Equation of State of Decompressed Quark Matter, and Observational Signatures of Quark-Star Mergers

TL;DR

This paper calculates the non-equilibrium equation of state of decompressed quark matter at finite temperature to predict observational signatures of quark-star mergers, potentially distinguishing them from neutron star mergers.

Contribution

It presents the first detailed modeling of ejecta from quark-star mergers, including physical processes like evaporation, cooling, and weak interactions, to identify observational differences.

Findings

Ejecta from quark-star mergers can differ markedly from neutron star mergers.

High binding energy quark matter may suppress r-process element production.

Future observations could constrain quark matter properties and quark star existence.

Abstract

Quark stars are challenging to confirm or exclude observationally because they can have similar masses and radii as neutron stars. By performing the first calculation of the non-equilibrium equation of state of decompressed quark matter at finite temperature, we determine the properties of the ejecta from binary quark-star or quark star-black hole mergers. We account for all relevant physical processes during the ejecta evolution, including quark nugget evaporation and cooling, and weak interactions. We find that these merger ejecta can differ significantly from those in neutron star mergers, depending on the binding energy of quark matter. For relatively high binding energies, quark star mergers are unlikely to produce r-process elements and kilonova signals. We propose that future observations of binary mergers and kilonovae could impose stringent constraints on the binding energy of quark matter and the existence of quark stars.