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GCN Circular 16190

Subject
GRB140430A: Swift detection of a burst with an optical counterpart
Date
2014-04-30T20:48:23Z (10 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
M. H. Siegel (PSU), W. H. Baumgartner (GSFC/UMBC),
M. M. Chester (PSU), V. D'Elia (ASDC), S. T. Holland (STScI),
J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC) and
T. N. Ukwatta (MSU) report on behalf of the Swift Team:

At 20:33:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140430A (trigger=597722).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 102.929, +23.009 which is 
   RA(J2000)  =  06h 51m 43s
   Dec(J2000) = +23d 00' 34"
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 10 sec.  The peak count rate
was ~4500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 20:34:27.3 UT, 50.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 102.9359, 23.0227 which is equivalent to:
   RA(J2000)  = +06h 51m 44.62s
   Dec(J2000) = +23d 01' 21.7"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
location is 54 arcseconds from the BAT onboard position, within the BAT
error circle. 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 3.99e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 183 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	06:51:44.61 = 102.93589
  DEC(J2000) = +23:01:25.2  =  23.02367
with a 90%-confidence error radius of about 0.62 arc sec. This position is 3.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.16 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.14. 

Burst Advocate for this burst is M. H. Siegel (siegel AT swift.psu.edu). 
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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