Relativistic tidal effects in non standard Kerr space-time

TL;DR

This paper investigates how non-standard Kerr space-time metrics, specifically the Johannsen-Psaltis parametrization, affect tidal effects around spinning black holes, revealing potential observable deviations in gravitational and electromagnetic signals.

Contribution

It introduces a method to compute tidal tensors in non-Kerr space-times and compares results with standard GR, highlighting significant differences that could impact binary evolution.

Findings

Significant deviations in tidal tensors from GR predictions at various distances.

Differences in binary evolution signatures due to non-standard space-time metrics.

Potential for observable signatures in gravitational-wave and electromagnetic spectra.

Abstract

Astrophysical phenomena involving massive black holes (BHs) in close binaries are expected to leave detectable signatures in the electromagnetic and gravitational-wave spectrum. Such imprints may provide precious information to probe the space-time around rotating BHs and to reveal new insights on the nature of gravity in the strong-field regime. To support this observational window, it is crucial to develop suitable tests to verify the predictions of General Relativity. In this framework, the metric recently proposed by Johannsen and Psaltis parametrizes strong-field deviations from a Kerr space-time in a theory-independent way. In the following, we make use of this approach to describe the tidal field produced by spinning BHs. We compute the gravito-magnetic and gravito-electric tidal tensors for particles moving on equatorial circular geodesics, comparing our results with those obtained in the standard General Relativity scenario. Our calculations show significant differences even for distances far form the last stable orbit, which may affect the evolution of the binary and leave detectable signatures. We test our framework computing quasiequilibrium sequences of BH-white dwarf systems by means of the affine model, for different binary configurations.