Research page 2
Globular Star Clusters and Stellar Collisions
Another aspect of my research is the study of globular star clusters.
I have supervised two PhD theses in this area
Alison Sills 1998), and a number of other graduate and undergraduate
projects. Much of this research is supported by a Long Term Space
Astrophysics grant from NASA. I have also been extending this work
to open star clusters as part of the
WIYN Open Cluster Survey (WOCS).
Globular clusters are dense spherical conglomorations of about a million
or so stars; there are about 150 of them in our galaxy, the biggest of
Omega Centaui which I am studying in collaboration with Adrienne
Cool and others.
In many of of these clusters, the density of stars is so great that
collisions or near collisions between stars are not uncommon. The
remnants of these collisions are often objects quite different from
anything which can be produced by the models of single star evolution
produced by several of my colleagues. For a review of the various
different kinds of stars which can be produced in this way, please
seem my article in the 1995 Annual Reviews in Astronomy and Astrophysics.
A short list of objects which may be produced through collisions or
near collisions includes
The number and nature of the collisions which give rise to these strange stars
are greatly influenced by the binary population in the clusters. Thus studies
of the underlying binary population, like that of Rubenstein & Bailyn
(1997, ApJ 474, 701) are critical for understanding stellar collisions.
New HST data similar to those reported by R&B have been obtained, and are
currently being analyzed by graduate student Bing Zhao. Astrometric studies
of HST data of globular clusters are being conducted with post-doc G. Drukier
Yale astrometry group.
- blue stragglers (e.g. Sills et al. 2000, ApJ 535, 298 and refs therein)
- blue subdwarfs (e.g. Edmonds et al. 1999, ApJ 516, 250 and refs therein)
- X-ray sources, both bright and faint