Second release of the CoRe database of binary neutron star merger waveforms

Abstract

We present the second data release of gravitational waveforms from binary neutron star merger simulations performed by the Computational Relativity (CoRe) collaboration. The current database consists of 254 different binary neutron star configurations and a total of 590 individual numerical-relativity simulations using various grid resolutions. The released waveform data contain the strain and the Weyl curvature multipoles up to l=m=4. They span a significant portion of the mass, mass-ratio,spin and eccentricity parameter space and include targeted configurations to the events GW170817 and GW190425. CoRe simulations are performed with 18 different equations of state, seven of which are finite temperature models, and three of which account for non-hadronic degrees of freedom. About half of the released data are computed with high-order hydrodynamics schemes for tens of orbits to merger; the other half is computed with advanced microphysics. We showcase a standard waveform error analysis and discuss the accuracy of the database in terms of faithfulness. We present ready-to-use fitting formulas for equation of state-insensitive relations at merger (e.g. merger frequency), luminosity peak, and post-merger spectrum.

Post-merger Gravitational-wave Signal from Neutron-star Binaries: A New Look at an Old Problem

“…Interestingly, we find that a quasi-universal relation exists for y f 0 4 as a function of the tidal deformability k 2 T and of the binary mass ratio q. Second, by employing a large number of BNS simulations, some of which are taken from the CoRe database (Gonzalez et al 2023), we obtain a new quasiuniversal relation for f mer as a function of k 2 T and q that not only requires a smaller number of coefficients but also provides a more accurate description of the data. Finally, as already suggested in Papenfort et al (2022), we provide evidence that the ℓ = 2, m = 1 GW mode could become the most powerful mode on secular timescales after the merger.…”

“…Our analysis is based on the GW signal computed via numerical simulations of BNS mergers in full general relativity computed with the codes described in Radice et al (2014aRadice et al ( , 2014b, Most et al (2019bMost et al ( , 2019c, Papenfort et al (2021), andTootle et al (2021) and using a number of different EOSs (see below). In addition, we employ part of the data contained in the CoRe database (Gonzalez et al 2023), from where we select only simulations with the highest resolution. The combined data of 118 irrotational binaries cover the range [2.4, 3.33] M e in the total Arnowitt-Deser-Misner (ADM) mass at infinite separation and [ ] k Î 33, 458 2 T in the tidal deformability.…”

“…In order to compare 1  and 2  , it is first necessary to distinguish the "pipeline," that is, the technical procedure employed to extract the frequencies from the data. We thus indicate with 1  the pipeline discussed above and with 2  that released in Gonzalez et al (2023). Naturally, each fitting function can be applied to either pipeline, so that ( )…”

“…Characterizing the properties of the post-merger GW signal is a rather "old" problem, which first emerged when a number of peculiar frequencies were shown to be related with the properties of the binary through quasi-universal relations, i.e., relations that are almost independent of the specific EOS. These relations have been suggested for the GW frequency at merger f mer (Read et al 2013;Bernuzzi et al 2014;Takami et al 2015;Rezzolla & Takami 2016;Bauswein et al 2019;Most et al 2019a;Weih et al 2020;Gonzalez et al 2023), the dominant frequency in the post-merger spectrum f 2 (see, e.g., Oechslin & Janka 2007;Bauswein & Janka 2012;Read et al 2013;Rezzolla & Takami 2016;Gonzalez et al 2023), and other frequencies identifiable in the transient period right after the merger (Bauswein & Stergioulas 2015;Takami et al 2015;Rezzolla & Takami 2016). Fits to these quasi-universal relations have been employed in a number of studies (see, e.g., Bauswein et al 2016;Baiotti & Rezzolla 2017 for some reviews).…”

On the Maximum Mass and Oblateness of Rotating Neutron Stars with Generic Equations of State

“…Our incomplete knowledge of the EOS is partially compensated by a number of quasi-universal, i.e., essentially EOS-independent, relations that have been found among certain neutron-star quantities over the years, in terms of both isolated rotating and nonrotating stars (see, e.g., Yagi & Yunes 2013;Chakrabarti et al 2014;Doneva et al 2014;Haskell et al 2014;Pappas & Apostolatos 2014;Breu & Rezzolla 2016;Weih et al 2018;Konstantinou & Morsink 2022;Nath et al 2023) and the gravitational-wave signal from binary systems (see, e.g., Bauswein & Janka 2012;Read et al 2013;Bernuzzi et al 2014;Takami et al 2015;Rezzolla & Takami 2016;Bauswein et al 2019;Most et al 2019;Weih et al 2020;Gonzalez et al 2023); see Yagi & Yunes (2017) for a review. Clearly, the robustness of these quasi-universal relations depends on the number of EOSs that are employed in determining the relations.…”