2, in excess of the Galactic column in this direction 
of 1.53x10^21 cm^-2. The observed (unabsorbed) flux over this time 
interval (75-800 s post-trigger) is 5.7x10^-12 (1.0x10^-11) erg cm^-2 
s^-1.

If the light-curve continues to decay with alpha ~ 1.6, the count rate 24 
hours after the burst is estimated to be 3.3x10^-5 count s^-1, which 
corresponds to an observed flux of 2x10^-15 erg cm^-2 s^-1.

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