[vsnet-grb-info 17793] GRB 160327A: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19235
SUBJECT: GRB 160327A: Swift detection of a burst
DATE:    16/03/27 09:35:51 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

J. L. Racusin (NASA/GSFC), A. P. Beardmore (U Leicester),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 09:16:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160327A (trigger=680655).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 146.689, +54.017 which is 
   RA(J2000) = 09h 46m 45s
   Dec(J2000) = +54d 01' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~3000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 09:17:08.2 UT, 60.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
146.7019, 54.0131 which is equivalent to:
   RA(J2000)  = 09h 46m 48.45s
   Dec(J2000) = +54d 00' 47.0"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 30 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 1.17
x 10^20 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 1.01e-09 erg cm^-2 s^-1 (0.2-10
keV). 

The prompt automatic UVOT analysis is not available at this time. 
However, there appears to be no credible afterglow candidate in the
initial data. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin 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.)