[vsnet-grb-info 4596] GRB 070429: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6355
SUBJECT: GRB 070429: Swift detection of a burst
DATE:    07/04/29 01:51:27 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

S. D. Barthelmy (GSFC), C. B. Markwardt (GSFC/UMD),
K. L. Page (U Leicester), D. M. Palmer (LANL), G. Sato (GSFC/ISAS),
M. Stamatikos (NASA/ORAU) and R. L. C. Starling (U Leicester) report
on behalf of the Swift Team:

At 01:35:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070429 (trigger=277571).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 297.687, -32.388 which is 
   RA(J2000)  =  19h 50m 45s
   Dec(J2000) = -32d 23' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image trigger GRBs,
the BAT light curve shows little obvious variation.  A detailed
light curve will require the data downlinked via Malindi. 

The XRT began observing the field at 01:37:42 UT, 153 seconds after the
BAT trigger. XRT found a fading, uncatalogued X-ray source
located at RA, Dec 297.7034, -32.4052 which is
   RA(J2000)  =  19h 50m 48.8s
   Dec(J2000) = -32d 24' 18.7"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). 
This location is 79 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 2.9e-09 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 161 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 18.5 mag. 
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
0.17 magnitudes.