Electromagnetically-Induced Frame-Dragging around Astrophysical Objects

TL;DR

This paper develops an analytic model to quantify electromagnetic contributions to frame-dragging effects around astrophysical objects with complex electromagnetic multipole moments, extending understanding beyond traditional gravitational effects.

Contribution

It introduces a new analytic solution to Einstein-Maxwell equations accounting for arbitrary electromagnetic multipoles, highlighting their impact on stellar dynamics and observable quantities.

Findings

Electromagnetic fields can induce frame dragging in astrophysical objects.

Magnetic and electric multipole moments significantly affect stellar properties.

Corrections to ISCO and epicyclic frequencies are quantified.

Abstract

Frame dragging (Lense-Thirring effect) is generally associated with rotating astrophysical objects. However, it can also be generated by electromagnetic fields if electric and magnetic fields are simultaneously present. In most models of astrophysical objects, macroscopic charge neutrality is assumed and the entire electromagnetic field is characterized in terms of a magnetic dipole component. Hence, the purely electromagnetic contribution to the frame dragging vanishes. However, strange stars may posses independent electric dipole and neutron stars independent electric quadrupole moments that may lead to the presence of purely electromagnetic contributions to the frame dragging. Moreover, recent observations have shown that in stars with strong electromagnetic fields, the magnetic quadrupole may have a significant contribution to the dynamics of stellar processes. As an attempt to characterized and quantify the effect of electromagnetic frame-dragging in this kind of astrophysical objects, an analytic solution to the Einstein-Maxwell equations is constructed here on the basis that the electromagnetic field is generated by the combination of arbitrary magnetic and electric dipoles plus arbitrary magnetic and electric quadrupole moments. The effect of each multipole contribution on the vorticity scalar and the Poynting vector is described in detail. Corrections on important quantities such the innermost stable circular orbit (ISCO) and the epyciclic frequencies are also considered.