Asteroseismology of HD 129929: Core Overshooting and Nonrigid Rotation

in Science (2003), 300

We have gathered and analyzed 1493 high-quality multicolor Geneva photometric data taken over 21 years of the B3V star HD 129929. We detect six frequencies, among which appear the effects of rotational ... [more ▼]

We have gathered and analyzed 1493 high-quality multicolor Geneva photometric data taken over 21 years of the B3V star HD 129929. We detect six frequencies, among which appear the effects of rotational splitting with a spacing of ~0.0121 cycles per day, which implies that the star rotates very slowly. A nonadiabatic analysis of the oscillations allows us to constrain the metallicity of the star to Z â [0.017,0.022], which agrees with a similar range derived from spectroscopic data. We provide evidence for the occurrence of core convective overshooting in the star, with alpha[SUB]ov[/SUB] = 0.10 +/- 0.05, and we rule out rigid rotation. [less ▲]

A new seismic analysis of Alpha Centauri

in Astronomy and Astrophysics (2003), 402(1), 293-297

Models of alpha Cen A & B have been computed using the masses determined by Pourbaix et al. (\cite{Po2002}) and the data derived from the spectroscopic analysis of Neuforge & Magain (\cite{Ne1997}). The ... [more ▼]

Models of alpha Cen A & B have been computed using the masses determined by Pourbaix et al. (\cite{Po2002}) and the data derived from the spectroscopic analysis of Neuforge & Magain (\cite{Ne1997}). The seismological data obtained by Bouchy & Carrier (\cite{Bo2001}, \cite{Bo2002}) do help improve our knowledge of the evolutionary status of the system. All the constraints are satisfied with a model which gives an age of about 6 Gyr for the binary. [less ▲]

A photometric mode identification method, including an improved non-adiabatic treatment of the atmosphere

in Astronomy and Astrophysics (2003), 398

We present an improved version of the method of photometric mode identification of Heynderickx et al. (\cite{hey}). Our new version is based on the inclusion of precise non-adiabatic eigenfunctions ... [more ▼]

We present an improved version of the method of photometric mode identification of Heynderickx et al. (\cite{hey}). Our new version is based on the inclusion of precise non-adiabatic eigenfunctions determined in the outer stellar atmosphere according to the formalism recently proposed by Dupret et al. (\cite{dup}). Our improved photometric mode identification technique is therefore no longer dependent on ad hoc parameters for the non-adiabatic effects. It contains the complete physical conditions of the outer atmosphere of the star, provided that rotation does not play a key role. We apply our method to the two slowly pulsating B stars HD 74560 and HD 138764 and to the beta Cephei star EN (16) Lac. Besides identifying the degree l of the pulsating stars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on parameters such as the metallicity and the mixing-length parameter alpha (a procedure we label non-adiabatic asteroseismology). The non-adiabatic eigenfunctions needed for the mode identification are available upon request from the authors. [less ▲]

Mode Identification and Seismic Modelling of the Cep Star EN(16)Lac

in Asteroseismology Across the HR Diagram (2003)

Not Available

Variable Blue Stragglers and the EASE Scenario

in Thompson, M. J.; Cunha, M. S.; Monteiro, M.J.P.F.G. (Eds.) Asteroseismology Across the HR Diagram (2003)

Not Available

Influence of non-adiabatic temperature variations on line profile variations of slowly rotating beta Cep stars and SPBs. I. Non-adiabatic eigenfunctions in the atmosphere of a pulsating star

in Astronomy and Astrophysics (2002), 385

In this study, we compute theoretical line profiles of a non-radially pulsating star, taking the non-adiabatic effects into account. These non-adiabatic effects are especially important in the atmosphere ... [more ▼]

In this study, we compute theoretical line profiles of a non-radially pulsating star, taking the non-adiabatic effects into account. These non-adiabatic effects are especially important in the atmosphere, where the spectral lines are formed, and must be accounted for. In this first paper of the series, we present a new treatment of the perturbed thermal and dynamical equations in the atmosphere of a pulsating star. We apply our formalism to the computation of non-adiabatic eigenfunctions in a typical beta Cephei star with low order p-modes and in a typical slowly pulsating B star with high-order g-modes. [less ▲]

The B-type variable HD 131120 modelled by rotational modulation

in Astronomy and Astrophysics (2001), 380

We present ground-based multi-colour Geneva photometry and high-resolution spectra of the variable B-type star HD 131120. All sets of data reveal a monoperiodic star with a period of 1.569 days. We ... [more ▼]

We present ground-based multi-colour Geneva photometry and high-resolution spectra of the variable B-type star HD 131120. All sets of data reveal a monoperiodic star with a period of 1.569 days. We compare the variability of the star with a non-radial g-mode pulsation model and with a rotational modulation model. The latter model appears to be the best explanation for the observed line-profile variations of the star. Moreover, contrary to the pulsational model, it is able to reproduce the behaviour of the first three moments of the Si and He lines as well as the large variability of their equivalent width. We therefore remove the star from the list of new Slowly Pulsating B stars found from Hipparcos data. Based on observations obtained with the Swiss photometric telescope and ESO's CAT/CES telescope, both situated at La Silla, Chile. [less ▲]

Upward Revision of the Individual Masses in Α Cen: Implications for the Evolutionary State of the System

in Hearnshaw, J. B.; Scarfe, C. D. (Eds.) Precise Stellar Radial Velocities: IAU Colloquium 170 : proceedings of a meeting held at Victoria, B.C., Canada, 21-26 June, 1998 (1999)

The recent upward revisions of the individual masses of the components of the binary system α Centauri (Pourbaix D., this meeting) led us to perform new calibrations of the system. The possibility of the ... [more ▼]

The recent upward revisions of the individual masses of the components of the binary system α Centauri (Pourbaix D., this meeting) led us to perform new calibrations of the system. The possibility of the onset a convective core in α Cen A is discussed together with its implications on the p-mode oscillation frequencies. [less ▲]

Influence of opacities, partition functions and hydrogen diffusion on the 5 min solar oscillations

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (1984), 55(1-2), 169-174

Several accuracy tests of the frequencies computation have been performed. They show that for a given model, the frequencies have errors lower than 2 micro-Hz. Several tests have also been made on the ... [more ▼]

Several accuracy tests of the frequencies computation have been performed. They show that for a given model, the frequencies have errors lower than 2 micro-Hz. Several tests have also been made on the Henyey code. They show that the use of the same opacity formula as Bahcall et al. (1983) allows to reproduce their model with a good accuracy. The model has however frequencies systematically 12 micro-Hz larger than found by Ulrich and Rhodes. A model with diffusion of H and He has also been studied. Its frequencies are nearly the same as those of the standard model. [less ▲]

Stability of g+ Modes in a 30 M_solar Star

in Bulletin de la Société Royale des Sciences de Liège (1975), 8