Triaxial Magnetars as Sources of Fast Radio Bursts

Abstract

Some of the mysterious temporal properties of Fast Radio Bursts (FRB) may be explained if they are produced by dynamically triaxial magnetars. If the bursts are narrowly collimated along open field lines, then observed repeating FRB are those few whose rotation axis, open field lines and infrequent radiation (analogous to pulsar giant pulses) point nearly to the observer. In apparently non-repeating FRB these are misaligned and the directions of the open field lines and infrequent radiation wander across the sky as they rotate, reducing their observed duty factors by several orders of magnitude. In repeaters a triaxial moment tensor moves the radiation pattern into or out of the line of sight on long (precessional) time scales, explaining periods of greater or lesser (or absent) activity. The dynamics of triaxial bodies may thwart the coherent integration of gravitational signals from rotating neutron stars.