[vsnet-grb-info 17689] GRB 160303A: Swift detection of a burst, possibly short

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19126
SUBJECT: GRB 160303A: Swift detection of a burst, possibly short
DATE:    16/03/03 11:14:26 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
P.A. Evans (U Leicester), L. M. McCauley (PSU),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 10:54:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160303A (trigger=677495).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 168.681, +22.742 which is 
   RA(J2000) = 11h 14m 44s
   Dec(J2000) = +22d 44' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
structure with a duration of about 0.5 s sec.  There is some suggestion
of additional peaks at T-1 and T+5.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~0.1 sec after the trigger. 

The XRT began observing the field at 10:56:26.1 UT, 104.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 168.7005,
22.7424 which is equivalent to:
   RA(J2000)  = 11h 14m 48.11s
   Dec(J2000) = +22d 44' 32.5"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 64 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 consistent with the Galactic value of 1.07
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 108 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
0.02. 

Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 
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.)