TITLE: GCN CIRCULAR NUMBER: 20733 SUBJECT: GRB 170220A: POLAR Observation DATE: 17/02/24 14:50:14 GMT FROM: Haulin Xiao at PSI/POLAR R. Marcinkowski (PSI), H.L. Xiao (PSI) and W. Hajdas (PSI) report on behalf of the POLAR collaboration: At 2017-02-20 18:48:01.00 UT(T0), during a routine on-ground search of data, POLAR detected short GRB 170220A, which was also observed by Konus at 18:47:58.467 UT. The POLAR light curve consists of 1 peak with duration (T90) of 0.3 +/- 0.1 s measured from T0. The 50 ms peak flux at T0 + 0.7 s is equal to 7300 +/- 100 counts/sec. POLAR recorded 1230 events from the burst. Above measurements are in the energy range of about 50 - 500 keV. LC_URL: http://polar.psi.ch/triggers/GRB_170220A_raw.png or http://polar.psi.ch/pub/lc.php?event=GRB+170220A 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.