Shadow geometry of Kerr MOG naked singularity and analysis of accretion disk luminosity

TL;DR

This paper investigates the shadow features and accretion disk luminosity of Kerr MOG naked singularities, revealing unique shadow structures and how MOG parameters influence observable properties, aiding in distinguishing them from black holes.

Contribution

It provides a detailed analysis of the shadow geometry and accretion disk luminosity of Kerr MOG naked singularities, highlighting features not present in standard black hole models.

Findings

KMNS shadows can be closed, open, or vanish depending on parameters.

Critical conditions for shadow gaps are identified.

MOG parameter alpha significantly affects disk luminosity and shadow features.

Abstract

Naked singularities are hypothetical astrophysical entities featuring gravitational singularities without event horizons. In this study, we analyze the shadow properties of Kerr Modified Gravity (Kerr MOG) naked singularities (KMNSs). We show that the KMNS shadow can appear closed, open, or even vanish, depending on the dimensionless spin parameter a, the modified gravity parameter alpha, and the observer's inclination angle. We identify the critical conditions under which the KMNS shadow develops a gap, a unique feature not present in BH shadows. We analyze the properties of a thin accretion disk surrounding a KMNS, within the framework of MOG characterized by the parameter alpha. The study includes a detailed examination of the spacetime geometry and the equations of motion for test particles. In addition, we adopt a simplified model for the disk's radiative flux, temperature distribution, and spectral luminosity. Our analysis primarily focuses on the flux distribution of the accretion disk around KMNS with identical mass but varying spin and MOG deformation parameters. This allows us to explore how modifications in rotation and the MOG parameter alpha influence the radiative properties of the disk. Further, these observational signatures may serve as effective tools for clearly distinguishing KMNS from standard Kerr naked singularities (KNSs), where the MOG parameter alpha = 0