Astrophysical Axion Bounds: The 2024 Edition

Understand

We review the current status of astrophysical bounds on QCD axions, primarily based on the observational effects of nonstandard energy losses on stars, including black-hole superradiance.

• Over the past few years, many of the traditional arguments have been reexamined both theoretically and using modern data and new ideas have been put forth.
• This compact review updates similar Lecture Notes written by one of us in 2006 [Lect.
• Notes Phys.