Probing dense matter in neutron stars with axialwmodes

Abstract

We study the problem of extracting information about composition and equation of state of dense matter in neutron star interior using axial $w$ modes. We determine complex frequencies of axial $w$ modes for a set of equations of state involving hyperons as well as Bose-Einstein condensates of antikaons adopting the continued fraction method. Hyperons and antikaon condensates result in softer equations of state leading to higher frequencies and lower damping times of first axial $w$ modes than those of the nuclear matter case. The presence of condensates may lead to the appearance of a new stable branch of superdense stars beyond the neutron star branch called the third family. The existence of the same mass compact stars in both branches is known as neutron star twins. Further investigation of twins reveals that first axial $w$-mode frequencies of superdense stars in the third family are higher than those of the corresponding twins in the neutron star branch.