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Excitation of f-modes during mergers of spinning binary neutron star

Ma, Sizheng and Yu, Hang and Chen, Yanbei (2020) Excitation of f-modes during mergers of spinning binary neutron star. Physical Review D, 101 (12). Art. No. 123020. ISSN 2470-0010. doi:10.1103/physrevd.101.123020.

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Tidal effects have important imprints on gravitational waves (GWs) emitted during the final stage of the coalescence of binaries that involve neutron stars (NSs). Dynamical tides can be significant when NS oscillations become resonant with orbital motion; understanding this process is important for accurately modeling GW emission from these binaries and for extracting NS information from GW data. In this paper, we use semianalytic methods to carry out a systematic study on the tidal excitation of fundamental modes (f-modes) of spinning NSs in coalescencing binaries, focusing on the case when the NS spin is antialigned with the orbital angular momentum—where the tidal resonance is most likely to take place. We first expand NS oscillations into stellar eigenmodes, and then obtain a Hamiltonian that governs the tidally coupled orbit-mode evolution. (Our treatment is at Newtonian order, including a gravitational radiation reaction at quadrupole order.) We then find a new approximation that can lead to analytic expressions of tidal excitations to a high accuracy, and are valid in all regimes of the binary evolution: adiabatic, resonant, and postresonance. Using the method of osculating orbits, we obtain semianalytic approximations to the orbital evolution and GW emission; their agreements with numerical results give us confidence in our understanding of the system’s dynamics. In particular, we recover both the averaged postresonance evolution, which differs from the preresonance point-particle orbit by shifts in orbital energy and angular momentum, as well as instantaneous perturbations driven by the tidal motion. Finally, we use the Fisher matrix technique to study the effect of dynamical tides on parameter estimation. We find that, for a system with component masses of (1.4,1.4) M_⊙ at 100 Mpc, the constraints on the effective Love number of the (2,2) mode at Newtonian order can be improved by a factor of 3 ∼ 4 if spin frequency is as high as 500 Hz. The relative errors are 0.7 ∼ 0.8 in the Cosmic Explorer, and they might be further improved by post-Newtonian effects. The constraints on the f-mode frequency and the spin frequency are improved by factors of 5 ∼ 6 and 19 ∼ 27, respectively. In the Cosmic Explorer case, the relative errors are 0.2 ∼ 0.4 and 0.7 ∼ 1.0, respectively. Hence, the dynamical tides may potentially provide an additional channel to study the physics of NSs. The method presented in this paper is generic and not restricted to f-mode; it can also be applied to other types of tides.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Ma, Sizheng0000-0002-4645-453X
Yu, Hang0000-0002-6011-6190
Chen, Yanbei0000-0002-9730-9463
Additional Information:© 2020 American Physical Society. (Received 4 March 2020; accepted 3 June 2020; published 18 June 2020) We thank Jocelyn Read for useful suggestions. The computations presented here were conducted on the Caltech High Performance Cluster, partially supported by a grant from the Gordon and Betty Moore Foundation. H. Y. is supported by the Sherman Fairchild Foundation. Y. C. and S. M. are supported by the Brinson Foundation, the Simons Foundation (Grant No. 568762), and the National Science Foundation, through Grants No. PHY-1708212 and PHY-1708213.
Group:Astronomy Department, TAPIR, Walter Burke Institute for Theoretical Physics
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Sherman Fairchild FoundationUNSPECIFIED
Brinson FoundationUNSPECIFIED
Simons Foundation568762
Issue or Number:12
Record Number:CaltechAUTHORS:20200624-104213052
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104008
Deposited By: George Porter
Deposited On:24 Jun 2020 19:01
Last Modified:16 Nov 2021 18:27

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