[vsnet-grb-info 18346] GRB 160815A: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19794
SUBJECT: GRB 160815A: Swift detection of a burst
DATE:    16/08/15 12:16:28 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

C. B. Markwardt (NASA/GSFC), P.A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC), B. Mingo (U Leicester),
K. L. Page (U Leicester), T. Sakamoto (AGU) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 11:45:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160815A (trigger=708598).  Swift slewed immediately to the burst. 
The BAT location calculated from the downlinked detector histogram is 
RA, Dec 288.733, 84.282 which is 
   RA(J2000) = 19h 14m 56s
   Dec(J2000) = +84d 16m 55.2s
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  No BAT lightcurve is immediately available
due to a gap in TDRSS coverage. 

Using promptly downlinked data we find a fading, uncatalogued X-ray
source with an enhanced position: RA, Dec 288.5364, 84.3138 which is
equivalent to:
   RA(J2000)  = 19h 14m 08.73s
   Dec(J2000) = +84d 18' 49.8"
with an uncertainty of 2.0 arcseconds (radius, 90% containment). This
location is 134 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received; 
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (7.52 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.6
(+1.72/-1.57) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
309 seconds after the BAT trigger. No credible afterglow candidate has been
found in the initial data products. Data from the 2.7'x2.7' sub-image are not
available at this time. The 8'x8' region for the list of sources generated
on-board covers none of the BAT error circle. No correction has been made for
extinction. 

Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt AT nasa.gov). 
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.)