The Liège Oscillation code

Baglin

et al. 2011

A&A

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111

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.

Section: Numerical Tools and Model Input Physicsmentioning

confidence: 99%

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

Briquet

Baglin

et al. 2011

A&A

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111

“…The probability of catching the star beyond the TAMS, i.e., in the Hertzsprung gap, is so low that it is not necessary to consider hydrogen-shell burning models. For each of the MS models along the 27 500 tracks, a theoretical oscillation frequency spectrum ignoring the effects of rotation, ν n , was computed in the adiabatic approximation with the code LOSC (Scuflaire et al 2008b), covering the range of the low-order (typically up to n = 7) p and g modes of degree from = 0 up to = 4. Following Ausseloos et al (2004), we did not restrict the model parameters a priori by imposing limits derived from classical spectroscopy, because discrepancies between the seismically and spectroscopically derived fundamental parameters have been reported for a few massive stars in the literature, in particular for the gravity (e.g., Briquet et al 2007; for the β Cep star θ Oph and Briquet et al 2011; for the O9V-type pulsator HD 46202).…”

Section: Modelling Proceduresmentioning

confidence: 99%

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

Briquet

Degroote

et al. 2011

A&A

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Context. We present modelling of the β Cep star HD 180642 based on its observational properties deduced from CoRoT and groundbased photometry as well as from time-resolved spectroscopy. Aims. We investigate whether present-day state-of-the-art models are able to explain the full seismic behaviour of this star, which has extended observational constraints for this type of pulsator. Methods. We constructed a dedicated database of stellar models and their oscillation modes tuned to fit the dominant radial mode frequency of HD 180642, by means of varying the hydrogen content, metallicity, mass, age, and core overshooting parameter. We compared the seismic properties of these models with those observed. Results. We find models that are able to explain the numerous observed oscillation properties of the star, for a narrow range in mass of 11.4-11.8 M and no or very mild overshooting (with up to 0.05 local pressure scale heights), except for an excitation problem of the = 3, p 1 mode. We deduce a rotation period of about 13 d, which is fully compatible with recent magnetic field measurements. The seismic models do not support the earlier claim of solar-like oscillations in the star. We instead ascribe the power excess at high frequency to non-linear resonant mode coupling between the high-amplitude radial fundamental mode and several of the low-order pressure modes. We report a discrepancy between the seismic and spectroscopic gravity at the 2.5σ level.

“…19). Stellar models were computed with cles (Scuflaire et al 2008b), adiabatic frequencies with losc (Scuflaire et al 2008a), and the stability of modes of degree = 0, 1, 2 was investigated with the code mad (Dupret et al 2003). In the case of δ Sct and γ Doradus stars, the nonadiabatic computations included the interaction between convection and pulsation as described by Grigahcène et al (2005).…”

Section: Comparison With Theoretical Predictionsmentioning

confidence: 99%

CoRoT's view of newly discovered B-star pulsators: results for 358 candidate B pulsators from the initial run's exoplanet field data

Degroote¹,

Ollivier

et al. 2009

A&A

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Context. We search for new variable B-type pulsators in the CoRoT data assembled primarily for planet detection, as part of CoRoT's additional programme. Aims. We aim to explore the properties of newly discovered B-type pulsators from the uninterrupted CoRoT space-based photometry and to compare them with known members of the β Cep and slowly pulsating B star (SPB) classes. Methods. We developed automated data analysis tools that include algorithms for jump correction, light-curve detrending, frequency detection, frequency combination search, and for frequency and period spacing searches. Results. Besides numerous new, classical, slowly pulsating B stars, we find evidence for a new class of low-amplitude B-type pulsators between the SPB and δ Sct instability strips, with a very broad range of frequencies and low amplitudes, as well as several slowly pulsating B stars with residual excess power at frequencies typically a factor three above their expected g-mode frequencies.Conclusions. The frequency data we obtained for numerous new B-type pulsators represent an appropriate starting point for further theoretical analyses of these stars, once their effective temperature, gravity, rotation velocity, and abundances will be derived spectroscopically in the framework of an ongoing FLAMES survey at the VLT.