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Astron. Astrophys. 360, 997-1002 (2000)

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On the origin of binaries with twin components

A.A. Tokovinin 1,2

1 Sternberg Astronomical Institute, 13 Universitetsky prosp., 119899 Moscow, Russia (toko@sai.msu.ru)
2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany

Received 17 January 2000 / Accepted 3 July 2000

Abstract

The existence of a statistically significant excess of dwarf binaries with mass ratios from 0.95 to 1, as first noted by Lucy & Ricco (1979), is confirmed by modern data. Excess of such binaries, called twins, is found only for periods shorter than 40 days, and in the 2-30 days period range they constitute [FORMULA]% of the total binary population. Twins must have been formed by a special mechanism. It cannot be a mass transfer in contact pre-main-sequence binaries, fission is also unlikely. As shown by Bate (2000), accretion onto a close binary shifts mass ratio towards 1, so twins may originate from binaries that became close while still surrounded by massive envelopes. Many twins are members of higher-multiplicity systems and/or clusters, which probably explains an early formation of a close binary by stellar dynamics.

Key words: stars: binaries: close – stars: binaries: general – stars: formation

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© European Southern Observatory (ESO) 2000

Online publication: August 23, 2000
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