GCN Circular 20624
Yuanhao Wang (IHEP), Shaolin Xiong (IHEP), Yi Zhao (IHEP) report on behalf of the POLAR collaboration: At 2017-02-06T10:51:57.70 UT (T0), during a routine on-ground search of data, POLAR detected the GRB 170206A, which was also detected by Fermi/GBM (trigger 508071122/170206453; A. von Kienlin et al. GCN 20616), Fermi/LAT(F. Fana Dirirsa et al. GCN 20617) and INTEGRAL/SPIACS(trigger_num 7680). The POLAR light curve consists of multiple peaks, with a duration (T90) of 1.194 s measured from T0+0.147 s. The 0.1s peak rate measured from T0+0.4s is 16145.2 cnts/s. The total counts is about 12918 cnts. LC_URL: http://polar.ihep.ac.cn/grb/2017/02/GRB170206A/lc/POLAR_lc_grb170206A.png The above result is not dead time corrected. The above measurements are in the energy range of about 20-500 keV. Using the best location from the Fermi/LAT, which is (J2000): RA: 212.79��[deg] Dec: +14.48��[deg] Err: 0.85����[deg] (90% containment, statistical error only) the incident angle in POLAR coordinate at T0 is: theta: 19.5 [deg] phi: 148.70 [deg] The Minimum Detectable Polarization(MDP) for this burst is estimated to be ~5.7% [1-sigma, statistical only]. Follow-up observations are strongly encouraged. 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/ .