Charles Bailyn
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 ( Eric Rubenstein 1997, 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 which is 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 and the Yale astrometry group.