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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/ .

This message is quotable in publications.

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TITLE:   GCN CIRCULAR
NUMBER:  20803
SUBJECT: GRB 170228B CALET Gamma-Ray Burst Monitor detection
DATE:    17/03/03 06:13:49 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

P. S. Marrocchesi (U of Siena)  A. Yoshida, T. Sakamoto, Y. Kawakubo,
M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA),
I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu,
T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU),
S. Ricciarini (U of Florence),
and the CALET collaboration:

The long-duration GRB 170228B (Fermi GBM trigger #509999585;
Xiao et al, GCN Circ. 20792) triggered the CALET Gamma-ray Burst
Monitor (CGBM) at 18:32:58.03 on 28 February 2017.  The burst signal
was seen by the HXM2 and SGM instrument.

The light curve of the SGM shows two peaks.  The first peak starts at T0,
peaks at T+5 sec and ends at T+18 sec.  The second peak starts at T+20 sec,
peaks at T+25 sec and ends at T+35 sec.  The T90 duration measured by
the SGM data is 32.2 +- 1.2 sec (40-1000 keV).

The light curve is available at

http://cgbm.calet.jp/cgbm_trigger/flight/1172341676/

The CALET data used in this analysis are provided by the Waseda
CALET Operation Center located at the Waseda University.