scholarly journals Acoustic modes of pulsating axion stars: Nonradial oscillations

2019 ◽  
Vol 28 (09) ◽  
pp. 1950111 ◽  
Author(s):  
Grigoris Panotopoulos ◽  
Ilídio Lopes
Keyword(s):  
Effective Potential ◽  
Small Frequency ◽  
Acoustic Modes ◽  
Oscillation Modes ◽  
Nonradial Oscillation ◽  
Nonradial Oscillations

We compute the lowest frequency nonradial oscillation modes of dilute axion stars. The effective potential that enters into the Schrödinger-like equation, several associated eigenfunctions and the large as well as the small frequency separations are shown as well.

scholarly journals NEUTRON STAR MATTER EQUATION OF STATE AND GRAVITATIONAL WAVE EMISSION

2005 ◽  
Vol 20 (31) ◽  
pp. 2335-2349 ◽  
Author(s):  
OMAR BENHAR
Keyword(s):  
Experimental Study ◽  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Gravitational Waves ◽  
Neutron Star Matter ◽  
Oscillation Modes ◽  
Nonradial Oscillation ◽  
Macroscopic Objects ◽  
Wave Emission

The EOS of strongly interacting matter at densities ten to fifteen orders of magnitude larger than the typical density of terrestrial macroscopic objects determines a number of neutron star properties, including the pattern of gravitational waves emitted following the excitation of nonradial oscillation modes. This paper reviews some of the approaches employed to model neutron star matter, as well as the prospects for obtaining new insights from the experimental study of gravitational waves emitted by neutron stars.

scholarly journals Quadratic and Cubic Couplings of Oscillation Modes of Stars

1995 ◽  
Vol 155 ◽  
pp. 287-288
Author(s):  
T. Van Hoolst
Keyword(s):  
Main Sequence ◽  
Oscillation Mode ◽  
The Self ◽  
Nonlinear Interactions ◽  
Nonlinear Coupling ◽  
Coupling Coefficients ◽  
Main Sequence Stars ◽  
Evolved Stars ◽  
Oscillation Modes ◽  
Nonradial Oscillation

The strength of nonlinear interactions of oscillation modes of stars is determined by the amplitudes as well as by the eigenfunctions of the oscillation modes. The intrinsic couplings of modes through their eigenfunctions can be described by coupling coefficients. Here, we concentrate on quadratic and cubic coupling coefficients that describe the nonlinear coupling of modes with itself and are called self-coupling coefficients.We considered radial and nonradial oscillation modes of polytropic models with degrees of central condensation that correspond to central condensations of main sequence stars to highly condensed evolved stars. We study the influence of the radial order and the degree of the oscillation mode on the self- coupling coefficients.

scholarly journals Nonradial oscillation modes of compact stars with a crust

2017 ◽  
Vol 96 (6) ◽  
Author(s):  
Cesar Vásquez Flores ◽  
Zack B. Hall ◽  
Prashanth Jaikumar
Keyword(s):  
Compact Stars ◽  
Oscillation Modes ◽  
Nonradial Oscillation

scholarly journals Forced Nonradial Oscillations in Early-Type Rotating Stars

2000 ◽  
Vol 176 ◽  
pp. 376-376
Author(s):  
M. G. Witte ◽  
G. J. Savonije
Keyword(s):  
Gravitational Force ◽  
Rotation Speed ◽  
Internal Damping ◽  
Rotating Stars ◽  
Stellar Rotation ◽  
Stellar Spectrum ◽  
Coriolis Forces ◽  
Nonradial Oscillation ◽  
External Driving ◽  
Nonradial Oscillations

A method of calculating nonradial oscillations in rotating stars is presented. Using this method, we are able to calculate the spectrum of g-, f- and p-mode eigenfunctions of a star for different stellar rotation speeds, and also the spectrum of rotational r modes. Stability of the modes as a function of stellar rotation speed can be investigated. By regarding the response of a star which undergoes periodic deformations due to the gravitational force of an orbiting companion as a forced nonradial oscillation, the problem of determining the eigenfrequencies of the star becomes one of finding resonances with the forcing potential. Expanding the potential of the orbiting (point mass) companion in terms of the usual spherical functions, the response of the star to each tidal term , with l and m fixed, can be calculated separately. By varying the forcing frequency σ we are then able to calculate the stellar spectrum. To calculate the response of the star we numerically solve the fully non-adiabatic, but linearised hydrodynamical equations for the star, in which the Coriolis forces due to stellar rotation are fully taken into account. To this end we utilise an implicit 2D finite difference scheme which solves the equations on an (r, ϑ) grid. A calculated solution describes the steady state in which the power σT due to the external driving force is in equilibrium with the internal damping. For results and more references see Witte & Savonije (1999).

scholarly journals Rotational and Tidal Perturbations of Nonradial Oscillations In a Polytropic Star

1980 ◽  
Vol 58 ◽  
pp. 649-652
Author(s):  
Hideyuki Saio
Keyword(s):  
Inertial Frame ◽  
Nonradial Oscillation ◽  
Tidal Perturbations ◽  
Rotating Star ◽  
Polytropic Star ◽  
Nonradial Oscillations

AbstractThe degeneracy of frequencies of nonradial oscillations is resolved in the presence of rotation. As observed in an inertial frame the frequency of a nonradial oscillation in a uniformly rotating star is given as

scholarly journals Discontinuity Modes in Polytropes

1989 ◽  
Vol 111 ◽  
pp. 254-254
Author(s):  
Bradley W. Carroll
Keyword(s):  
Large Amplitude ◽  
Solar Mass ◽  
Mode Spectrum ◽  
Density Discontinuity ◽  
Fractional Density ◽  
Stellar Pulsation ◽  
Oscillation Modes ◽  
Nonradial Oscillation ◽  
Small Density ◽  
Avoided Crossings

AbstractIn the calculation of linear nonradial oscillation modes in composite polytropes with a small density discontinuity, a discontinuity mode may occur. This mode consists of a wave propagating along the discontinuity interface with a large amplitude that declines exponentially away from the interface. The period P of this mode is well-estimated (to within 10%) bywhere Δρ/<ρ> is the fractional density discontinuity and k is the horizontal wavenumber (c.f. Gabriel and Scuflaire 1980, in Nonradial and Nonlinear Stellar Pulsation, eds. H. Hill and W. Dziembowski, Springer-Verlag). For a 12 solar-mass polytrope with a radius of 4.27 R⊙, a 3% density discontinuity at fractional radius 0.15 produces a discontinuity mode with a period of 7.329 hours. As the density discontinuity increases the period P decreases, resulting in avoided crossings with the normal g-mode spectrum. Between these avoided crossings, the discontinuity mode has an unusually large amplitude at the location of the discontinuity.

scholarly journals About Seismological Properties of Intermediate Mass Stars

1993 ◽  
Vol 137 ◽  
pp. 544-546 ◽  
Author(s):  
N. Audard ◽  
J. Provost
Keyword(s):  
Sound Speed ◽  
Frequency Separation ◽  
Intermediate Mass ◽  
Small Frequency ◽  
Rapid Variation ◽  
Intermediate Mass Stars ◽  
Low Degree ◽  
Oscillation Modes ◽  
Convective Core ◽  
Order Quantities

AbstractStars more massive than about 1.2M⊙ are characterised by a convective core, which induces at its frontier a rapid variation of the sound speed and of the Brunt-Väissälä frequency, close to a discontinuity. We present preliminary results about the search of the signature this core could have on the p-mode spectra. For a set of frequencies of three stars of 1, 1.5 and 2 M⊙, we study in particular the small frequency separation Δν0,2, ~ νn,l, νn-1,l+2 for high order and low degree oscillation modes, which is particularly sensitive to the interior of stars. We underline characteristic behaviours of the 1.5 and 2 M⊙ stars, through the comparison between computed frequencies and their approximation obtained by asymptotic and polynomial fittings, and also through second order quantities relatively to the frequencies.

On a Nonlinear Dispersion Effect of Geodesic Acoustic Modes

2013 ◽  
Vol 8 (0) ◽  
pp. 1403010-1403010 ◽  
Author(s):  
Makoto SASAKI ◽  
Kimitaka ITOH ◽  
Naohiro KASUYA ◽  
Klaus HALLATSCHEK ◽  
Sanae-I. ITOH
Keyword(s):  
Nonlinear Dispersion ◽  
Dispersion Effect ◽  
Acoustic Modes
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