TITLE: GCN CIRCULAR NUMBER: 20272 SUBJECT: GRB 161205A: POLAR observation DATE: 16/12/16 12:30:18 GMT FROM: Zhao Yi at POLAR Y. Zhao (IHEP), M. Z. Feng(IHEP), Z. H. Li (IHEP), Y. H. Wang (IHEP), J. C. Sun (IHEP), H. C. Li (IHEP), S. L. Xiong (IHEP), T. Batsch(NCBJ), T. Bernasconi (ISDC/UniGe), F. Cadoux (DPNC/UniGe), Y. W. Dong (IHEP), M. Y. Ge (IHEP),W.Hajdas (PSI),Y. Huang (IHEP), Karol Jedrzejczak (NCBJ), M. R. Kole (DPNC/UniGe), F. J. Lu (IHEP), R. Marcinkowski(PSI), M. Pohl (DPNC/UniGe), N. Produit (ISDC/UniGe),A. Rutczynska (NCBJ), D. Rybka (NCBJ),L. M. Song (IHEP), J. Szabelski (NCBJ), X. Wen (IHEP), B. B. Wu (IHEP),X. Wu (DPNC/UniGe), H. L. Xiao (PSI), M. Xu (IHEP), J. Zhang (IHEP),L. Y. Zhang (IHEP), P. Zhang (PSI), S. N. Zhang (IHEP), Y. J. Zhang (IHEP), A. Zwolinska (NCBJ) report for the POLAR collaboration: At 2016-12-05T13:27:18UT(T0), during a routine on-ground search of data, POLAR detected the GRB 161205A, which was also observed by the Fermi/GBM (trigger502637242/161205561). The POLAR light curve consists of multiple peaks with a duration (T90) of 26.6s measured from T0-0.66s. The 1s peak flux, measured from T0+7.00s, is 271.8cnts/s. The total counts is about 1416cnts. The above measurements are in the energy range of about 80-500 keV. LC_URL: http://polar.ihep.ac.cn/grb/2016/GRB161205A/lc/POLAR_lc_grb161205560.jpg Using the best location from the Fermi/GBM, which is (J2000): RA: 318.980 [deg] Dec: +47.650 [deg] Err: 5.42 [deg] the incident angle at T0 in POLAR detector coordinate is: theta: 63.7 [deg] phi: -3.7 [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/