2006/07/31 by Andrea Passamonti
Engineering · Physics and Astronomy · #Astrophysics #Classical mechanics #Coupling (piping) #Geophysics and Sensor Technology #Gravitational wave #Harmonics #Mode coupling #Nonlinear system #Physics #Pulsars and Gravitational Waves Research #Quantum mechanics #Spherical harmonics #Stars #Stellar pulsation #Stellar, planetary, and galactic studies #astro-ph #gr-qc
paper · pdf · doi:10.1088/1742-6596/68/1/012052
172 pages, 32 figures, PhD thesis, University of Portsmouth
arxiv created 2006/07/31 · openalex publication_date 2007/05/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Nonlinear stellar oscillations can be studied by using a multiparameter perturbative approach, which is appropriate for investigating the low and mild nonlinear dynamical regimes. We present the main properties of our perturbative framework for describing, in the time domain, the nonlinear coupling between the radial and nonradial perturbations of spherically symmetric and perfect fluid compact stars. This particular coupling can be described by gauge invariant quantities that obeys a system of partial differential equations with source terms, which are made up of product of first order radial and nonradial perturbations. We report the results of numerical simulations for both the axial and polar coupling perturbations, that exhibit in the stellar dynamics and in the associated gravitational wave signal some interesting nonlinear effects, such as combination harmonics and resonances. In particular, we concentrate on the axial case, where the linear axial perturbations describe a harmonic component of a differentially rotating neutron star. The gravitational wave signal of this stellar configuration mirrors at second perturbative order the spectral features of the linear radial normal modes. In addition, a signal amplification appears when one of the radial frequencies is close to the axial w -mode frequencies of the star.