August 28
One Population, Many Faces: Geometry and Kinetic Constraints in Magnetar-Powered Fast Radio Bursts
Speaker: Prof. Paz Beniamini, Open University of Israel / GWU
Abstract: Magnetars are widely invoked as the engines of fast radio bursts (FRBs), yet a basic question remains unresolved: can a single magnetar framework account for the full diversity of observed behavior? FRBs span orders of magnitude in activity, exhibit diverse polarization properties, and show striking spectro-temporal differences between repeating and apparently non-repeating sources - features often treated as evidence for distinct source classes. I will argue that this diversity does not require multiple populations. Instead, it reflects a combination of geometric selection effects and a single, robust physical constraint: at the site of coherent emission, the burst energy must be carried in kinetic form - by a relativistic particle beam or bulk flow. This requirement, largely independent of emission radius, sharply limits how energy can be generated, transported, and dissipated in magnetar environments, and disfavors scenarios in which radiation is produced without efficient local particle acceleration. Within this framework, I will show that the alignment between the magnetic and rotation axes plays a central role in shaping the observed phenomenology, naturally accounting for the apparent dichotomy between repeaters and non-repeaters. I will further argue that FRBs are most likely produced within the magnetosphere, where efficient in-situ particle acceleration is expected. If correct, this picture reduces the apparent complexity of FRBs to a small set of geometric and energetic constraints, and positions FRBs as clean probes of neutron star magnetospheres.
Host: Robert Stein & Jillian Rastinejad