[vsnet-grb-info 4646] GRB 070510: Swift detection of a possible burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6401
SUBJECT: GRB 070510: Swift detection of a possible burst
DATE:    07/05/10 06:44:48 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

P. Schady (MSSL-UCL), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), O. Godet (U Leicester),
T. Mineo (INAF-IASFPA), P. T. O'Brien (U Leicester), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
E. Troja (INAF-IASFPA) report on behalf of the Swift Team:

At 05:56:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located possible GRB 070510 (trigger=278987) as it was approaching 
the South Atlantic Anomaly (SAA), with a processing delay of 
approximately 1 minute due to the data backlog from the high count 
rates.  Swift slewed immediately to the burst.  The BAT on-board 
calculated location is 
RA, DEC 343.014, +47.933 which is
  RA(J2000) =  22h 52m 03s
  Dec(J2000)= +47d 56' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single short
peak of ~1000 counts/s at the time of the trigger, but the elevated
background (4x normal) makes it difficult to characterize the burst
using only the TDRSS data.  The data is terminated by entrance 
into the SAA at T+17 s. 

The XRT began taking data at 05:58:50 UT, 131 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in
the image and no prompt position is available due to the spacecraft
entering the SAA during the slew. We are waiting for down-linked data
to detect and determine a position for the source. 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650nm) filter starting 1361 seconds after the BAT trigger. No
afterglow candidate has been found in the initial data products. The
typical 3-sigma upper limit has been about 18.5 mag. No correction
has been made for the expected extinction corresponding to E(B-V) of
0.20 magnitudes.