Geneva photometry of HD 129929 (Aerts+, 2004)

in SIMBAD (2003), 341

We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V {beta} Cep star Hd 129929. The dataset has a time base of 21.2 years. The occurrence of a ... [more ▼]

We have gathered and analysed a timeseries of 1493 high-quality multicolour Geneva photometric data of the B3V {beta} Cep star Hd 129929. The dataset has a time base of 21.2 years. The occurrence of a beating phenomenon is evident from the data. We find evidence for the presence of at least six frequencies, among which we see components of two frequency multiplets with an average spacing of ~0.0121c/d which points towards very slow rotation. This result is in agreement with new spectroscopic data of the star and also with previously taken UV spectra. We provide the amplitudes of the six frequencies in all seven photometric filters. The metal content of the star is Z=0.018+/-0.004. All these observational results will be used to perform detailed seismic modelling of this massive star in a subsequent paper. (1 data file). [less ▲]

A Hare and Hound in a BAG: Asteroseismology of Beta Cephei stars

in Communications in Asteroseismology (2003), 143

Several members of the COROT Seismology Working Group (SWG) have performed several ``hare-and-hound'' exercises to prepare the data exploitation of the mission in the past few years. These exercises ... [more ▼]

Several members of the COROT Seismology Working Group (SWG) have performed several ``hare-and-hound'' exercises to prepare the data exploitation of the mission in the past few years. These exercises consist in reproducing a theoretical model on the basis of a light curve obtained from a frequency spectrum computed from an ``unknown'' theoretical model of a solar-like or a Delta Scuti star. Members of the BAG (Belgian Asteroseismology Group) have now shown that such an exercise in the mass range of Beta Cephei stars is extremely convincing, making these stars excellent targets for asteroseismology space missions. [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 ▲]

p-mode Oscillations of alpha Cen A

in Astrophysics & Space Science (2003), 284

Models of alpha Cen A & B have been computed using the masses determined by Pourbaix et al. (2002) and the data derived from the spectroscopic analysis of Neuforge and Magain (1997). The seismological ... [more ▼]

Models of alpha Cen A & B have been computed using the masses determined by Pourbaix et al. (2002) and the data derived from the spectroscopic analysis of Neuforge and Magain (1997). The seismological data obtained by Bouchy and Carrier (2001, 2002) 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 ▲]

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

Accretion of gas by globular cluster stars

in Astronomy and Astrophysics (2002), 383

Some recent observations of the abundances of s-process, r-process, and alpha elements in metal-poor stars have led to a new scenario for their formation. According to this scenario, these stars were born ... [more ▼]

Some recent observations of the abundances of s-process, r-process, and alpha elements in metal-poor stars have led to a new scenario for their formation. According to this scenario, these stars were born in a globular cluster and accreted the s-process enriched gas expelled by cluster stars of higher-mass, thereby modifying their surface abundances. Later on, these polluted stars evaporated from the globular cluster to constitute an important fraction of the current halo population. In addition, there are now many direct observations of abundance anomalies not only in globular cluster giant stars but also in subgiant and main-sequence stars. Accretion again provides a plausible explanation for (at least some of) these peculiarities. Here we investigate further the efficiency of the accretion scenario. We find that in concentrated clusters with large escape velocities, accretion is very efficient and can indeed lead to major modifications of the stellar surface abundances. [less ▲]

Evidence For a Self-Enrichment Process in Galactic Halo Globular Clusters

in Grebel, E.; Bradner, W. (Eds.) Modes of Star Formation and the Origin of Field Populations (2002)

Not Available

The Old Halo metallicity gradient: the trace of a self-enrichment process

in Astronomy and Astrophysics (2000), 363

Based on a model of globular cluster self-enrichment published in a previous paper, we present an explanation for the metallicity gradient observed throughout the galactic Old Halo. Our self-enrichment ... [more ▼]

Based on a model of globular cluster self-enrichment published in a previous paper, we present an explanation for the metallicity gradient observed throughout the galactic Old Halo. Our self-enrichment model is based on the ability of globular cluster progenitor clouds to retain the ejecta of a first generation of Type II Supernovae. The key point is that this ability depends on the pressure exerted on the progenitor cloud by the surrounding protogalactic medium and therefore on the location of the cloud in the protoGalaxy. Since there is no significant (if any) metallicity gradient in the whole halo, we also present a review in favour of a galactic halo partly built via accretions and mergers of satellite systems. Some of them bear their own globular clusters and therefore ``contaminate'' the system of globular clusters formed ``in situ'', namely within the original potential well of the Galaxy. Therefore, the comparison between our self-enrichment model and the observational data should be limited to the genuine galactic globular clusters, the so-called Old Halo group. [less ▲]

The Galactic halo. From globular clusters to field stars. Proceedings.

Book (2000)

The following topics were dealt with: early galactic nucleosynthesis; chemical composition of metal-poor stars; metal-poor components of our Galaxy; HR diagrams of globular clusters; chemical and ... [more ▼]

The following topics were dealt with: early galactic nucleosynthesis; chemical composition of metal-poor stars; metal-poor components of our Galaxy; HR diagrams of globular clusters; chemical and dynamical evolution of globular clusters. [less ▲]