The light pseudoscalar particle, dubbed the axion, borne out of the Peccei-Quinn solution to the strong CP problem in QCD remains elusive. One avenue of inferring its existence is through its coupling to electromagnetic radiation. So far, laboratory experiments have dedicated all efforts to detect the axion in the mass range 10-6<ma<10-3eV with a photon-axion coupling strength gaγγ<10-10GeV-1, where the limits are derived from astrophysical considerations. In this study, we present a novel way of constraining gaγγ by looking at the level of linear polarization in the radiation emerging from magnetic white dwarfs. We find that photon-axion oscillations in white dwarf magnetospheres can enhance the degree of linear polarization. Observing that most magnetic white dwarfs show only 5% linear polarization, we derive upper limits on gaγγ for different axion masses.
Physical Review D
- Pub Date:
- October 2011
- Faint blue stars white dwarfs degenerate stars nuclei of planetary nebulae;
- Astrophysics - High Energy Astrophysical Phenomena;
- High Energy Physics - Phenomenology
- Accepted for publication in PRD. 10 pages, 5 figs. Main results are changed, new references are added, Results section is extended to incorporate the changes. Outlook section is also extended with new references. Fig. 2 and 4 are modified