Orbital spin dynamics of a millisecond pulsar around a massive BH with a general mass quadrupole

Abstract

ABSTRACT We investigate the spin dynamics of a millisecond pulsar (MSP) in compact orbit around a Kerr-like massive BH 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 space–time 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.