[vsnet-grb-info 6890] GRB 081104: refined XRT analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8481
SUBJECT: GRB 081104: refined XRT analysis
DATE:    08/11/05 11:11:44 GMT
FROM:    Vanessa Mangano at INAF-IASFPA  <vanessa at ifc.inaf.it>

V. Mangano, V. La Parola, B. Sbarufatti (INAF-IASF PA)
report on behalf the Swift-XRT Team:

Swift XRT follow-up observation of the field of GRB 081104
(trigger=333666, Parsons et al., GCN Circ. 8473) started on
2008 11 04 at 10:18:45 UT (about 40 min after the trigger).

We have analysed the first four orbits of PC mode XRT data
accumulated from T+2640 s to T+22153 s (6.5 ks exposure).
The light curve of the X-ray source given in Mangano e. at,
GCN Circ. 8474 shows a power-law decay with slope -1.0 +/- 0.2,
with an initial count rate at the level of 0.1 counts/s.
If decaying at this rate the source will reach a count rate
level of 3.e-3 counts/s at T+24 hours.

The average spectrum of the source have been fitted with Cash
statistics. It can be modeled with a highly absorbed power law,
with NH=(1.5 +/ -0.4)e22 cm^-2 (significantly in excess with respect
to the Galactic absorption along the line of sight, of 7.0e20  cm^-2;
Kalberla et al. 2005) and a photon index of 5.2 +/- 1.0
(C-statistic=84.4 with 93 bins).


With the power law fit, the average observed (unabsorbed) flux
in the 0.3-10 keV energy range is of 8.0e-13 (1.9e-10) erg cm^-2 s^-1.

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