[vsnet-grb-info 20601] Swift Trigger 831888: a possible GRB or Galactic transient

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22699
SUBJECT: Swift Trigger 831888: a possible GRB or Galactic transient
DATE:    18/05/11 08:51:18 GMT
FROM:    Boris Sbarufatti at PSU  <bxs60 at psu.edu>

A. Tohuvavohu (PSU), P. A. Evans (U Leicester), J.D. Gropp (PSU),
J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester)
and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 07:15:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible burst or a Galactic transient (trigger=831888).  
Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 214.508, -62.457 which is 
   RA(J2000) = 14h 18m 02s
   Dec(J2000) = -62d 27' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve does not show anything
significant, as it typical for image triggers (duration is 10.4 min 
in this case). 

The XRT began observing the field at 07:33:44.3 UT, 1085.3 seconds
after the BAT trigger. No source was detected in 764 s of promptly
downlinked data. We are waiting for the full dataset to detect and
localise the XRT counterpart. 
We note that the BAT error circle was not covered by the promptly 
downlinked data. 

Because of a known bug in the onboard identification software that 
affects image triggers longer than 7 minutes happening at the time of 
a spacecraft slew we believe the identification with a known source  
in the on-board catalog is incorrect. Since the BAT position is close
to the galactic plane (l,b = 312.76,-1.25) at the moment we cannot
confidently determine if this is a GRB or a galactic source. We are
waiting for the full dataset  to properly identify the nature of this
trigger. 

Burst Advocate for this burst is A. Tohuvavohu (aaronb AT swift.psu.edu). 
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.)