Decadal evolution of a repeating fast radio burst source

TL;DR

This study provides the first evidence of decadal evolution in a repeating FRB source, showing significant changes in its local environment over time, which offers clues about its origin.

Contribution

It reports long-term environmental changes in a repeating FRB, revealing decadal evolution in dispersion and rotation measures, a novel observation in FRB studies.

Findings

7% decline in dispersion measure over a decade

70% decrease in rotation measure since 2016

Reduced environmental complexity indicated by $\sigma_{RM}$ decrease

Abstract

The origin of fast radio bursts (FRBs), the brightest cosmic radio explosions, is still unknown. Bearing critical clues to FRBs' origin, the long-term evolution of FRBs has yet to be confirmed, since the field is still young and most FRBs were seen only once. Here we report clear evidence of decadal evolution of FRB~20121102A, the first precisely localized repeater. In conjunction with archival data, our FAST and GBT monitoring campaign since 2020 reveals a significant 7% decline of local dispersion measure (DM). The rotation measure (RM) of 30,755$\pm$16 $\mathrm{rad\,m^{-2}}$ detected in the last epoch represents a 70% decrease compared to that from December 2016. The $\sigma_{RM}$ parameter, which describes the complexity of the magneto-ionic environment surrounding the source, was shown to have decreased by 13%. These general trends reveal an evolving FRB environment, which could originate from an early-phase supernova associated with an enhanced pair wind from the FRB central engine.