Photon Ring Dimming as a Signature of Photon-Axion Conversion in Janis-Newman-Winicour Naked Singularity

TL;DR

This paper explores how photon-axion conversion near a naked singularity could cause photon ring dimming, offering a potential observational signature for axions in high-energy astrophysics.

Contribution

It investigates photon-axion conversion in JNW spacetime and predicts observable photon ring dimming as a novel signature of axions near naked singularities.

Findings

Photon-axion conversion is efficient for axion masses below 100 neV.

Conversion probability depends on JNW spacetime parameters.

Photon ring dimming could be observable in X-ray and gamma-ray spectra.

Abstract

The possible existence of axions in the universe introduces the intriguing possibility of photon-axion conversion in strong magnetic fields, particularly near compact objects like supermassive black holes or even naked singularity. In this study, we investigate the conversion of photons into axions in the vicinity of a Janis-Newman-Winicour (JNW) spacetime, a well-known naked singularity solution. Our analysis reveals that photons can efficiently convert into axions with masses less than $100 \rm \ neV$. We calculate the conversion probability and find that it is significantly influenced by the characteristic parameter of the JNW spacetime. The potential observational signatures of this conversion, would be the dimming of photon ring in the X-ray and gamma-ray spectrum. Our findings suggest that compact objects like M87* could be prime candidates for detecting photon-axion conversion effects, provided future advances in high-resolution observations.