TITLE:   GCN CIRCULAR
NUMBER:  7314
SUBJECT: GRB 080218B: Swift detection of a burst
DATE:    08/02/19 00:37:50 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

P. Schady (MSSL-UCL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA),
F. E. Marshall (NASA/GSFC), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (NASA/UMBC), G. Sato (GSFC/ISAS),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
D. E. Vanden Berk (PSU) and P. A. Ward (MSSL-UCL) report on behalf of
the Swift Team:

At 23:57:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080218B (trigger=303631).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 177.951, -53.100 which is 
   RA(J2000) = 11h 51m 48s
   Dec(J2000) = -53d 06' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of at least 12 sec, up to an
interruption in the available data caused by a TDRSS gap. 
The peak count rate was  ~1300 counts/sec (15-350 keV), 
at ~0 sec after the trigger. 

Using prompt downlinked data starting 931 s after the BAT trigger,
we find a bright X-ray source located at RA, Dec 177.9560, -53.0960
which is
   RA(J2000)  = 11 51 49.44
   Dec(J2000) = -53 05 45.7
with an uncertainty of 3.0 arcsec (radius, 90% containment). 
This location is 18 arcseconds from the BAT on-board position,
within the BAT error circle. 

UVOT took a finding chart exposure of 99 seconds with the White
(160-650 nm) filter starting 551 seconds after the BAT trigger.  No
afterglow candidate has been found in the initial data products.  The
UVOT image covers 100% of the XRT error circle and has an estimated
3-sigma limiting magnitude of white = 20.6.  No correction has been
made for the expected extinction corresponding to a reddening of
E(B-V) = 0.17 mag. 

Burst Advocate for this burst is P. Schady (ps 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.)