GCN Circular 20563
R. Marcinkowski (PSI), H.L. Xiao (PSI), W. Hajdas (PSI), Yi Zhao (IHEP), M. Kole (DPNC) and S.L. Xiong (IHEP) report on behalf of the POLAR collaboration: At 2017-01-27 01:35:48.7 UT(T0), during a routine on-ground search of data, POLAR detected GRB 170127C, which was also observed by Fermi GBM (trigger # 507173752) and reported by Fermi GBM (Bissaldi et al. GCN 20543), Fermi-LAT (E. Moretti et al. GCN 20544), Agile (A. Ursi et al. GCN 20545) and AstroSat (V. Sharma et al. GCN 20561). The POLAR light curve consists of 1 short (~0.15 s), strong peak followed by longer and weaker multi peak structure with duration (T90) of 22.0 +/- 0.2 s measured from T0. The light curve is compatible with the one from Fermi-GBM. The 0.2 s peak flux at T0 + 0.2 s is equal to 13000 +/- 140 counts/sec. POLAR recorded 3600 +/- 140 events from the burst. Above measurements are in the energy range of about 20 - 500 keV. LC_URL: http://polar.psi.ch/triggers/GRB_170127C_raw.png or http://polar.psi.ch/pub/lc.php?event=GRB+170127C Using the best location from Fermi LAT (E. Moretti et al. GCN 20544), which is: RA : 339.3 [deg] Dec: -63.9 [deg] Err: 0.4 [deg] the incident angle in the POLAR coordinate at T0 is: Theta: 41.8 [deg] Phi: 157.6 [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.