TITLE:   GCN CIRCULAR
NUMBER:  18027
SUBJECT: GRB 150716A: Swift detection of a burst
DATE:    15/07/16 07:19:03 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

D. Kocevski (NASA/GSFC/ORAU), A. Y. Lien (GSFC/UMBC),
A. Maselli (INAF-IASFPA), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 07:06:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150716A (trigger=649157).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 278.466, -13.017 which is 
   RA(J2000) = 18h 33m 52s
   Dec(J2000) = -13d 01' 00"
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 30 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began observing the field at 07:08:01.2 UT, 78.1 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 278.4873, -12.9787 which is equivalent to:
   RA(J2000)  = +18h 33m 56.95s
   Dec(J2000) = -12d 58' 43.3"
with an uncertainty of 5.3 arcseconds (radius, 90% containment). This
location is 156 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-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 127 seconds with the White filter
starting 86 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. Because of the density of catalogued stars, further
analysis is required to report an upper limit for any afterglow in the
sub-image. The 8'x8' region for the list of sources generated on-board covers
0.00% of the XRT error circle. Because of the density of catalogued stars,
further analysis is required to report an upper limit for any afterglow in the
region. No correction has been made for the large, but uncertain extinction
expected. 

Burst Advocate for this burst is D. Kocevski (dankocevski 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/too.html.)