Modeling matter in seobnrv5thm: Generating fast and accurate effective-one-body waveforms for spin-aligned binary neutron stars

We present 5, an accurate and fast gravitational-waveform model for quasicircular, spinning, nonprecessing binary neutron stars (BNSs) within the effective-one-body (EOB) formalism. It builds on the binary–black-hole approximant 5 and, compared to its predecessor 4, it (i) incorporates recent high-order post-Newtonian results in the inspiral, including higher-order adiabatic tidal contributions, spin-induced multipoles and dynamical tides for spin-aligned neutron stars, (ii) includes the gravitational modes <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo stretchy="false">(</a:mo><a:mo>ℓ</a:mo><a:mo>,</a:mo><a:mo stretchy="false">|</a:mo><a:mi>m</a:mi><a:mo stretchy="false">|</a:mo><a:mo stretchy="false">)</a:mo><a:mo>=</a:mo><a:mo stretchy="false">(</a:mo><a:mn>2</a:mn><a:mo>,</a:mo><a:mn>2</a:mn><a:mo stretchy="false">)</a:mo><a:mo>,</a:mo><a:mo stretchy="false">(</a:mo><a:mn>3</a:mn><a:mo>,</a:mo><a:mn>3</a:mn><a:mo stretchy="false">)</a:mo><a:mo>,</a:mo><a:mo stretchy="false">(</a:mo><a:mn>2</a:mn><a:mo>,</a:mo><a:mn>1</a:mn><a:mo stretchy="false">)</a:mo><a:mo>,</a:mo><a:mo stretchy="false">(</a:mo><a:mn>4</a:mn><a:mo>,</a:mo><a:mn>4</a:mn><a:mo stretchy="false">)</a:mo><a:mo>,</a:mo><a:mo stretchy="false">(</a:mo><a:mn>5</a:mn><a:mo>,</a:mo><a:mn>5</a:mn><a:mo stretchy="false">)</a:mo><a:mo>,</a:mo><a:mo stretchy="false">(</a:mo><a:mn>3</a:mn><a:mo>,</a:mo><a:mn>2</a:mn><a:mo stretchy="false">)</a:mo></a:math>, and (4,3), (iii) has a time of merger calibrated to BNS numerical-relativity (NR) simulations, (iv) accurately models the premerger (2,2) mode through a novel phenomenological ansatz, and (v) is 100 to 1000 times faster than its predecessor model for BNS systems with total mass <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mi>M</s:mi><s:mo>≥</s:mo><s:mn>2</s:mn><s:msub><s:mi>M</s:mi><s:mo stretchy="false">⊙</s:mo></s:msub></s:math>. Thus, 5 can be used in Bayesian parameter estimation, which we perform for two BNS events observed by the LIGO-Virgo collaboration, GW170817 and GW190425. The model accurately reproduces and NR waveforms with errors comparable to or lower than the intrinsic NR uncertainty. We validate the model against the other state-of-the-art BNS waveform models 3 and and find differences only for highly spinning and highly tidally deformable BNSs, where there is no NR coverage and the models employ different spin prescriptions. Our model serves as a foundation for the development of subsequent waveform models with matter that incorporate further effects, such as spin precession and eccentricity, to be employed for upcoming observing runs of the LIGO-Virgo-KAGRA collaboration and future facilities on the ground.