GCN Circular 5154

J. A. Kennea, D. C. Morris and D. Fox (PSU) report on behalf of the
Swift/XRT Team:

We have analysed the first 4 orbits of Swift/XRT data of GRB 060522 (Fox 
et al., GCN 5150
Not found
 
 
) which equates to 4496+126 seconds of data. We find a 
refined XRT position for this burst of:

RA(J2000)  = 21:31:44.91
Dec(J2000) = +2:53:08.14

with an error of 3.7 arcseconds radius (90% containment). This position is 
58 arcseconds from the refined BAT position quoted by Krimm et al. (GCN 
5153
Not found
 
 
), 0.4 arcseconds from the original XRT position from Fox et al., and 
2.8 arcseconds from the optical counterpart reported by UVOT and confirmed 
by TNG (D'Avanzo et al., GCN 5151
Not found
 
 
).

The afterglow shows several states: from T+150 to T+190 the lightcurve was 
bright (~6 XRT c/s) and relatively flat, at T+190 the lightcurve breaks 
and rapidly decays with a power-law slope of -4.0. The lightcurve breaks 
again at T+233s and flattens to a slope of -1.77. Centered at T+540 there 
is a small flare in the lightcurve. From T+1000s to T+5500s there is no 
data in the lightcurve, however the lightcurve appears to have flattened 
in this time. Data from T+5000 onwards shows the lightcurve is decaying 
with a slope of -1.3.

The average spectrum of the burst is well fit by an absorbed power-law 
model. The parameters of this fit are N_H = (4.6 +/- 2.5) x 10^20 cm^-2, 
and a power-law photon index of 1.97 +/- 0.21 (errors 90% confidence). The 
expected galactic absorption from this position in the sky is 4.83 x 10^20 
cm^-2, so there is no evidence of excess absorption in this burst 
afterglow.

The prediction for the brightness of the burst 24 hours after the BAT 
trigger is approximately 2x10^-3 XRT Counts/s which is equivalent to a 
flux of ~7x10^-14 erg/s/cm^2 (0.2-10 keV).

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