Polarized image of equatorial emission in horizonless spacetimes I: traversable wormholes

TL;DR

This study investigates the polarization signatures of accretion disks around traversable wormholes, identifying distinctive features in strongly lensed and throat-crossing radiation that could differentiate wormholes from black holes.

Contribution

It introduces a polarization analysis of accretion disks around static traversable wormholes, highlighting observable signatures in strongly lensed and throat-crossing images that distinguish them from black holes.

Findings

Polarization patterns are similar for small inclination angles.

Strongly lensed images show polarization intensity up to ten times higher in wormholes.

Radiation crossing the wormhole throat creates unique ring structures with distinct polarization properties.

Abstract

We study the linear polarization from the accretion disk around a class of static traversable wormholes. Applying the simplified model of a magnetized fluid ring orbiting in the equatorial plane, we search for characteristic signatures, which could distinguish wormhole from black hole spacetimes by their polarization properties. For the purpose we analyse the direct polarized images for different inclination angles, the strongly lensed indirect images, and the polarized radiation which reaches the asymptotic observer through the wormhole throat, and compare to the Schwarzschild black hole. For small inclination angles the two types of compact objects lead to a very similar polarization pattern of the direct images. More significant distinctions are observed for the strongly lensed indirect images, where the polarization intensity in the wormhole spacetimes can grow up to an order of magnitude compared to the Schwarzschild black hole. Detecting radiation from the region across the wormhole throat leads to the formation of an additional structure of ring images with distinct polarization properties. The twist of the polarization vector around the ring is less pronounced, thus modifying the polarization pattern, and the polarization intensity can increase with an order of magnitude compared to the radiation from our universe. Thus, while it could be difficult to distinguish wormhole spacetimes by their direct polarized images, the strongly lensed images and the polarization of the radiation through the wormhole throat provide characteristic signatures which can serve as probes for horizonless objects.