Time-varying Polarized Gamma-Rays from GRB 160821A: Evidence for Ordered Magnetic Fields

Vidushi Sharma, Shabnam Iyyani, Dipankar Bhattacharya, Tanmoy Chattopadhyay, A. R. Rao, E. Aarthy, Santosh V. Vadawale, N. P.S. Mithun, Varun B. Bhalerao, Felix Ryde, Asaf Pe'Er

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

GRB 160821A is the third most energetic gamma-ray burst observed by the Fermi gamma-ray space telescope. Based on the observations made by the Cadmium Zinc Telluride Imager on board AstroSat, here we report the most conclusive evidence to date of (i) high linear polarization ( detection), and (ii) variation of polarization angle with time, occurring twice during the rise and decay phase of the burst at 3.5σ and 3.1σ detections, respectively. All confidence levels are reported for two parameters of interest. These observations strongly suggest synchrotron radiation produced in magnetic field lines that are highly ordered on angular scales of 1/Γ, where Γ is the Lorentz factor of the outflow.

Original languageEnglish
Article numberL10
JournalAstrophysical Journal Letters
Volume882
Issue number1
DOIs
StatePublished - 1 Sep 2019

Bibliographical note

Publisher Copyright:
© 2019. The American Astronomical Society. All rights reserved..

Funding

FundersFunder number
Horizon 2020 Framework Programme773062

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