[vsnet-grb-info 2818] GRB 060204B: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4655
SUBJECT: GRB 060204B: Swift detection of a burst
DATE:    06/02/04 15:26:50 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott at lheamail.gsfc.nasa.gov>

A. Falcone (PSU), L. Barbier (GSFC), S. Barthelmy (GSFC),
D. Burrows (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC),
S. Hunsberger (PSU), J. Kennea (PSU), H. Krimm (GSFC/USRA),
F. Marshall (GSFC), D. Morris (PSU), D. Palmer (LANL),
E. Rol (U Leicester), T. Sakamoto (GSFC)
on behalf of the Swift team:

At 14:34:24 UT, Swift-BAT triggered and located GRB 060204B (trigger=180241).
The spacecraft slewed immediately.  The BAT on-board calculated location is
RA,Dec 211.795d,+27.683d {14h 07m 11s,+27d 40' 60"} (J2000), with an uncertainty
of 3 arcmin (radius, 90% containment, stat+sys).  There is missing data
in the BAT TDRSS lightcurve message, so we can not say anything about the
lightcurve at this initial quicklook.  However, it appears to be a long burst.
We will have to wait for the full Malindi data download.

The spacecraft slewed promptly and the XRT began observing the GRB at
14:35:59 UT, 94.5 sec after the BAT trigger.  A bright, uncatalogued,
flaring source was found by the on-board centroiding algorithm at
RA(J2000)=+14h 07m 14.6s
DEC(J2000)=+27d 40' 34"
with an uncertainty of 6 arcseconds radius (90% containment).
This position lies 57 arcseconds from the center of the BAT error circle. 

UVOT took a finding chart exposure of 200 seconds with the V filter
starting 101 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 18th 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 18.0 mag.  No correction has been made for
the expected extinction of about 0.1 magnitudes.

We note there is a cluster of galaxies at z=0.156 in this field.

Even though the initial Notices went out with the Star Tracker Loss-of-Lock
flag set, ground analysis has shown that the s/c was tracking accurately
and that the position is good.

We are currently in the Malindi telemetry downlink gap.  We will not have
further data for another 8 hours.