[vsnet-grb-info 4961] GRB 070729: Swift detection of a short hard burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6678
SUBJECT: GRB 070729: Swift detection of a short hard burst
DATE:    07/07/29 00:48:05 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

C. Guidorzi (Univ Bicocca&INAF-OAB), L. M. Barbier (NASA/GSFC),
S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), A. Moretti (INAF-OAB),
D. M. Palmer (LANL), M. Stamatikos (NASA/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 00:25:53 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070729 (trigger=286373).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 56.322, -39.312 which is 
   RA(J2000)  =  03h 45m 17s
   Dec(J2000) = -39d 18' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows three overlapping
peaks with a total duration of about 1.5 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began taking data at 00:27:21 UT, 87 seconds after the BAT
trigger.  The XRT on-board centroid algorithm did not find a source
in the image. 
Using prompt downlinked data, we find an uncatalogued X-ray
source located at RA, Dec 56.3147, -39.3234 which is
   RA(J2000)  = 03 45 15.52
   Dec(J2000) = -39 19 24.2
with an uncertainty of 5.7 arcsec (radius, 90% containment). 
This location is 45 arcseconds from the BAT on-board position,
within the BAT error circle. 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 91 seconds after the BAT trigger. No
afterglow candidate has been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical
3-sigma upper limit has been about 18.5 mag. No correction has been
made for the expected Galactic extinction corresponding to a
reddening of 0.02 mag. 

Burst Advocate for this burst is C. Guidorzi (cristiano.guidorzi AT brera.inaf.it). 
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.)