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GCN Circular 6377

GRB070506: Swift XRT refined analysis
2007-05-06T17:16:51Z (17 years ago)
Claudio Pagani at PSU/Swift-XRT <>
C. Pagani, L. Vetere, J. L. Racusin and J. A. Kennea (PSU) report on  
behalf of the Swift Team:

We have analysed the first two orbits of Swift XRT data from GRB  
070506 (trigger number 278693, GCN Circ 6375.), for a total photon  
counting mode exposure of 2.8ks.
The XRT started collecting data in Image mode at 05:38:05 UT, 127  
seconds after the BAT trigger, but observations in Photon Counting  
mode were delayed due to the SAA, starting 432 seconds after the  
trigger. The refined XRT position from 2.8ks of PC data is
RA,DEC(J200) = 347.2179, +10.7217
which is
RA(J2000) = 23d 08m 52.30s
DEC(J200) = +10d 43' 18.2"

with an uncertainty of 5.4 arcsec (radius, 90% containment).
This is  5.1 arcsec from the initial X-ray position and 2.4 arcsec  
from the UVOT optical counterpart (GCN 6375).

The XRT light curve created from the first two orbits of PC data  
reveals a decaying source with hints of flaring activity. A power law  
fit yields a decay slope of 0.55+/-0.06.

The X-ray spectrum of the PC data, modeled with an absorbed power law  
gives a photon index of 2.5+/-0.5 and a total column density of NH= 
(1.8+/-1.1)e21 cm**-2, in excess of the Galactic value of 0.4e21 cm**-2.
The absorbed (unabsorbed) 0.3-10.0keV flux for this spectrum was  
3.0E-12 (5.5E-12) ergs cm^-2 s^-1.

Assuming the source continues to decay at the same rate, we predict  
an XRT count rate of 2.2e-2 count/s at T+24 hours, which corresponds  
to an observed (unabsorbed) flux of 0.8E-12 (1.5E-12) ergs cm^-2 s^-1.

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