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GCN Circular 4514

Subject
GRB 060115: Swift XRT refined analysis
Date
2006-01-15T20:16:30Z (18 years ago)
From
Matteo Perri at ISAC/ASDC <perri@asdc.asi.it>
M. Perri (ASDC), G. Chincarini (Univ. Milano-Bicocca), G. Tagliaferri
(INAF-OAB), D.N. Burrows (PSU), M. Tripicco (GSFC-SSAI) and F. Marshall
(GSFC) report on behalf of the Swift XRT team:

We have analyzed the first two orbits of XRT data from GRB 060115
(trigger 177408, GCN 4509). A 1260s Photon Counting mode image
provides a refined XRT position:

RA(J2000) = 03h 36m 08.49s,
Dec(J2000) = +17d 20m 45.3s

with an uncertainty of 3.8 arcsec (90% containment). This position
is 1.7 arcsec away from the on-board XRT position (Tagliaferri et al.,
GCN 4509) and includes the latest XRT boresight correction. This
position is 2.6 arcsec from the optical afterglow position (which
also has an uncertainty of 2 arcsec) reported by Yanagisawa et al.
(GCN 4510).

The X-ray light curve in the first two orbits can be fit with a broken
power-law with an initial decay slope of -3.3+/-0.1, a break at
T+570+/-40 s, and a post-break slope of -0.7+/-0.1. At around T+400s
some flare activity is also evident.

A power-law fit to the X-ray spectrum from T+121s to T+153s gave a
photon index of 1.8+/-0.1 and a column density of (1.5+/-0.6)E21 cm**-2,
consistent with the Galactic hydrogen column density in the direction
of the burst of 1.3E21cm**-2.

If the burst continues to decay at the current rate we estimate an XRT
count rate of 8E-3 counts/s at T+24hr, which corresponds to an observed
0.3-10.keV flux of ~4E-13 ergs cm**-2 s**-1.
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