Shadows and photon rings of a spherically accreting Kehagias-Sfetsos black hole

TL;DR

This paper explores the optical appearance and shadow features of Kehagias-Sfetsos black holes within Hořava-Lifshitz gravity, analyzing how the Hořava parameter influences observable properties and constraining it using EHT data.

Contribution

It provides the first detailed analysis of shadows and photon rings of Kehagias-Sfetsos black holes, linking theoretical predictions with observational constraints.

Findings

Increasing Hořava parameter decreases shadow size.

Luminosity of shadows and photon rings increases with the Hořava parameter.

Constraints on the Hořava parameter are derived from EHT observations of M87* and Sgr A*.

Abstract

By considering Kehagias-Sfetsos black hole in the framework of the Ho\v{r}ava-Lifshitz gravity, we study the optical appearance of such black holes surrounded by spherical accretion flow. For the static/infalling spherical accretion flow, we compute the observed specific intensity as a function of impact parameter. We also investigate the effect of the Ho\v{r}ava parameter and accreting matter on the luminosity of shadows and photon rings. It is found that an increase in the Ho\v{r}ava parameter decreases the shadow size, while the shadows and photon rings luminosities increase. Moreover, we constrain the Ho\v{r}ava parameter from the observational data reported by the Event Horizon Telescope for M87* and Sgr A*.