TITLE:   GCN CIRCULAR
NUMBER:  19830
SUBJECT: GRB 160821A: Swift detection of a bright burst
DATE:    16/08/21 20:45:20 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

M. H. Siegel (PSU), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC),
D. Malesani (DARK/NBI), K. L. Page (U Leicester) and D. M. Palmer (LANL)
report on behalf of the Swift Team:

At 20:34:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160821A (trigger=709351).  Swift did not slew due to
Sun observing constraint.  The BAT on-board calculated location is 
RA, Dec 171.248, +42.343, which is 
   RA(J2000)  =  11h 24m 59s
   Dec(J2000) = +42d 20' 35"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several small peaks and then
a large peak at ~T+130 sec with a total duration of at least 160 sec. 
The peak count rate was ~24,000 counts/sec (15-350 keV), at ~138 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 10:53 UT on 2016 September 29. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is M. H. Siegel (siegel AT swift.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/too.html.)

[GCN OPS NOTE(21aug16): Per SDB, DM was added to the author list.]