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GCN Circular 14620

Subject
GRB 130511A: Swift detection of a burst with an optical counterpart
Date
2013-05-11T11:42:24Z (11 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
H. A. Krimm (CRESST/GSFC/USRA), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 11:30:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130511A (trigger=555600).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 196.639, +18.698 which is 
   RA(J2000) = 13h 06m 33s
   Dec(J2000) = +18d 41' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single short
peak of duration ~0.5 sec followed by a 10-second tail. The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 11:31:58.9 UT, 71.6 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 196.64698, 18.70893 which is equivalent
to:
   RA(J2000)  = 13h 06m 35.28s
   Dec(J2000) = +18d 42' 32.1"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 47 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.08 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+1.47/-1.33) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 74 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	13:06:34.96 = 196.64567
  DEC(J2000) = +18:42:36.0  =  18.70999
with a 90%-confidence error radius of about 0.64 arc sec. This position is 7.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.18 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.03. 

Burst Advocate for this burst is H. A. Krimm (krimm 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.)
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