TITLE:   GCN CIRCULAR
NUMBER:  7643
SUBJECT: GRB 080426: Swift-XRT refined analysis
DATE:    08/04/26 22:03:22 GMT
FROM:    Andy Beardmore at U Leicester  <apb@star.le.ac.uk>

A.P. Beardmore (U. Leicester) and H. Ziaeepour (UCL-MSSL) report on behalf
of the Swift-XRT team :

The Swift-XRT began observing GRB 080426 (trigger=310219, Ziaeepour et
al.  GCN Circ. 7639) in Photon Counting mode, 230 s after the BAT
trigger.  The best XRT position for this burst is the UVOT-enhanced
position reported by Beardmore et al. (GCN Circ. 7641).

Three orbits of data out to T+13 ks, totalling 5.7 ks of exposure,
reveal a light curve which follows a simple power-law decay, with an
index of -1.07 +/- 0.08.

The spectrum from the first three orbits is well fit by an absorbed
power-law model, with a photon index of 2.01 +/- 0.25 and column density
of (5.3 +/- 1.3)e21 cm^-2, which is slightly in excess of the average
Galactic column density in this direction of 3.7e21 cm^-2. The
observed (unabsorbed) 0.3-10 keV flux is 5.1e-12 (9.1e-12)
erg cm^-2 s^-1.

If the burst continues to decay at the same rate, we predict an
XRT count rate of 2.0e-3 count/s at T+24 hours, which corresponds
to an observed 0.3-10 keV flux of approximately 1.2e-13 erg cm^-2 s^-1.

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