FRBs from rapid spindown neutron stars

TL;DR

This paper proposes that fast radio bursts originate from rapidly spinning neutron stars in globular clusters, with highly beamed giant pulses explaining observed energetics and rates, challenging magnetar models.

Contribution

It introduces a novel model where FRBs are caused by beamed giant pulses from recycled millisecond neutron stars with moderate magnetic fields in globular clusters.

Findings

Recycled neutron stars can produce FRBs with observed energetics.

Beaming significantly reduces the energy requirements for FRB emission.

The model explains the spatial distribution and frequency variations of some FRBs.

Abstract

A fast radio burst (FRB) localized to a globular cluster (GC) challenges FRB models involving ordinary young magnetars. In this paper, we examine the rapid spindown millisecond neutron star (NS) scenario, which favours the dynamic environment in GCs. Fast spindown corresponds to a larger magnetic field than regular millisecond pulsars, which empirically favours giant pulse (GP) emission. The kinetic energy in millisecond NSs can readily exceed the magnetic energy in magnetars. The high inferred isotropic luminosity of most FRBs is challenging to explain in spin-down powered pulsars. A recent observation of a GP from the Crab pulsar, on the other hand, suggests highly Doppler-beamed emission, making the required energy orders of magnitude smaller than estimated with isotropic assumptions. Considering this strong beaming effect, GPs from a recycled pulsar with a modest magnetic field could explain the energetics and burst rates for a wide range of FRBs. The short life span accounts for a paucity of bright FRBs in the Milky Way neighbourhood. We point out that tidal disruption spin-up from a main sequence star can provide sufficient accretion rate to recycle a NS with mild magnetic field. It can also explain the observed source density and the spatial offset in the GC for FRB 20200120E. Frequency variation in the scattering tail for some of the brightest FRBs is expected in this scenario.