Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2010

Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot

Résumé

Context. Double-lined, detached eclipsing binaries are our main source for accurate stellar masses and radii. In this paper we focus on the 1.15-1.70 M&sun; interval where convective core overshoot is gradually ramped up in theoretical evolutionary models.
Aims: We aim to determine absolute dimensions and abundances for the F-type detached eclipsing binary BK Peg, and to perform a detailed comparison with results from recent stellar evolutionary models, including a sample of previously studied systems with accurate parameters.
Methods: uvby light curves and uvbybeta standard photometry were obtained with the Strömgren Automatic Telescope, ESO, La Silla, and high-resolution spectra were acquired with the FIES spectrograph at the Nordic Optical Telescope, La Palma.
Results: The 5 fd 49 period orbit of BK Peg is slightly eccentric (e = 0.053). The two components are quite different with masses and radii of (1.414 ± 0.007 M&sun;, 1.988 ± 0.008 Rsun) and (1.257 ± 0.005 M&sun;, 1.474 ± 0.017 Rsun), respectively. The measured rotational velocities are 16.6 ± 0.2 (primary) and 13.4 ± 0.2 (secondary) km s-1. For the secondary component this corresponds to (pseudo)synchronous rotation, whereas the primary component seems to rotate at a slightly lower rate. We derive an iron abundance of [Fe/H] = -0.12 ± 0.07 and similar abundances for Si, Ca, Sc, Ti, Cr and Ni. The stars have evolved to the upper half of the main-sequence band. Yonsei-Yale and Victoria-Regina evolutionary models for the observed metal abundance reproduce BK Peg at ages of 2.75 and 2.50 Gyr, respectively, but tend to predict a lower age for the more massive primary component than for the secondary. We find the same age trend for three other upper main-sequence systems in a sample of well studied eclipsing binaries with components in the 1.15-1.70 M&sun; range. We also find that the Yonsei-Yale models systematically predict higher ages than the Victoria-Regina models. The sample includes BW Aqr, and as a supplement we have determined a [Fe/H] abundance of -0.07 ± 0.11 for this late F-type binary.
Conclusions: We propose to use BK Peg, BW Aqr, and other well-studied 1.15-1.70 M&sun; eclipsing binaries to fine-tune convective core overshoot, diffusion, and possibly other ingredients of modern theoretical evolutionary models.

Dates et versions

hal-03732224 , version 1 (21-07-2022)

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J. V. Clausen, Søren Frandsen, H. Bruntt, E. H. Olsen, B. E. Helt, et al.. Absolute dimensions of eclipsing binaries. XXVIII. BK Pegasi and other F-type binaries: Prospects for calibration of convective core overshoot. Astronomy and Astrophysics - A&A, 2010, 516, pp.42. ⟨10.1051/0004-6361/201014266⟩. ⟨hal-03732224⟩
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