Date/Time
Date(s) - 22/06/2011
10:20 am - 11:20 am

Title: The Origins of Blue Stragglers in Star Clusters

Speaker: Dr. Aaron Geller

Institute:

Location: ABB 102

Description:

In a coeval stellar population, blue stragglers are observed to be brighter and/or bluer than normal main-sequence stars, and therefore are not predicted by standard stellar evolution theory. Yet they are found in every rich stellar population and are abundant in tar clusters. Current formation hypotheses include mass transfer in binaries, mergers of binaries, and stellar collisions induced during dynamical encounters that often involve binaries. Thus the community agrees that binary stars play a central role in blue straggler production, and understanding the origins of blue stragglers requires a marriage of many fundamental astrophysical theories. Indirect evidence suggests that certain formation mechanisms may dominate in different stellar environments. However the debate over the origins of blue stragglers has long suffered from a lack of direct and definitive observational evidence. Today, after more than a decade of observing the blue stragglers in the old (7 Gyr) open cluster NGC 188, we have gathered these critical data. Comparisons of the observed blue straggler binary properties to those predicted by sophisticated N-body open cluster models now allow us to identify the dominant formation mechanism for the NGC 188 blue stragglers. In this talk, I will present our observations and simulations, examine what they tell us about the origins of the NGC 188 blue stragglers, and discuss how these blue stragglers relate to those formed in both the Galactic field and globular clusters.