On P-mode oscillations in stars from 1M ? to 2M ?

Audard, N.; Provost, J.

doi:10.1007/bf01473224

Cited by 17 publications

(25 citation statements)

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“…As for the A&A 550, A126 (2013) Sun, one may question using the asymptotic expansion, since the quality of the data usually allows one to go beyond this approximate relation. Moreover, modeling has shown that acoustic glitches due to discontinuities or important gradients in the stellar structure may hamper the use of the asymptotic expansion (e.g., Audard & Provost 1994).…”

Section: Introductionmentioning

confidence: 99%

Asymptotic and measured large frequency separations

Mosser¹,

Michel²,

Belkacem³

et al. 2013

A&A

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182

303

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Context. With the space-borne missions CoRoT and Kepler, a large amount of asteroseismic data is now available and has led to a variety of work. So-called global oscillation parameters are inferred to characterize the large sets of stars, perform ensemble asteroseismology, and derive scaling relations. The mean large separation is such a key parameter, easily deduced from the radial-frequency differences in the observed oscillation spectrum and closely related to the mean stellar density. It is therefore crucial to measure it with the highest accuracy in order to obtain the most precise asteroseismic indices. Aims. As the conditions of measurement of the large separation do not coincide with its theoretical definition, we revisit the asymptotic expressions used for analyzing the observed oscillation spectra. Then, we examine the consequence of the difference between the observed and asymptotic values of the mean large separation. Methods. The analysis is focused on radial modes. We use series of radial-mode frequencies in published analyses of stars with solarlike oscillations to compare the asymptotic and observational values of the large separation. This comparison relies on the proper use of the second-order asymptotic expansion. Results. We propose a simple formulation to correct the observed value of the large separation and then derive its asymptotic counterpart. The measurement of the curvature of the radial ridges in the échelle diagram provides the correcting factor. We prove that, apart from glitches due to stellar structure discontinuities, the asymptotic expansion is valid from main-sequence stars to red giants. Our model shows that the asymptotic offset is close to 1/4, as in the theoretical development, for low-mass, main-sequence stars, subgiants and red giants. Conclusions. High-quality solar-like oscillation spectra derived from precise photometric measurements are definitely better described with the second-order asymptotic expansion. The second-order term is responsible for the curvature observed in the échelle diagrams used for analyzing the oscillation spectra, and this curvature is responsible for the difference between the observed and asymptotic values of the large separation. Taking it into account yields a revision of the scaling relations, which provides more accurate asteroseismic estimates of the stellar mass and radius. After correction of the bias (6% for the stellar radius and 3% for the mass), the performance of the calibrated relation is about 4% and 8% for estimating, respectively, the stellar radius and the stellar mass for masses less than 1.3 M ; the accuracy is twice as bad for higher mass stars and red giants.

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Section: Introductionmentioning

confidence: 99%

Asymptotic and measured large frequency separations

Mosser¹,

Michel²,

Belkacem³

et al. 2013

A&A

Self Cite

182

303

View full text Add to dashboard Cite

show abstract

“…However, the expressions of the scaled small separation and of the σ l−1l+1 (n) are obtained from an approximative expression of frequency ν n,l , which is inaccurate (Roxburgh & Vorontsov 1994a;Audard & Provost 1994). Although Eqs.…”

Section: Discussionmentioning

confidence: 99%

“…1, we compare the separations d ll+2 (n)/(2l + 3) and σ l−1l+1 (n) obtained from the asymptotic formulas (10) and (15) with the separations obtained from the numerically computed frequencies. The discrepancy between the asymptotic and the numerical values is large, as has been shown by Roxburgh & Vorontsov (1994a) and Audard & Provost (1994). Equations (10) and (15) obtained from the asymptotic formula (6) are inaccurate.…”

Section: Asymptotic Formula and Frequency Separationsmentioning

confidence: 95%

“…Formula (6) is a secondorder asymptotic description of low-degree p-modes under the Cowling approximation, in which the effects of gravitational perturbations are neglected. This formula is inaccurate except for very high frequencies (Roxburgh & Vorontsov 1994a,b;Audard & Provost 1994). Using the definitions (1), (2), and the asymptotic formula (6), Gough & Novotny (1990) obtained the large separation…”

Section: Asymptotic Formula and Frequency Separationsmentioning

confidence: 99%

“…The frequency separations including small separation and large separation have been successfully applied to extract information on stellar interior from oscillation frequencies in asteroseismology and have been investigated by many authors (Christensen-Dalsgaard 1984, 1993Ulrich 1986Ulrich , 1988Gough 1987Gough , 1990Gough , 2003Gough & Novotny 1990;Roxburgh & Vorontsov 1994a,b, 2000, 2003Audard & Provost 1994;Roxburgh 2005;Oti Floranes et al 2005). The usual frequency separations are the large separation defined by…”

Section: Introductionmentioning

confidence: 99%

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The frequency separations of stellar p-modes

Yang

Bi²

2007

A&A

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Aims. The purpose of this work is to investigate the characteristics of a new frequency separation of stellar p-modes. Methods. Frequency separations are deduced from the asymptotic formula of stellar p-modes. Then, using the theoretical adiabatic frequencies of stellar model, we compute the frequency separations. Results. A new separation σ l−1l+1 (n), which is similar to the scaled small separation d ll+2 (n)/(2l + 3), is obtained from the asymptotic formula of stellar p-modes. The separations σ l−1l+1 (n) and d ll+2 (n)/(2l+3) have the same order. And like the small separation, σ l−1l+1 (n) is mainly sensitive to the conditions in the stellar core. However, with the decrease in the central hydrogen abundance of stars, the separations σ 02 and σ 13 deviate more and more from the scaled small separation. This characteristic could be used to extract the information on the central hydrogen abundance of stars.

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The effect of turbulent mixing on the g‐mode spectrum of MS stars

Montalbán¹,

Miglio

Eggenberger

et al. 2008

Astron Nachr

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The understanding of transport processes inside the stars is one of the main goals of asteroseismology. Chemical turbulent mixing can affect the internal distribution of \mu near the energy generating core, having an effect on the evolutionary tracks similar to that of overshooting. This mixing leads to a smoother chemical composition profile near the edge of the convective core, which is reflected in the behavior of the buoyancy frequency and, therefore, in the frequencies of gravity modes. We describe the effects of convective overshooting and turbulent mixing on the frequencies of gravity modes in B-type main sequence stars. In particular, the cases of p-g mixed modes in beta Cep stars and high-order modes in SPBs are considered.Comment: 6 pages, Astron. Nachrichten, accepte

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On P-mode oscillations in stars from 1M ? to 2M ?

Cited by 17 publications

References 1 publication

Asymptotic and measured large frequency separations

Asymptotic and measured large frequency separations

The frequency separations of stellar p-modes

The effect of turbulent mixing on the g‐mode spectrum of MS stars

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