Axion searches with Fermi and IACTs

TL;DR

This paper explores how axion-like particles could influence gamma-ray spectra from distant sources, proposing observational strategies with Fermi and Cherenkov telescopes to detect their signatures and address existing spectral puzzles.

Contribution

It introduces a comprehensive framework considering photon/axion mixing both at the source and in intergalactic space, offering new insights for ALP detection strategies.

Findings

Photon/axion mixing can explain spectral anomalies in gamma-ray sources.

The framework suggests specific observational signatures for ALPs.

Strategies for detecting ALPs with current gamma-ray telescopes are outlined.

Abstract

Axion Like Particles (ALPs), postulated to solve the strong-CP problem, are predicted to couple with photons in the presence of magnetic fields, which may lead to a significant change in the observed spectra of gamma-ray sources such as AGNs. Here we simultaneously consider in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. We show that photon/axion mixing could explain recent puzzles regarding the observed spectra of distant gamma-ray sources as well as the recently published lower limit to the EBL intensity. We finally summarize the different signatures expected and discuss the best strategy to search for ALPs with the Fermi satellite and current Cherenkov telescopes like CANGAROO, HESS, MAGIC and VERITAS.