GCN Circular 4487

M. Perri (ASDC), S. Barthelmy (GSFC), P. Boyd (GSFC), D. Burrows (PSU),
J. Cummings (GSFC/NRC), N. Gehrels (GSFC), C. Gronwall (PSU),
J. Kennea (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
F. Marshall (GSFC), D. Palmer (LANL), T. Sakamoto (GSFC)
on behalf of the Swift team:

At 20:15:43 UT, Swift-BAT triggered and located GRB 060111B (trigger=176918).
The spacecraft slewed immediately.  The BAT on-board calculated location is
RA,Dec 286.337d,+70.360d {19h 05m 21s,+70d 21' 35"} (J2000), with an
uncertainty of 3 arcmin (radius, 90% containment, stat+sys).
The BAT light curve shows a main peak with a total duration of at least 25 sec.
There is a possible second peak at T+55 sec.  The peak count rate was
~2000 counts/sec (15-350 keV), at ~2 seconds after the trigger.

XRT began observing the field at 20:17:02 UT, 79 seconds after the BAT trigger.
On-board centroiding found a previously uncatalogued fading X-ray source
in the field of view at the following coordinates:
RA(J2000) = 19 05 42.3
Dec(J2000)= 70 22 37
This location is 124 arcseconds from the BAT position.  The estimated
uncertainty is 8 arcseconds (90% confidence radius), including
a systematic error of about 5 arcseconds due to an XRT boresight offset not
currently corrected on-board. The initial flux was 1.7e-09 ergs/cm2/s (0.2-10 keV).

UVOT took a finding chart exposure of 200 seconds with the B filter
starting 84 seconds after the BAT trigger.  There is a candidate
afterglow in the list of sources generated on-board at (RA,DEC) (J2000)
of (286.4270,70.3760) or (19h 05m 42.48s,+70d 22' 33.6") with a 1-sigma
error radius of about 0.5 arc sec.  This position is 3.6 arc sec. from
the center of the XRT error circle.  The estimated V magnitude is 17.2
with a 1-sigma error of about 0.5 mag.  No correction has been made for
the expected visual extinction of about 0.4 magnitudes.  This source
was detected in a 200 sec B finding chart image taken beginning at
20:20:34 UT with a B magnitude of 19.55.  We did not receive the V finding
chart through TDRSS, so are unable to confirm the V magnitude from the
V parameterized source list.