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GCN Circular 16214

Subject
GRB 140506A: Swift detection of a burst with an optical counterpart
Date
2014-05-06T21:28:16Z (10 years ago)
From
David Burrows at PSU/Swift <burrows@astro.psu.edu>
B.P. Gompertz (U Leicester), D. N. Burrows (PSU), S. B. Cenko (GSFC),
S. T. Holland (Eureka), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (NASA/GSFC/ORAU), V. Mangano (PSU),
K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of
the Swift Team:

At 21:07:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140506A (trigger=598284).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 276.790, -55.562 which is 
   RA(J2000) = 18h 27m 10s
   Dec(J2000) = -55d 33' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 10 sec.  The peak count rate
was ~6500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 21:09:14.7 UT, 97.9 seconds after
the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located
at RA, Dec 276.7752, -55.6353 which is equivalent to:
   RA(J2000)  = +18h 27m 6.05s
   Dec(J2000) = -55d 38' 07.1"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 265 arcseconds from the BAT onboard position. 
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 1.01e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
320 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	18:27:06.03 = 276.77513
  DEC(J2000) = -55:38:08.8  = -55.63577
with a 90%-confidence error radius of about 0.63 arc sec. This position is 1.7
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.46 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.09. 

Burst Advocate for this burst is B.P. Gompertz (bpg6 AT 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.)
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