Properties of Galactic early-type O-supergiants A combined FUV-UV and optical analysis
Identifieur interne : 000546 ( France/Analysis ); précédent : 000545; suivant : 000547Properties of Galactic early-type O-supergiants A combined FUV-UV and optical analysis
Auteurs : J.-C. Bouret [France] ; D. J. Hillier [États-Unis] ; T. Lanz [France] ; A. W. Fullerton [États-Unis]Source :
- Astronomy and astrophysics : (Berlin. Print) [ 0004-6361 ] ; 2012.
Descripteurs français
- Pascal (Inist)
- Supergéante, Type spectral, Perte masse, Taux perte, Etoile O, Distribution vent, Ecart équilibre thermodynamique local, Température effective, Luminosité, Gravité surface, Abondance, Facteur remplissage, Age, Etoile massive, Isochrone, Masse stellaire, Composition chimique, Modèle, Mélangeage, Rotateur, Etoile premier type, Vent stellaire, Evolution stellaire.
English descriptors
- KwdEn :
- Abundance, Age, Chemical composition, Early type stars, Effective temperature, Fill factor, Isochrone, Loss rate, Luminosity, Mass loss, Massive stars, Mixing, Models, Non-LTE, O stars, Rotator, Spectral type, Stellar evolution, Stellar mass, Stellar winds, Supergiant stars, Surface gravity, Wind field.
Abstract
Aims. We aim to constrain the properties and evolutionary status of early and mid-spectral type supergiants (from 04 to O7.5). These posses the highest mass-loss rates among the O stars, and exhibit conspicuous wind profiles. Methods. Using the non-LTE wind code CMFGEN we simultaneously analyzed the FUV-UV and optical spectral range to determine the photospheric properties and wind parameters. We derived effective temperatures, luminosities, surface gravities, surface abundances, mass-loss rates, wind terminal velocities, and clumping filling factors. Results. The supergiants define a very clear evolutionary sequence, in terms of ages and masses, from younger and more massive stars to older stars with lower initial masses. O4 supergiants cluster around the 3 Myr isochrone and are more massive than 60 M◦., while the O5 to 07.5 stars have masses in the range 50-40 Mo and are 4 ± 0.3 Myr old. The surface chemical composition is typical of evolved O supergiants (nitrogen-rich, carbon- and oxygen-poor). While the observed ranges of carbon and nitrogen mass-fractions are compatible with those expected from evolutionary models for the measured stellar masses, the N/C ratios as a function of age are inconsistent with the theoretical predictions for the four earliest (O4 spectral type) stars of the sample. We question the efficiency of rotational mixing as a function of age for these stars and suggest that another mechanism may be needed to explain the observed abundance patterns. Mass-loss rates derived with clumped-models range within a factor of three of the theoretical mass-loss rates. The corresponding volume-filling factors associated with small-scale clumping are 0.05 ± 0.02. Clumping is found to start close to the photosphere for all but three stars, two of which are fast rotators.
Affiliations:
- France, États-Unis
- Pennsylvanie, Provence-Alpes-Côte d'Azur
- Marseille, Nice, Pittsburgh
- Université de Pittsburgh
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Pascal:12-0411601Le document en format XML
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Hillier</name><affiliation wicri:level="4"><inist:fA14 i1="02"><s1>Department of Physics and Astronomy, University of Pittsburgh</s1><s2>Pittsburgh, PA 15260</s2><s3>USA</s3><sZ>2 aut.</sZ></inist:fA14><country>États-Unis</country><placeName><settlement type="city">Pittsburgh</settlement><region type="state">Pennsylvanie</region></placeName><orgName type="university">Université de Pittsburgh</orgName></affiliation></author><author><name sortKey="Lanz, T" sort="Lanz, T" uniqKey="Lanz T" first="T." last="Lanz">T. Lanz</name><affiliation wicri:level="3"><inist:fA14 i1="03"><s1>Laboratoire J.-L. Lagrange, UMR 7293, Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, BP 4229</s1><s2>06304 Nice</s2><s3>FRA</s3><sZ>3 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Provence-Alpes-Côte d'Azur</region><settlement type="city">Nice</settlement></placeName></affiliation></author><author><name sortKey="Fullerton, A W" sort="Fullerton, A W" uniqKey="Fullerton A" first="A. W." last="Fullerton">A. W. 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Bouret</name><affiliation wicri:level="3"><inist:fA14 i1="01"><s1>Laboratoire d'Astrophysique de Marseille, Université d'Aix-Marseille & CNRS, UMR7326, 38 rue F. Joliot-Curie</s1><s2>13388 Marseille</s2><s3>FRA</s3><sZ>1 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Provence-Alpes-Côte d'Azur</region><settlement type="city">Marseille</settlement></placeName></affiliation></author><author><name sortKey="Hillier, D J" sort="Hillier, D J" uniqKey="Hillier D" first="D. J." last="Hillier">D. J. Hillier</name><affiliation wicri:level="4"><inist:fA14 i1="02"><s1>Department of Physics and Astronomy, University of Pittsburgh</s1><s2>Pittsburgh, PA 15260</s2><s3>USA</s3><sZ>2 aut.</sZ></inist:fA14><country>États-Unis</country><placeName><settlement type="city">Pittsburgh</settlement><region type="state">Pennsylvanie</region></placeName><orgName type="university">Université de Pittsburgh</orgName></affiliation></author><author><name sortKey="Lanz, T" sort="Lanz, T" uniqKey="Lanz T" first="T." last="Lanz">T. Lanz</name><affiliation wicri:level="3"><inist:fA14 i1="03"><s1>Laboratoire J.-L. Lagrange, UMR 7293, Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, BP 4229</s1><s2>06304 Nice</s2><s3>FRA</s3><sZ>3 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Provence-Alpes-Côte d'Azur</region><settlement type="city">Nice</settlement></placeName></affiliation></author><author><name sortKey="Fullerton, A W" sort="Fullerton, A W" uniqKey="Fullerton A" first="A. W." last="Fullerton">A. W. Fullerton</name><affiliation wicri:level="1"><inist:fA14 i1="04"><s1>Space Telescope Science Institute, 3700 San Martin Drive</s1><s2>Baltimore, MD 21218</s2><s3>USA</s3><sZ>4 aut.</sZ></inist:fA14><country>États-Unis</country><wicri:noRegion>Baltimore, MD 21218</wicri:noRegion></affiliation></author></analytic><series><title level="j" type="main">Astronomy and astrophysics : (Berlin. Print)</title><title level="j" type="abbreviated">Astron. astrophys. : (Berl., Print)</title><idno type="ISSN">0004-6361</idno><imprint><date when="2012">2012</date></imprint></series></biblStruct></sourceDesc><seriesStmt><title level="j" type="main">Astronomy and astrophysics : (Berlin. Print)</title><title level="j" type="abbreviated">Astron. astrophys. : (Berl., Print)</title><idno type="ISSN">0004-6361</idno></seriesStmt></fileDesc><profileDesc><textClass><keywords scheme="KwdEn" xml:lang="en"><term>Abundance</term><term>Age</term><term>Chemical composition</term><term>Early type stars</term><term>Effective temperature</term><term>Fill factor</term><term>Isochrone</term><term>Loss rate</term><term>Luminosity</term><term>Mass loss</term><term>Massive stars</term><term>Mixing</term><term>Models</term><term>Non-LTE</term><term>O stars</term><term>Rotator</term><term>Spectral type</term><term>Stellar evolution</term><term>Stellar mass</term><term>Stellar winds</term><term>Supergiant stars</term><term>Surface gravity</term><term>Wind field</term></keywords><keywords scheme="Pascal" xml:lang="fr"><term>Supergéante</term><term>Type spectral</term><term>Perte masse</term><term>Taux perte</term><term>Etoile O</term><term>Distribution vent</term><term>Ecart équilibre thermodynamique local</term><term>Température effective</term><term>Luminosité</term><term>Gravité surface</term><term>Abondance</term><term>Facteur remplissage</term><term>Age</term><term>Etoile massive</term><term>Isochrone</term><term>Masse stellaire</term><term>Composition chimique</term><term>Modèle</term><term>Mélangeage</term><term>Rotateur</term><term>Etoile premier type</term><term>Vent stellaire</term><term>Evolution stellaire</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Aims. We aim to constrain the properties and evolutionary status of early and mid-spectral type supergiants (from 04 to O7.5). These posses the highest mass-loss rates among the O stars, and exhibit conspicuous wind profiles. Methods. Using the non-LTE wind code C<sub>MFGE</sub>N we simultaneously analyzed the FUV-UV and optical spectral range to determine the photospheric properties and wind parameters. We derived effective temperatures, luminosities, surface gravities, surface abundances, mass-loss rates, wind terminal velocities, and clumping filling factors. Results. The supergiants define a very clear evolutionary sequence, in terms of ages and masses, from younger and more massive stars to older stars with lower initial masses. O4 supergiants cluster around the 3 Myr isochrone and are more massive than 60 M<sub>◦.</sub>, while the O5 to 07.5 stars have masses in the range 50-40 M<sub>o</sub> and are 4 ± 0.3 Myr old. The surface chemical composition is typical of evolved O supergiants (nitrogen-rich, carbon- and oxygen-poor). While the observed ranges of carbon and nitrogen mass-fractions are compatible with those expected from evolutionary models for the measured stellar masses, the N/C ratios as a function of age are inconsistent with the theoretical predictions for the four earliest (O4 spectral type) stars of the sample. We question the efficiency of rotational mixing as a function of age for these stars and suggest that another mechanism may be needed to explain the observed abundance patterns. Mass-loss rates derived with clumped-models range within a factor of three of the theoretical mass-loss rates. The corresponding volume-filling factors associated with small-scale clumping are 0.05 ± 0.02. Clumping is found to start close to the photosphere for all but three stars, two of which are fast rotators.</div></front></TEI><affiliations><list><country><li>France</li><li>États-Unis</li></country><region><li>Pennsylvanie</li><li>Provence-Alpes-Côte d'Azur</li></region><settlement><li>Marseille</li><li>Nice</li><li>Pittsburgh</li></settlement><orgName><li>Université de Pittsburgh</li></orgName></list><tree><country name="France"><region name="Provence-Alpes-Côte d'Azur"><name sortKey="Bouret, J C" sort="Bouret, J C" uniqKey="Bouret J" first="J.-C." last="Bouret">J.-C. Bouret</name></region><name sortKey="Lanz, T" sort="Lanz, T" uniqKey="Lanz T" first="T." last="Lanz">T. Lanz</name></country><country name="États-Unis"><region name="Pennsylvanie"><name sortKey="Hillier, D J" sort="Hillier, D J" uniqKey="Hillier D" first="D. J." last="Hillier">D. J. Hillier</name></region><name sortKey="Fullerton, A W" sort="Fullerton, A W" uniqKey="Fullerton A" first="A. W." last="Fullerton">A. W. 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