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.
Categories: astro-ph.HE hep-ph