A quantitative study of O stars in NGC 2244 and the Monoceros OB2 association
Identifieur interne : 000603 ( France/Analysis ); précédent : 000602; suivant : 000604A quantitative study of O stars in NGC 2244 and the Monoceros OB2 association
Auteurs : F. Martins [France] ; L. Mahy [Belgique] ; D. J. Hillier [États-Unis] ; G. Rauw [Belgique]Source :
- Astronomy and astrophysics : (Berlin. Print) [ 0004-6361 ] ; 2012.
Descripteurs français
- Pascal (Inist)
- Etoile O, Association stellaire OB, Vent stellaire, Amas stellaire, Perte masse, Taux perte, Mélangeage, Etoile massive, Matière interstellaire, Formation stellaire, Spectre optique, Spectre UV, Modèle atmosphère, Binaire, Age, Abondance, Vitesse rotation, Interaction forte, Luminosité, Incertitude, Etoile type avancé, Etoile premier type, Région HII.
English descriptors
- KwdEn :
- Abundance, Age, Atmosphere model, Binary stars, Early type stars, HII regions, Interstellar matter, Late type stars, Loss rate, Luminosity, Mass loss, Massive stars, Mixing, O stars, OB stellar association, Optical spectrum, Rotation speed, Star clusters, Star formation, Stellar winds, Strong interactions, Ultraviolet spectra, Uncertainty.
Abstract
Aims. Our goal is to determine the stellar and wind properties of seven O stars in the cluster NGC 2244 and three O stars in the OB association Mon OB2. These properties give us insight into the mass loss rates of O stars. They allow us to both check the validity of rotational mixing in massive stars and to better understand the effects of the ionizing flux and wind mechanical energy release on the surrounding interstellar medium and its influence on triggered star formation. Methods. We collected optical and UV spectra of the target stars that we analyzed by means of atmosphere models computed with the code CMFGEN. The spectra of binary stars were disentangled and the components studied separately. Results. All stars have an evolutionary age less than 5 million years, with the most massive stars being among the youngest. Nitrogen surface abundances show no clear relation with projected rotational velocities. Binaries and single stars show the same range of enrichment. This is attributed to the youth and/or wide separation of the binary systems in which the components have not (yet) experienced strong interaction. A clear trend toward greater enrichment in higher luminosity objects is observed, consistent with what evolutionary models with rotation predict for a population of O stars at any given age. We confirm the weakness of winds in late O dwarfs. In general, mass loss rates derived from UV lines are lower than mass loss rates obtained from Hα. The UV mass loss rates are even lower than the single-line driving limit in the latest type dwarfs. These issues are discussed in the context of the structure of massive stars winds. The evolutionary and spectroscopic masses are in agreement above 25 Mo, but the uncertainties are large. Below this threshold, the few late-type O stars studied here indicate that the mass discrepancy still seems to hold.
Affiliations:
- Belgique, France, États-Unis
- Languedoc-Roussillon, Occitanie (région administrative), Pennsylvanie, Province de Liège
- Liège, Montpellier, Pittsburgh
- Université Montpellier 2, Université de Liège, Université de Pittsburgh
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Pascal:12-0177678Le document en format XML
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Martins</name><affiliation wicri:level="4"><inist:fA14 i1="01"><s1>LUPM-UMR 5299, CNRS & Université Montpellier II, Place Eugène Bataillon</s1><s2>34095 Montpellier</s2><s3>FRA</s3><sZ>1 aut.</sZ></inist:fA14><country>France</country><placeName><region type="region" nuts="2">Occitanie (région administrative)</region><region type="old region" nuts="2">Languedoc-Roussillon</region><settlement type="city">Montpellier</settlement><settlement type="city">Montpellier</settlement></placeName><orgName type="university">Université Montpellier 2</orgName></affiliation></author><author><name sortKey="Mahy, L" sort="Mahy, L" uniqKey="Mahy L" first="L." last="Mahy">L. Mahy</name><affiliation wicri:level="4"><inist:fA14 i1="02"><s1>Institut d'Astrophysique et de Géophysique, Université de Liege, Bât. B5C, Allée du 6 Aout 17</s1><s2>4000 Liege</s2><s3>BEL</s3><sZ>2 aut.</sZ><sZ>4 aut.</sZ></inist:fA14><country>Belgique</country><placeName><region type="province" nuts="2">Province de Liège</region><settlement type="city">Liège</settlement><settlement type="city">Liège</settlement></placeName><orgName type="university">Université de Liège</orgName></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="03"><s1>Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street</s1><s2>Pittsburgh, PA 15260</s2><s3>USA</s3><sZ>3 aut.</sZ></inist:fA14><country>États-Unis</country><wicri:noRegion>Pittsburgh, PA 15260</wicri:noRegion><orgName type="university">Université de Pittsburgh</orgName><placeName><settlement type="city">Pittsburgh</settlement><region type="state">Pennsylvanie</region></placeName></affiliation></author><author><name sortKey="Rauw, G" sort="Rauw, G" uniqKey="Rauw G" first="G." last="Rauw">G. Rauw</name><affiliation wicri:level="4"><inist:fA14 i1="02"><s1>Institut d'Astrophysique et de Géophysique, Université de Liege, Bât. B5C, Allée du 6 Aout 17</s1><s2>4000 Liege</s2><s3>BEL</s3><sZ>2 aut.</sZ><sZ>4 aut.</sZ></inist:fA14><country>Belgique</country><placeName><region type="province" nuts="2">Province de Liège</region><settlement type="city">Liège</settlement><settlement type="city">Liège</settlement></placeName><orgName type="university">Université de Liège</orgName></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>Atmosphere model</term><term>Binary stars</term><term>Early type stars</term><term>HII regions</term><term>Interstellar matter</term><term>Late type stars</term><term>Loss rate</term><term>Luminosity</term><term>Mass loss</term><term>Massive stars</term><term>Mixing</term><term>O stars</term><term>OB stellar association</term><term>Optical spectrum</term><term>Rotation speed</term><term>Star clusters</term><term>Star formation</term><term>Stellar winds</term><term>Strong interactions</term><term>Ultraviolet spectra</term><term>Uncertainty</term></keywords><keywords scheme="Pascal" xml:lang="fr"><term>Etoile O</term><term>Association stellaire OB</term><term>Vent stellaire</term><term>Amas stellaire</term><term>Perte masse</term><term>Taux perte</term><term>Mélangeage</term><term>Etoile massive</term><term>Matière interstellaire</term><term>Formation stellaire</term><term>Spectre optique</term><term>Spectre UV</term><term>Modèle atmosphère</term><term>Binaire</term><term>Age</term><term>Abondance</term><term>Vitesse rotation</term><term>Interaction forte</term><term>Luminosité</term><term>Incertitude</term><term>Etoile type avancé</term><term>Etoile premier type</term><term>Région HII</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Aims. Our goal is to determine the stellar and wind properties of seven O stars in the cluster NGC 2244 and three O stars in the OB association Mon OB2. These properties give us insight into the mass loss rates of O stars. They allow us to both check the validity of rotational mixing in massive stars and to better understand the effects of the ionizing flux and wind mechanical energy release on the surrounding interstellar medium and its influence on triggered star formation. Methods. We collected optical and UV spectra of the target stars that we analyzed by means of atmosphere models computed with the code CMFGEN. The spectra of binary stars were disentangled and the components studied separately. Results. All stars have an evolutionary age less than 5 million years, with the most massive stars being among the youngest. Nitrogen surface abundances show no clear relation with projected rotational velocities. Binaries and single stars show the same range of enrichment. This is attributed to the youth and/or wide separation of the binary systems in which the components have not (yet) experienced strong interaction. A clear trend toward greater enrichment in higher luminosity objects is observed, consistent with what evolutionary models with rotation predict for a population of O stars at any given age. We confirm the weakness of winds in late O dwarfs. In general, mass loss rates derived from UV lines are lower than mass loss rates obtained from Hα. The UV mass loss rates are even lower than the single-line driving limit in the latest type dwarfs. These issues are discussed in the context of the structure of massive stars winds. The evolutionary and spectroscopic masses are in agreement above 25 M<sub>o</sub>, but the uncertainties are large. Below this threshold, the few late-type O stars studied here indicate that the mass discrepancy still seems to hold.</div></front></TEI><affiliations><list><country><li>Belgique</li><li>France</li><li>États-Unis</li></country><region><li>Languedoc-Roussillon</li><li>Occitanie (région administrative)</li><li>Pennsylvanie</li><li>Province de Liège</li></region><settlement><li>Liège</li><li>Montpellier</li><li>Pittsburgh</li></settlement><orgName><li>Université Montpellier 2</li><li>Université de Liège</li><li>Université de Pittsburgh</li></orgName></list><tree><country name="France"><region name="Occitanie (région administrative)"><name sortKey="Martins, F" sort="Martins, F" uniqKey="Martins F" first="F." last="Martins">F. Martins</name></region></country><country name="Belgique"><region name="Province de Liège"><name sortKey="Mahy, L" sort="Mahy, L" uniqKey="Mahy L" first="L." last="Mahy">L. Mahy</name></region><name sortKey="Rauw, G" sort="Rauw, G" uniqKey="Rauw G" first="G." last="Rauw">G. Rauw</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></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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