Axions and the pulsation periods of variable white dwarfs revisited

TL;DR

This paper investigates how the existence of axions, hypothetical particles, could influence the pulsation periods of variable white dwarfs, providing potential independent evidence for axions through stellar evolution observations.

Contribution

It demonstrates that axions could significantly affect white dwarf cooling rates and pulsation period changes, offering a new method to detect or constrain axion properties.

Findings

Rate of period change in G117-B15A aligns with axion models

Axions could cause noticeable perturbations in DBV star pulsation periods

White dwarf luminosity function supports axion existence with a few meV mass

Abstract

Axions are the natural consequence of the introduction of the Peccei-Quinn symmetry to solve the strong CP problem. All the efforts to detect such elusive particles have failed up to now. Nevertheless, it has been recently shown that the luminosity function of white dwarfs is best fitted if axions with a mass of a few meV are included in the evolutionary calculations. Our aim is to show that variable white dwarfs can provide additional and independent evidence about the existence of axions. The evolution of a white dwarf is a slow cooling process that translates into a secular increase of the pulsation periods of some variable white dwarfs, the so-called DAV and DBV types. Since axions can freely escape from such stars, their existence would increase the cooling rate and, consequently, the rate of change of the periods as compared with the standard ones. The present values of the rate of change of the pulsation period of G117-B15A are compatible with the existence of axions with the masses suggested by the luminosity function of white dwarfs, in contrast with previous estimations. Furthermore, it is shown that if such axions indeed exist, the drift of the periods of pulsation of DBV stars would be noticeably perturbed.