GCN Circular 20354

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


At 2016-12-29T21:03:49.00 UT (T0), during a routine on-ground 
search of data, POLAR detected the GRB 161229A, 
which was also detected by the Fermi/GBM (trigger 504738232/161229877).


The POLAR light curve consists of multiple peaks,
with a duration (T90) of 35.77 s measured from T0+0.39 s.
The 1-s peak rate measured from T0+30.00 s is 2307.8 cnts/s,
The total counts is about 35134 cnts.The above measurements 
are in the energy range of about 80-500 keV.


LC_URL:
http://polar.ihep.ac.cn/grb/2016/GRB161229A/lc/POLAR_lc_grb161229877.jpg


Using the best location from the Fermi/GBM, which is (J2000):
RA:    81.030  [deg]
Dec:   +6.310  [deg]
Err:   1.00    [deg]


the incident angle in POLAR coordinate at T0 is:
theta:   87.6    [deg]
phi:     -103.7  [deg]


The Minimum Detectable Polarization (MDP) for this burst is estimated
to be ~46% [3-sigma, statistical only].


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/.