[vsnet-grb-info 7148] GRB 081226: Swift detection of a possible short-hard burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8729
SUBJECT: GRB 081226: Swift detection of a possible short-hard burst
DATE:    08/12/26 01:21:22 GMT
FROM:    David Burrows at PSU/Swift  <dxb15 at psu.edu>

O. Godet (U Leicester), W. H. Baumgartner (GSFC/UMBC),
D. N. Burrows (PSU), E. A. Hoversten (PSU), J. A. Kennea (PSU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 01:03:37 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 081226 (trigger=338177).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 120.527, -69.006 which is 
   RA(J2000) = 08h 02m 06s
   Dec(J2000) = -69d 00' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a short hard burst
structure with a duration of about 0.5 sec.  The peak count rate
was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 01:05:11.9 UT, 94.6 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 120.50054, -69.02994 which is
equivalent to:
   RA(J2000)  = 08h 02m 0.13s
   Dec(J2000) = -69d 01' 47.8"
with an uncertainty of 4.5 arcseconds (radius, 90% containment). This
location is 92 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
1.19e+21 cm^-2 (Kalberla et al. 2005). 

The UVOT data has not yet been received so it is not possible to
comment on the UV/optical nature of the burst at this time.  There is
a 7th magnitude source nearby which will complicate UVOT observations. 

Burst Advocate for this burst is O. Godet (og19 AT star.le.ac.uk). 
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.)