Solar and alpha Centauri A and B models improved by opacity enhancement - a possible explanation for oversize cool stars

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dc.contributor.authorYildiz, M.
dc.date.accessioned2019-10-27T21:24:33Z
dc.date.available2019-10-27T21:24:33Z
dc.date.issued2011
dc.departmentEge Üniversitesien_US
dc.description.abstractThe Sun and alpha Cen A and B are the nearest stars to us. Despite the general agreement between their models and seismic and non-seismic constraints, there are serious problems pertaining to their interiors. The good agreement between the sound speed and base radius of the convective zone of the Sun and the solar models is broken apart by a recent revision in solar chemical composition. For alpha Cen A and B, however, it is not possible to fit models with the same age and chemical composition to all seismic and non-seismic observational constraints. At the age deduced from seismic constraints, the luminosity ratio (L-A/L-B) of the models is significantly lower than the ratio taken from the observed luminosities. Enhancement of opacity as a function of temperature is one way to restore the agreement between solar models and the Sun, but such an enhancement does not alter the situation for alpha Cen A and B. The reason is that models of both components are influenced in a similar manner and consequently the luminosity ratio does not change much. In the present study, problems pertaining to the interiors of these three stars with a single expression for opacity enhancement are modelled. The opacity enhancement is expressed as a function of density, ionization degree of heavy elements (oxygen) and temperature. According to this expression, for improvement of the models the required opacity enhancement for alpha Cen A and B at log(T) = 6.5, for example, is about 7 and 22 per cent, respectively. The enhancement takes place in the region in which pressure ionization is effective, and is higher for low-mass stars than for high-mass stars. This result seems to be a possible explanation for the serious differences between models and observational results for cool stars.en_US
dc.description.sponsorshipScientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK)en_US
dc.description.sponsorshipThe author thanks W. Dappen for his critiques and suggestions. This work is supported by the Scientific and Technological Research Council of Turkey (TUBITAK).en_US
dc.identifier.doi10.1111/j.1365-2966.2010.18075.x
dc.identifier.endpage2578en_US
dc.identifier.issn0035-8711
dc.identifier.issue4en_US
dc.identifier.startpage2571en_US
dc.identifier.urihttps://doi.org/10.1111/j.1365-2966.2010.18075.x
dc.identifier.urihttps://hdl.handle.net/11454/44579
dc.identifier.volume412en_US
dc.identifier.wosWOS:000289295800034en_US
dc.identifier.wosqualityQ1en_US
dc.indekslendigikaynakWeb of Scienceen_US
dc.language.isoenen_US
dc.publisherWiley-Blackwellen_US
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen_US
dc.relation.publicationcategoryMakale - Uluslararası Hakemli Dergi - Kurum Öğretim Elemanıen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectSun: interioren_US
dc.subjectstars: evolutionen_US
dc.subjectstars: individual: alpha Cenen_US
dc.subjectstars: interiorsen_US
dc.titleSolar and alpha Centauri A and B models improved by opacity enhancement - a possible explanation for oversize cool starsen_US
dc.typeArticleen_US

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