Axion effects in the stability of hybrid stars
Bruno S. Lopes, Ricardo L. S. Farias, Verônica Dexheimer, Aritra Bandyopadhyay, Rudnei O. Ramos
Abstract
We investigate the effects of including strong $CP$ violating effects through axion fields in the microscopic equation of state of massive hybrid neutron stars. We assume that their cores contain deconfined quark matter and include the effects of axions via an effective `t Hooft determinant interaction. The hadronic crusts are described using different approaches in order to make our results more general. We find that the presence of axions stabilizes massive hybrid neutron stars against gravitational collapse by weakening the deconfinement phase transition and bringing it to lower densities. This enables to reproduce hybrid neutron stars in agreement with modern astrophysical constraints.