EDP Sciences
Free access
Volume 486, Number 3, August II 2008
Page(s) 919 - 921
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:200809530
Published online 29 May 2008

A&A 486, 919-921 (2008)
DOI: 10.1051/0004-6361:200809530

Research Note

On the origin and evolutionary state of RZ Cassiopeiae, KO Aquilae, and S Equulei

N. Mennekens1, J.-P. De Greve1, W. Van Rensbergen1, and L. R. Yungelson2

1  Astrophysical Institute, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
    e-mail: [nmenneke;jpdgreve;wvanrens]@vub.ac.be
2  Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya St., 119017 Moscow, Russia
    e-mail: lry@inasan.ru

Received 7 February 2008 / Accepted 30 April 2008

Aims. We determine the present evolutionary state and the restrictions on the initial mass ratios of RZ Cas, KO Aql and S Equ.
Methods. We compare mass-gaining stars with evolutionary models of single stars with the same mass and subsequently compare them with accretion tracks from simultaneous conservative binary evolution.
Results. The gainers are in an early main sequence stage ($X_{\rm c}$ > 0.5), with KO Aql being almost unevolved (assuming quasi-thermal equilibrium). The initial donor/gainer mass ratios $M_{\rm di} / M_{\rm gi}$ must be larger than three to obtain the present mass and luminosity of the gainers.

Key words: stars: binaries: eclipsing -- stars: binaries: close -- stars: individual: RZ Cas -- stars: individual: KO Aql -- stars: individual: S Equ

© ESO 2008