GCN Circular 20355

Hancheng Li (IHEP), Yuanhao Wang (IHEP), Zhengheng Li (IHEP)
report on the behalf of the POLAR collaboration:


At 2017-01-01T02:26:00.66 UT (T0), during a routine on-ground 
search of data, POLAR detected the GRB 170101A, which was also
detected by the Swift/BAT (trigger #729293).


The POLAR light curve consists of a single peak,
with a duration (T90) of 2.82 s measured from T0+0.00 s.
The 0.2-s peak rate measured from T0+0.20 s is 8836 cnts/s,
the total counts is about 5379 cnts.  The above measurements
are in the energy range of approximately 80-500 keV. 


LC_URL:
http://polar.ihep.ac.cn/grb/2017/01/GRB170101A/lc/GRB170101A.png


Using the best location from the Swfit/BAT, which is (J2000):
RA:    267.103     [deg]
Dec:   +11.654     [deg]
Err:     3.00      [arcmin]


the incident angle in POLAR coordinate at T0 is:
theta:  6.04  [deg]  
phi:   72.86  [deg] 


The Minimum Detectable Polarization(MDP) for this burst is
estimated to be ~6.0% [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/html/ .