Shadows of Multi-Black Holes: Analytic Exploration

TL;DR

This paper analytically explores the complex shadow structures of multi-black hole systems, revealing how black hole interactions create distinctive features like eyebrows and deformations, aiding understanding of colliding black hole shadows.

Contribution

It provides the first analytic estimates of multi-black hole shadow features using static solutions and extends analysis to colliding black holes in the Kastor-Traschen solution.

Findings

Eyebrow width relates to black hole separation.

Shadows deform into ellipses due to multiple black holes.

Analytic models help understand black hole collision shadows.

Abstract

Shadows of multi-black holes have structures distinct from the mere superposition of the shadow of a single black hole: the eyebrow-like structures outside the main shadows and the deformation of the shadows. We present analytic estimates of these structures using the static multi-black hole solution (Majumdar-Papapetrou solution). We show that the width of the eyebrow is related with the distance between the black holes and that the shadows are deformed into ellipses due to the presence of the second black holes. These results are helpful to understand qualitatively the features of the shadows of colliding black holes. We also present the shadows of colliding/coalescing black holes in the Kastor-Traschen solution.