TITLE:   GCN CIRCULAR
NUMBER:  20236
SUBJECT: GRB 161129A: POLAR Detection
DATE:    16/12/05 14:22:18 GMT
FROM:    Shaolin Xiong at IHEP  <xiongsl@ihep.ac.cn>

J. C. Sun (IHEP), M. R. Kole (DPNC/UniGe), Y. H. Wang (IHEP),

S. L. Xiong (IHEP),Z. H. Li (IHEP),H. C. Li (IHEP),

Y. Zhao (IHEP), T. Batsch(NCBJ),T. Bernasconi (ISDC/UniGe),

  F. Cadoux (DPNC/UniGe), Y. W. Dong (IHEP),M. Z. Feng

(IHEP), M. Y. Ge (IHEP), W.Hajdas (PSI),Y. Huang (IHEP),

Karol Jedrzejczak (NCBJ), F. J. Lu (IHEP), R. Marcinkowski

(PSI), M. Pohl (DPNC/UniGe),N. Produit (ISDC/UniGe),

A. Rutczynska (NCBJ), D. Rybka (NCBJ),L. M. Song (IHEP),

J. Szabelski (NCBJ), X. Wen (IHEP), B. B. Wu (IHEP),X. Wu

(DPNC/UniGe), H. L. Xiao (PSI), M. Xu (IHEP), J. Zhang

(IHEP),L. Y. Zhang (IHEP), P. Zhang (PSI), S. N. Zhang

(IHEP),Y. J. Zhang (IHEP), A. Zwolinska (NCBJ)

report on behalf of the POLAR team:

At 2016-11-29T07:11:40.00 UT(T0), during a routine

on-ground search of data, POLAR detected the GRB 161129A,

which was also observed by the Swift/BAT (trigger

#724438), Fermi/GBM (trigger 502096303/161129300), and

Astrosat/CZTI (V. Sharma et al., GCN Circ. 20214). The

detection of this GRB happened on the tail of a big Solar Flare.

The POLAR light curve consists of multiple peaks

with a duration (T90) of 41.5 s measured from T0+3.75 s.

The 500-ms peak flux, measured from T0+27.25 s, is 705.7

cnts/sec. The above measurements are in the preliminary

calculated energy range of about 80 – 500 keV.

LC_URL:

http://www.isdc.unige.ch/polar/lc/161129A/lcr.png

The incident angle at T0 in POLAR detector coordinate is:

theta:  42.6   [deg]

phi:    52.3   [deg]

These direction is computed using the best location from

the Swift/BAT, which is (J2000):

RA:   316.221  [deg]

Dec:  32.137   [deg]

Err:  1.8      [arcmin]

The distribution of the GRB signal among its 25 detector

modules is also consistent with this incident geometry.

Preliminary calculations of the MDP show that a

polarimetric measurement of this burst can be attempted.


The analysis results presented above are preliminary. The

calibration work is ongoing.


POLAR is a dedicated Gamma-Ray Burst polarimeter which was

launchedon-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.ihep.ac.cn/en/_.