On the appearance of compact objects at radio and optical frequencies

TL;DR

This paper explores how dark energy stars, as transparent, lens background light at radio and optical frequencies, creating distinctive luminous disk images and emission features influenced by rotation and viewing angle.

Contribution

It provides simple analytic formulas to distinguish emission features of rotating dark energy stars based on angular momentum and viewing angle.

Findings

Features can appear within the black hole shadow for rapid rotation

Luminous disks reflect background brightness due to transparency

Analytic formulas enable separation of emission features

Abstract

In the dark energy star picture a compact object is transparent at radio and optical frequencies, and acts as a defocusing lens. Thus the object itself appears as a luminous disk whose surface brightness reflects the surface brightness of the background. In the case of rotating dark energy stars the image will also contain background independent emission features. In this note we provide simple analytic formulae for the separation of these features as a function of angular momentum and viewing angle. In the case of rapid rotation these features will appear to lie within the shadow expected if the compact object were a black hole.