Periodic Emission Frequency Modulation in a Hyperactive Fast Radio Burst

TL;DR

This paper reports the discovery of a 112-day periodic modulation in the central emission frequency of FRB 20240114A, revealing complex spectral evolution and suggesting new physical mechanisms.

Contribution

It presents the first detection of a periodic frequency modulation in an FRB, providing new insights into its radiation mechanism and propagation effects.

Findings

Detected a 112-day periodic modulation in FRB frequency

Frequency drifts systematically from lower to higher within each period

Statistical significance exceeds 6 sigma using Lomb-Scargle and phase-folding methods

Abstract

Fast radio bursts (FRBs) are intense, short-duration radio transients of mysterious origin. They have been detected across a wide range of frequencies from 110 MHz to 8 GHz. Their spectral properties, remaining poorly understood, are essential for understanding the intrinsic radiation mechanism and propagation effects. Here, we report the discovery of a periodic modulation in the central emission frequency of FRB 20240114A, based on more than one thousand bursts collected by an ultra-wideband receiving system. The burst central frequencies reveals a significant modulation with a period of $\sim 112$ days. The statistical significance of this detected periodicity exceeds $6\sigma$ for both the Lomb-Scargle and phase-folding methods. Within a single period, the central emission frequency exhibits a systematic drift from lower to higher values. We evaluate several physical mechanisms for this unique spectral evolution. The free-free absorption together with cyclotron resonant absorption in a binary system or free precession models could potentially explain such behavior. The discovery of this periodic frequency modulation unveils a new layer of complexity in the underlying radiation mechanism and propagation effect of FRBs.