Maximum mass of a hybrid star having a mixed phase region in the light of pulsar PSR J1614-2230

TL;DR

This paper investigates the maximum mass of hybrid stars with a mixed quark-hadron phase, finding that under certain conditions, they can reach about 2.01 solar masses, consistent with recent pulsar observations.

Contribution

It introduces a model for hybrid stars with a mixed phase using a density-dependent bag constant to match observed high pulsar masses.

Findings

Hybrid stars with a mixed phase can reach 2.01 solar masses.

A small mixed phase region is sufficient for high mass limits.

Density-dependent bag constants are crucial for maximum mass achievement.

Abstract

Recent observation of pulsar PSR J1614-2230 with mass about 2 solar masses poses a severe constraint on the equations of state (EOS) of matter describing stars under extreme conditions. Neutron stars (NS) can reach the mass limits set by PSR J1614-2230. But stars having hyperons or quark stars (QS) having boson condensates, with softer EOS can barely reach such limits and are ruled out. QS with pure strange matter also cannot have such high mass unless the effect of strong coupling constant or colour superconductivity are taken into account. In this work I try to calculate the upper mass limit for a hybrid stars (HS) having a quark-hadron mixed phase. The hadronic matter (having hyperons) EOS is described by relativistic mean field theory and for the quark phase I use the simple MIT bag model. I construct the intermediate mixed phase using Glendenning construction. HS with a mixed phase cannot reach the mass limit set by PSR J1614-2230 unless I assume a density dependent bag constant. For such case the mixed phase region is small. The maximum mass of a mixed hybrid star obtained with such mixed phase region is $2.01 M_{\odot}$.