Axions and the pulsation periods of variable white dwarfs revisited
J. Isern1,2, E. García-Berro2,3, L. G. Althaus3,4 and A. H. Córsico4,5
Institut de Ciències de l'Espai (CSIC),
Facultat de Ciències,
Spain e-mail: email@example.com
2 Institut d'Estudis Espacials de Catalunya, c/ Gran Capità 2–4, 08034 Barcelona, Spain
3 Departament de Física Aplicada, Escola Politècnica Superior de Castelldefels, Universitat Politècnica de Catalunya, Avda. del Canal Olímpic s/n, 08860 Castelldefels, Spain
4 Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de la Plata Paseo del Bosque, s/n, (1900), La Plata, Argentina
5 Instituto de Astrofísica La Plata, CONICET, Argentina
Accepted: 16 January 2010
Context. 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.
Aims. Our aim is to show that variable white dwarfs can provide additional and independent evidence about the existence of axions.
Methods. 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.
Results. 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.
Key words: elementary particles / white dwarfs / stars: oscillations
© ESO, 2010