# Images of the accretion disk in Hybrid metric-Palatini gravity

## TL;DR

This study models accretion disk images around black holes in hybrid metric-Palatini gravity, revealing how scalar fields influence observable features and potentially distinguish these from General Relativity.

## Contribution

First to generate and analyze accretion disk images in hybrid metric-Palatini gravity using semi-analytic ray-tracing methods.

## Key findings

- Scalar field parameters significantly affect disk images.
- Extreme scalar values produce cooler, dimmer disks than in General Relativity.
- Secondary ring structures show deviations from GR predictions.

## Abstract

In this paper we obtain and study images of accretion disks around static spherically symmetric black holes in hybrid metric-Palatini gravity. We use Novikov-Thorne thin-disk model. Semi-analytic ray-tracing methods in curved spacetime are employed to generate the images of the disk for different scalar field configurations, including both Higgs-type potentials and cases without a potential. The resulting images, including both redshift and intensity maps, are analyzed. The results show that the scalar field parameters play a significant role in shaping both the direct and secondary images of the disk, while the inclination angle primarily affects the asymmetry and brightness distribution. In particular, configurations with extreme scalar field values lead to cooler and dimmer disk compared to General Relativity. Furthermore, the structure and angular size of the secondary ring exhibit noticeable deviations from General Relativity, offering a potential observational signature. This work should be regarded as a first step toward modeling realistic accretion disks within the hybrid metric-Palatini gravity framework, and toward assessing their potential observational distinguishability from General Relativity predictions.