New light rings from multiple critical curves as observational signatures of black hole mimickers

TL;DR

The paper proposes that observing multiple light rings in black hole shadows could indicate the presence of black hole mimickers with multiple critical curves, supported by models of wormhole geometries.

Contribution

It introduces the concept that additional light rings can serve as observational signatures of black hole mimickers with multiple critical curves, supported by specific wormhole models.

Findings

Multiple light rings can occur in wormhole geometries

Optical appearance of wormholes with accretion disks shows distinct signatures

Multiple critical curves are theoretically plausible in spherically symmetric models

Abstract

We argue that the appearance of additional light rings in a shadow observation - beyond the infinite sequence of exponentially demagnified self-similar rings foreseen in the Kerr solution - would make a compelling case for the existence of black hole mimickers having multiple critical curves. We support this claim by discussing three different scenarios of spherically symmetric wormhole geometries having two such critical curves, and explicitly work out the optical appearance of one such object when surrounded by an optically and geometrically thin accretion disk.