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NASA Swift: GRB 060522: Swift/XRT Team refined analysis

Status Report From: Goddard Space Flight Center
Posted: Wednesday, May 24, 2006

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TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5154
SUBJECT: GRB 060522: Swift/XRT Team refined analysis
DATE: 06/05/22 17:43:27 GMT
FROM: Jamie A. Kennea at PSU/Swift-XRT kennea@astro.psu.edu

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) 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), 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).

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.

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