[vsnet-grb-info 18837] GRB 161218B: POLAR observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20288
SUBJECT: GRB 161218B: POLAR observation
DATE:    16/12/18 19:04:42 GMT
FROM:    Yuanhao Wang at IHEP/CAS  <wangyuanhao at ihep.ac.cn>

Y. H. Wang (IHEP), Z. H. Li (IHEP), S. L. Xiong (IHEP) 
report for the POLAR collaboration:

At 2016-12-18T08:32:41.341 UT (T0), during a routine on-ground 
search of data, POLAR detected the GRB 161218B, which was also
detected by the Fermi/GBM (trigger 503742764/161218356).

The POLAR light curve consists of multiple peaks,
with a duration (T90) of 26.28 s measured from T0+1.0 s .
The 1s peak rate measured from T0+1.25 s is 9849 cnts/s,
The total counts is about 29340 cnts.The above measurements are
in the energy range of about 80-500 keV.

The preliminary estimation of minimum detectable polarization(MDP) 
is 36.8%[3-sigma, statistical only]. Follow-up observations are 
strongly encouraged.

LC_URL:
http://polar.ihep.ac.cn/grb/2016/GRB161218B/lc/POLAR_lc_grb161218356.png

Using the best location from the Fermi/GBM, which is (J2000):
RA:    358.640     [deg]
Dec:   -16.950     [deg]
Err:     1.00      [deg]

the incident angle in POLAR coordinate at T0 is:
theta:  77.7612  [deg]
phi:   252.239  [deg]

The analysis results presented above are preliminary.

POLAR is a dedicated Gamma-Ray Burst polarimeter (50-500 keV) on-board 
the Chinese space laboratory Tiangong-2 launched on Sep 15, 2016. More 
information about POLAR can be found at http://polar.ihep.ac.cn/en/, 
http://isdc.unige.ch/polar/ and http://polar.psi.ch/html/