Blue Stragglers (BSs) can be formed by stellar mergers. The most likely channels are the coalescence of short-period binaries or mergers induced by collisions. We focus on open clusters, where collisions are less likely to play a major role role than they do in globular clusters. We investigate the production of BSs from binary coalescence, combining the initial distribution of binaries over period, initial mass function and an empirical prescription for angular momentum loss. We find that the coalescence of close binaries can reproduce the observed number of BSs in clusters older than about 1 Gyr. For such clusters the number of BSs produced is relatively insensitive to the initial mass function and details of the prescription for angular momentum loss. However, coalescence is unable to produce a sufficient number of BSs for young populations, and some additional mechanism is required. We demonstrate that lifetime extension of MS stars by rotational mixing may be responsible. Together with coalescence this mechanism is able to reproduce observed number of BSs for very wide range of ages, from about 50 Myr to 10 Gyr.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2003