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GCN Circular 4992

GRB 060421: Swift-XRT refined analysis
2006-04-21T15:32:18Z (18 years ago)
Kim Page at U.of Leicester <>
M.R. Goad, K.L. Page (U Leicester) and D.N. Burrows (PSU) report on 
behalf of the Swift-XRT team:

We have analysed the first 14 ks of Photon Counting (PC) mode data,
starting 97 seconds after the BAT trigger time, determining a refined
position of

RA (J2000):   22 54 32.63
Dec(J2000):  +62 43 50.07
with an estimated uncertainty of 3.8 arcsec (90% containment). This is 1.7 
arcsec from the initial XRT position given by Goad & Page in GCN 4987 and 
16.2 arcsec from the on-board BAT position quoted in GCN 4985 (Goad et 

The X-ray source was initially quite faint, with a peak count rate of only
~1 count s^-1. The light-curve shows a flat decay of alpha = 0.49 +/-
0.29, breaking to a steeper slope of alpha = 1.54 +/- 0.36, approximately
1500 seconds after the burst.

Because of the faintness of the afterglow, only 3 seconds of data were
obtained in Windowed Timing mode before switching into PC. The first orbit
of PC data (97-717 seconds post-trigger) can be modelled with a simple
power-law of Gamma = 1.54 +/- 0.34, with the Galactic absorbing column of
1e22 cm^-2. The observed (unabsorbed) flux over 0.3-10 keV for this time
period is 3.78e-11 (5.64e-11) erg cm^-2 s^-1.

Assuming the current rate of decay continues, the estimated count rate at 
24 hours is 4.2e-3 count s^-1, corresponding to an observed (unabsorbed) 
flux of 4.55e-14 (6.38e-14) erg cm^-2 s^-1.

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