A sudden change and recovery in the magnetic environment around a repeating fast radio burst.

Li, Y; Zhang, S B; Yang, Y P; Tsai, C W; Yang, X; Law, C J; Anna-Thomas, R; Chen, X L et al. · Science · 2026

basic_science · Level V

Where this comes from

Abstract

Fast radio bursts (FRBs) are millisecond-duration radio transients from extragalactic sources. Some repeating FRBs exhibit variations in their Faraday rotation measure (RM) due to changes in their magneto-ionic environment. We report magneto-ionic variations of FRB 20220529, a repeating FRB from a disk galaxy at redshift 0.18. For the first 17 months of observations, the RM had a median of 17 radians per square meter (rad m<sup>-2</sup>) and a scatter of 101 rad m<sup>-2</sup>. In December 2023, the RM jumped to 1977 ± 84 rad m<sup>-2</sup>, then gradually returned to typical values within 2 weeks. This sudden RM variation indicates that a dense magnetized clump of plasma passed across the line of sight. We discuss potential explanations, including a coronal mass ejection from a companion star, high plasma turbulence, or binary orbital motion.