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
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 ) 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
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 ), 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
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 ).

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.