GCN Circular 5451

A. Moretti (INAF-OAB), C. Guidorzi (Univ. Bicocca & INAF-OAB),
P. Romano (INAF-OAB) report on behalf of the Swift-XRT team:

We have analysed the first 4 orbits of Swift-XRT data obtained for GRB
060814 (trigger number 224552). The data consist of 428 s in Windowed
Timing (WT) mode, starting 72 seconds after the BAT trigger and 9.2 ks
in Photon Counting (PC) mode. Using PC data we obtain a refined
position of:

RA(J2000) =   14 45 21.48
Dec(J2000) = +20 35 11.8

with an estimated uncertainty radius of 3.5 arcsec (90% containment).

The light-curve, initially, shows a steep decay (alpha1=2.3+/-0.1) up to a
break at t_break1=1292+/-140.s. On top of this steep decay there is a
flare peaking at 150 s. After the break, the afterglow shows a
shallow decay (alpha2=0.3+/-0.1) up to t_break2=7500+/-2000 s, when
the light-curve steepens (alpha3=1.0+/-0.2).

The spectrum formed from all the WT data (< t_break1) can be modelled
with a power-law of photon index Gamma = 1.67 +/- 0.03, with an excess
absorbing column of NH = (2.7 +/- 0.2)e21 cm^-2 in addition to the
Galactic value of 2.40e20 cm^-2. The spectrum formed from the PC data
(> t_break1) is significantly softer than the pre-break spectrum: it
can be modelled with a power-law of photon index Gamma = 2.2 +/- 0.10,
with an absorbing column of NH = (3.6 +/- 0.4)e21 cm^-2, which is
marginally consistent with the previous one.

Assuming the light-curve continues to decay with alpha3=1.0, the
count rate at 24 hours is predicted to be 0.030 count s^-1. This
corresponds to an observed (unabsorbed) flux of 1.5e-12 (2.7e-12)
erg cm^-2 s^-1.

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


[GCN OPS NOTE(15aug06): This Circular was delayed by ~4 hrs due to problems
at the GCN end.]