Probing dense matter in neutron stars with axial w-modes

TL;DR

This paper investigates how axial w-modes can reveal the internal composition and equation of state of neutron stars, especially considering hyperons and antikaon condensates, and explores the implications for neutron star twins and the third family.

Contribution

It introduces a method to analyze axial w-modes for various equations of state, including exotic matter, and examines their impact on neutron star properties and stability.

Findings

Hyperons and antikaon condensates lead to higher axial w-mode frequencies.

Presence of condensates can create a third family of superdense stars.

Axial w-mode frequencies differ between neutron star twins in different branches.

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 of first axial w-modes than that of nuclear matter case, whereas the opposite happens in case of damping times. 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 same mass compact stars in both branches are known as neutron star twins. Further investigation of twins reveal 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.