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The equation of state (EOS) of dense strongly interacting matter can be probed by astrophysical observations of neutron stars (NS), such as X-ray detections of pulsars or the measurement of the tidal deformability of NSs during the inspiral stage of NS mergers. These observations constrain the EOS at most up to the density of the maximum-mass configuration,nTOV, which is the highest density that can be explored by stable NSs for a given EOS. However, under the right circumstances, binary neutron star (BNS) mergers can create a postmerger remnant that explores densities abovenTOV. In this work, we explore whether the EOS abovenTOVcan be measured from gravitational-wave or electromagnetic observations of the postmerger remnant. We perform a total of 25 numerical-relativity simulations of BNS mergers for a range of EOSs and find no case in which different descriptions of the matter abovenTOVhave a detectable impact on postmerger observables. Hence, we conclude that the EOS abovenTOVcan likely not be probed through BNS merger observations for the current and next generation of detectors.
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This content will become publicly available on July 28, 2027
Probing Binary Neutron Star Merger Ejecta and Remnants with Gravitational-wave and Radio Observations
Abstract We present a study aimed at quantifying the detectability of radio counterparts of binary neutron star (BNS) mergers with total masses ≲3M⊙, which may form neutron star remnants. We focus on mergers localized by gravitational-wave (GW) observations to sky areas ≲10 deg2, a precision that greatly facilitates optical counterpart identification and enables radio discovery even without detections at other wavelengths. Widely separated GW detectors are essential for building samples of well-localized BNS mergers accessible to radio telescopes, with minimum yearly detection rates (assuming the smallest values of the BNS local merger rate) ranging from a few with current GW detectors to hundreds with next-generation GW instruments. Current GW networks limit well-localized detections toz ≲ 0.2, while next-generation GW detectors extend the reach toz ≲ 0.8, encompassing the median redshift of short gamma-ray bursts (GRBs). With next-generation radio arrays operating at several tens of GHz and providing an order of magnitude improvement in sensitivity compared to the most sensitive ones available today, short GRB-like jet afterglows can be detected for a large fraction of the considered BNS mergers. At lower radio frequencies, detections with current radio interferometric arrays are feasible, though subject to synchrotron self-absorption effects. The enhanced sensitivity and survey speed of future radio interferometers operating at a few GHz, combined with the higher detection rate of well-localized BNSs enabled by next-generation GW observatories, are key to probing disk-wind and dynamical ejecta afterglows, as well as remnant diversity.
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- Award ID(s):
- 2431072
- PAR ID:
- 10708407
- Publisher / Repository:
- https://iopscience.iop.org/article/10.3847/1538-4357/ae80ab
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 1006
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 215
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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