TITLE: GCN CIRCULAR NUMBER: 20361 SUBJECT: GRB 170101B: POLAR observation DATE: 17/01/03 15:05:07 GMT FROM: Yuanhao Wang at IHEP/CAS Hancheng Li (IHEP), Yuanhao Wang (IHEP), Zhengheng Li (IHEP) report on the behalf of the POLAR collaboration: At 2017-01-01T02:47:18.27 UT (T0), during a routine on-ground search of data, POLAR detected the GRB 170101B, which was also detected by the Fermi/GBM (trigger 504953918/170101374). The POLAR light curve consists of multiple peaks, with a duration (T90) of 11.2 s measured from T0+0.3 s. The 0.2-s peak rate measured from T0+8.1 s is 968 cnts/s, the total counts is about 5217 cnts. The above measurements are in the energy range of approximately 80-500 keV. LC_URL: http://polar.ihep.ac.cn/grb/2017/01/GRB170101B/lc/GRB170101B.JPG Using the best location from the Fermi/GBM, which is (J2000): RA: 70.640[deg] Dec: -1.580[deg] Err: 1.2[deg] the incident angle in POLAR coordinate at T0 is: theta: 63.43[deg] phi: -110.01[deg] The Minimum Detectable Polarization(MDP) for this burst is estimated to be ~23.5% [1-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/html/. [GCN OPS NOTE(03jan17): Per operator, the SUBJECT-line was corrected from "170101A" to "170101B".]