White dwarfs as a probe of exceptionally light QCD axions

Understand

We study the effects of exceptionally light QCD axions on the stellar configuration of white dwarfs.

• At finite baryon density, the non-derivative coupling of the axion to nucleons displaces the axion from its in-vacuum minimum which implies a reduction of the nucleon mass.
• This dramatically alters the composition of stellar remnants.
• In particular, the modifications of the mass-radius relationship of white dwarfs allow us to probe large regions of unexplored parameter space without requiring that axions are dark matter.