[vsnet-grb-info 14955] GRB 140512A: Swift detection of a burst with an optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16249
SUBJECT: GRB 140512A: Swift detection of a burst with an optical counterpart
DATE:    14/05/12 19:56:20 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at milkyway.gsfc.nasa.gov>

C. Pagani (U Leicester), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
J. A. Kennea (PSU), V. Mangano (PSU), C. J. Mountford (U Leicester),
K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), C. A. Swenson (PSU) and T. N. Ukwatta (MSU) report
on behalf of the Swift Team:

At 19:31:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140512A (trigger=598819).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 289.371, -15.100 which is 
   RA(J2000)  =  19h 17m 29s
   Dec(J2000) = -15d 05' 59"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a multi-peak event
with a total duration of about 170 sec.  The peak count rate
was ~8000 counts/sec (15-350 keV), at ~122 sec after the trigger. 

The XRT began observing the field at 19:33:27.5 UT, 98.4 seconds after
the BAT trigger. The position determined from promptly downlinked data
differs significantly from the on-board position, suggesting that the
XRT may have centroided on a cosmic ray; the initial XRT position
notice should be treated with caution. Using promptly downlinked data
we find an uncatalogued X-ray source located at RA, Dec 289.36925,
-15.09492 which is equivalent to:
   RA(J2000)  = 19h 17m 28.62s
   Dec(J2000) = -15d 05' 41.7"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 19 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. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 106 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	19:17:28.78 = 289.36991
  DEC(J2000) = -15:05:39.2  = -15.09423
with a 90%-confidence error radius of about 0.61 arc sec. This position is 3.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
15.01 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.16. 

Burst Advocate for this burst is C. Pagani (cp232 AT star.le.ac.uk). 
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.)