Stellar Evolution Bounds on the ALP-Photon Coupling: new Results and Perspectives

TL;DR

This paper reviews stellar evolution constraints on the axion-like particle (ALP) photon coupling, presenting new bounds from horizontal branch stars that improve existing limits across a broad mass range.

Contribution

It offers a comprehensive review and a novel analysis of bounds from helium burning stars, establishing the strongest constraints on g_{a extgamma} to date.

Findings

New bounds from horizontal branch stars are the most stringent to date.

The analysis covers a wide ALP mass range.

Stellar evolution provides critical limits on ALP-photon interactions.

Abstract

Stellar evolution considerations are of fundamental importance in our understanding of the axion/ALP-photon coupling, g_{a\gamma}. Helium burning stars are the best laboratories to study this coupling. Here, we will review the bounds from massive and low mass helium burning stars, and present a new analysis of the bound from the horizontal branch stars. The analysis provides the strongest bound to date on g_{a\gamma} in a wide mass range.