TITLE:   GCN CIRCULAR
NUMBER:  20792
SUBJECT: GRB 170228B: POLAR Observation
DATE:    17/03/02 12:28:20 GMT
FROM:    Haulin Xiao at PSI/POLAR  <hualin.xiao@psi.ch>

H.L. Xiao (PSI) , W. Hajdas (PSI) and R. Marcinkowski (PSI)  report on behalf of the POLAR collaboration:

At 2017-02-28 18:32:56 UT(T0), during a routine on-ground search of data, POLAR detected GRB 170228B,
which was also observed by  Fermi GBM (trigger #509999585).

The POLAR lightcurve consists of two peaks with duration (T90) of 35.00 +/- 1.00 s measured from T0.
The 1.0 s peak flux at T0 + 24.5 s  is equal to 390 +/- 50 counts/sec.
POLAR five modules recorded 4680 events from the burst.
Above measurements are in the energy range of about 80 - 500 keV.

LC_URL: http://polar.psi.ch/triggers/GRB_170228B_raw.png
     or http://polar.psi.ch/pub/lc.php?event=GRB+170228B

Using the best location from Fermi GBM, which is (J2000):
RA : 355.94 [deg]
Dec: 15.73 [deg]
the incident angle in the POLAR coordinate at T0 is:
Theta: 24.09 [deg]
Phi: 264.49 [deg]

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/ .

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