[vsnet-grb-info 4638] GRB 070509: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6394
SUBJECT: GRB 070509: Swift detection of a burst
DATE:    07/05/09 03:17:03 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

L. Vetere (PSU), S. D. Barthelmy (GSFC), M. M. Chester (PSU),
D. Grupe (PSU), S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC),
C. Pagani (PSU), D. M. Palmer (LANL), J. L. Racusin (PSU),
M. Stamatikos (NASA/ORAU) and D. E. Vanden Berk (PSU) report on
behalf of the Swift Team:

At 02:48:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070509 (trigger=278903).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 237.927, -78.681 which is 
   RA(J2000)  =  15h 51m 42s
   Dec(J2000) = -78d 40' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single FRED-like peak
with a duration of about 10 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began taking data at 02:49:35 UT, 68 seconds after the BAT
trigger. XRT found a faint, uncatalogued X-ray source. The ground 
calculated location is  RA, Dec 237.9592, -78.6511 which is   
   RA(J2000) = 15h 51m 50.2s   
   Dec(J2000) = -78d 39'04.0" 
with an uncertainty of 4.6 arcsec (radius, 90% containment,
including  systematic uncertainty). This location is 1.8 arcmin from
the BAT on-board position, within the BAT error circle. 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 72 seconds after the BAT trigger, and a
finding chart exposure of 400 seconds in V starting 177 seconds after
the BAT trigger. No afterglow candidate has been found in the initial
data products. The 2.7'x2.7' sub-image covers none of the XRT error
circle; the 8'x8' region for the list of sources generated on-board
covers 100% of the XRT 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 0.14.