TITLE:   GCN CIRCULAR
NUMBER:  24807
SUBJECT: GRB 190613B: Swift detection of a burst with an optical counterpart
DATE:    19/06/13 10:58:54 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC),
J.D. Gropp (PSU), N. J. Klingler (PSU), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 10:47:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 190613B (trigger=908329).  Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 305.422, -4.664 which is
   RA(J2000) = 20h 21m 41s
   Dec(J2000) = -04d 39' 49" 
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 15 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~1 sec after the trigger.

The XRT began observing the field at 10:48:39.5 UT, 97.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 305.4294, -4.6461 which is equivalent to:
   RA(J2000)  = 20h 21m 43.06s
   Dec(J2000) = -04d 38' 46.0"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 69 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 4.90e-09 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 105 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =  20:21:43.65 = 305.43189
  DEC(J2000) = -04:38:47.9  =  -4.64665
with a 90%-confidence error radius of about 0.62 arc sec. This position is 9.2
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.76 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.07.

Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it).
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/)