f-mode imprints on gravitational waves from coalescing binaries involving aligned spinning neutron stars

Hao-Jui Kuan and Kostas D. Kokkotas
Phys. Rev. D 106, 064052 – Published 29 September 2022

Abstract

The excitation of f-mode in a neutron star member of coalescing binaries accelerates the merger course, and thereby introduces a phase shift in the gravitational waveform. Emphasizing the tidal phase shift by aligned, rotating stars, we provide an accurate, yet economical, method to generate f-mode-involved, premerger waveforms using realistic spin-modulated f-mode frequencies for some viable equations of state. We find for slow-rotating stars that the dephasing effects of the dynamical tides can be uniquely, equation-of-state-independently determined by the direct observables (chirp mass M, symmetric ratio η, and the mutual tidal deformability Λ˜), while this universality is gradually lost for increasing spin. For binaries with fast rotating members (800Hz) the phase shift due to the f-mode will exceed the uncertainty in the waveform phase at reasonable signal-to-noise ratio (ρ=25) and cutoff frequency of 400Hz. Assuming a high cutoff frequency of 103Hz and fast (800Hz) members, a significant phase shift of 100 rads has been found. For systems involving a rapidly spinning star (potentially the secondary of GW190814), neglecting the f-mode effect in the waveform templates can therefore lead to considerable systemic errors in the relevant analysis. In particular, the dephasing due to f-mode is larger than that caused by equilibrium tides by a factor of 5, which may lead to a considerably overestimated tidal deformability if dynamical tidal contribution is not accounted. The possibility of accompanying precursors flares due to f-mode excitation is also discussed.

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  • Received 3 May 2022
  • Accepted 6 September 2022

DOI:https://doi.org/10.1103/PhysRevD.106.064052

© 2022 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Hao-Jui Kuan1,2,* and Kostas D. Kokkotas1

  • 1Theoretical Astrophysics, IAAT, University of Tübingen, Tübingen, D-72076, Germany
  • 2Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan

  • *hao-jui.kuan@uni-tuebingen.de

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Vol. 106, Iss. 6 — 15 September 2022

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