TITLE:   GCN CIRCULAR
NUMBER:  14140
SUBJECT: GRB 130122A: Swift detection of a burst with an optical counterpart
DATE:    13/01/22 23:57:00 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

A. Y. Lien (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
N. Gehrels (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU)
and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift Team:

At 23:44:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130122A (trigger=546731).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 194.218, +59.015 which is 
   RA(J2000)  =  12h 56m 52s
   Dec(J2000) = +59d 00' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 30 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 23:46:06.3 UT, 116.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 194.28337, 59.01331 which
is equivalent to:
   RA(J2000)  = 12h 57m 08.01s
   Dec(J2000) = +59d 00' 47.9"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 121 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 9.34
x 10^19 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 121 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
  RA(J2000)  =	12:57:08.34 = 194.28476
  DEC(J2000) = +59:00:53.9  =  59.01496
with a 90%-confidence error radius of about 1.10 arc sec. This position is 6.2
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.95. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.01. 

Burst Advocate for this burst is A. Y. Lien (yarleen 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/too.html.)