References of "Parmentier, Geneviève"
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See detailAbundance correlations in mildly metal-poor stars. II. Light elements (C to Ca)
Decauwer, Hélène; Jehin, Emmanuel ULg; Parmentier, Geneviève ULg et al

in Astronomy and Astrophysics (2005), 433

Accurate relative abundances have been obtained for carbon, oxygen, sodium, aluminium, silicon, and calcium in a sample of mildly metal-poor stars. This analysis complements a previous study carried out ... [more ▼]

Accurate relative abundances have been obtained for carbon, oxygen, sodium, aluminium, silicon, and calcium in a sample of mildly metal-poor stars. This analysis complements a previous study carried out by Jehin et al. ([CITE], A&A, 341, 241), which provided the basis for the EASE scenario. This scenario postulates that field metal-poor stars were born in self-enriched proto-globular cluster clouds. By further investigating the correlations between the different alpha-element abundances, we propose a modified scenario for the formation of intermediate metallicity stars, in which the stars exhibiting lower than average alpha/Fe abundance ratios would form in low mass clouds, unable to sustain the formation of very massive stars (M ⪠30~M_o). Moreover, the carbon-to-iron ratio is found to decrease as one climbs the so-called Population IIb branch, i.e. when the s-element abundance increases. In the framework of the EASE scenario, we interpret this anticorrelation between the carbon and the s-element abundances as a signature of a hot bottom burning process in the metal-poor AGB stars which expelled the matter subsequently accreted by our Population IIb stars. Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO Programmes 56.E-0384, 57.E-0400 and 59.E-0257). [less ▲]

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See detailVariable Blue Stragglers and the EASE Scenario
Noels-Grötsch, Arlette ULg; Scuflaire, Richard ULg; Magain, Pierre ULg et al

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

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See detailAccretion of gas by globular cluster stars
Thoul, Anne ULg; Jorissen, Alain; Goriely, Stéphane et al

in Astronomy and Astrophysics (2001), 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 ▲]

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See detailThe Old Halo metallicity gradient: the trace of a self-enrichment process
Parmentier, Geneviève ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

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 ▲]

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See detailA new orbital solution for the massive binary system HD 93403
Rauw, Grégor ULg; Sana, H.; Gosset, Eric ULg et al

in Astronomy and Astrophysics (2000), 360

We present a spectroscopic analysis of the early-type massive binary system HD 93403. Using high resolution optical spectra, we clearly separate the primary and secondary components. For the first time ... [more ▼]

We present a spectroscopic analysis of the early-type massive binary system HD 93403. Using high resolution optical spectra, we clearly separate the primary and secondary components. For the first time, we are able to provide an orbital solution for both stars. Our new orbital parameters show discrepancies with the previous solution published by Thackeray & Emerson (?). We further discuss several spectral features of HD 93403. We finally derive qualitative constraints on the inclination of the system and we discuss its evolutionary status and the position of both components in the Hertzsprung-Russell diagram. Based on observations collected at the European Southern Observatory (La Silla, Chile) and the Cerro Tololo Inter-American Observatory (CTIO). [less ▲]

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See detailWere the Old Halo globular clusters able to sustain a self-enrichment phase?
Parmentier, Geneviève ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in New Astronomy Reviews (2000), 44

It has been argued for a long time that the self-enrichment process could not occur within proto-globular clouds because of the supernova energetics. We revisit this argument and demonstrate that it may ... [more ▼]

It has been argued for a long time that the self-enrichment process could not occur within proto-globular clouds because of the supernova energetics. We revisit this argument and demonstrate that it may not be true. Since not all the kinetic energy of Type II Supernovae is deposited as kinetic energy of the ISM, we suggest comparing the binding energy of the progenitor cloud to the kinetic energy of the ISM instead of the kinetic energy of the Type II Supernova ejecta. This criterion is used to study the disruptive ability of Type II Supernovae onto proto-globular clouds. It is found that the early chemical history of globular clusters is greatly influenced by the pressure exerted by the external medium on their progenitor clouds. [less ▲]

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See detailThe Galactic halo. From globular clusters to field stars. Proceedings.
Noels-Grötsch, Arlette ULg; Magain, Pierre ULg; Caro, Denise ULg et al

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 ▲]

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See detailThe EASE Scenario: A New Origin for Metal-Poor Stars?
Jehin, Emmanuel ULg; Magain, Pierre ULg; Noels-Grötsch, Arlette ULg et al

in Weiss, A.; Abell, T.; Hill, V. (Eds.) The First Stars (2000)

We have analysed high resolution and high signal-to-noise spectra of 21 mildly metal-poor stars. The correlations between the relative abundances of 16 elements have been studied, with a special emphasis ... [more ▼]

We have analysed high resolution and high signal-to-noise spectra of 21 mildly metal-poor stars. The correlations between the relative abundances of 16 elements have been studied, with a special emphasis on the neutron-capture ones. This analysis reveals the existence of two sub-populations of field metal-poor stars which differ by the behaviour of the s-process elements versus the alpha and r-process elements. We suggest a scenario for the formation of metal-poor stars, which closely relates the origin of these stars to the evolution of globular clusters. [less ▲]

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See detailThe EASE Scenario: Dynamical Study of the Supernova Phase
Parmentier, Geneviève ULg; Jehin, Emannuel; Magain, Pierre ULg et al

in Weiss, A.; Abell, T.; Hill, V. (Eds.) The First Stars (2000)

We revisit the most often encountered argument against self-enrichment in globular clusters, namely the ability of a few number of supernovae to disrupt the proto-globular cloud. We show that, within the ... [more ▼]

We revisit the most often encountered argument against self-enrichment in globular clusters, namely the ability of a few number of supernovae to disrupt the proto-globular cloud. We show that, within the context of the Fall and Rees theory, primordial proto-globular cluster clouds may sustain several hundreds of Type II supernovae. Furthermore, the corresponding self-enrichment level is in agreement with galactic halo globular cluster metallicities. [less ▲]

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See detailObservational Constraints on a Self-Enrichment Model in Galactic Halo Globular Clusters
Parmentier, Geneviève ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in Favata, F.; Kaas, A.; Wilson, A. (Eds.) Star Formation from the Small to the Large Scale (2000)

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See detailAbundance correlations in thick disk and halo stars
Jehin, Emmanuel ULg; Magain, Pierre ULg; Noels-Grötsch, Arlette ULg et al

in Noels-Grötsch, Arlette; Magain, Pierre; Caro, Denise (Eds.) et al Liege International Astrophysical Colloquia (2000)

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See detailPuzzling locations of mildly metal-poor stars in the HR diagram
Jehin, Emmanuel ULg; Noels-Grötsch, Arlette ULg; Magain, Pierre ULg et al

in Noels-Grötsch, Arlette; Magain, Pierre; Caro, Denise (Eds.) et al Liege International Astrophysical Colloquia (2000)

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See detailOn the possibility of self-enrichement in globular clusters
Parmentier, Geneviève ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in Noels-Grötsch, Arlette; Magain, Pierre; Caro, Denise (Eds.) et al Liege International Astrophysical Colloquia (2000)

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See detailWhat Happens to the Gas in Globular Clusters?
Thoul, Anne ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in Astronomische Gesellschaft Meeting Abstracts (2000)

Observations of globular clusters show that they contain much too little gas or dust, compared to what should be present due to the mass-losing stars in the cluster. Many authors have been intrigued by ... [more ▼]

Observations of globular clusters show that they contain much too little gas or dust, compared to what should be present due to the mass-losing stars in the cluster. Many authors have been intrigued by the fate of the gas in globular clusters. They have suggested various mechanisms by which the gas could escape from the cluster, such as stellar UV radiation, cluster winds driven by X-ray bursters, novae, or flare-stars, relativistic winds from millisecond pulsars, condensation into stars, accretion processes drawing upon a central gas reservoir, continuous sweeping of the cluster gas by the gaseous medium of the Galactic halo dots. Recent results also show that globular cluster stars show many abundance anomalies. Accretion of interstellar gas by the cluster stars has been suggested as a plausible mechanism to explain these anomalies. It is also a major ingredient of the EASE scenario linking halo field stars to globular clusters, which we have recently developed to explain strong r-and s-elements correlations in halo field dwarf stars. Here we will briefly review the status of gas and dust detection in globular clusters, as well as the possible gas removal mechanisms. We will explore in more details the gas and dust accretion processes onto main sequence stars. In particular, we will study the efficiency of this mechanism in removing gas from the globular clusters interstellar medium. [less ▲]

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See detailAccretion processes onto globular cluster stars
Thoul, Anne ULg; Jorissen, A.; Goriely, S. et al

in Noels-Grötsch, Arlette; Magain, Pierre; Caro, Denise (Eds.) et al Liege International Astrophysical Colloquia (2000)

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See detailThe metallicity gradient of the old halo
Parmentier, Geneviève ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in Noels-Grötsch, Arlette; Magain, Pierre; Caro, Denise (Eds.) et al Liege International Astrophysical Colloquia (2000)

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See detailAccretion from AGB winds.
Thoul, Anne ULg; Jorissen, A.; Goriely, S. et al

in Memorie della Società Astronomica Italiana : Journal of the Italian Astronomical Society (2000), 71

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See detailThe self-enrichment of galactic halo globular clusters. A clue to their formation?
Parmentier, Geneviève ULg; Jehin, Emmanuel ULg; Magain, Pierre ULg et al

in Astronomy and Astrophysics (1999), 352

We present a model of globular cluster self-enrichment. In the protogalaxy, cold and dense clouds embedded in the hot protogalactic medium are assumed to be the progenitors of galactic halo globular ... [more ▼]

We present a model of globular cluster self-enrichment. In the protogalaxy, cold and dense clouds embedded in the hot protogalactic medium are assumed to be the progenitors of galactic halo globular clusters. The massive stars of a first generation of metal-free stars, born in the central areas of the proto-globular cluster clouds, explode as Type II supernovae. The associated blast waves trigger the expansion of a supershell, sweeping all the material of the cloud, and the heavy elements released by these massive stars enrich the supershell. A second generation of stars is born in these compressed and enriched layers of gas. These stars can recollapse and form a globular cluster. This work aims at revising the most often encountered argument against self-enrichment, namely the presumed ability of a small number of supernovae to disrupt a proto-globular cluster cloud. We describe a model of the dynamics of the supershell and of its progressive chemical enrichment. We show that the minimal mass of the primordial cluster cloud required to avoid disruption by several tens of Type II supernovae is compatible with the masses usually assumed for proto-globular cluster clouds. Furthermore, the corresponding self-enrichment level is in agreement with halo globular cluster metallicities. [less ▲]

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See detailAbundance correlations in mildly metal-poor stars
Jehin, Emmanuel ULg; Magain, Pierre ULg; Neuforge, Corinne et al

in Astronomy and Astrophysics (1999), 341

Accurate relative abundances have been obtained for a sample of 21 mildly metal-poor stars from the analysis of high resolution and high signal-to-noise spectra. In order to reach the highest coherence ... [more ▼]

Accurate relative abundances have been obtained for a sample of 21 mildly metal-poor stars from the analysis of high resolution and high signal-to-noise spectra. In order to reach the highest coherence and internal precision, lines with similar dependency on the stellar atmospheric parameters were selected, and the analysis was carried out in a strictly differential way within the sample. With these accurate results, correlations between relative abundances have been searched for, with a special emphasis on the neutron capture elements. This analysis shows that the r elements are closely correlated to the alpha elements, which is in agreement with the generally accepted idea that the r-process takes place during the explosion of massive stars. The situation is more complex as far as the s elements are concerned. Their relation with the alpha elements is not linear. In a first group of stars, the relative abundance of the s elements increases only slightly with the alpha elements overabundance until the latter reaches a maximum value. For the second group, the s elements show a rather large range of enhancement and a constant (and maximum) value of the alpha elements overabundance. This peculiar behaviour leads us to distinguish between two sub-populations of metal-poor stars, namely Pop IIa (first group) and Pop IIb (second group). We suggest a scenario of formation of metal-poor stars based on two distinct phases of chemical enrichment, a first phase essentially consisting in supernova explosions of massive stars, and a second phase where the enrichment is provided by stellar winds from intermediate mass stars. More specifically, we assume that all thick disk and field halo stars were born in globular clusters, from which they escaped, either during an early disruption of the cluster (Pop IIa) or, later, through an evaporation process (Pop IIb). Based on observations obtained at the European Southern Observatory, La Silla, Chile. [less ▲]

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See detailLinking Field Metal-Poor Stars and Globular Clusters: The Ease Scenario
Jehin, Emmanuel ULg; Magain, Pierre ULg; Neuforge, Corinne et al

in Spite, M. (Ed.) Galaxy Evolution: Connecting the Distant Universe with the Local Fossil Record (1999)

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