Multi-wave band Synchrotron Polarization of Gamma-Ray Burst Afterglows

Jiro Shimoda, Kenji Toma

Research output: Contribution to journalArticlepeer-review

Abstract

Multi-wave band synchrotron linear polarization of gamma-ray burst (GRB) afterglows is studied under the assumption of an anisotropic turbulent magnetic field with a coherence length of the plasma skin-depth scale in the downstream of forward shocks. We find that for typical GRBs, in comparison to optical polarization, the degree of radio polarization shows a similar temporal evolution but a significantly smaller peak value. This results from differences in observed intensity image shapes between the radio and optical bands. We also show that the degree of the polarization spectrum undergoes a gradual variation from the low- to the high-polarization regime above the intensity of the spectral peak frequency, and that the difference in polarization angles in the two regimes is zero or 90 . Thus, simultaneous multi-wave band polarimetric observations of GRB afterglows would be a new determinative test of the plasma-scale magnetic field model. We also discuss theoretical implications from the recent detection of radio linear polarization in GRB 171205A with the Atacama Large Millimeter/submillimeter Array and other models of magnetic field configuration.

Original languageEnglish
Article number58
JournalAstrophysical Journal
Volume913
Issue number1
DOIs
Publication statusPublished - 2021 May 20

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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