TITLE:   GCN CIRCULAR
NUMBER:  14841
SUBJECT: GRB 130609B: Swift detection of a burst with an optical counterpart
DATE:    13/06/09 21:46:41 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), J. A. Kennea (PSU), D. Malesani (DARK/NBI),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC) and
A. Maselli (INAF-IASFPA) report on behalf of the Swift Team:

At 21:38:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130609B (trigger=557828).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 53.754, -40.153 which is 
   RA(J2000) = 03h 35m 01s
   Dec(J2000) = -40d 09' 11"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
with a total duration of at least 200 sec.  The peak count rate
was ~8500 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 21:39:56.4 UT, 76.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 53.7695, -40.1747 which is equivalent to:
   RA(J2000)  = +03h 35m 4.68s
   Dec(J2000) = -40d 10' 28.9"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
location is 89 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. 

UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting 84 seconds after the BAT trigger. There is a candidate
afterglow in the list of sources generated on-board at
  RA(J2000)  =	03:35:05.11 =  53.77128
  DEC(J2000) = -40:10:26.6  = -40.17406
with a 90%-confidence error radius of about 1.10 arc sec. This position is 5.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
15.71. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.01. 

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.)