The role of magnetic and rotation axis alignment in driving fast radio burst phenomenology

Abstract

We propose a scenario that can describe a broad range of FRB phenomenology, from non-repeating bursts to highly prolific repeaters. Coherent radio waves in these bursts are produced in the polar cap region of a magnetar, where magnetic field lines are open. The angle between the rotation and magnetic axes, relative to the angular size of the polar cap region, partially determines the repetition rate and polarization properties of FRBs. We discuss how many of the properties of repeating FRBs-such as their lack of periodicity, energetics, small PA swing, spectro-temporal correlation and inferred low source density are explained by this scenario. The systematic PA swing and the periodic modulation of long duration bursts from non-repeaters are also natural outcomes. We derive a lower limit of about 400 on the Lorentz factor of FRB sources applying this scenario to bursts with a linear polarization degree greater than 95\%.