[vsnet-grb-info 4075] GRB 061202: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5886
SUBJECT: GRB 061202: Swift detection of a burst
DATE:    06/12/02 08:37:28 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

T. Sakamoto (NASA/ORAU), S. D. Barthelmy (GSFC),
W. B. Landsman (NASA/GSFC), K. M. McLean (LANL/UTD), C. Pagani (PSU),
D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Perri (ASDC),
G. Stratta (ASDC) and L. Vetere (PSU) report on behalf of the Swift
Team:

At 08:11:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061202 (trigger=241963).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is RA, Dec 105.642, -74.665 which is 
   RA(J2000)  =  07h 02m 34s
   Dec(J2000) = -74d 39' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a weak peak with
a duration of about 10 sec.  The peak count rate
was ~400 counts/sec (15-350 keV), at ~2 sec after the trigger.  We note
that during the slew there is a large increase in the count rate (T+70 to
T+100 sec) which may be due to the GRB or it may be due to a source
passing through the FOV during the slew. 

The XRT began observing the field at 08:13:43 UT, 119 seconds after
the BAT trigger. XRT found a fading X-ray source located at RA(J2000)
= 07h 02m 06.5s, Dec(J2000) = -74d 41' 55.9", with an estimated
uncertainty of 4.1 arcseconds (90% confidence radius). This is a
ground calculated position based on prompt downlinked data. This
location is 165 arcseconds from the BAT on-board position, within the
BAT error circle. The initial flux in the 2.5s image was 3.6e-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 128 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
0.15.