GCN Circular 20837
R. Marcinkowski (PSI), H.L. Xiao (PSI) and W. Hajdas (PSI) report on behalf of the POLAR collaboration: At 2017-03-05 06:09:06.8 UT(T0), during a routine on-ground search of data, POLAR detected GRB 170305A, which was also observed by Fermi GBM (trigger # 510386951; GCN 20818, M. Stanbro) and Konus-Wind, INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and Swift (BAT) (GCN 20824, K. Hurley et al.). The POLAR light curve consists of 1 peak with duration (T90) of 0.3 +/- 0.05 s measured from T0. The 64ms peak flux at T0 + 0.1 s is equal to 9630 +/- 120 counts/sec. POLAR recorded 2400 events from the burst. Above measurements are in the energy range of about 20 - 500 keV. LC_URL: http://polar.psi.ch/triggers/GRB_170305A_raw.png or http://polar.psi.ch/pub/lc.php?event=GRB+170305A Using the best location from IPN Triangulation (GCN 20824, K. Hurley et al.), which is (J2000): RA : 39.66 deg Dec: 9.90 deg the incident angle in the POLAR coordinate at T0 is: Theta: 31.4 deg Phi: 239.1 deg The analysis results presented above are preliminary. 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.