Details

Autor(en) / Beteiligte

• Costa, Guglielmo
• Girardi, Léo
• Bressan, Alessandro
• Marigo, Paola
• Rodrigues, Thaíse S
• Chen, Yang
• Lanza, Antonio
• Goudfrooij, Paul

Titel

Mixing by overshooting and rotation in intermediate-mass stars

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2019-06, Vol.485 (4), p.4641-4657

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2019

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Abstract Double-line eclipsing binaries (DLEBs) have been recently used to constrain the amount of central mixing as a function of stellar mass, with contrasting results. In this work, we reanalyse the DLEB sample by Claret & Torres, using a Bayesian method and new parsec tracks that account for both convective core overshooting and rotational mixing. Using overshooting alone, we obtain that, for masses larger than about 1.9 M⊙, the distribution of the overshooting parameter, λov, has a wide dispersion between 0.3 and 0.8, with essentially no values below λov = 0.3 and 0.4. While the lower limit supports a mild convective overshooting efficiency, the large dispersion derived is difficult to explain in the framework of current models of that process, which leave little room for large randomness. We suggest that a simple interpretation of our results can be rotational mixing: Different initial rotational velocities, in addition to a fixed amount of overshooting, could reproduce the high dispersion derived for intermediate-mass stars. After a reanalysis of the data, we find good agreement with models computed with a fixed overshooting parameter, $\mbox{$\lambda _\mathrm{ov}$}=0.4$, and initial rotational rates, ω, uniformly distributed in a wide range between 0 and 0.8 times the break-up value, at varying initial mass. We also find that our best-fitting models for the components of α Aurigae and TZ Fornacis agree with their observed rotational velocities, thus providing independent support to our hypothesis. We conclude that a constant efficiency of overshooting in concurrence with a star-to-star variation in the rotational mixing might be crucial in the interpretation of such data.