[vsnet-grb-info 10726] Swift Trigger 457076: a possible GRB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12149
SUBJECT: Swift Trigger 457076: a possible GRB
DATE:    11/07/11 20:16:56 GMT
FROM:    David Burrows at PSU/Swift  <burrows at astro.psu.edu>

H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. Campana (INAF-OAB), M. M. Chester (PSU),
J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC),
C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), V. Mangano (INAF-IASFPA),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), T. Sakamoto (NASA/UMBC), C. J. Saxton (UCL-MSSL),
G. Stratta (ASDC), C. A. Swenson (PSU), G. Tagliaferri (INAF-OAB) and
T. N. Ukwatta (MSU) report on behalf of the Swift Team:

At 19:44:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible GRB (trigger=457076).  Swift slewed
immediately to the on-board location. 
The BAT on-board calculated location is 
RA, Dec 344.491, -65.600, which is 
   RA(J2000)  =  22h 57m 58s
   Dec(J2000) = -65d 36' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows nothing significant,
which is typical for an image trigger.  We note that because of an observing
constraint, Swift slewed 2.9 minutes after the trigger, so there will be
little real-time XRT and UVOT data on this target. 

The XRT began observing the field at 19:47:29.9 UT, 153.1 seconds after
the BAT trigger. No source was detected in 135 s of promptly downlinked
data. We are waiting for the full dataset to search for an
XRT counterpart. 

UVOT took a finding chart exposure of 144 seconds with the White filter
starting 157 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of
the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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 expected extinction corresponding to E(B-V) of
0.03. 

Due to the marginal significance of the trigger (7.04 sigma),
the loss of some TDRSS data due to a telemetry dump,
and the delayed and short observation of the source with
the narrow field instruments, we will not be able to
confirm or refute this event as a GRB until we have analyzed the
full downlinked data. 

Burst Advocate for this burst is H. A. Krimm (krimm 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.)