The theoretical modelling of FRB progenitors and emission mechanisms

Abstract

Magnetars remain the leading candidates for powering fast radio bursts (FRBs), yet their ability to reproduce the full diversity of observed behaviors is far from settled. In this talk, I will present two recent advances that sharpen the constraints on what magnetars can - and cannot - explain about FRBs. First, a population-level analysis shows that repeating and apparently non-repeating FRBs can be described by a single unified distribution of sources with a power-law distribution of activity rates. This framework explains why repeaters tend to be nearer and reproduces the wide range of inferred activity rates, the fraction of repeaters to non-repeaters and its weak dependence on survey observation time and sensitivity. Second, we model FRB emission from magnetar polar caps, showing how the orientation of the magnetic and spin axes controls observed repetition behavior, inferred energetics and polarization and spectro/temporal properties. The results imply that geometry may account for much of the apparent FRB diversity. At the same time, the small inferred emission regions and burst energetics rule out broad classes of emission scenarios, tightening the viable range of magnetar-based models. Together, these results provide stringent tests of the magnetar hypothesis. I will outline the specific observational signatures - in repetition statistics, polarization behavior, and energetics - that can confirm or refute magnetars as the dominant FRB progenitors.