Accuracy and precision of gravitational-wave models of inspiraling neutron star -- black hole binaries with spin: comparison with numerical relativity in the low-frequency regime

Coalescing binaries of neutron stars (NS) and black holes (BH) are one of the most important sources of gravitational waves for the upcoming network of ground based detectors. Detection and extraction of astrophysical information from gravitational-wave signals requires accurate waveform models. The Effective-One-Body and other phenomenological models interpolate between analytic results and $10-30$ orbit numerical relativity (NR) merger simulations. In this paper we study the accuracy of these models using new NR simulations that span $36-88$ orbits, with mass-ratios and black hole spins $(q,\chi_{BH}) = (7, \pm 0.4), (7, \pm 0.6)$, and $(5, -0.9)$. We find that: (i) the recently published SEOBNRv1 and SEOBNRv2 models of the Effective-One-Body family disagree with each other (mismatches of a few percent) for black hole spins $\geq 0.5$ or $\leq -0.3$, with waveform mismatch accumulating during early inspiral; (ii) comparison with numerical waveforms indicate that this disagreement is due to phasing errors of SEOBNRv1, with SEOBNRv2 in good agreement with all of our simulations; (iii) Phenomenological waveforms disagree with SEOBNRv2 over most of the NSBH binary parameter space; (iv) comparison with NR waveforms shows that most of the model's dephasing accumulates near the frequency interval where it switches to a phenomenological phasing prescription; and finally (v) both SEOBNR and post-Newtonian (PN) models are effectual for NSBH systems, but PN waveforms will give a significant bias in parameter recovery. Our results suggest that future gravitational-wave detection searches and parameter estimation efforts targeted at NSBH systems with $q\lesssim 7$ and $\chi_\mathrm{BH} \approx [-0.9, +0.6]$ will benefit from using SEOBNRv2 templates. For larger black hole spins and/or binary mass-ratios, we recommend the models be further investigated as suitable NR simulations become available.Comment: 20 pages, 18 figure

Gravitational waveforms of binary neutron star inspirals using post-Newtonian tidal splicing

The tidal deformations of neutron stars within an inspiraling compact binary alter the orbital dynamics, imprinting a signature on the gravitational wave signal. Modeling this signal could be done with numerical-relativity simulations, but these are too computationally expensive for many applications. Analytic post-Newtonian treatments are limited by unknown higher-order nontidal terms. This paper further builds upon the “tidal splicing” model in which post-Newtonian tidal terms are “spliced” onto numerical relativity simulations of black-hole binaries. We improve on previous treatments of tidal splicing by including spherical harmonic modes beyond the (2,2) mode, expanding the post-Newtonian expressions for tidal effects to 2.5 order, including dynamical tide corrections, and adding a partial treatment of the spin-tidal dynamics. Furthermore, instead of numerical relativity simulations, we use the spin-aligned binary black hole (BBH) surrogate model “NRHybSur3dq8” to provide the BBH waveforms that are input into the tidal slicing procedure. This allows us to construct spin-aligned, inspiraling TaylorT2 and TaylorT4 splicing waveform models that can be evaluated quickly. These models are tested against existing binary neutron star and black hole–neutron star simulations. We implement the TaylorT2 splicing model as an extension to “NRHybSur3dq8,” creating a model that we call “NRHybSur3dq8Tidal.

The Impact of Dreissenid Mussels on Growth of the Fragile Papershell (Leptodea fragilis), the Most Abundant Unionid Species in Lake Erie

The arrival of zebra mussels (Dreissena polymorpha (Pallas, 1771)) and subsequently quagga mussels (Dreissena bugensis Andrusov, 1897) (Dreissenidae) in the Great Lakes in the 1980s induced many changes, most notably the devastation of native freshwater mussel species. Recently, empty shells of the fragile papershell (Leptodea fragilis (Rafinesque, 1820)) have become common, particularly in the western basin of Lake Erie, suggesting that this fast-growing species may be increasing in numbers in the lake. To examine continued competition with dreissenids, shell age and length of L. fragilis were used to contrast lifespan and growth rate, estimated as the slope of age on shell length, for shells from two beach localities where byssal threads were present on most shells and two sites where dreissenids were rare or absent. Few recent shells from Lake Erie beaches exceeded 5 years of age, and byssal thread counts were more numerous on older shells. Growth and lifespan were estimated to be significantly lower where dreissenid mussels remained numerous than when measured either from historic collections along Lake Erie or from protected populations. Therefore, even for this early-reproducing species, competition from dreissenids may continue to interfere with growth and shorten lifespan, which are effects few other unionid species can likely tolerate sufficiently to sustain population growt

A Quantitative Evaluation of Growth in Leptodea Fragilis Before and After the Arrival of Zebra Mussels in Lake Erie

The arrival of zebra mussels in the Great Lakes in the 1980’s marked several environmental changes, most notably in freshwater mussels in the Unionidae. There are no studies of population demographics of native Great Lake species before this period of time. In this study, several recent shell collections of Leptodea fragilis, a fast-growing freshwater mussel, were made on various beaches along Lake Erie. To compare the effects of the zebra mussels on L. fragilis, we compared growth rates, determined from size and estimated age of shells, to additional collections of L. fragilis from 1941 to 1967available at the Cleveland Museum of Natural History. The growth rates of this species are exceptional for their speed among freshwater mussels. A modern comparison of growth rates and age are presented with a sexually dimorphic unionid river species, Lampsilis siliquoidea, that were collected in Summer 2013. We hypothesized that the arrival of zebra mussels could affect the growth rate of L. fragilis by selecting on age of reproduction or growth to reach a minimum size for reproduction, results that could shift growth curves and/or age demography of current populations, and help them persist where zebra mussels remain abundant.https://engagedscholarship.csuohio.edu/u_poster_2013/1006/thumbnail.jp

Spectral Cauchy-characteristic extraction of the gravitational wave news function

We present an improved spectral algorithm for Cauchy-characteristic extraction and characteristic evolution of gravitational waves in numerical relativity. The new algorithms improve spectral convergence both at the poles of the spherical-polar grid and at future null infinity, as well as increase the temporal resolution of the code. The key to the success of these algorithms is a new set of high-accuracy tests, which we present here. We demonstrate the accuracy of the code and compare with the existing pittnull implementation

Spectral Cauchy-characteristic extraction of the gravitational wave news function

We present an improved spectral algorithm for Cauchy-characteristic extraction and characteristic evolution of gravitational waves in numerical relativity. The new algorithms improve spectral convergence both at the poles of the spherical-polar grid and at future null infinity, as well as increase the temporal resolution of the code. The key to the success of these algorithms is a new set of high-accuracy tests, which we present here. We demonstrate the accuracy of the code and compare with the existing PittNull implementation.Comment: 26 pages, 8 figures, published versio

Gravitational waveforms for neutron star binaries from binary black hole simulations

Gravitational waves from binary neutron star (BNS) and black-hole/neutron star (BHNS) inspirals are primary sources for detection by the Advanced Laser Interferometer Gravitational-Wave Observatory. The tidal forces acting on the neutron stars induce changes in the phase evolution of the gravitational waveform, and these changes can be used to constrain the nuclear equation of state. Current methods of generating BNS and BHNS waveforms rely on either computationally challenging full 3D hydrodynamical simulations or approximate analytic solutions. We introduce a new method for computing inspiral waveforms for BNS/BHNS systems by adding the post-Newtonian (PN) tidal effects to full numerical simulations of binary black holes (BBHs), effectively replacing the non-tidal terms in the PN expansion with BBH results. Comparing a waveform generated with this method against a full hydrodynamical simulation of a BNS inspiral yields a phase difference of < 1 radian over ~ 15 orbits. The numerical phase accuracy required of BNS simulations to measure the accuracy of the method we present here is estimated as a function of the tidal deformability parameter ⋋

The SXS Collaboration catalog of binary black hole simulations

Accurate models of gravitational waves from merging black holes are necessary for detectors to observe as many events as possible while extracting the maximum science. Near the time of merger, the gravitational waves from merging black holes can be computed only using numerical relativity. In this paper, we present a major update of the Simulating eXtreme Spacetimes (SXS) Collaboration catalog of numerical simulations for merging black holes. The catalog contains 2018 distinct configurations (a factor of 11 increase compared to the 2013 SXS catalog), including 1426 spin-precessing configurations, with mass ratios between 1 and 10, and spin magnitudes up to 0.998. The median length of a waveform in the catalog is 39 cycles of the dominant $\ell=m=2$ gravitational-wave mode, with the shortest waveform containing 7.0 cycles and the longest 351.3 cycles. We discuss improvements such as correcting for moving centers of mass and extended coverage of the parameter space. We also present a thorough analysis of numerical errors, finding typical truncation errors corresponding to a waveform mismatch of $\sim 10^{-4}$. The simulations provide remnant masses and spins with uncertainties of 0.03% and 0.1% ($90^{\text{th}}$ percentile), about an order of magnitude better than analytical models for remnant properties. The full catalog is publicly available at https://www.black-holes.org/waveforms .Comment: 33+18 pages, 13 figures, 4 tables, 2,018 binaries. Catalog metadata in ancillary JSON file. v2: Matches version accepted by CQG. Catalog available at https://www.black-holes.org/waveform