Three-dimensional general relativistic Poynting-Robertson effect II: Radiation field from a rigidly rotating spherical source

TL;DR

This paper models the three-dimensional general relativistic Poynting-Robertson effect around rotating neutron stars or black hole coronae, deriving particle dynamics influenced by a realistic radiation field in Kerr spacetime.

Contribution

It extends previous models by incorporating a rotating spherical radiation source, deriving equations of motion, and analyzing the shape and particle trajectories on the critical hypersurface.

Findings

Critical hypersurface shape varies with spin and luminosity.

Particles can be stabilized on the hypersurface in specific conditions.

The model recovers classical and weak-field limits.

Abstract

We investigate the three-dimensional, general relativistic Poynting-Robertson effect in the case of rigidly rotating spherical source which emits radiation radially in the local comoving frame. Such radiation field is meant to approximate the field produced by the surface of a rotating neutron star, or by the central radiating hot corona of accreting black holes; it extends the purely radial radiation field that we considered in a previous study. Its angular momentum is expressed in terms of the rotation frequency and radius of the emitting source. For the background we adopt a Kerr spacetime geometry. We derive the equations of motion for test particles influenced by such radiation field, recovering the classical and weak-field approximation for slow rotation. We concentrate on solutions consisting of particles orbiting along circular orbits off and parallel to the equatorial plane, which are stabilized by the balance between gravitational attraction, radiation force and PR drag. Such solutions are found to lie on a critical hypersurface, whose shape may morph from prolate to oblate depending on the Kerr spin parameter and the luminosity, rotation and radius of the radiating sphere. For selected parameter ranges, the critical hypersurface intersects the radiating sphere giving rise to a bulging equatorial region or, alternatively, two lobes above the poles. We calculate the trajectories of test particles in the close vicinity of the critical hypersurface for a selected set of initial parameters and analyze the spatial and angular velocity of test particles captured on the critical hypersurface.