Convection-pulsation coupling

Dupret, Marc‐Antoine; Grigahcène, A.; Garrido, R.; Gabriel, M.; Scuflaire, R.

doi:10.1051/0004-6361:20041817

Cited by 297 publications

(381 citation statements)

References 22 publications

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“…Of the sixteen δ Sct stars, Scuflaire et al 2008). The input physics included is similar to the one used in Dupret et al (2005) with the following values for the modelling parameters α MLT = 1.8, α ov = 0.2 and Z = 0.02. The solid thick black and light grey lines mark the blue and red edge of the observed instability strips of δ Sct and γ Dor stars, as described by Rodríguez & Breger (2001) and Handler & Shobbrook (2002), respectively.…”

Section: Characterization Of Stars That Show No Clear Periodic Variabmentioning

confidence: 99%

TheKeplercharacterization of the variability among A- and F-type stars

Uytterhoeven

Moya

Grigahcène

et al. 2011

A&A

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329

316

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Context. The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. Aims. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between γ Doradus (γ Dor), δ Scuti (δ Sct), and hybrid stars. Methods. We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each star and extract the pulsational frequencies using different frequency analysis methods. We construct two new observables, "energy" and "efficiency", related to the driving energy of the pulsation mode and the convective efficiency of the outer convective zone, respectively. Results. We propose three main groups to describe the observed variety in pulsating A-F type stars: γ Dor, δ Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much higher fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities within the γ Dor and δ Sct range, also between 5 and 10 d −1 , which is a challenge for the current models. We find indications for the existence of δ Sct and γ Dor stars beyond the edges of the current observational instability strips. The hybrid stars occupy the entire region within the δ Sct and γ Dor instability strips and beyond. Non-variable stars seem to exist within the instability strips. The location of γ Dor and δ Sct classes in the (T eff , log g)-diagram has been extended. We investigate two newly constructed variables, "efficiency" and "energy", as a means to explore the relation between γ Dor and δ Sct stars. Conclusions. Our results suggest a revision of the current observational instability strips of δ Sct and γ Dor stars and imply an investigation of pulsation mechanisms to supplement the κ mechanism and convective blocking effect to drive hybrid pulsations. Accurate physical parameters for all stars are needed to confirm these findings.

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Section: Characterization Of Stars That Show No Clear Periodic Variabmentioning

confidence: 99%

TheKeplercharacterization of the variability among A- and F-type stars

Uytterhoeven

Moya

Grigahcène

et al. 2011

A&A

Self Cite

329

316

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“…At these temperatures, the interaction between convection and pulsation described by Grigahcène et al (2005) and Dupret et al (2005) may change the non-adiabatic eigenfunctions significantly.…”

Section: Amplitude Ratios Vs Phase Differencesmentioning

confidence: 99%

A comprehensive asteroseismic modelling of the high-amplitude δ Scuti star RV Arietis

Casas¹,

Suárez

Moya

et al. 2006

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We present a comprehensive asteroseismic study of the double-mode high-amplitude δ Scuti star HD 187642 (RV Ari). The modelling includes some of the most recent techniques: 1) effects of rotation on both equilibrium models and adiabatic oscillation spectrum, 2) non-adiabatic study of radial and non-radial modes, 3) relationship between the fundamental radial mode and the first overtone in the framework of Petersen diagrams. The analysis reveals that two of the observed frequencies are very probably identified as the fundamental and first overtone radial modes. Analysis of the colour index variations, together with theoretical non-adiabatic calculations, points to models in the range of [7065, 7245] K in effective temperature and of [1190, 1270] Myr in stellar age. These values were found to be compatible with those obtained using the three other asteroseismic techniques.

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“…These A-and F-type Appendices A and B are available in electronic form at http://www.aanda.org stars are pulsating with high-order, non-radial g-modes (Guzik et al 2000;Miglio et al 2008). Theoretical stability analyses adopting time-dependent convection predict an instability strip (IS) to occur close to where γ Dor are observed, involving a fluxblocking excitation mechanism (Guzik et al 2000;Dupret et al 2005). However, Dupret et al (2004) showed that the agreement between observations and theory depends very sensitively on the exact treatment of convection.…”

Section: Introductionmentioning

confidence: 99%

Relating turbulent pressure and macroturbulence across the HR diagram with a possible link toγDoradus stars

Grassitelli

Fossati

Langer

et al. 2015

A&A

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A significant fraction of the envelope of low-and intermediate-mass stars is unstable to convection, leading to sub-surface turbulent motion. Here, we consider and include the effects of turbulence pressure in our stellar evolution calculations. In search of an observational signature, we compare the fractional contribution of turbulent pressure to the observed macroturbulent velocities in stars at different evolutionary stages. We find a strong correlation between the two quantities, similar to what was previously found for massive OB stars. We therefore argue that turbulent pressure fluctuations of finite amplitude may excite high-order, high-angular degree stellar oscillations, which manifest themselves at the surface an additional broadening of the spectral lines, i.e., macroturbulence, across most of the HR diagram. When considering the locations in the HR diagram where we expect high-order oscillations to be excited by stochastic turbulent pressure fluctuations, we find a close match with the observational γ Doradus instability strip, which indeed contains high-order, non-radial pulsators. We suggest that turbulent pressure fluctuations on a percentual level may contribute to the γ Dor phenomenon, calling for more detailed theoretical modeling in this direction.

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Convection-pulsation coupling

Cited by 297 publications

References 22 publications

TheKeplercharacterization of the variability among A- and F-type stars

TheKeplercharacterization of the variability among A- and F-type stars

A comprehensive asteroseismic modelling of the high-amplitude δ Scuti star RV Arietis

Relating turbulent pressure and macroturbulence across the HR diagram with a possible link toγDoradus stars

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