GCN Circular 8209

M. De Pasquale (UCL-MSSL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), N. Gehrels (NASA/GSFC),
C. Gronwall (PSU), J. A. Kennea (PSU), J. Mao (INAF-OAB),
C. B. Markwardt (CRESST/GSFC/UMD) and G. Tagliaferri (INAF-OAB)
report on behalf of the Swift Team:

At 12:52:21 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a source which is spatially consistant with LS I +61 303
(trigger=324362).  Swift slewed immediately to the source. 
The BAT on-board calculated location is 
RA, Dec 40.074, +61.257, which is 
   RA(J2000)  =  02h 40m 18s
   Dec(J2000) = +61d 15' 26"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single spike
structure with a duration of about 200 milisec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 13:07:42.8 UT, 921.1 seconds after
the BAT trigger. XRT was not able to localize any source in the field, 
the reported centroid being on a cosmic ray event. We are currently 
awaiting a full data downlink in approximately 3 hours to determine if the 
source was detected by XRT. 

We note that LS I +61 303 is one of the 23 sources in the Fermi/LAT
public release list. 

Burst Advocate for this burst is M. De Pasquale (mdp AT mssl.ucl.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.)