TITLE: GCN CIRCULAR NUMBER: 20600 SUBJECT: GRB 170131A: POLAR Observation DATE: 17/02/04 03:20:19 GMT FROM: Zhao Yi at POLAR Yi Zhao (IHEP), Xing Wen (IHEP), Yuanhao Wang (IHEP) report on behalf of the POLAR collaboration: At 2017-01-31T23:14:59.00 UT (T0), during a routine on-ground search of data, POLAR detected the GRB 170131A, which was also detected by the Fermi/GBM (trigger 507597304/170131969, Circ 20572), Swift (Circ 20570) and Konus-Wind. The POLAR light curve consists of multiple peaks, with a duration (T90) of 21.88 s measured from T0-1.21 s. The 1-s peak rate measured from T0+16.00 s is 888.4 cnts/s. The total counts is about 7085 cnts. The above measurements are in the energy range of about 20-500 keV. LC_URL: http://polar.ihep.ac.cn/grb/2017/01/GRB170131A/lc/POLAR_lc_grb170131A.png Using the best location from the Swift/BAT, which is (J2000): RA: 341.447 [deg] Dec: +64.006 [deg] Err: 3.00 [arcmin] the incident angle in POLAR coordinate at T0 is: theta: 76.5 [deg] phi: 22.2 [deg] 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/pub/.