Structure Functions of Rotation Measures Revealing the Origin of Fast Radio Bursts

TL;DR

This study uses structure function analysis of rotation measures to identify a binary origin for FRB 20201124A, revealing a geometric component caused by binary orbital motion and providing a new diagnostic tool for binary detection.

Contribution

It demonstrates the presence of a periodic geometric component in the structure functions of RM for an FRB, linking it to binary orbital motion, which is a novel diagnostic approach.

Findings

Detection of a periodic geometric component in RM structure functions

Evidence supporting a binary origin for FRB 20201124A

The geometric component can diagnose binary companions in FRBs

Abstract

The structure function (SF) analysis is a powerful tool for studying plasma turbulence. Theoretically, the SF of Faraday rotation measure (RM) is expected to include a geometric component due to the relative orientation of sightlines through an ordered magnetic field. However, observational evidence for this component remains elusive. Here, we report that the SFs of the binary PSR B1744-24A and the repeating fast radio burst (FRB) 20201124A exhibit both a periodic geometric component, caused by binary orbital motion, and a flat statistical component. The statistical component, induced by stochastic fluctuations in electron density and magnetic field, aligns with RM scatter derived from pulse depolarization. These findings indicate that FRB 20201124A has a binary origin and suggest that the periodic geometric component can serve as a diagnostic tool to identify binary companions.