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How Binary Stars affect Galactic Chemical Evolution

Published online by Cambridge University Press:  25 May 2016

Christopher A. Tout
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
Amanda I. Karakas
Affiliation:
Dept of Mathematics, Monash University, Clayton, Vic. 3168, Australia
John C. Lattanzio
Affiliation:
Dept of Mathematics, Monash University, Clayton, Vic. 3168, Australia
Jarrod R. Hurley
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
Onno R. Pols
Affiliation:
Instituto de Astrofísica de Canarias, Via Láctea, 38200 La Laguna, Tenerife, Spain

Abstract

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At least 60% of stars appear to be binary and about half of these are close enough to interact. Because of the enormous expansion on the AGB, many of these interactions will involve an AGB star and a relatively compact companion, anything from a low-mass main-sequence star to a degenerate remnant. Mass loss plays the dominant role in determining the lifetime and the extent of nuclear processing of the AGB phase. Binary interaction will increase the mass loss from the AGB star and curtail its evolution, either through Roche-lobe overflow, common-envelope evolution or the driving of an enhanced stellar wind. These processes will tend to reduce the metals, particularly carbon, returned to the inter-stellar medium. On the other hand merged systems or companions that accrete a substantial amount of mass themselves evolve into AGB stars that can synthesize and return more carbon than the two individuals would have alone. By synthesizing large populations of stars, with nucleosynthesis and binary interaction, we estimate a reduction in carbon yield owing to binary star evolution of as much as 15%.

Type
Part 5. Non-Spherical Mass Loss, Binarity, Post-AGB Evolution
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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