Observational properties of relativistic fluid spheres with thin accretion disks

Abstract

In this work we analyze the observational properties of incompressible relativistic fluid spheres with and without thin-shells, when surrounded by thin accretion disks. We consider a set of six configurations with different combinations of the star radius $R$ and the thin-shell radius $r_{\Sigma }$ to produce solutions with neither thin-shells nor light-rings, with either of those features, and with both. Furthermore, we consider three different models for the intensity profile of the accretion disk, based on the Gralla-Lupsasca-Marrone (GLM) disk model, for which the peaks of intensity occur at the Innermost Stable Circular Orbit (ISCO), the Light-Ring (LR), and the center of the star. The observed images and intensity profiles for an asymptotic observer are produced using a Mathematica-based ray-tracing code. Our results indicate that, in the absence of a light-ring, the presence of a thin-shell produces a negligible effect in the observational properties of the stars. However, when the spacetime features a light-ring, the portion of the mass of the star that is stored in the thin-shell has a strong effect on its observational properties, particularly in the magnitude of the central gravitational redshift effect responsible for causing a central shadow-like dimming in the observed images. A comparison with the Schwarzschild spacetime is also provided and the most compact configurations are shown to produce observational imprints similar to those of black-hole solutions, with subtle qualitative differences, most notably extra secondary image components that decrease the radius of the shadow and are potentially observable.

22 pages, 25 figures

References in corpus (11)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• Advection-Dominated Accretion and the Black Hole Event Horizon
• Light ring stability in ultra-compact objects
• Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole
• How to tell a gravastar from a black hole
• Ultralight boson cloud depletion in binary systems
• Images and photon ring signatures of thick disks around black holes
• Superradiance in stars
• Existence and stability of relativistic fluid spheres supported by thin shells

Cited by in corpus (2)

• Investigating shadow images and rings of the charged Horndeski black hole illuminated by various thin accretions
• Light Ring behind Wormhole Throat: Geodesics, Images and Shadows