Testing Models of Periodically Modulated FRB Activity

TL;DR

This paper investigates models explaining the periodic activity of repeating FRBs, testing their predictions against observational data to understand the underlying mechanisms and environments of these enigmatic bursts.

Contribution

It compares different models of FRB periodicity, especially those involving precessing disks and beam wandering, and discusses how measurements can constrain or validate these models.

Findings

Models with period derivatives insensitive to uncertain parameters can be tested via measurements.

Emission mechanisms may operate in diverse environments, including non-accreting neutron stars.

Periodic modulation can result from beam wandering in precessing accretion disks.

Abstract

The activity of the repeating FRB 20180916B is periodically modulated with a period of 16.3 days, and FRB 121102 may be similarly modulated with a period of about 160 days. In some models of this modulation the period derivative is insensitive to the uncertain parameters; these models can be tested by measurement of or bounds on the derivative. In other models values of the uncertain parameters can be constrained. Periodic modulation of aperiodic bursting activity may result from emission by a narrow beam wandering within a cone or funnel along the axis of a precessing disc, such as the accretion discs in X-ray binaries. The production of FRB 200428 by a neutron star that is neither accreting nor in a binary then shows universality: coherent emission may occur in a wide range of environments.