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Suárez Juan Carlos, Goupil Marie-José, Reese Daniel, Samadi Davoud-Reza, Lignières François, Rieutord Michel, Lochard Jérémie

On the Interpretation of Echelle Diagrams for Solar-like Oscillations Effect of Centrifugal Distortion

The Astrophysical Journal, 2010, vol. 721, pp. 537-546

Référence DOI : 10.1088/0004-637X/721/1/537
Référence ADS : 2010ApJ...721..537S

Résumé :

This work aims at determining the impact of slow to moderate rotation on the regular patterns often present in solar-like oscillation spectra, i.e., the frequency spacings. We focus on the well-known asteroseismic diagnostic echelle diagrams, examining how rotation may modify the estimates of the large and small spacings, as well as the identification of modes. We illustrate the work with a real case: the solar-like star etaBootis. We study a main-sequence 1.3 M <SUB>sun</SUB> star as a typical case. The modeling takes into account rotation effects on the equilibrium models through an effective gravity and on the oscillation frequencies through both perturbative and non-perturbative calculations. We compare the results of both type of calculations in the context of the regular spacings (like the small spacings and the scaled small spacings) and echelle diagrams. We show that for echelle diagrams the perturbative approach remains valid for rotational velocities up to 40-50 km s<SUP>-1</SUP>. We show that for the rotational velocities measured in solar-like stars, i.e., vsin i up to 20-30 km s<SUP>-1</SUP>, rotation effects must be taken into account in the modeling for a correct interpretation of the observed oscillations. In particular, theoretical oscillation frequencies must be corrected up to the second order in terms of rotation rate, including near degeneracy effects. For rotational velocities of about 16 km s<SUP>-1</SUP> and higher, diagnostics on large spacings and on modal identification through echelle diagrams can be significantly altered by the presence of the m != 0 components of the rotationally split modes. We found these effects to be detectable in the observed frequency range. Analysis of the effects of rotation on small spacings and scaled small spacings reveals that these can be of the order of or even larger than surface effects, typically turbulence, microscopic diffusion, etc. Furthermore, we show that scaled spacings are significantly affected by stellar distortion even for small stellar rotational velocities (from 10 to 15 km s<SUP>-1</SUP>) and therefore some care must be taken when using them as indicators for probing deep stellar interiors.

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