[vsnet-grb-info 15239] GRB 140706A: Swift detection of a burst with an optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16531
SUBJECT: GRB 140706A: Swift detection of a burst with an optical counterpart
DATE:    14/07/06 19:42:34 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),
S. B. Cenko (GSFC), J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 19:33:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140706A (trigger=603587).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 49.306, -38.059 which is 
   RA(J2000) = 03h 17m 13s
   Dec(J2000) = -38d 03' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows two main peaks
with a total duration of about 55 sec.  The peak count rate
was ~1700 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 19:34:46.0 UT, 72.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 49.29517, -38.05083 which
is equivalent to:
   RA(J2000)  = 03h 17m 10.84s
   Dec(J2000) = -38d 03' 03.0"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This
location is 42 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 5.09e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
  RA(J2000)  =	03:17:10.40 =  49.29332
  DEC(J2000) = -38:03:07.4  = -38.05205
with a 90%-confidence error radius of about 1.10 arc sec. This position is 4.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.05. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.02. 

Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). 
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.)