TITLE:   GCN CIRCULAR
NUMBER:  31347
SUBJECT: GRB 220101A: Swift detection of a burst with a bright optical counterpart
DATE:    22/01/01 05:32:40 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. Tohuvavohu (U Toronto), J.D. Gropp (PSU), J. A. Kennea (PSU),
A. Y. Lien (U Tampa), D. M. Palmer (LANL),
T. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (PSU) and
M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 05:09:55 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 220101A (trigger=1091101).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 1.380, +31.753 which is 
   RA(J2000) = 00h 05m 31s
   Dec(J2000) = +31d 45' 09"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT lightcurve shows a complex lightcurve
extending to at least T+170 with a peak of 7000 counts/s (15-350 keV), 
at ~89 sec after the trigger. 

The XRT began observing the field at 05:11:32.2 UT, 80.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 1.3561, 31.7702 which is equivalent to:
   RA(J2000)  = 00h 05m 25.46s
   Dec(J2000) = +31d 46' 12.7"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 95 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. 

The initial flux in the 2.5 s image was 1.30e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 89 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	00:05:24.82 =	1.35340
  DEC(J2000) = +31:46:08.5  =  31.76903
with a 90%-confidence error radius of about 0.61 arc sec. This position is 9.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
14.60 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.056. 

Burst Advocate for this burst is A. Tohuvavohu (aaron.tohu AT gmail.com). 
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/)