Resonant Excitation of Nonradial Modes in RR Lyr Stars

• Autorzy: Nowakowski R. M. , Dziembowski W. A.
• Języki publikacji: EN

Abstrakty

EN

We study a nonlinear development of radial pulsation instability to a resonant excitation of nonradial modes. Our theory covers the cases of axisymmetric (m=0) modes as well as (m,-m) pairs. Adopting a simplified treatment of the radial and nonradial mode coupling we find that the asymptotic state is a pulsation with constant amplitudes and we evaluate the relative amplitude of the nonradial component. Observable consequence of the m=0 mode excitation is a small period change and a more significant amplitude change, especially in the case of a dipole mode (l=1). Such a mode has a fairly large excitation probability. Significant amplitude and phase modulation is predicted in the case of excitation of a m=±1 pair. We suggest that this may explain Blazhko-type modulation in RR Lyr stars. If this model is correct, the modulation period is determined by the rotation rate and the Brunt-Väisälä frequency in the deepest part of the radiative interior.

Słowa kluczowe

EN

stars: oscillations; stars: variables: RR Lyr

• Wydawca: Copernicus Foundation for Polish Astronomy
• Czasopismo: Acta Astronomica
• Rocznik: 2001
• Tom: Vol. 51, No. 1
• Strony: 5--47
• Opis fizyczny: Bibliogr. 31 poz., rys., wykr.

Twórcy

autor

Nowakowski R. M.

• Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland

autor

Dziembowski W. A.

• Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
• Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland

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