Identifying a first-order phase transition in neutron star mergers through gravitational waves

TL;DR

This paper demonstrates that a first-order hadron-quark phase transition in neutron star mergers can be detected through deviations in the gravitational-wave frequency post-merger, indicating the presence of quark matter cores.

Contribution

It introduces a method to identify a first-order phase transition in neutron stars via gravitational-wave signatures, highlighting a potential observational probe for quark matter.

Findings

Significant deviation in postmerger GW frequency indicates phase transition.

Only mergers with strong first-order phase transitions show this GW imprint.

Future GW observations can confirm the existence of quark matter cores in neutron stars.

Abstract

We identify an observable imprint of a first-order hadron-quark phase transition at supranuclear densities on the gravitational-wave (GW) emission of neutron star mergers. Specifically, we show that the dominant postmerger GW frequency f_peak may exhibit a significant deviation from an empirical relation between f_peak and the tidal deformability if a strong first-order phase transition leads to the formation of a gravitationally stable extended quark matter core in the postmerger remnant. A comparison of the GW signatures from a large, representative sample of microphysical, purely hadronic equations of state indicates that this imprint is only observed in those systems which undergo a strong first-order phase transition. Such a shift of the dominant postmerger GW frequency can be revealed by future GW observations, which would provide evidence for the existence of a strong first-order phase transition in the interior of neutron stars.