Thin accretion disk images of rotating hairy Horndeski black holes

TL;DR

This paper models thin accretion disks around rotating hairy black holes in Horndeski gravity, revealing how the hair parameter influences disk efficiency and shadow size, with implications for observational signatures.

Contribution

It introduces a detailed analysis of accretion disk properties and images for rotating hairy black holes in Horndeski gravity, extending previous Kerr black hole models.

Findings

Decreasing hair parameter reduces the innermost stable circular orbit radius.

Accretion disks become more efficient with lower hair parameter.

Black hole shadow size is affected by the hair parameter.

Abstract

By considering the steady-state Novikov-Thorne model, we study thin accretion disk processes for rotating hairy black holes in the framework of the Horndeski gravity. We obtain the electromagnetic properties of accretion disk around such black holes and investigate the effects of the hair parameter $h$ on them. We find that by decreasing the hair parameter from the Kerr limit, $h\rightarrow0$, the radius of the innermost stable circular orbit decreases which makes thin accretion disks around rotating hairy black holes in Horndeski gravity more efficient than that for the Kerr black hole in general relativity. Furthermore, using the numerical ray-tracing method, we plot thin accretion disk images around these black holes and investigate the effects of hair parameter on the central shadow area of accretion disk.