Estimation of the MTOV precision for ET, CE, and NEMO from the post-merger of BNS coalescences

TL;DR

The paper tackles how precisely the maximum mass of a cold non-rotating neutron star $M_{ m{TOV}}$ can be inferred from post-merger gravitational-wave signals of binary neutron star mergers observed by next-generation detectors. It combines numerical-relativity post-merger waveforms from two CoRe datasets with amplitude spectral-density analyses and matched-filtering against ET, CE, and NEMO sensitivity curves to assess detectability and infer the remnant mass distribution, then couples this with electromagnetic NS-mass distributions to project MTOV precision via a simple scaling with the number of detections. The results show CE provides the strongest PM-SNRs on average (e.g., mean $\mathrm{SNR}$ around 20 for Dataset 1) and yields the best MTOV precision (about $8\%\,M_{0}$) in optimistic merger-rate scenarios; however, precision degrades for mass-asymmetric systems (Dataset 2) and remains modest unless high-frequency sensitivity is substantially improved. The study underscores the need for enhanced high-frequency performance to tighten MTOV constraints, suggesting that long-arm CE-like detectors or targeted high-frequency enhancements are essential for robust PM-based MTOV estimation.

Abstract

The detection of the gravitational waves produced after the coalescence of two neutron stars is greatly anticipated because it will be able to provide information about matter in extreme conditions, especially if the remnant turns out to go through a hypermassive or a supermassive neutron star state before collapsing into a black hole. Next-generation gravitational wave detectors such as ET, CE, and NEMO are expected to observe high-frequency gravitational wave signals, that is, the post-merger stage of the coalescence of binary neutron stars; then from these signals one can estimate the maximum mass that a spinless neutron star (MTOV) can have. In this paper, we investigate the problem of the determination of the MTOV precision from the post-merger detected by next-generation observatories. The results show that CE achieves the best mass precision with approximately 8% $M_{\odot}$ for the maximum merger rate (250 Gpc-3yr-1). Therefore, based on the results obtained in this study, it will still be necessary to improve the sensitivity at high frequencies of future ground-based gravitational wave observatories if one wants to obtain greater precision in the MTOV estimation. One possibility would be to improve the sensitivity in a frequency range that allows us to determine whether or not a black hole was formed in the coalescence.

Figures (13)

• Figure 1: Strain time-series of the Dataset 1. The simulations were extracted at a distance $40\,\textrm{Mpc}$. They have components of equal mass or mass ratio equal to one. Each simulation has a different equation of state. The PM stage is the purple line.
• Figure 2: Strain time-series of the Dataset 2 located at $40\,\textrm{Mpc}$. The equation of state is fixed for all simulations: SLy. The mass ratio is not necessarily equal to one. The PM stage is marked as a purple line.
• Figure 3: Amplitude Spectral Density for Dataset 1. They are $q=1$ simulations that differ in the EoS. The main peaks are between $2.49-3.62\;\textrm{kHz}$, being the lowest value for the stiff EoS H4 and the highest value for the soft EoS SLy. In (A) we see that BAM0001 is particularly different from the rest of spectra because its time-domain has the shape of a prompt-collapse black hole, then it is possible to find additional peaks at $f\sim 6-8\,\textrm{kHz}$.
• Figure 4: Amplitude Spectral Density for Dataset 2. They have the same SLy EoS, but their mass ratio is not necessarily equal to $1$. The main peak frequencies are between $2.51-3.44\,\textrm{kHz}$. (F) shows a single peak at $2.5\,\textrm{kHz}$ from a, most probably, hypermassive neutron star (HMNS). In general, the spectra are less smooth compared to the spectra of data set 1, probably because of the mass-asymmetry and therefore, the irregularities in the oscillation of the remnant.
• Figure 5: Comparing the PM stage of the frequency-domain signal with the sensitivity curves of the ET, CE, NEMO detectors. The PM signal in this figure corresponds to BAM0095 (SLy EoS with $m_1=m_2=1.35\;M_{\odot}$) and its main peak ($3.405\;\rm{kHz}$) lies above the sensitivity curves, indicating it is potentially detectable.