An Approximate Kerr-Newman-like Metric Endowed with a Magnetic Dipole and Mass Quadrupole

TL;DR

This paper introduces approximate spacetimes with five multipole moments, including magnetic dipole and quadrupole, useful for modeling astrophysical objects and their electromagnetic fields.

Contribution

It presents new approximate metrics with multiple multipole moments, extending Kerr-Newman and Hartle-Thorne solutions for better astrophysical modeling.

Findings

Metrics incorporate five relativistic multipole moments.

The metrics satisfy Einstein-Maxwell equations approximately.

Numerical implementations are straightforward and versatile.

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-Perj\'es 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.