References of "Vauclair, G"
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See detailAmplitude and frequency variations of oscillation modes in the pulsating DB white dwarf star KIC~08626021. The likely signature of nonlinear resonant mode coupling
Zong, W.; Charpinet, S.; Vauclair, G. et al

in Astronomy and Astrophysics (2016), 585

Context. The signatures of nonlinear effects affecting stellar oscillations are difficult to observe from ground observatories because of the lack of continuous high-precision photometric data spanning ... [more ▼]

Context. The signatures of nonlinear effects affecting stellar oscillations are difficult to observe from ground observatories because of the lack of continuous high-precision photometric data spanning extended enough time baselines. The unprecedented photometric quality and coverage provided by the Kepler spacecraft offers new opportunities to search for these phenomena. Aims: We use the Kepler data accumulated on the pulsating DB white dwarf KIC 08626021 to explore in detail the stability of its oscillation modes, searching, in particular, for evidence of nonlinear behaviors. Methods: We analyze nearly two years of uninterrupted short-cadence data, concentrating on identified triplets that are caused by stellar rotation and that show intriguing behaviors during the course of the observations. Results: We find clear signatures of nonlinear effects that could be attributed to resonant mode coupling mechanisms. These couplings occur between the components of the triplets and can induce different types of behaviors. We first notice that a structure at 3681 μHz, identified as a triplet in previous published studies, is in fact forming a doublet, with the third component being an independent mode. We find that a triplet at 4310 μHz and this doublet at 3681 μHz (most likely the two visible components of an incomplete triplet) have clear periodic frequency and amplitude modulations, which are typical of the so-called intermediate regime of the resonance, with timescales consistent with theoretical expectations. Another triplet at 5073 μHz is likely in a narrow transitory regime in which the amplitudes are modulated while the frequencies are locked. Using nonadiabatic pulsation calculations, based on a model representative of KIC 08626021 to evaluate the linear growth rates of the modes in the triplets, we also provide quantitative information that could be useful for future comparisons with numerical solutions of the amplitude equations. Conclusions: The observed modulations are the clearest hints of nonlinear resonant couplings occurring in white dwarf stars identified so far. These should resonate as a warning to projects that aim at measuring the evolutionary cooling rate of KIC 08626021, and of white dwarf stars in general. Nonlinear modulations of the frequencies can potentially jeopardize any attempt to measure such rates reliably, unless they can be corrected beforehand. These results should motivate further theoretical work to develop the nonlinear stellar pulsation theory. [less ▲]

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, A.; Weiss, W. W. et al

in Communications in Asteroseismology (2008), 156

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first ... [more ▼]

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first results to illustrate how these data of unprecedented quality shed a new light on the field of stellar seismology. [less ▲]

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See detailThe Seismology Programme of CoRoT
Michel, Eric; Baglin, A.; Auvergne, M. et al

in Proceedings of "The CoRoT Mission Pre-Launch Status - Stellar Seismology and Planet Finding (2006, November 01)

We introduce the main lines and specificities of the CoRoT Seismology Core Programme. The development and consolidation of this programme has been made in the framework of the CoRoT Seismology Working ... [more ▼]

We introduce the main lines and specificities of the CoRoT Seismology Core Programme. The development and consolidation of this programme has been made in the framework of the CoRoT Seismology Working Group. With a few illustrative examples, we show how CoRoT data will help to address various problems associated with present open questions of stellar structure and evolution. [less ▲]

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See detailAdditional science potential for COROT
Weiss, W. W.; Aerts, C.; Aigrain, S. et al

in Favata, F.; Aigrain, S.; Wilson, A. (Eds.) Stellar Structure and Habitable Planet Finding (2004, January 01)

Space experiments which are aiming towards asteroseismology and the detection of exoplanets, like COROT or MOST, Eddington and Kepler, are designed to deliver high precision photometric data. Obviously ... [more ▼]

Space experiments which are aiming towards asteroseismology and the detection of exoplanets, like COROT or MOST, Eddington and Kepler, are designed to deliver high precision photometric data. Obviously, they can be used also for other purposes than the primary science goals and in addition many other targets can or will be automatically observed simultaneously with the primary targets. As a consequence, fascinating possibilities for additional (parallel, secondary) science projects emerge. For COROT a dedicated working group was thus established with the goal to contribute any useful information which may optimize the scientific output of the mission. [less ▲]

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