Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

A second-scale periodicity in an active repeating fast radio burst source

Chen Du, Yong-Feng Huang, Jin-Jun Geng, Hao-Xuan Gao, Li Zhang, Chen Deng, Lang Cui, Jie Liao, Peng-Fei Jiang, Liang Zhang, Pei Wang, Chen-Ran Hu, Xiao-Fei Dong, Fan Xu, Liang Li, Ze-Cheng Zou, Abdusattar Kurban

Abstract

Fast radio bursts (FRBs) are fierce radio flashes from the deep sky. Abundant observations have indicated that highly magnetized neutron stars might be involved in these energetic bursts, but the underlying trigger mechanism is still enigmatic. Especially, the widely expected periodicity connected to the spin of the central engine has never been discovered, which leads to further debates on the nature of FRBs. Here we report the first discovery of a $\sim 1.7\,\mathrm{s}$ period in the repeating source of FRB 20201124A. This is an active repeater, from which more than 2800 FRBs have been observed on a total of 49 days. The phase-folding method is adopted to analyze the bursts on each day separately. While no significant periodic signal is found in all other datasets, a clear periodicity does appear on two specific days, i.e. a period of $1.706024(13)\,\mathrm{s}$ on MJD 59310, and a slightly larger period of $1.707968(9)\,\mathrm{s}$ on MJD 59347. A period derivative of $6.11(5)\times 10^{-10}\,\mathrm{s\,s^{-1}}$ can be derived from these two periods, which further implies a surface magnetic field strength of $1.03\times 10^{15}\,\mathrm{G}$ and a spin-down age of 44 years for the central engine. A joint analysis on these two days yields a significance of $7.3σ$ for the periodicity. It is concluded that FRB 20201124A should be associated with a young magnetar.

A second-scale periodicity in an active repeating fast radio burst source

Abstract

Fast radio bursts (FRBs) are fierce radio flashes from the deep sky. Abundant observations have indicated that highly magnetized neutron stars might be involved in these energetic bursts, but the underlying trigger mechanism is still enigmatic. Especially, the widely expected periodicity connected to the spin of the central engine has never been discovered, which leads to further debates on the nature of FRBs. Here we report the first discovery of a period in the repeating source of FRB 20201124A. This is an active repeater, from which more than 2800 FRBs have been observed on a total of 49 days. The phase-folding method is adopted to analyze the bursts on each day separately. While no significant periodic signal is found in all other datasets, a clear periodicity does appear on two specific days, i.e. a period of on MJD 59310, and a slightly larger period of on MJD 59347. A period derivative of can be derived from these two periods, which further implies a surface magnetic field strength of and a spin-down age of 44 years for the central engine. A joint analysis on these two days yields a significance of for the periodicity. It is concluded that FRB 20201124A should be associated with a young magnetar.

Paper Structure

This paper contains 16 sections, 14 equations, 16 figures, 1 table.

Table of Contents

  1. Introduction
  2. Data
  3. Results
  4. Implications
  5. Summary
  6. Methods
  7. Extended Data Figures and Tables

Figures (16)

  • Figure 1: Number of bursts detected on each day for FRB 20201124A. The X-axis represents the observation date (MJD), and the Y-axis represents the number of bursts detected on that day. Bursts detected by FAST during the first active episode are shown in green, while the bursts of the second active episode are shown in blue. The bursts detected by uGMRT (purple) and Effelsberg (orange) are also included. The two days with periodicity detected (MJDs 59310 and 59347) are marked by red boxes.
  • Figure 1: $\chi^2$ periodograms of the bursts observed on each day for FRB 20201124A. The X-axis represents the trial period, and the Y-axis represents the reduced $\chi^2$. The observation date and the telescope are marked correspondingly in each panel. The number of bursts detected on each day is also marked. The red dashed lines indicate a significance level of $3\sigma$. To be continued on the next page.
  • Figure 2: The periodograms and the folded phase histograms for the bursts on MJD 59310 (top panels) and MJD 59347 (bottom panels). The left two panels show the $\chi^2$ periodograms, with the horizontal dotted line indicating a significance level of $3\sigma$ derived from the theoretical $\chi^2$ distribution. The red arrows in the periodograms indicate the periods identified in the blind search: 1.70603 s on MJD 59310 and 1.70797 s on MJD 59347. On MJD 59310, an additional peak ($\sim$ 3.4 s) is also seen, which is a harmonic of the $\sim$ 1.7 s period. The right two panels show the phase histograms for each day, folded by the refined periods of 1.706024 s and 1.707968 s, respectively. For clarity of visualization, two complete cycles are plotted. The mean TOA of bursts observed on each day is taken as the time of the zero phase point.
  • Figure 2: $\chi^2$ periodograms of the bursts observed on each day for FRB 20201124A. The X-axis represents the trial period, and the Y-axis represents the reduced $\chi^2$. The observation date and the telescope are marked correspondingly in each panel. The number of bursts detected on each day is also marked. The red dashed lines indicate a significance level of $3\sigma$. To be continued on the next page.
  • Figure 3: The position of each burst in the phase space when folded according to the refined period. Bursts on MJDs 59310 and 59347 are illustrated separately. The X-axis is the folded phase, the Y-axis shows the arrival time, and the Z-axis illustrates the flux density (in arbitrary units). For clarity of visualization, two complete cycles are plotted. The mean TOA of bursts observed on each day is taken as the time of the zero phase point.
  • ...and 11 more figures