Evidence for nonlinear resonant mode coupling in the $\mathsf{\beta}$ Cephei star
HD 180642 (V1449 Aquilae) from CoRoT photometry

Degroote, P.; Briquet, Maryline; Catala, C.; Uytterhoeven, K.; Lefever, K.; Morel, Thierry; Aerts, C.; Carrier, F.; Auvergne, M.; Baglin, A.; Michel, E.

doi:10.1051/0004-6361/200911782

Cited by 121 publications

(164 citation statements)

References 29 publications

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“…We extracted the oscillation frequencies from the simulated data using a prewhitening method, as described by Degroote et al (2009), in combination with the comparison criterion defined in Sect. 3, using α = 0.5.…”

Section: Simulationsmentioning

confidence: 99%

Detecting non-uniform period spacings in theKeplerphotometry ofγDoradus stars: methodology and case studies

Reeth

Tkachenko

Aerts

et al. 2015

A&A

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Context. The analysis of stellar oscillations is one of the most reliable ways to probe stellar interiors. Recent space missions such as Kepler have provided us with an opportunity to study these oscillations with unprecedented detail. For many multi-periodic pulsators such as γ Doradus stars, this led to the detection of dozens to hundreds of oscillation frequencies that could not be found from groundbased observations. Aims. We aim to detect non-uniform period spacings in the Fourier spectra of a sample of γ Doradus stars observed by Kepler. Such detection is complicated by both the large number of significant frequencies in the space photometry and by overlapping nonequidistant rotationally split multiplets. Methods. Guided by theoretical properties of gravity-mode oscillation of γ Doradus stars, we developed a period-spacing detection method and applied it to Kepler observations of a few stars, after having tested the performance from simulations. Results. The application of the technique resulted in the clear detection of non-uniform period spacing series for three out of the five treated Kepler targets. Disadvantages of the technique are also discussed, and include the disability to distinguish between different values of the spherical degree and azimuthal order of the oscillation modes without additional theoretical modelling. Conclusions. Despite the shortcomings, the method is shown to allow solid detections of period spacings for γ Doradus stars, which will allow future asteroseismic analyses of these stars.

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Section: Simulationsmentioning

confidence: 99%

Detecting non-uniform period spacings in theKeplerphotometry ofγDoradus stars: methodology and case studies

Reeth

Tkachenko

Aerts

et al. 2015

A&A

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“…It turns out that BIC gives the best value, which is always within a factor 1.5 of the correct result. Degroote et al (2009b) also used BIC in preference over the (uncorrected) AIC as a stopping criterion in their study of the β Cep star HD 180642.…”

Section: Stopping Criteriamentioning

confidence: 99%

Variability in the CoRoT photometry of three hot O-type stars

Blomme

Mahy

Catala

et al. 2011

A&A

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Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. Aims. We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. Methods. We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. Results. A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. Conclusions. The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible.

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“…The error estimate on the frequency is computed as in Degroote et al (2009a), i.e., using the formula of Montgomery & O'Donoghue (1999), but also taking correlation effects into account according to the formalism by Schwarzenberg-Czerny (2003). Recent studies of CoRoT light curves of B-type stars highlighted variations in the amplitude of frequencies and in the frequencies themselves as a function of time (e.g., in the β Cep star HD 180642, Degroote et al 2009b; in the B0.5IVe star HD 49330, Huat et al 2009). In order to check the stability of the frequencies of HD 46202 listed in Table 1, we applied a short time Fourier transform.…”

Section: Frequency Analysis On Corot Photometrymentioning

confidence: 99%

An asteroseismic study of the O9V star HD 46202 from CoRoT space-based photometry

Briquet

Aerts

Baglin

et al. 2011

A&A

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The O9V star HD 46202, which is a member of the young open cluster NGC 2244, was observed by the CoRoT satellite in October/November 2008 during a short run of 34 days. From the very high-precision light curve, we clearly detect β Cep-like pulsation frequencies with amplitudes of ∼0.1 mmag and below. A comparison with stellar models was performed using a χ 2 as a measure for the goodness-of-fit between the observed and theoretically computed frequencies. The physical parameters of our best-fitting models are compatible with the ones deduced spectroscopically. A core overshooting parameter α ov = 0.10 ± 0.05 pressure scale height is required. None of the observed frequencies are theoretically excited with the input physics used in our study. More theoretical work is thus needed to overcome this shortcoming in how we understand the excitation mechanism of pulsation modes in such a massive star. A similar excitation problem has also been encountered for certain pulsation modes in β Cep stars recently modelled asteroseismically.

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Evidence for nonlinear resonant mode coupling in the $\mathsf{\beta}$ Cephei star HD 180642 (V1449 Aquilae) from CoRoT photometry

Cited by 121 publications

References 29 publications

Detecting non-uniform period spacings in theKeplerphotometry ofγDoradus stars: methodology and case studies

Detecting non-uniform period spacings in theKeplerphotometry ofγDoradus stars: methodology and case studies

Variability in the CoRoT photometry of three hot O-type stars

An asteroseismic study of the O9V star HD 46202 from CoRoT space-based photometry

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