GCN Circular 10317

L. Vetere (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), C. Gronwall (PSU),
D. Grupe (PSU), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), C. B. Markwardt (CRESST/GSFC/UMD),
C. Pagani (PSU), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on
behalf of the Swift Team:

At 04:12:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100111A (trigger=382399).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 247.038, +15.557 which is 
   RA(J2000) = 16h 28m 09s
   Dec(J2000) = +15d 33' 25"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a small precursor
peak followed by a main FRED peak for a total duration of about 30 sec. 
The peak count rate was ~3800 counts/sec (15-350 keV), at ~1 sec after
the trigger. 

The XRT began observing the field at 04:13:52.1 UT, 63.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 247.04766, 15.55090 which is equivalent
to:
   RA(J2000)  = 16h 28m 11.44s
   Dec(J2000) = +15d 33' 03.2"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 40 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (4.09e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2 (+2.19/-1.28)
x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 67 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	16:28:11.60 = 247.04833
  DEC(J2000) = +15:33:02.3  = 15.55064
with a 90%-confidence error radius of about 0.62 arc sec. This position is 3.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.58 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.05. 

Burst Advocate for this burst is L. Vetere (vetere AT astro.psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)