GCN Circular 15765

M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC),
P. A. Evans (U Leicester), J. A. Kennea (PSU),
A. Y. Lien (NASA/GSFC/ORAU), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL),
M. H. Siegel (PSU) and C. A. Swenson (PSU) report on behalf of the
Swift Team:

At 12:51:09 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140129B (trigger=585149).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 326.763, +26.207 which is 
   RA(J2000) = 21h 47m 03s
   Dec(J2000) = +26d 12' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 2 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 12:52:16.5 UT, 67.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 326.7574, 26.2065 which
is equivalent to:
   RA(J2000)  = 21h 47m 01.77s
   Dec(J2000) = +26d 12' 23.3"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 18 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 (5.58 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.7
(+2.52/-2.09) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 356 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	21:47:01.67 = 326.75695
  DEC(J2000) = +26:12:22.9  =  26.20637
with a 90%-confidence error radius of about 0.61 arc sec. This position is 1.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.92 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.09. 

Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.inaf.it). 
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.)