Thin accretion disk signatures of slowly rotating black holes in Ho\v{r}ava gravity

TL;DR

This paper investigates how accretion disk emissions around slowly rotating black holes in Hořava gravity differ from those in general relativity, proposing observational tests to distinguish between these theories.

Contribution

It provides a detailed analysis of accretion disk properties in Hořava gravity, highlighting observable differences from Kerr black holes that could test the theory.

Findings

Higher energy flux in Hořava black holes compared to Kerr.

Greater efficiency in converting accreted mass into radiation.

Distinct electromagnetic signatures in accretion disk spectra.

Abstract

In the present work, we consider the possibility of observationally testing Ho\v{r}ava gravity by using the accretion disk properties around slowly rotating black holes of the Kehagias-Sfetsos solution in asymptotically flat spacetimes. The energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and compared to the standard slowly rotating general relativistic Kerr solution. Comparing the mass accretion in a slowly rotating Kehagias-Sfetsos geometry in Ho\v{r}ava gravity with the one of a slowly rotating Kerr black hole, we verify that the intensity of the flux emerging from the disk surface is greater for the slowly rotating Kehagias-Sfetsos solution than for rotating black holes with the same geometrical mass and accretion rate. We also present the conversion efficiency of the accreting mass into radiation, and show that the rotating Kehagias-Sfetsos solution provides a much more efficient engine for the transformation of the accreting mass into radiation than the Kerr black holes. Thus, distinct signatures appear in the electromagnetic spectrum, leading to the possibility of directly testing Ho\v{r}ava gravity models by using astrophysical observations of the emission spectra from accretion disks.