[vsnet-grb-info 2642] GRB 060111: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4479
SUBJECT: GRB 060111: Swift detection of a burst
DATE:    06/01/11 05:05:37 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott at lheamail.gsfc.nasa.gov>

S. Zane (MSSL-UCL), S. Barthelmy (GSFC), A. Beardmore (U Leicester),
A. J. Blustin (UCL-MSSL), D. Burrows (PSU), J. Cummings (GSFC/NRC),
N. Gehrels (GSFC), M. Goad (U Leicester), J. Kennea (PSU),
C. Markwardt (GSFC/UMD), F. Marshall (GSFC), D. Palmer (LANL)
on behalf of the Swift team:

At 04:23:06 UT, Swift-BAT triggered and located GRB 060111 (trigger=176818).
The spacecraft slewed immediately.  The BAT on-board calculated location is
RA,Dec 276.212d,+37.602d {18h 24m 51s,+37d 36' 08"} (J2000), with an
uncertainty of 3 arcmin (radius, 90% containment, stat+sys).  The BAT light
curve shows a  single peak structure with a total duration of ~20 sec.
The peak count rate was ~3000 counts/sec (15-350 keV), at ~5 sec
after the trigger.

The XRT began observing the field at 04:24:12 UT (66 sec after the burst).
The instrument found a bright, variable, uncataloged X-ray source located at:
RA(J2000) = 18h 24m 48.9s
Dec(J2000) = +37d 36' 21"
This location is 27.4 arcseconds from the BAT position.  The estimated
uncertainty is 8 arcseconds (90% confidence radius), including about 5
arcseconds systematic error due to an XRT boresight offset not currently
corrected on-board.  The initial flux was 8E-10 ergs/cm2/s (0.2-10 keV).

UVOT took a finding chart exposure of 200 seconds with the V filter
starting 72 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 visual extinction of about 0.1 magnitudes.

We are currently in the portion of the orbits where the spacecraft does not 
pass over the Malindi downlink station.  Therefore, it will be at least
7 hours before we have access to the full data set for the refined analyses.