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GCN Circular 7882

Subject
GRB 080613A: Swift-XRT detection of the afterglow
Date
2008-06-14T09:15:27Z (16 years ago)
From
Cristiano Guidorzi at INAF-OAB <cristiano.guidorzi@brera.inaf.it>
C. Guidorzi (INAF-OAB) and C. B. Markwardt (CRESST/GSFC/UMD) report
on behalf of the Swift-XRT team:

The Swift XRT began observing the INTEGRAL GRB 080613A
(Gotz et al., GCN Circ 7871) on June 13, 16:19 UT, 24.2 ks after
the INTEGRAL trigger. The data consist of 3.6 ks observed in Photon 
Counting
mode.

We detect a single X-ray source within the INTEGRAL error circle at the 
position
RA, Dec = 213.27213, +5.17256 which is equivalent to:

RA (J2000):  14 13 05.31
Dec (J2000): +05 10 21.2

with an uncertainty of 5.2 arcsec (radius, 90% confidence).
This position lies 4.9" from the optical afterglow found with the 
Faulkes Telescope North
(Guidorzi et al., GCN Circ. 7872) and later confirmed by GROND (Clemens 
et al. GCN Circ. 7880)
and Swift-UVOT (Hoversten and Holland, GCN Circ. 7881), and is
therefore consistent with being the X-ray afterglow of GRB 080613A.

Presently there is marginal evidence for fading: a power-law fit of the 
light curve
gives a decay index of 1.2 � 1.5, so still compatible with a constant 
rate of
of (2.8 � 0.3)e-2 counts/s.

Forced by the small number of counts, we extracted the 0.3-10 keV spectrum
from a 10-pixel radius circular region and adopted the Cash statistics.
The spectrum can be fit with a power law with an absorbing column
density fixed to the Galactic value (2.0e20 cm-2) and a photon index of
1.3 � 0.3. The observed (unabsorbed) 0.3-10 keV flux
is 1.50 (1.53)e-12 erg cm-2 s-1.

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