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GCN Circular 8000

Subject
GRB 080723: Swift detection of a burst
Date
2008-07-23T04:40:07Z (16 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
M. Stamatikos (NASA/ORAU), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), S. T. Holland (CRESST/USRA/GSFC),
S. D. Hunsberger (PSU), H. A. Krimm (CRESST/GSFC/USRA),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 04:19:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080723 (trigger=317662).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 274.512, -6.923 which is 
   RA(J2000) = 18h 18m 03s
   Dec(J2000) = -06d 55' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Because the BAT light curve has not been
received, we cannot comment on the burst profile at this time.  However,
there is a strong 8.4 sigma excess detected in the scaled map image, 
which strongly suggests a real gamma-ray burst occurred. 

The XRT began observing the field at 04:20:50.2 UT, 85.8 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 274.48985,
-6.89931 which is equivalent to:
   RA(J2000)  = 18h 17m 57.56s
   Dec(J2000) = -06d 53' 57.5"
with an uncertainty of 2.7 arcseconds (radius, 90% containment). This
location is 116 arcseconds from the BAT onboard position, within the
BAT error circle. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (3.94e+21
cm^-2, Kalberla et al. 2005), with an excess column of 5.7
(+6.36/-4.59) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 92 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 0% of
the XRT error circle.  The 8'x8' region for the list of sources generated on-
board covers 100% of the BAT error circle. The list of sources is typically 
complete to about 18 mag.  No correction has been made for the large Galactic 
expected extinction corresponding to E(B-V) of 1.3 mag. 

Burst Advocate for this burst is M. Stamatikos (michael AT milkyway.gsfc.nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
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