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GCN Circular 3752

Subject
GRB 050803: early Swift XRT analysis results
Date
2005-08-04T03:50:32Z (19 years ago)
From
Judith Racusin at PSU <racusin@astro.psu.edu>
J. Racusin (PSU), C. Pagani (INAF-OAB), D. Burrows (PSU), K. Page (U. 
Leicester), on behalf on the Swift XRT team:

We have analyzed the first 3 orbits of Swift XRT data from GRB 050803 
(Band et al., GCN 3748).  The refined coordinates from the downlinked 
ground processed data of the X-ray afterglow are:

RA(J2000): 23h 22m 37.8s
Dec(J2000): +5d 47' 5.5"

This position is 60 arcseconds from the BAT position given in GCN 3748 
(Band et al.), and 2.1 arcseconds from the on-board determined XRT 
position reported in GCN 3748.  We estimate an uncertainty of 6 arcseconds 
radius (90% containment).

Data in Window Timing (WT) mode began at 19:16:40 UT, 160 seconds after 
the BAT trigger, and continued for 84s before switching into Photon 
Counting (PC) mode.  The 0.3-10 keV afterglow light curve shows a rapidly 
fading X-ray source which can be fitted with a power law of slope 
alpha=-5.4+/-0.1 up to a break around 290 s, after which the light curve 
flattens where it can be fitted with a power law of slope 
alpha=-0.53+/-0.02 as far as current data extends.

The predicted flux at 24 hours after the trigger is 2.96E-12 erg cm^-2 
s^-1.

A preliminary spectral fit to this data gives a spectral power law photon 
index of 1.8 +/- 0.1 with nH=(19.8+/-3.2)E20 cm^-2.  This is significantly 
higher than the Galactic nH along the line of sight which is 5.6E+20 
cm^-2.
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