Axion Mass Limits from Cooling Neutron Stars

Abstract

The thermal evolution of a neutron star is studied by including the energy loss due to axion emission. Two axion models and three types of neutron-star matter equation of state are used with the effects of nucleon superfluidity properly taken into account. In comparison with the observational data of PSR0656+14 from ROSAT, the upper limits on the axion mass are found to be $m_a<0.06-0.3$ eV and 0.08$-$ 0.8 eV for the KSVZ and DFSZ axion models, respectively, with the soft equation of state giving the most stringent limits.

1 PostScript file, Proceedings of the Symposium (17-20 November 1997, Tokyo) ``Neutron Stars and Pulsars'' eds. N. Shibazaki et al. (World Scientific), P.213, 1998