An approximate Kerr–Newman-like metric endowed with a magnetic dipole and mass quadrupole

Abstract

Approximate all-terrain spacetimes for astrophysical applications are presented. The metrics possess five relativistic multipole moments,
namely mass, rotation, mass quadrupole, charge, and magnetic dipole moment. All these spacetimes approximately satisfy the Einstein-
Maxwell field equations. The first metric is generated by means of the Hoenselaers-Perjés method from given relativistic multipoles. The
second metric is a perturbation of the Kerr-Newman metric, which makes it a relevant approximation for astrophysical calculations. The
last metric is an extension of the Hartle-Thorne metric that is important for obtaining internal models of compact objects perturbatively.
The electromagnetic field is calculated using Cartan forms for locally nonrotating observers. These spacetimes are relevant to infer properties of compact objects from astrophysical observations. Furthermore, the numerical implementations of these metrics are straightforward, making them versatile for simulating the potential astrophysical applications.