[vsnet-grb-info 5359] GRB 071104: Swift-XRT Team Refined Analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7045
SUBJECT: GRB 071104: Swift-XRT Team Refined Analysis 
DATE:    07/11/05 08:15:55 GMT
FROM:    Kim Page at U.of Leicester  <kpa at star.le.ac.uk>

K.L. Page (U Leicester) reports on behalf of the Swift-XRT Team:

Seven orbits (15.6 ks) of Swift-XRT data have now been obtained and 
analysed for the SuperAGILE burst GRB 071104 (Donnarumma et al., GCN Circ 
7042), all in Photon Counting mode. The XRT position was given in GCN 
Circ. 7043 and has not been further improved.

Although the X-ray light-curve can, to first order, be fitted by a single 
power-law, there is an indication that the decay has broken (around 43 ks 
after the trigger) from an initial slope of alpha ~ 0.6 to a steeper 
value of ~2.9, although this decay slope is not well-constrained because 
of the limited data after the break time (a 90% range of alpha = 0.5 - 5.3 
is estimated).

A spectrum formed from all the data (20.5 - 50.9 ks after the trigger) can 
be modelled with a power-law of Gamma = 1.9 +/- 0.3 absorbed by the 
Galactic column density of 2.69e21 cm^-2. (The 90% upper limit on this 
absorption is 4.9e21 cm^-2.) Over this period, the 0.3-10 keV observed 
flux is 1.1e-12 erg cm^-2 s^-1, with the unabsorbed value being 1.5e-12 
erg cm^-2 s^-1.

Using the range of possible decay slopes, the count-rate is expected to be 
between 0.018 and 7e-4 count s^-1 at 24 hours, corresponding to an 
observed flux range of between 1.0e-12 and 4.0e-14 erg cm^-2 s^-1 over 
0.3-10 keV (1.4e-12 - 5.4e-14 erg cm^-2 s^-1 unabsorbed).

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