[vsnet-grb-info 6389] GRB 080723A: Swift-XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8004
SUBJECT: GRB 080723A: Swift-XRT refined analysis
DATE:    08/07/23 15:35:27 GMT
FROM:    Andy Beardmore at U Leicester  <apb at star.le.ac.uk>

A.P. Beardmore (U. Leicester) and M. Stamatikos (NASA/ORAU)
report on behalf of the Swift-XRT team :

We have analysed the first two orbits of Swift-XRT data obtained
from GRB 080723A (trigger 317662;  Stamatikos et al., GCN Circ. 8000).
The data were taken in photon counting mode and have an exposure of
2.83 ks,  spanning 88 s to 7.44 ks after the trigger. The UVOT-enhanced
XRT position was given by Beardmore et al. in GCN Circ. 8001.

The light curve can be modelled by a doubly broken power-law, with
an inital decay of alpha1 = 1.77 +0.34 -0.25 which flattens to a shallow
decay of alpha2 = 0.05 +/- 0.24 at a time tbreak1 = 365 +68 -46 s. This is
followed by a further steepening to  alpha3 = 1.39 +/- 0.75 at a time
tbreak2 = 3.4 +1.2 -1.8 ks.

The spectrum of the photon counting mode data from the first two orbits
can be fit with an absorbed power-law to give a photon index gamma =
2.39 +0.30 -0.28 and NH = (7.7 +2.5 -2.2)e21 cm^-2, in addition to the
Galactic column of 3.9e+21 cm^-2 in the direction of the GRB. The observed
0.3-10 keV flux is  (1.14 +0.10 -0.22)e-11 erg cm^-2 s^-1, which corresponds
to an unabsorbed flux of 3.57e-11 erg cm^-2 s^-1.

If the light curve continues to decay at the same rate we estimate the count
rate will be 3.2e-2 count/s  one day after the trigger, which corresponds to
an observed  flux of 1.9e-13 erg cm^-2 s^-1.

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