Optical Signatures of q-deformed solution in Einstein-Maxwell-dilaton Gravity

TL;DR

This paper investigates the optical signatures and photon trajectories around spherically symmetric objects in Einstein-Maxwell-Dilaton gravity, analyzing deflection angles, photon rings, and accretion disk images to understand observational features.

Contribution

It introduces a detailed analysis of null geodesics, photon rings, and accretion disk images in Einstein-Maxwell-Dilaton gravity with variable coupling and charges, extending previous studies.

Findings

Photon deflection angles vary with dilaton coupling, flux, and magnetic charge.

Photon ring width correlates with Lyapunov exponent, indicating stability properties.

Optical images depend on emission profiles and ISCO radius calculations.

Abstract

We consider null geodesics in the background of spherically symmetric object in Einstein-Maxwell-Dilaton (EMD) theory with coupling function $f(\Phi)=e^{-2\lambda \Phi}$. The spherical solution is characteristically described by dilaton coupling $\lambda$, integrated dilaton flux $D$ and magnetic charge $P$. Then, we derive geodesic equations by using the Hamilton-Jacobi approach. The radial photon orbital equation on equatorial plane and effective potential are analyzed. The total deflection angle and trajectories of photon as a function of impact parameter $b$ are plotted with the variation of $\lambda,D$ and $P$. Furthermore, the relation between photon ring's width and the Lyapunov exponent is also explored. In addition, we use the Gralla-Lupsasca-Marrone (GLM) model to model intensity profile of optically thin accretion disk around the object. Hence, we construct optical images of the object surrounded by three distinct emission profiles. Lastly, we investigate the radius of innermost stable circular orbit (ISCO) for timelike geodesics.