High-energy hyperbolic scattering by neutron stars and black holes

TL;DR

This paper analyzes the hyperbolic scattering of various particles by Kerr black holes and deformed sources, providing analytical and series solutions for the scattering angle to infer properties of binary systems.

Contribution

It offers new analytical and series-based methods to compute scattering angles for particles interacting with rotating and quadrupolar gravitational sources.

Findings

Derived closed-form and series expressions for scattering angles.

Showed how scattering angles depend on source and particle parameters.

Proposed scattering measurements to determine binary system characteristics.

Abstract

We investigate the hyperbolic scattering of test particles, spinning test particles and particles with spin-induced quadrupolar structure by a Kerr black hole in the ultrarelativistic regime. We also study how the features of the scattering process modify if the source of the background gravitational field is endowed with a nonzero mass quadrupole moment as described by the (approximate) Hartle-Thorne solution. We compute the scattering angle either in closed analytical form, when possible, or as a power series of the (dimensionless) inverse impact parameter. It is a function of the parameters characterizing the source (intrinsic angular momentum and mass quadrupole moment) as well as the scattered body (spin and polarizability constant). Measuring the scattering angle thus provides useful information to determine the nature of the two components of the binary system undergoing high-energy scattering processes.