TITLE:   GCN CIRCULAR
NUMBER:  20357
SUBJECT: GRB 161228C: POLAR observation
DATE:    17/01/03 02:06:49 GMT
FROM:    Zhao Yi at POLAR  <yizhao@ihep.ac.cn>

Yi Zhao (IHEP), Yuanhao Wang (IHEP) and Zhengheng Li (IHEP)
report on behalf of the POLAR collaboration:

At 2016-12-28T00:46:20.00 UT (T0), during a routine on-ground 
search of data, POLAR detected the GRB 161228C, 
which was also detected by the Fermi/GBM (trigger504578783/161228032).

The POLAR light curve consists of multiple peaks,
with a duration (T90) of 31.67 s measured from T0-6.29 s.
The 1-s peak rate measured from T0+16.00 s is 327.9 cnts/s.
The total counts is about 4408 cnts.The above measurements
arein the energy range of about 80-500 keV.

LC_URL:
http://polar.ihep.ac.cn/grb/2016/GRB161228C/lc/POLAR_lc_grb161228032.jpg

Using the best location from the Fermi/GBM, which is (J2000):
RA:   115.820  [deg]
Dec:  +25.760  [deg]
Err:  3.14     [deg]

The incident angle in POLAR coordinate at T0 is:
theta:  52.2   [deg]
phi:    -75.6  [deg]

All 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/pub/ .