From Search to Characterisation: Optical Studies of Spider Pulsars

Abstract

Millisecond pulsars (MSPs) are the fastest-spinning and heaviest pulsars, believed to be the result of the "recycling scenario," where mass transfer from a companion star spins up the pulsar. This process gives rise to the binary MSP systems known as "black widows" and "redbacks," where the companions, having undergone significant mass loss, are left as low-mass stars. These "spider" pulsars consist of an MSP and a low-mass main-sequence or semi-degenerate star in a tight orbit (Porb ≲ 1 day). The pulsar’s relativistic emissions produce extreme effects such as intrabinary shocks and intense irradiation of the companion star. The irradiated and tidally distorted companions produce sinusoidal orbital modulations with large flux amplitudes, which can be used to search for spider pulsars using optical telescopes. In our ongoing project, we have identified several potential spider candidates, most notably discovering the black widow PSR J1544−2554. Modelling the optical light curves of redbacks, such as PSRs J1036−4353, J1803−6707, and J1431−4715, has provided evidence for deep energy deposition in the companion’s photosphere and suggests different gravity darkening models may be necessary for spider companions. Furthermore, variations in the Roche-lobe filling of PSR J1803−6707 highlight the importance of long-term monitoring of redback systems to investigate the underlying mechanisms driving their binary evolution.

Date of Award	7 Mar 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Rene Breton (Main Supervisor) & Patrick Weltevrede (Co Supervisor)