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/.