Transitional millisecond pulsars

TL;DR

Transitional millisecond pulsars are a key class of systems that switch between radio and accretion-powered states, providing insights into binary evolution and plasma-electromagnetic interactions, with recent discoveries spanning from radio to gamma-ray observations.

Contribution

This review consolidates current knowledge on the properties, candidates, and models of transitional millisecond pulsars, highlighting recent observational and theoretical advances.

Findings

Identification of three confirmed transitional millisecond pulsars.

Evidence of state switching from radio to gamma-ray emissions.

Various models proposed to explain the complex behaviour of these systems.

Abstract

Millisecond pulsars in tight binaries have recently opened new challenges in our understanding of physical processes governing the evolution of binaries and the interaction between astrophysical plasma and electromagnetic fields. Transitional systems that showed changes from rotation-powered to accretion powered states and vice versa have bridged the populations of radio and accreting millisecond pulsars, eventually demonstrating the tight evolutionary link envisaged by the recycling scenario. A decade of discoveries and theoretical efforts have just grasped the complex phenomenology of transitional millisecond pulsars from the radio to the gamma-ray band. This review summarises the main properties of the three transitional millisecond pulsars discovered so far, as well as of candidates and related systems, discussing the various models proposed to cope with the multifaceted behaviour.