On the appearance of compact objects at radio and optical frequencies

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.