Mixing in massive stellar mergers
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Author(s)
Gaburov, Evghenii
Lombardi, James C., Jr. (Jamie)
Portegies Zwart, Simon
Date Issued
September 21, 2007
Abstract
The early evolution of dense star clusters is possibly dominated by close interactions between stars, and physical collisions between stars may occur quite frequently. Simulating a stellar collision event can be an intensive numerical task, as detailed calculations of this process require hydrodynamic simulations in three dimensions. We present a computationally
inexpensive method in which we approximate the merger process, including shock heating, hydrodynamic mixing and mass loss, with a simple algorithm based on conservation laws and a basic qualitative understanding of the hydrodynamics of stellar mergers. The algorithm relies on Archimedes’ principle to dictate the distribution of the fluid in the stable equilibrium
situation. We calibrate and apply the method to mergers of massive stars, as these are expected to occur in young and dense star clusters. We find that without the effects of microscopic mixing, the temperature and chemical composition profiles in a collision product can become double-valued functions of enclosed mass. Such an unphysical situation is mended by simulating microscopic mixing as a post-collision effect. In this way we find that head-on collisions between stars of the same spectral type result in substantial mixing, while mergers between stars of different spectral type, such as type B and O stars (∼10 and ∼40 M respectively), are subject to relatively little hydrodynamic mixing. Our algorithm has been implemented in
an easy-to-use software package, which we have made publicly available for download.
Journal
Monthly Notices of the Royal Astronomical Society
Department
Physics
Citation
Gaburov, E., Lombardi, J.C. Jr, Portegies Zwart, S. (2008). Mixing in massive stellar mergers. Month Notices of the Royal Astronomical Society 383: L5-L9. doi:10.1111/j.1745-3933.2007.00399.x
Publisher
Oxford University Press
Version of Article
Published article
DOI
10.1111/j.1745-3933.2007.00399.x
Rights
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2008 Gaburov, Lombardi, and Portegies Zwart Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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