Abstract
We present the first set of numerical relativity simulations of binary neutron mergers that include spin precession effects and are evolved with multiple resolutions. Our simulations employ consistent initial data in general relativity with different spin configurations and dimensionless spin magnitudes $\sim 0.1$. They start at a gravitational-wave frequency of $\sim392$~Hz and cover more than $1$ precession period and about 15 orbits up to merger. We discuss the spin precession dynamics by analyzing coordinate trajectories, quasi-local spin measurements, and energetics, by comparing spin aligned, antialigned, and irrotational configurations. Gravitational waveforms from different spin configuration are compared by calculating the mismatch between pairs of waveforms in the late inspiral. We find that precession effects are not distinguishable from nonprecessing configurations with aligned spins for approximately face-on binaries, while the latter are distinguishable from a nonspinning configurations. Spin precession effects are instead clearly visible for approximately edge-on binaries. For the parameters considered here, precession does not significantly affect the characteristic postmerger gravitational-wave frequencies nor the mass ejection. Our results pave the way for the modeling of spin precession effects in the gravitational waveform from binary neutron star events.
Highlights
The recent observation of gravitational waves (GW) and electromagnetic (EM) signals from the merger of two neutron stars (NSs) marks a breakthrough in the field of multi-messenger astronomy [1, 2]
In [32] and [14] we found that employing high-order schemes leads to a constant convergence order for the GW phase for multiple Equations of State (EOSs) and grid setups
The computed mismatch between precessing systems and spinning systems with the same effective spin is of the order of 10−3, which shows that for a face-on detection of a binary neutron star (BNS) hardly any precession effect might be visible from the late inspiral phase, see e.g. [52]
Summary
The recent observation of gravitational waves (GW) and electromagnetic (EM) signals from the merger of two neutron stars (NSs) marks a breakthrough in the field of multi-messenger astronomy [1, 2]. Considering the recent BNS detection [1] a PostNewtonian (PN) approximant [11, 12] and an approximant incorporating results from the effective-one-body model [13] with a phenomenological representation of tidal effects [14] have been used Both models describe binaries in which the spins are aligned/anti-aligned with the orbital angular momentum and precession does not occur. The article is structured as follows: in Sec. II we give an overview of the studied configurations and the employed numerical methods; in Sec. III accuracy measures for the simulations are presented; in Sec. IV we discuss the dynamics focusing on the precession dynamics and the conservative dynamics in terms of binding energy vs specific angular momentum plots; in Sec. V and Sec. VI we discuss gravitational waves and the dynamical ejecta. This ensures initially the same spinorbit coupling for SLy( ) and SLy(↓↓)
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