On the interpretation of echelle diagrams for solar-like oscillations. Effect of centrifugal distortion - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




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Abstract: This work aims at determining the impact of slow to moderate rotation on theregular patterns often present in solar-like oscillation spectra. We focus onthe well-known asteroseismic diagnostic echelle diagrams, examining howrotation may modify the estimates of the large and small spacings, as well asthe identification of modes. We illustrate the work with a real case: thesolar-like star $\eta$ Bootis. The modeling takes into account rotation effectson the equilibrium models through an effective gravity and on the oscillationfrequencies through both perturbative and non-perturbative calculations. Wecompare the results of both type of calculations in the context of the regularspacings like the small spacings and the scaled small spacings and echellediagrams. We show that for echelle diagrams the perturbative approach remainsvalid for rotational velocities up to 40-50 km-s. We show that for therotational velocities measured in solar-like stars, theoretical oscillationfrequencies must be corrected up to the second-order in terms of rotation rate,including near degeneracy effects. For rotational velocities of about 16 km-Sand higher, diagnostics on large spacings and on modal identification throughechelle diagrams can be significantly altered by the presence of the $m eq0$components of the rotationally split modes. We found these effects to bedetectable in the observed frequency range. Analysis of the effects of rotationon small spacings and scaled small spacings reveals that these can be of theorder of, or even larger than surface effects, typically turbulence,microscopic diffusion, etc. Furthermore, we show that scaled spacings aresignificantly affected by stellar distortion even for small stellar rotationalvelocities from 10-15 km-s and therefore some care must be taken when usingthem as indicators for probing deep stellar interiors.



Author: J.C. Suárez, M.J. Goupil, D.R.Reese, R. Samadi, F. Lignieres, M. Rieutord, J. Lochard

Source: https://arxiv.org/







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