Theoretical seismic properties of pre-main sequence<i>γ</i> Doradus pulsators

Bouabid, M.-P.; Montalbán, J.; Miglio, A.; Dupret, Marc‐Antoine; Grigahcène, A.; Noels, A.

doi:10.1051/0004-6361/201116440

Cited by 24 publications

(24 citation statements)

References 35 publications

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“…Young stars rotate faster and are more likely to exhibit r-modes in the detection region (0.2 to 2 d), hence we find more r-modes in stars near the ZAMS. We do not take the possibility of pre-main sequence γ Dor stars into account, although they were predicted by Bouabid et al (2011). Another factor is that the low mass stars enter the γ Dor instability strip at the beginning of main sequence and stay in it longer than high mass stars.…”

Section: Stars On the Hr Diagrammentioning

confidence: 95%

Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars

Reeth

Bedding

et al. 2019

Monthly Notices of the Royal Astronomical Society

110

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Rossby modes are the oscillations in a rotating fluid, whose restoring force is the Coriolis force. They provide an additional diagnostic to understand the rotation of stars, which complicates asteroseismic modelling. We report 82 γ Doradus stars for which clear period spacing patterns of both gravity and Rossby modes have been detected. The period spacings of both show a quasi-linear relation with the pulsation period but the slope is negative for the gravity modes and positive for the Rossby modes. Most Rossby modes have k = −2, m = −1. For only one star a series of k = −1, m = −1 modes is seen. For each pattern, the mean pulsation period, the mean period spacing, and the slope are measured. We find that the slope correlates with the mean period for Rossby mode patterns. The traditional approximation of rotation is used to measure the near-core rotation rate, assuming the star rotates rigidly. We report the near-core rotation rates, the asymptotic period spacings, and the radial orders of excited modes of these 82 main-sequence stars. The near-core rotation rates lie between 0.6 d −1 and 2.3 d −1 . Six stars show surface rotation modulations, among which only KIC 3341457 shows differential rotation while the other five stars have uniform rotations. The radial orders of excited modes show different distributions for the dipole and quadrupole gravity modes versus the Rossby modes.

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Section: Stars On the Hr Diagrammentioning

confidence: 95%

Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars

Reeth

Bedding

et al. 2019

Monthly Notices of the Royal Astronomical Society

110

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“…1, stars exhibiting purely γ Dor or δ Sct pulsations seem to exist beyond the current blue and red edge of the respective instability strips. Moreover, it is worth investigating if the evolutionary phase of γ Dor stars can be derived from properties in their frequency spectra, as is recently suggested by Bouabid et al (2011), based on a theoretical study of seismic properties of MS and pre-MS γ Dor pulsators.…”

Section: Summary Discussion and Future Prospectsmentioning

confidence: 99%

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

Uytterhoeven

Moya

Grigahcène

et al. 2011

A&A

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331

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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“…Interestingly, the region of high P turb shown in Fig. 1 broadly overlaps with the theoretical instability strips of γ Dor stars, which are indeed high-order, g-mode pulsators (Bouabid et al 2011). …”

Section: The γ Dor Instability Stripmentioning

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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Theoretical seismic properties of pre-main sequenceγ Doradus pulsators

Cited by 24 publications

References 35 publications

Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars

Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars

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

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

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