Orbital spin dynamics of a millisecond pulsar around a massive black hole with an general mass quadrupole

TL;DR

This paper models the spin dynamics of a millisecond pulsar orbiting a Kerr-like black hole with a quadrupole moment, revealing observable timing variations and pulse profile modifications relevant for astrophysical measurements.

Contribution

It introduces a detailed analysis of pulsar spin and orbital dynamics considering black hole quadrupole effects using the Mathisson-Papetrou-Dixon framework, advancing understanding of pulsar timing in strong gravity.

Findings

Timing variations in Einstein and Roemer delays observed.

Modifications to pulsar pulse profiles due to spin-orbit interactions.

Potential for improved black hole quadrupole measurements through pulsar timing.

Abstract

We investigate the spin dynamics of a millisecond pulsar (MSP) in compact orbit around a Kerr-like massive black hole with an general mass quadrupole. We use the Mathisson-Papetrou-Dixon formulation to compute the orbital and spin evolution of the MSP, accounting for the non-linear interaction of the pulsar's energy-momentum tensor on the background spacetime metric. We investigate how the MSP spin and BH quadrupole moment manifest in the pulsar spin-orbital dynamics. We discuss the astrophysical observational implications of these spin and orbital dynamics on the timing of a radio pulsar in an Extreme Mass Ratio Binary, e.g. a Galactic Centre pulsar. In particular, notable timing variations in the Einstein delay and Roemer delay are observed, along with modifications to the pulsar pulse profile.