Flux Variations of Fast Radio Bursts and Their Persistent Radio Sources: Evidence for a Shared Progenitor

Abstract

Fast radio bursts (FRBs) are millisecond-duration extragalactic radio transients, some of which are associated with compact persistent radio sources (PRSs), hinting at a physical connection. While several models have been proposed to explain PRSs and their connection to FRBs, direct observational tests remain limited. Here, we report for the first time a correlated trend between the long-term variation of the PRS flux density and the burst energetics of FRB 20190520B and FRB 20240114A, suggesting that both the PRS and FRB activity may be powered by a shared energy reservoir. We further examine additional repeaters with compact PRSs and find no clear correlation between PRS luminosity and burst activity, likely due to the limited observations. These results are consistent with scenarios in which both the PRS and FRB activity may be powered by a common energy reservoir, such as the magnetic or rotational energy of a magnetar.

Figures (7)

• Figure 1: PRS flux density of FRB 20190520B and the corresponding daily FRB activity proxy $P_{\rm day}$. The smaller orange symbols denote individual PRS flux-density measurements, which have been uniformly converted to the S band under the assumption of a power-law spectrum. The smaller blue markers represent the daily energy-output proxy $P_{\rm day}$, calculated from FRB bursts detected by FAST. The detailed values of the S-band–converted PRS flux densities and the corresponding $P_{\rm day}$ are listed in Appendix Table \ref{['tab:2']} and Table \ref{['tab:3']}. The larger orange and blue symbols indicate the binned PRS flux density and $P_{\rm day}$, respectively, obtained using a 30-day binning scheme starting from the first PRS observation. In addition, the VLA observations obtained in June 2023 were analyzed in both 2024ApJ...976..165Y and Balasubramanian_2025, yielding slightly different results due to differences in the data-reduction procedures. In this work, we adopt the most recent processing results presented in Balasubramanian_2025.
• Figure 2: Co-variation of PRS Flux Density and FRB Activity in FRB 20190520B and FRB 20240114A. Both panels show binned results. A 30-day bin size (Segment A data) is adopted for FRB 20190520B, while a 7-day binning scheme is used for FRB 20240114A. Because a single bin for FRB 20240114A may contain measurements from multiple telescopes, the binned PRS data are not further distinguished by telescope symbols.
• Figure 3: Permutation-test results for segment A of FRB 20190520B based on the ICCF analysis.
• Figure 4: S-band PRS flux density of FRB 20121102A and the corresponding daily FRB activity proxy, $P_{\rm day}$. The symbol definitions are the same as those used for FRB 20190520B. Unlike FRB 20190520B, however, the S-band PRS flux densities shown here are direct measurements and are not converted from other frequencies using a spectral index. The red markers along the bottom indicate VLA burst-search epochs in May 2016, during which no FRB bursts were detected. Given the limited number of data points and the relatively short temporal coverage, the binned values are computed using a 7-day binning scheme starting from the first PRS observation. Previous studies have shown that FRB 20121102A exhibits activity cycles in the L band, with a period of approximately 159 days(2025AA...693A..40B;espinozadupouy2026chromaticactivitywindowperiodic), of which about 84 days correspond to an active phase. The light-green shaded regions indicate the time intervals during which the source is expected to be in a relatively active state.
• Figure 5: Permutation-test results for FRB 20121102A based on the ICCF analysis over the 2016 April–November interval.