[vsnet-grb-info 26024] GRB 200716C: Swift detection of a burst with an optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28124
SUBJECT: GRB 200716C: Swift detection of a burst with an optical counterpart
DATE:    20/07/16 23:10:50 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J.D. Gropp (PSU), N. J. Klingler (PSU),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and B. Sbarufatti (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 22:57:41 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 200716C (trigger=982707).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 196.013, +29.630 which is 
   RA(J2000) = 13h 04m 03s
   Dec(J2000) = +29d 37' 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 10 sec.  The peak count rate
was ~30000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 22:59:04.2 UT, 82.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 196.0100, 29.6465 which is equivalent to:
   RA(J2000)  = 13h 04m 2.40s
   Dec(J2000) = +29d 38' 47.4"
with an uncertainty of 6.6 arcseconds (radius, 90% containment). This
location is 60 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 0.1 s image was 1.10e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 93 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 13:04:02.43 = 196.01011
DEC(J2000) = +29:38:40.6 = 29.64460
with a 90%-confidence error radius of about 0.75 arc sec. This position is 6.85
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.34 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.01. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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/)