Gravitational Wave Signal for Quark Matter with Realistic Phase Transition

TL;DR

This paper demonstrates that gravitational wave signals from neutron star mergers can reveal the presence of quark matter and the nature of the phase transition, using realistic equations of state constrained by ab initio methods.

Contribution

It introduces a method to identify quark matter signatures in gravitational waves using realistic EOS constraints, advancing the understanding of dense matter in neutron stars.

Findings

Early black hole formation indicates softening of the EOS due to quark matter.

Gravitational wave signatures can distinguish between hadron-quark phase transition scenarios.

Electromagnetic counterparts can further constrain the phase transition properties.

Abstract

The cores of neutron stars (NSs) near the maximum mass realize the most highly compressed matter in the universe where quark degrees of freedom may be liberated. Such a state of dense matter is hypothesized as quark matter (QM) and its presence has awaited to be confirmed for decades in nuclear physics. Gravitational waves from binary NS mergers are expected to convey useful information called the equation of state (EOS). However, the signature for QM with realistic EOS is not yet established. Here, we show that the gravitational wave in the post-merger stage can distinguish the theory scenarios with and without a transition to QM. Instead of adopting specific EOSs as studied previously, we compile reliable EOS constraints from the ab initio approaches. We demonstrate that early collapse to a black hole after NS merger signifies softening of the EOS associated with the onset of QM in accord with ab initio constraints. Nature of hadron-quark phase transition can be further constrained by the condition that electromagnetic counterparts need to be energized by the material left outside the remnant black hole.