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Astron. Astrophys. 363, 660-666 (2000)


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Orbital elements of barium stars formed through a wind accretion scenario

J.H. Liu 1,2, B. Zhang 1,5, Y.C. Liang 3 and Q.H. Peng 4,5

1 Department of Physics, Hebei Normal University, Shijiazhuang 050016, P.R. China
2 Department of Physics, Shijianzhuang Teachers' College, Shijiazhuang 050041, P.R. China
3 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100012, P.R. China
4 Department of Astronomy, Nanjing University, Nanjing 210093, P.R. China
5 Chinese Academy of Sciences - Peking University Joint Beijing Astrophysical Center, Beijing 100871, P.R. China

Received 3 July 2000 / Accepted 11 September 2000

Abstract

Taking the total angular momentum conservation in place of the tangential momentum conservation, and considering the square and higher power terms of orbital eccentricity e, the changes of orbital elements of binaries are recalculated for wind accretion scenario. These new equations of orbital elements are used to calculate the properties of barium stars. Our results show that, during the evolution of a binary system, the system widens as it loses mass, and the orbital period increases, while orbital eccentricity remains nearly constant, which can quantitatively explain the observed (e,logP) properties of normal G, K giants and those of barium stars. The results reflect the evolution from G, K giant binaries to barium binaries, namely, the orbits of barium stars have been modified by the mass-transfer process responsible for their chemical peculiarities, whereas most of the G, K giant binaries are probably pre-mass transfer binaries. Moreover, the results showed that the barium stars with longer orbital period P[FORMULA]1600 days may be formed by accreting part of the ejecta from the intrinsic AGB stars through wind accretion, while those with shorter orbital period may be formed through dynamically stable late case C mass transfer or common envelope ejection.

Key words: stars: late-type – stars: chemically peculiar – stars: AGB and post-AGB – stars: mass-loss – stars: binaries: spectroscopic – accretion, accretion disks

Send offprint requests to: Y.C. Liang (lyc@yac.bao.ac.cn)

© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000

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