Images of the accretion disk in hybrid metric-Palatini gravity

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 (GR). Furthermore, the structure and angular size of the secondary ring exhibit noticeable deviations from GR, 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 GR predictions.