Lecture Notes: WISPs in gamma-ray astrophysics

TL;DR

This paper provides an overview of WISPs, especially axions and ALPs, in gamma-ray astrophysics, highlighting their observational signatures, phenomenology, and potential to probe physics beyond the Standard Model.

Contribution

It offers a comprehensive review of WISP-related astrophysical phenomena, including ALP-photon conversion and decay signatures, with practical tutorials on data analysis.

Findings

ALP-photon conversion can modify gamma-ray spectra and polarization.

Distinctive signatures in astrophysical observations can indicate WISP presence.

Tutorials demonstrate methods to analyze gamma-ray data for WISP signals.

Abstract

These lecture notes provide an overview of high-energy astrophysical processes involving axions, axion-like particles (ALPs), and other weakly interacting slim particles (WISPs) focusing on their potential observational signatures in astrophysical environments. After introducing key concepts in high-energy astrophysics, we present the fundamental properties of WISPs, emphasizing their phenomenological implications. Particular attention is given to ALP-photon conversion in strong magnetic fields and the possible decay signatures of ALPs in sources such as active galactic nuclei, galaxy clusters, and cosmic-ray accelerators. These effects can lead to distinctive modifications in astrophysical spectra, spatial distributions, and polarization patterns, providing unique probes of physics beyond the Standard Model. We discuss their role in dark matter scenarios and their potential impact on high-energy observations. The lecture series is supplemented by hands-on tutorials, including exercises on axion electrodynamics and an analysis of gamma-ray data from NGC 1275 to search for ALP-photon conversion signatures.