TITLE:   GCN CIRCULAR
NUMBER:  14563
SUBJECT: GRB 130505A: Swift detection of a burst with optical afterglow
DATE:    13/05/05 08:36:39 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
A. Melandri (INAF-OAB), P. T. O'Brien (U Leicester),
B. Sbarufatti (INAF-OAB/PSU) and M. Stamatikos (OSU/NASA/GSFC) report
on behalf of the Swift Team:

At 08:22:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130505A (trigger=555163).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 137.060, +17.485 which is 
   RA(J2000)  =  09h 08m 14s
   Dec(J2000) = +17d 29' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a bright peak
followed by a much weaker peak with a total duration of about 20 sec. 
The peak count rate was ~35,500 counts/sec (15-350 keV), at ~0 sec 
after the trigger. 

The XRT began observing the field at 08:24:04.7 UT, 96.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 137.0626, 17.4857 which is equivalent to:
   RA(J2000)  = +09h 08m 15.02s
   Dec(J2000) = +17d 29' 08.5"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 9.3 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 7.35e-09 erg cm^-2 s^-1 (0.2-10
keV). 

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)  =	09:08:14.64 = 137.06100
  DEC(J2000) = +17:29:05.2  =  17.48479
with a 90%-confidence error radius of about 0.74 arc sec. This position is 6.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
14.14 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.04. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo 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.)