GCN Circular 7045

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
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 ), all in Photon Counting mode. The XRT position was given in GCN 
Circ. 7043
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  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.