Journal Article

Mass transfer from a giant star to a main-sequence companion and its contribution to long-orbital-period blue stragglers

Xuefei Chen and Zhanwen Han

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 4, pages 1416-1430
Published in print July 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2008.13334.x
Mass transfer from a giant star to a main-sequence companion and its contribution to long-orbital-period blue stragglers

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Binary population synthesis shows that mass transfer from a giant star to a main-sequence (MS) companion may account for some observed long-orbital-period blue stragglers. However, little attention is paid to this blue straggler formation scenario as dynamical instability often happens when the mass donor is a giant star. In this paper, we have studied the critical mass ratio, qc, for dynamically stable mass transfer from a giant star to a MS companion using detailed evolution calculations. The results show that a more evolved star is generally less stable for Roche lobe overflow. Meanwhile, qc almost linearly increases with the amount of the mass and angular momentum lost during mass transfer, but has little dependance on stellar wind. To conveniently use the result, we give a fit of qc as a function of the stellar radius at the onset of Roche lobe overflow and of the mass-transfer efficiency during the Roche lobe overflow.

To examine the formation of blue stragglers from mass transfer between giants and MS stars, we have performed Monte Carlo simulations with various qc. The simulations show that some binaries with the mass donor on the first giant branch may contribute to blue stragglers with qc obtained in this paper but will not from previous qc. Meanwhile, from our qc, blue stragglers from the mass transfer between an asymptotic giant branch star and a MS companion may be more numerous and have a wider range of orbital periods than those from the other qc.

Keywords: binaries: close; blue stragglers; stars: evolution

Journal Article.  11627 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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