[vsnet-grb-info 5839] GRB 080319D: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7490
SUBJECT: GRB 080319D: Swift XRT refined analysis
DATE:    08/03/20 20:01:09 GMT
FROM:    Dirk Grupe at PSU/Swift-XRT  <grupe at astro.psu.edu>

Dirk Grupe and Peter Brown (PSU)  report on behalf of the Swift-XRT team:

The Swift-XRT started observing GRB 080319D (trigger=306793, Brown et 
al. GCN
7453) at 17:07:37 UT, 148 seconds after the BAT trigger.

The astrometrically corrected X-ray position (using the XRT-UVOT 
alignment and
matching UVOT field sources to the USNO-B1 catalogue) is: RA, Dec = 
99.47254,
+23.94275 which is equivalent to:

RA (J2000):  06 37 53.41
Dec (J2000): +23 56 33.9

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

The 0.3-10 keV X-ray light curve starts with three flares up to 20 
counts/s. The
afterglow decays very fast and started to flatten at about 1000 s after the
burst. The light curves shows another break at about 5 ks after the 
burst and is
currently decaying with a decay slope of 1.3.

The spectrum of the PC data can be well fit by an absorbed single
powerlaw with photon  index 2.12 ± 0.27 and column density of
 (3.8 ± 1.4)e21 cm-2.  This is in excess of
the Galactic column density of 2.17e21 cm-2 in this direction.
Using this spectrum we estimated a count rate to flux conversion of
1 count/s converts to 6.28e-11 ergs/cm2/s.

If the underlying powerlaw decay continues as is, we predict an XRT 
count rate
of 1.6e-3 counts/s at T+24 hours and 6.5e-4 counts/s at T+48 hours
after the burst, or 1.0e-13 ergs/s/cm2 and 4.1e-14 ergs/s/cm2, 
respectively.

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