//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20348 SUBJECT: GRB 161228B: POLAR Observation DATE: 16/12/30 11:53:28 GMT FROM: Haulin Xiao at PSI/POLAR Radoslaw Marcinkowski (PSI), Hualin Xiao (PSI) and Wojtek Hajdas (PSI) report on behalf of the POLAR collaboration: At 2016-12-28T13:15:40.0 UT(T0), during a routine on-ground search of data, POLAR detected the GRB 161228B, which was also observed by Fermi GBM (trigger #504623745) and SPIACS (trigger: 2016-12-28T13-15-39.8537-31044-07056-0). The POLAR light curve consists of one peak with duration (T90) of 8.5 +- 0.5 s measured from T0. The 0.5 s peak flux at T0 + 3.25 s is equal to 450 +- 40 cnts/sec. Above measurements are in the energy range of about 80 - 500 keV. LC_URL: http://polar.psi.ch/triggers/GRB_161228B_raw.png and http://polar.psi.ch/pub/lc.php?event=GRB+161228B Using the best location from the Fermi-GBM, which is (J2000): RA: 129.290 [deg] Dec: 43.670 [deg] Err: 2.24 [deg] the incident angle in the POLAR coordinate at T0 is: Theta: 28.7 [deg] Phi: 13.9 [deg] The analysis results presented above are preliminary. Calibration of the instrument is ongoing. POLAR is a dedicated Gamma-Ray Burst polarimeter which was launched on-board the Chinese space laboratory Tiangong-2 (TG-2) on Sep 15, 2016. The energy detection range of POLAR is ~ 50-500 keV. More information about POLAR can be found at http://polar.psi.ch/pub , http://polar.ihep.ac.cn/en/ and http://isdc.unige.ch/polar/ . This message is quotable in publications.