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GCN Circular 5396

Subject
GRB 060804: Swift-XRT Team Refined Analysis
Date
2006-08-04T19:29:01Z (18 years ago)
From
Kim Page at U.of Leicester <kpa@star.le.ac.uk>
K.L. Page (U. Leicester) & H.Z. Ziaeepour (UCL-MSSL) report on behalf of
the Swift-XRT team:

We have analysed the first 6 orbits of the XRT data obtained for GRB
060804 (trigger 222546). Using these 4340 seconds of data, we find a
refined position of:

RA(J2000)  =  07 28 49.40
Dec(J2000) = -27 12 58.7

with an uncertainty of 3.6 arcsec (90% containment). This is 0.2 arcsec
from the initial XRT position stated in GCN 5394 (Ziaeepour et al.) and
53.8 arcsec from the refined BAT position in GCN 5395 (Tueller et al.)

The X-ray afterglow was sufficiently faint for the XRT to collect data 
only in Photon Counting mode. During the first orbit, the count rate 
remained close to constant, at ~1.5 count s^-1. Orbits 2-6, however, show 
a power-law decay, with a slope alpha = 0.86 +/- 0.22.

There is no evidence for spectral evolution between the first orbit (where 
the light-curve is flat) and the later decay, with the spectrum being well 
fitted with a simple power-law of Gamma = 2.24 +/- 0.22, with the Galactic 
absorbing column of 5.34e21 cm^-2; no excess NH is required. Between 130 
and 700 seconds after the burst, the 0.3-10 keV observed (unabsorbed) flux 
was 6.95e-11 (1.44e-10) erg cm^-2 s^-1.

If the afterglow continues to decay at the same rate, the count rate at 24 
hours is predicted to be 0.012 count s^-1, corresponding to an observed 
(unabsorbed) flux of 6.02e-13 (1.25e-12).

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