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Title: Gravitational waves from nonlinear couplings of radial and polar nonradial modes in relativistic stars

Abstract

The postbounce oscillations of newly-born relativistic stars are expected to lead to gravitational-wave emission through the excitation of nonradial oscillation modes. At the same time, the star is oscillating in its radial modes, with a central density variation that can reach several percent. Nonlinear couplings between radial oscillations and polar nonradial modes lead to the appearance of combination frequencies (sums and differences of the linear mode frequencies). We study such combination frequencies using a gauge-invariant perturbative formalism, which includes bilinear coupling terms between different oscillation modes. For typical values of the energy stored in each mode we find that gravitational waves emitted at combination frequencies could become detectable in galactic core-collapse supernovae with advanced interferometric or wideband resonant detectors.

Authors:
;  [1];  [2]
  1. Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)
  2. Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Turin (Italy) and INFN, Sezione di Torino, Via Pietro Giuria 1, Turin (Italy)
Publication Date:
OSTI Identifier:
21020407
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevD.75.084038; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COSMOLOGY; COUPLING; DENSITY; EMISSION; EXCITATION; GAUGE INVARIANCE; GRAVITATIONAL WAVES; NONLINEAR PROBLEMS; OSCILLATION MODES; OSCILLATIONS; RELATIVISTIC RANGE; STARS; VARIATIONS

Citation Formats

Passamonti, Andrea, Stergioulas, Nikolaos, and Nagar, Alessandro. Gravitational waves from nonlinear couplings of radial and polar nonradial modes in relativistic stars. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.084038.
Passamonti, Andrea, Stergioulas, Nikolaos, & Nagar, Alessandro. Gravitational waves from nonlinear couplings of radial and polar nonradial modes in relativistic stars. United States. doi:10.1103/PHYSREVD.75.084038.
Passamonti, Andrea, Stergioulas, Nikolaos, and Nagar, Alessandro. Sun . "Gravitational waves from nonlinear couplings of radial and polar nonradial modes in relativistic stars". United States. doi:10.1103/PHYSREVD.75.084038.
@article{osti_21020407,
title = {Gravitational waves from nonlinear couplings of radial and polar nonradial modes in relativistic stars},
author = {Passamonti, Andrea and Stergioulas, Nikolaos and Nagar, Alessandro},
abstractNote = {The postbounce oscillations of newly-born relativistic stars are expected to lead to gravitational-wave emission through the excitation of nonradial oscillation modes. At the same time, the star is oscillating in its radial modes, with a central density variation that can reach several percent. Nonlinear couplings between radial oscillations and polar nonradial modes lead to the appearance of combination frequencies (sums and differences of the linear mode frequencies). We study such combination frequencies using a gauge-invariant perturbative formalism, which includes bilinear coupling terms between different oscillation modes. For typical values of the energy stored in each mode we find that gravitational waves emitted at combination frequencies could become detectable in galactic core-collapse supernovae with advanced interferometric or wideband resonant detectors.},
doi = {10.1103/PHYSREVD.75.084038},
journal = {Physical Review. D, Particles Fields},
number = 8,
volume = 75,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • We investigate the nonlinear coupling between radial and nonradial oscillations of static spherically-symmetric neutron stars as a possible mechanism for the generation of gravitational waves that may lead to observable signatures. In this paper we concentrate on the axial sector of the nonradial perturbations. By using a multiparameter perturbative framework we introduce a complete description of the nonlinear coupling between radial and axial nonradial oscillations; we study the gauge-invariant character of the associated perturbative variables and develop a computational scheme to evolve the nonlinear coupling perturbations in the time domain. We present results of simulations corresponding to different physical situationsmore » and discuss the dynamical behavior of this nonlinear coupling. Of particular interest is the occurrence of signal amplifications in the form of resonance phenomena when a frequency associated with the radial pulsations is close to a frequency associated with one of the axial w-modes of the star. Finally, we mention possible extensions of this work and improvements towards more astrophysically motivated scenarios.« less
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  • The eigenfrequencies of the axial w-modes of oscillating neutron stars are studied using the continued fraction method with an equation of state (EOS) partially constrained by the recent terrestrial nuclear laboratory data. It is shown that the density dependence of the nuclear symmetry energy E{sub sym}({rho}) affects significantly both the frequencies and the damping times of these modes. Besides confirming the previously found universal behavior of the mass-scaled eigenfrequencies as functions of the compactness of neutron stars, we explored several alternative universal scaling functions. Moreover, the w{sub II}-mode is found to exist only for neutron stars having a compactness ofmore » M/R{>=}0.1078 independent of the EOS used.« less