TITLE:   GCN CIRCULAR
NUMBER:  11473
SUBJECT: GRB 101219B: Swift detection of a burst with an optical afterglow
DATE:    10/12/19 16:52:57 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

J. M. Gelbord (PSU), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
M. M. Chester (PSU), S. T. Holland (CRESST/USRA/GSFC),
J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), D. M. Palmer (LANL) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 16:27:53 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 101219B (trigger=440635).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 12.257, -34.532 which is 
   RA(J2000)  =  00h 49m 02s
   Dec(J2000) = -34d 31' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  This is an image trigger so as is typical,
the BAT lightcurve does not show anything. 

The XRT began observing the field at 16:30:19.8 UT, 146.3 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 12.2306, -34.5662 which is equivalent to:
   RA(J2000)  = 00h 48m 55.34s
   Dec(J2000) = -34d 33' 58.3"
with an uncertainty of 5.6 arcseconds (radius, 90% containment). This
location is 145 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 156 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	00:48:55.35 =  12.23061
  DEC(J2000) = -34:33:59.5  = -34.56652
with a 90%-confidence error radius of about 0.62 arc sec. This position is 1.2
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.84 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is J. M. Gelbord (jgelbord 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.)