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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 660735.0, MPI für Astronomie / Publikationen_mpia
On the evolutionary and pulsation mass of classical Cepheids. III. The case of the eclipsing binary Cepheid CEP0227 in the Large Magellanic Cloud
Authors:Prada Moroni, P. G.; Gennaro, M.; Bono, G.; Pietrzyński, G.; Gieren, W.; Pilecki, B.; Graczyk, D.; Thompson, I. B.
Date of Publication (YYYY-MM-DD):2012
Journal Abbrev.:The Astrophysical Journal
Issue / Number:2
Start Page:id.108
Audience:Not Specified
Abstract / Description:We present a new Bayesian approach to constrain the intrinsic parameters (stellar mass and age) of the eclipsing binary system—CEP0227—in the Large Magellanic Cloud (LMC). We computed several sets of evolutionary models covering a broad range in chemical compositions and in stellar mass. Independent sets of models were also constructed either by neglecting or by including a moderate convective core overshooting (βov = 0.2) during central hydrogen-burning phases. Sets of models were also constructed either by neglecting or by assuming a canonical (η = 0.4, 0.8) or an enhanced (η = 4) mass-loss rate. The most probable solutions were computed in three different planes: luminosity-temperature, mass-radius, and gravity-temperature. By using the Bayes factor, we found that the most probable solutions were obtained in the gravity-temperature plane with a Gaussian mass prior distribution. The evolutionary models constructed by assuming a moderate convective core overshooting (βov = 0.2) and a canonical mass-loss rate (η = 0.4) give stellar masses for the primary (Cepheid)—M = 4.14+0.04 - 0.05 M &sun;—and for the secondary—M = 4.15+0.04 - 0.05 M &sun;—that agree at the 1% level with dynamical measurements. Moreover, we found ages for the two components and for the combined system—t = 151+4 - 3 Myr—that agree at the 5% level. The solutions based on evolutionary models that neglect the mass loss attain similar parameters, while those ones based on models that either account for an enhanced mass loss or neglect convective core overshooting have lower Bayes factors and larger confidence intervals. The dependence on the mass-loss rate might be the consequence of the crude approximation we use to mimic this phenomenon. By using the isochrone of the most probable solution and a Gaussian prior on the LMC distance, we found a true distance modulus—18.53+0.02 - 0.02 mag—and a reddening value—E(B - V) = 0.142+0.005 - 0.010 mag—that agree quite well with similar estimates in the literature.
Free Keywords:binaries: eclipsing; Magellanic Clouds; stars: distances; stars: evolution; stars: oscillations; stars: variables: Cepheids
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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