http://arxiv.org/abs/1908.10885
GRB 160821A is the third most energetic gamma ray burst observed by the {\it Fermi} gamma-ray space telescope. Based on the observations made by Cadmium Zinc Telluride Imager (CZTI) on board {\it AstroSat}, here we report the most conclusive evidence to date of (i) high linear polarization ($66^{+26}_{-27} \%$; $5.3 \sigma$ detection), and (ii) variation of its polarization angle with time happening twice during the rise and decay phase of the burst at $3.5 \sigma$ and $3.1 \sigma$ detections respectively. All confidence levels are reported for two parameters of interest. These observations strongly suggest synchrotron radiation produced in magnetic field lines which are highly ordered on angular scales of $1/\Gamma$, where $\Gamma $ is the Lorentz factor of the outflow.
V. Sharma, S. Iyyani, D. Bhattacharya, et. al.
Fri, 30 Aug 19
40/58
Comments: 12 pages, 6 figures, accepted for publication in The Astrophysical Journal Letters