Asteroseismic modelling of the solar-type subgiant star β Hydri
Identifieur interne : 006D15 ( Main/Exploration ); précédent : 006D14; suivant : 006D16Asteroseismic modelling of the solar-type subgiant star β Hydri
Auteurs : I. M. Brandao [Portugal] ; G. Dogan [Danemark] ; J. Christensen-Dalsgaard [Danemark] ; M. S. Cunha [Portugal] ; T. R. Bedding [Australie] ; T. S. Metcalfe [États-Unis] ; H. Kjeldsen [Danemark] ; H. Bruntt [Danemark, France] ; T. Arentoft [Danemark]Source :
- Astronomy and astrophysics : (Berlin. Print) [ 0004-6361 ] ; 2011.
Descripteurs français
- Pascal (Inist)
English descriptors
- KwdEn :
Abstract
Context. Comparing models and data of pulsating stars is a powerful way to understand the stellar structure better. Moreover, such comparisons are necessary to make improvements to the physics of the stellar models, since they do not yet perfectly represent either the interior or especially the surface layers of stars. Because β Hydri is an evolved solar-type pulsator with mixed modes in its frequency spectrum, it is very interesting for asteroseismic studies. Aims. The goal of the present work is to search for a representative model of the solar-type star β Hydri, based on up-to-date non-seismic and seismic data. Methods. We present a revised list of frequencies for 33 modes, which we produced by analysing the power spectrum of the published observations again using a new weighting scheme that minimises the daily sidelobes. We ran several grids of evolutionary models with different input parameters and different physics, using the stellar evolutionary code ASTEC. For the models that are inside the observed error box of β Hydri, we computed their frequencies with the pulsation code ADIPLS. We used two approaches to find the model that oscillates with the frequencies that are closest to the observed frequencies of β Hydri: (i) we assume that the best model is the one that reproduces the star's interior based on the radial oscillation frequencies alone, to which we have applied the correction for the near-surface effects; (ii) we assume that the best model is the one that produces the lowest value of the chi-square (χ2), i.e. that minimises the difference between the observed frequencies of all available modes and the model predictions, after all model frequencies are corrected for near-surface effects. Results. We show that after applying a correction for near-surface effects to the frequencies of the best models, we can reproduce the observed modes well, including those that have mixed mode character. The model that gives the lowest value of the χ2 is a post-main-sequence model with a mass of 1.04 M◦. and a metallicity slightly lower than that of the Sun. Our results underscore the importance of having individual frequencies to constrain the properties of the stellar model.
Affiliations:
- Australie, Danemark, France, Portugal, États-Unis
- Colorado, Nouvelle-Galles du Sud
- Sydney
- Université de Sydney
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Bruntt</name><affiliation wicri:level="1"><inist:fA14 i1="03"><s1>Department of Physics and Astronomy, Aarhus University</s1><s2>8000 Aarhus</s2><s3>DNK</s3><sZ>2 aut.</sZ><sZ>3 aut.</sZ><sZ>7 aut.</sZ><sZ>8 aut.</sZ><sZ>9 aut.</sZ></inist:fA14><country>Danemark</country><wicri:noRegion>8000 Aarhus</wicri:noRegion></affiliation><affiliation wicri:level="1"><inist:fA14 i1="06"><s1>Observatoire de Paris, LESIA, 5 place Jules Janssen</s1><s2>92195 Meudon</s2><s3>FRA</s3><sZ>8 aut.</sZ></inist:fA14><country>France</country><wicri:noRegion>92195 Meudon</wicri:noRegion><wicri:noRegion>5 place Jules Janssen</wicri:noRegion><wicri:noRegion>92195 Meudon</wicri:noRegion></affiliation></author><author><name sortKey="Arentoft, T" sort="Arentoft, T" uniqKey="Arentoft T" first="T." last="Arentoft">T. 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M." last="Brandao">I. M. Brandao</name><affiliation wicri:level="1"><inist:fA14 i1="01"><s1>Centro de Astrofísica da Universidade do Porto, Rua das Estrelas</s1><s2>4150-762 Porto</s2><s3>PRT</s3><sZ>1 aut.</sZ><sZ>4 aut.</sZ></inist:fA14><country>Portugal</country><wicri:noRegion>4150-762 Porto</wicri:noRegion></affiliation><affiliation wicri:level="1"><inist:fA14 i1="02"><s1>Departamento de Fisica e Astronomia, Faculdade de Ciencias da Universidade do Porto</s1><s3>PRT</s3><sZ>1 aut.</sZ></inist:fA14><country>Portugal</country><wicri:noRegion>Departamento de Fisica e Astronomia, Faculdade de Ciencias da Universidade do Porto</wicri:noRegion></affiliation></author><author><name sortKey="Dogan, G" sort="Dogan, G" uniqKey="Dogan G" first="G." last="Dogan">G. Dogan</name><affiliation wicri:level="1"><inist:fA14 i1="03"><s1>Department of Physics and Astronomy, Aarhus University</s1><s2>8000 Aarhus</s2><s3>DNK</s3><sZ>2 aut.</sZ><sZ>3 aut.</sZ><sZ>7 aut.</sZ><sZ>8 aut.</sZ><sZ>9 aut.</sZ></inist:fA14><country>Danemark</country><wicri:noRegion>8000 Aarhus</wicri:noRegion></affiliation></author><author><name sortKey="Christensen Dalsgaard, J" sort="Christensen Dalsgaard, J" uniqKey="Christensen Dalsgaard J" first="J." last="Christensen-Dalsgaard">J. Christensen-Dalsgaard</name><affiliation wicri:level="1"><inist:fA14 i1="03"><s1>Department of Physics and Astronomy, Aarhus University</s1><s2>8000 Aarhus</s2><s3>DNK</s3><sZ>2 aut.</sZ><sZ>3 aut.</sZ><sZ>7 aut.</sZ><sZ>8 aut.</sZ><sZ>9 aut.</sZ></inist:fA14><country>Danemark</country><wicri:noRegion>8000 Aarhus</wicri:noRegion></affiliation></author><author><name sortKey="Cunha, M S" sort="Cunha, M S" uniqKey="Cunha M" first="M. S." last="Cunha">M. S. Cunha</name><affiliation wicri:level="1"><inist:fA14 i1="01"><s1>Centro de Astrofísica da Universidade do Porto, Rua das Estrelas</s1><s2>4150-762 Porto</s2><s3>PRT</s3><sZ>1 aut.</sZ><sZ>4 aut.</sZ></inist:fA14><country>Portugal</country><wicri:noRegion>4150-762 Porto</wicri:noRegion></affiliation></author><author><name sortKey="Bedding, T R" sort="Bedding, T R" uniqKey="Bedding T" first="T. R." last="Bedding">T. R. Bedding</name><affiliation wicri:level="4"><inist:fA14 i1="04"><s1>Sydney Institute for Astronomy (SIFA), School of Physics, University of Sydney</s1><s3>AUS</s3><sZ>5 aut.</sZ></inist:fA14><country>Australie</country><placeName><settlement type="city">Sydney</settlement><region type="état">Nouvelle-Galles du Sud</region></placeName><orgName type="university">Université de Sydney</orgName></affiliation></author><author><name sortKey="Metcalfe, T S" sort="Metcalfe, T S" uniqKey="Metcalfe T" first="T. S." last="Metcalfe">T. S. Metcalfe</name><affiliation wicri:level="2"><inist:fA14 i1="05"><s1>High Altitude Observatory and Technology Development Division, NCAR</s1><s2>Boulder, Colorado</s2><s3>USA</s3><sZ>6 aut.</sZ></inist:fA14><country>États-Unis</country><placeName><region type="state">Colorado</region></placeName></affiliation></author><author><name sortKey="Kjeldsen, H" sort="Kjeldsen, H" uniqKey="Kjeldsen H" first="H." last="Kjeldsen">H. Kjeldsen</name><affiliation wicri:level="1"><inist:fA14 i1="03"><s1>Department of Physics and Astronomy, Aarhus University</s1><s2>8000 Aarhus</s2><s3>DNK</s3><sZ>2 aut.</sZ><sZ>3 aut.</sZ><sZ>7 aut.</sZ><sZ>8 aut.</sZ><sZ>9 aut.</sZ></inist:fA14><country>Danemark</country><wicri:noRegion>8000 Aarhus</wicri:noRegion></affiliation></author><author><name sortKey="Bruntt, H" sort="Bruntt, H" uniqKey="Bruntt H" first="H." last="Bruntt">H. Bruntt</name><affiliation wicri:level="1"><inist:fA14 i1="03"><s1>Department of Physics and Astronomy, Aarhus University</s1><s2>8000 Aarhus</s2><s3>DNK</s3><sZ>2 aut.</sZ><sZ>3 aut.</sZ><sZ>7 aut.</sZ><sZ>8 aut.</sZ><sZ>9 aut.</sZ></inist:fA14><country>Danemark</country><wicri:noRegion>8000 Aarhus</wicri:noRegion></affiliation><affiliation wicri:level="1"><inist:fA14 i1="06"><s1>Observatoire de Paris, LESIA, 5 place Jules Janssen</s1><s2>92195 Meudon</s2><s3>FRA</s3><sZ>8 aut.</sZ></inist:fA14><country>France</country><wicri:noRegion>92195 Meudon</wicri:noRegion><wicri:noRegion>5 place Jules Janssen</wicri:noRegion><wicri:noRegion>92195 Meudon</wicri:noRegion></affiliation></author><author><name sortKey="Arentoft, T" sort="Arentoft, T" uniqKey="Arentoft T" first="T." last="Arentoft">T. Arentoft</name><affiliation wicri:level="1"><inist:fA14 i1="03"><s1>Department of Physics and Astronomy, Aarhus University</s1><s2>8000 Aarhus</s2><s3>DNK</s3><sZ>2 aut.</sZ><sZ>3 aut.</sZ><sZ>7 aut.</sZ><sZ>8 aut.</sZ><sZ>9 aut.</sZ></inist:fA14><country>Danemark</country><wicri:noRegion>8000 Aarhus</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="2011">2011</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>Astroseismology</term><term>Corrections</term><term>Frequency spectrum</term><term>Metallicity</term><term>Oscillation frequency</term><term>Power spectra</term><term>Pulsating variable stars</term><term>S stars</term><term>Solar type star</term><term>Star models</term><term>Stellar structure</term><term>Subgiant star</term><term>Sun</term><term>Surface effect</term></keywords><keywords scheme="Pascal" xml:lang="fr"><term>Etoile type solaire</term><term>Sous géante</term><term>Modèle stellaire</term><term>Etoile variable pulsante</term><term>Structure stellaire</term><term>Spectre fréquence</term><term>Spectre puissance</term><term>Etoile S</term><term>Fréquence oscillation</term><term>Correction</term><term>Effet surface</term><term>Métallicité</term><term>Soleil</term><term>Astéroséismologie</term></keywords></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">Context. Comparing models and data of pulsating stars is a powerful way to understand the stellar structure better. Moreover, such comparisons are necessary to make improvements to the physics of the stellar models, since they do not yet perfectly represent either the interior or especially the surface layers of stars. Because β Hydri is an evolved solar-type pulsator with mixed modes in its frequency spectrum, it is very interesting for asteroseismic studies. Aims. The goal of the present work is to search for a representative model of the solar-type star β Hydri, based on up-to-date non-seismic and seismic data. Methods. We present a revised list of frequencies for 33 modes, which we produced by analysing the power spectrum of the published observations again using a new weighting scheme that minimises the daily sidelobes. We ran several grids of evolutionary models with different input parameters and different physics, using the stellar evolutionary code ASTEC. For the models that are inside the observed error box of β Hydri, we computed their frequencies with the pulsation code ADIPLS. We used two approaches to find the model that oscillates with the frequencies that are closest to the observed frequencies of β Hydri: (i) we assume that the best model is the one that reproduces the star's interior based on the radial oscillation frequencies alone, to which we have applied the correction for the near-surface effects; (ii) we assume that the best model is the one that produces the lowest value of the chi-square (χ<sup>2</sup>), i.e. that minimises the difference between the observed frequencies of all available modes and the model predictions, after all model frequencies are corrected for near-surface effects. Results. We show that after applying a correction for near-surface effects to the frequencies of the best models, we can reproduce the observed modes well, including those that have mixed mode character. The model that gives the lowest value of the χ<sup>2</sup> is a post-main-sequence model with a mass of 1.04 M<sub>◦.</sub> and a metallicity slightly lower than that of the Sun. Our results underscore the importance of having individual frequencies to constrain the properties of the stellar model.</div></front></TEI><affiliations><list><country><li>Australie</li><li>Danemark</li><li>France</li><li>Portugal</li><li>États-Unis</li></country><region><li>Colorado</li><li>Nouvelle-Galles du Sud</li></region><settlement><li>Sydney</li></settlement><orgName><li>Université de Sydney</li></orgName></list><tree><country name="Portugal"><noRegion><name sortKey="Brandao, I M" sort="Brandao, I M" uniqKey="Brandao I" first="I. M." last="Brandao">I. M. Brandao</name></noRegion><name sortKey="Brandao, I M" sort="Brandao, I M" uniqKey="Brandao I" first="I. M." last="Brandao">I. M. Brandao</name><name sortKey="Cunha, M S" sort="Cunha, M S" uniqKey="Cunha M" first="M. S." last="Cunha">M. S. Cunha</name></country><country name="Danemark"><noRegion><name sortKey="Dogan, G" sort="Dogan, G" uniqKey="Dogan G" first="G." last="Dogan">G. Dogan</name></noRegion><name sortKey="Arentoft, T" sort="Arentoft, T" uniqKey="Arentoft T" first="T." last="Arentoft">T. Arentoft</name><name sortKey="Bruntt, H" sort="Bruntt, H" uniqKey="Bruntt H" first="H." last="Bruntt">H. Bruntt</name><name sortKey="Christensen Dalsgaard, J" sort="Christensen Dalsgaard, J" uniqKey="Christensen Dalsgaard J" first="J." last="Christensen-Dalsgaard">J. Christensen-Dalsgaard</name><name sortKey="Kjeldsen, H" sort="Kjeldsen, H" uniqKey="Kjeldsen H" first="H." last="Kjeldsen">H. Kjeldsen</name></country><country name="Australie"><region name="Nouvelle-Galles du Sud"><name sortKey="Bedding, T R" sort="Bedding, T R" uniqKey="Bedding T" first="T. R." last="Bedding">T. R. Bedding</name></region></country><country name="États-Unis"><region name="Colorado"><name sortKey="Metcalfe, T S" sort="Metcalfe, T S" uniqKey="Metcalfe T" first="T. S." last="Metcalfe">T. S. Metcalfe</name></region></country><country name="France"><noRegion><name sortKey="Bruntt, H" sort="Bruntt, H" uniqKey="Bruntt H" first="H." last="Bruntt">H. Bruntt</name></noRegion></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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