TITLE:   GCN CIRCULAR
NUMBER:  19014
SUBJECT: GRB 160216A: Swift detection of a burst
DATE:    16/02/16 19:23:21 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

E. Troja (NASA/GSFC/UMCP), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), S. B. Cenko (GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC),
L. M. McCauley (PSU), T. G. R. Roegiers (PSU),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 19:10:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160216A (trigger=673978).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 311.706, -71.555 which is 
   RA(J2000)  =  20h 46m 49s
   Dec(J2000) = -71d 33' 17"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several bright peaks
with a duration of about 30 sec.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 19:12:05.3 UT, 93.9 seconds after
the BAT trigger. The position determined from promptly downlinked data
differs significantly from the on-board position, suggesting that the
XRT may have centroided on a cosmic ray; the initial XRT position
notice should be treated with caution. Using promptly downlinked data
we find a fading, uncatalogued X-ray source located at RA, Dec
311.68630, -71.54787 which is equivalent to:
   RA(J2000)  = 20h 46m 44.71s
   Dec(J2000) = -71d 32' 52.3"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 34 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 (4.50 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.1
(+0.67/-0.50) x 10^22 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 100 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. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.05. 

Burst Advocate for this burst is E. Troja (eleonora.troja 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.)