TITLE:   GCN CIRCULAR
NUMBER:  27756
SUBJECT: GRB 200519A: Swift detection of a burst with an optical afterglow
DATE:    20/05/19 11:42:49 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

B. Sbarufatti (PSU), S. B. Cenko (GSFC), C. Gronwall (PSU),
J.D. Gropp (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC) and K. L. Page (U Leicester) report on
behalf of the Neil Gehrels Swift Observatory Team:

At 11:20:23 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200519A (trigger=973140).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 255.334, -30.380 which is 
   RA(J2000) = 17h 01m 20s
   Dec(J2000) = -30d 22' 47"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 80 sec.  The peak count rate
was ~37000 counts/sec (15-350 keV), at ~23 sec after the trigger. 

The XRT began observing the field at 11:21:13.3 UT, 49.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 255.3327, -30.3782 which is equivalent to:
   RA(J2000)  = 17h 01m 19.85s
   Dec(J2000) = -30d 22' 41.5"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 7.6 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 1.36e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 57 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	17:01:20.00 = 255.33335
  DEC(J2000) = -30:22:40.9  = -30.37803
with a 90%-confidence error radius of about 0.61 arc sec. This position is 2.1
arc sec. from the center of the XRT error circle. The estimated magnitude is
15.38 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.47. 

Burst Advocate for this burst is B. Sbarufatti (bxs60 AT 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/)