Do the periodic activities of repeating fast radio bursts represent the spins of neutron stars?

TL;DR

This paper investigates whether the observed periodic activities of repeating fast radio bursts can be explained by the spin periods of neutron stars or magnetars, considering the effects of disk winds on their spin evolution.

Contribution

It analyzes the maximum possible spin periods of isolated neutron stars/magnetars influenced by disk winds, proposing that long periods like 16-160 days are feasible.

Findings

Disk winds significantly affect neutron star spin evolution.

Without disk wind, maximum spin period is tens of hours.

With disk wind, spin periods can reach hundreds of hours or more.

Abstract

Fast radio bursts (FRBs) are mysterious radio transients with millisecond durations. Recently, a periodic activity of $\sim$16 day and a possible periodicity of $\sim$159 day were detected to arise from FRB 180916.J0158+65 and FRB 121102, respectively, and the spin period of a slow-rotation magnetar was further considered to be one of possibilities to explain the periodic activities of repeating FRBs. For isolated neutron stars, the spin evolution suggests that it's difficult to reach several hours. In this work, we mainly focus on the possible maximum spin period of isolated NSs / magnetars dominated by an interaction between star's magnetic field and the disk. We find that the disk wind plays an important role in spin evolution, whose influence varies the power law index in the evolution equation of mass flow rate. For a magnetar without disk wind, the longest spin period is tens of hours. When the disk wind with a classical parameter is involved, the maximum spin period can reach hundreds of hours. But for a much extremely large index of mass flow rate due to disk wind or other angular momentum extraction processes, a spin period of $\sim$(16-160) days is still possible.