Connections Between Stellar Oscillations and Turbulent Convection

Belkacem, K.; Samadi, R.

doi:10.1007/978-3-642-33380-4_9

Cited by 7 publications

(4 citation statements)

References 63 publications

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“…Belkacem & Samadi 2013). From the analysis of activity in eclipsing binary stars, Gaulme et al (2014) suggested that such effects lead to additional damping of solarlike oscillations.…”

Section: Effect Of Activity On the Mode Linewidthmentioning

confidence: 99%

Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796

Beck

Kallinger

Pavlovski

et al. 2018

A&A

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Context. Binaries in double-lined spectroscopic systems (SB2) provide a homogeneous set of stars. Differences of parameters, such as age or initial conditions, which otherwise would have strong impact on the stellar evolution, can be neglected. The observed differences are determined by the difference in stellar mass between the two components. The mass ratio can be determined with much higher accuracy than the actual stellar mass. Aims. In this work, we aim to study the eccentric binary system KIC 9163796, whose two components are very close in mass and both are low-luminosity red-giant stars. Methods. We analyse four years of Kepler space photometry and we obtained high-resolution spectroscopy with the Hermes instrument. The orbital elements and the spectra of both components were determined using spectral disentangling methods. The effective temperatures, and metallicities were extracted from disentangled spectra of the two stars. Mass and radius of the primary were determined through asteroseismology. The surface rotation period of the primary is determined from the Kepler light curve. From representative theoretical models of the star, we derived the internal rotational gradient, while for a grid of models, the measured lithium abundance is compared with theoretical predictions. Results. From seismology the primary of KIC 9163796 is a star of 1.39±0.06 M ⊙ , while the spectroscopic mass ratio between both components can be determined with much higher precision by spectral disentangling to be 1.015±0.005. With such mass and a difference in effective temperature of 600 K from spectroscopy, the secondary and primary are, respectively, in the early and advanced stage of the first dredge-up event on the red-giant branch. The period of the primary's surface rotation resembles the orbital period within 10 days.The radial rotational gradient between the surface and core in KIC 9163796 is found to be 6.9 +2.0 −1.0 . This is a low value but not exceptional if compared to the sample of typical single field stars. The seismic average of the envelope's rotation agrees with the surface rotation rate. The lithium abundance is in agreement with quasi rigidly-rotating models. Conclusions. The agreement between the surface rotation with the seismic result indicates that the full convective envelope is rotating quasi-rigidly. The models of the lithium abundance are compatible with a rigid rotation in the radiative zone during the main sequence. Because of the many constraints offered by oscillating stars in binary systems, such objects are important test beds of stellar evolution.

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“…Belkacem & Samadi 2013). From the analysis of activity in eclipsing binary stars, Gaulme et al (2014) suggested that such effects lead to additional damping of solarlike oscillations.…”

Section: Effect Of Activity On the Mode Linewidthmentioning

confidence: 99%

Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796

Beck

Kallinger

Pavlovski

et al. 2018

A&A

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“…Both seismic indices, Δ and max are directly related to stellar physical properties such as the mean density < >, the surface gravity and the effective temperature ef f (see e.g. Belkacem et al, 2011;Brown, Gilliland, Noyes, & Ramsey, 1991;Kjeldsen & Bedding, 1995;Ulrich, 1986). Therefore, it is possible to deduce the seismic mass and radius (Kallinger, Mosser, et al, 2010) to a very good precision and therefore, study stellar populations (see e.g.…”

Section: Introductionmentioning

confidence: 99%

A new method for extracting seismic indices and granulation parameters: Results for more than 20,000 CoRoT andKeplerred giants

2018

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We have developed a new automated method intended to perform the simultaneous-and thus more consistent-measurement of both the seismic indices characterizing the oscillations and the parameters characterizing the granulation signature of red giant stars. This method, called MLEUP, takes advantage of the Maximum Likelihood Estimate (MLE) algorithm combined with the parameterized representation of red giant pulsation spectra following the universal pattern (UP). Its performances have been tested on Monte Carlo simulations for observation conditions representative of CoRoT and Kepler data. These simulations allowed us to determine, calibrate, and propose corrections for the biases on the parameter estimates as well as on the error estimates produced with MLEUP. Finally, we applied MLEUP to CoRoT and Kepler data. In total, MLEUP yields seismic indices for 20,122 red giant stars and granulation parameters for 17,109 of them. These data have been made available in the stellar seismic indices database (http://ssi.lesia. obspm.fr/).

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“…Turbulent convection is known to play a decisive role in the stochastic forcing, self-excitation and damping of pulsation modes across the HR diagram (see, e.g., Houdek 2000, Dupret et al 2004, Xiong & Deng 2007, Belkacem & Samadi 2013. Moreover, a recent study by Antoci et al (2014) showed that turbulent pressure in the hydrogen ionization zone is likely to explain the high-frequency, coherent pulsation modes observed in the δ Scuti pulsator HD 187547.…”

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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Connections Between Stellar Oscillations and Turbulent Convection

Cited by 7 publications

References 63 publications

Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796

Seismic probing of the first dredge-up event through the eccentric red-giant and red-giant spectroscopic binary KIC 9163796

A new method for extracting seismic indices and granulation parameters: Results for more than 20,000 CoRoT andKeplerred giants

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

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