An asteroseismic study of the β Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling

Desmet, M.; Briquet, Maryline; Thoul, Anne; Zima, W.; Cat, P. De; Handler, G.; Ilyin, I.; Kambe, Eiji; Krzesiński, J.; Lehmann, H.; Masuda, Seiji; Mathias, P.; Mkrtichian, D. E.; Telting, J. H.; Uytterhoeven, K.; Yang, S.; Aerts, C.

doi:10.1111/j.1365-2966.2009.14790.x

Cited by 54 publications

(70 citation statements)

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“…This is not necessarily the case for the gravity of the seismically modelled β Cep stars. While good agreement was found for several stars (e.g., HD 129929, Dupret et al 2004;12 Lac;Desmet et al 2009), the spectroscopic log g turned out to be 0.15 dex higher than the seismic log g for the star θ Oph (Briquet et al 2007). For HD 46202, the discrepancy even amounted to 0.24 dex .…”

Section: Constraints Imposed By Spectroscopymentioning

confidence: 87%

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

Aerts

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.

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Section: Constraints Imposed By Spectroscopymentioning

confidence: 87%

“…In addition, the predicted frequency of this = 1, p 2 mode for appropriate models was found to be shifted with respect to the observed value for both ν Eri and γ Peg. A similar excitation problem occurred for the star 12 Lac (Dziembowski & Pamyatnykh 2008;Desmet et al 2009). …”

Section: Requesting Mode Excitation For the Dominant Modementioning

confidence: 91%

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

Aerts

Briquet

Degroote

et al. 2011

A&A

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“…F: HD214993. The star is one of the most intensely studied β Cephei pulsators (Desmet et al 2009, and references therein). Our preliminary modelling encounters difficulties, which may be resolved assuming helium-enrichment of the atmosphere.…”

Section: Stars Excluded From the Analysismentioning

confidence: 99%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

422

506

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Context. Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstellar medium (ISM) or H ii regions. Aims. A carefully selected sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Quantitative spectroscopy is used to characterise their atmospheric properties in a self-consistent way. Present-day abundances for the astrophysically most interesting chemical elements are derived in order to investigate whether a present-day cosmic abundance standard can be established. Methods. High-resolution and high-S/N FOCES, FEROS and ELODIE spectra of well-studied sharp-lined early B-type stars are analysed in non-LTE. Line-profile fits based on extensive model grids and an iterative analysis methodology are used to constrain stellar parameters and elemental abundances at high accuracy and precision. Atmospheric parameters are derived from the simultaneous establishment of independent indicators, from multiple ionization equilibria and the Stark-broadened hydrogen Balmer lines, and they are confirmed by reproduction of the stars' global spectral energy distributions. Results. Effective temperatures are constrained to 1-2% and surface gravities to less than 15% uncertainty, along with accurate rotational, micro-and macroturbulence velocities. Good agreement of the resulting spectroscopic parallaxes with those from the new reduction of the Hipparcos catalogue is obtained. Absolute values for abundances of He, C, N, O, Ne, Mg, Si and Fe are determined to better than 25% uncertainty. The synthetic spectra match the observations reliably over almost the entire visual spectral range. Three sample stars, γ Ori, o Per and θ 1 Ori D, are identified as double-lined, indicating the presence of an early/mid B-type companion. Conclusions. A present-day cosmic abundance standard is established from a sample of 29 early B-type stars, indicating abundance fluctuations of less than 10% around the mean. Our results (i) resolve the long-standing discrepancy between a chemical homogeneous gas-phase ISM and a chemically inhomogeneous young stellar component out to several hundred parsec from the Sun, (ii) facilitate the amount of heavy elements locked up in the interstellar dust to be constrained precisely -the results imply that carbonaceous dust is largely destroyed inside the Orion H ii region, unlike the silicates, and that graphite is only a minority species in interstellar dust -, (iii) show that the mixing of CNO-burning products in the course of massive star evolution follows tightly the predicted nuclear path, (iv) provide reliable present-day reference points for anchoring Galactic chemical evolution models to observation, and (v) imply that the Sun has migrated outwards from the inne...

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“…This concerns the stars ν Eri (Handler et al 2004;De Ridder et al 2004), 12 Lac (Handler et al 2006;Desmet et al 2009) and γ Peg (Handler et al 2009). In all these examples, however, the pressure modes are dominant over the gravity modes.…”

Section: Introductionmentioning

confidence: 99%

The CoRoT B-type binary HD 50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings

Degroote

Aerts

Michel

et al. 2012

A&A

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Context. B-type stars are promising targets for asteroseismic modelling, since their frequency spectrum is relatively simple. Aims. We deduce and summarise observational constraints for the hybrid pulsator, HD 50230, earlier reported to have deviations from a uniform period spacing of its gravity modes. The combination of spectra and a high-quality light curve measured by the CoRoT satellite allow a combined approach to fix the position of HD 50230 in the HR diagram. Methods. To describe the observed pulsations, classical Fourier analysis was combined with short-time Fourier transformations and frequency spacing analysis techniques. Visual spectra were used to constrain the projected rotation rate of the star and the fundamental parameters of the target. In a first approximation, the combined information was used to interpret multiplets and spacings to infer the true surface rotation rate and a rough estimate of the inclination angle. Results. We identify HD 50230 as a spectroscopic binary and characterise the two components. We detect the simultaneous presence of high-order g modes and low-order p and g-modes in the CoRoT light curve, but were unable to link them to line profile variations in the spectroscopic time series. We extract the relevant information from the frequency spectrum, which can be used for seismic modelling, and explore possible interpretations of the pressure mode spectrum.

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An asteroseismic study of the β Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling

Cited by 54 publications

References 54 publications

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

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

Present-day cosmic abundances

The CoRoT B-type binary HD 50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings

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