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GCN Circular 20563

GRB 170127C: POLAR Observation
2017-01-29T07:32:35Z (7 years ago)
Radek Marcinkowski at PSI/POLAR <>
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 

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.


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 , and .

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