Maximum mass of hybrid star formed via shock induced phase transition in cold neutron stars

TL;DR

This paper investigates the maximum mass of hybrid stars formed via shock-induced phase transitions in cold neutron stars, using equations of state and combustion adiabat conditions to determine mass limits and transition energetics.

Contribution

It introduces a method to determine maximum mass limits of hybrid stars through combustion adiabat analysis considering exothermic and endothermic phase transitions.

Findings

Exothermic transitions lead to smaller hybrid stars than parent neutron stars.

Global maximum pressure corresponds to the maximum mass of hybrid stars.

Massive hybrid stars can form with external energy input or under certain EoS conditions.

Abstract

This article studies the maximum mass limit of the quark star formed after the shock-induced phase transition of a cold neutron star. By employing hadronic and quark equation of state that satisfies the current mass bound, we use combustion adiabat conditions to find such a limit. The combustion adiabat condition results in a local or a global maximum pressure at an intermediate density range. The maximum pressure corresponds to a local or global maximum mass for the phase transformed hybrid star. The phase transition is usually exothermic if we have a local maximum mass. The criteria for exothermic or endothermic phase transition depend on whether the quark pressure/energy ratios to nuclear pressure/energy are smaller or greater than 1. We find that exothermic phase transition in a cold neutron star usually results in hybrid stars whose mass is smaller than a parent neutron star. The phase transition is endothermic for a global maximum pressure; thereby, one gets a global maximum mass. Hybrid stars much massive than phase transformed local maximum mass can be formed, provided there is some external energy source during the phase transition process. However, for some cases, even massive hybrid stars can form with exothermic phase transition for EoSs having global maximum pressure.