ORSOLA DE MARCO, AMERICAN MUSEUM OF NATURAL HISTORY

PRINCETON ASTRONOMY COLLOQUIUM - APRIL 6, 2004

ABSTRACT

HST/STIS spectroscopy of a large sample of Blue Stragglers in four Globular Clusters

Blue Stragglers are those stars that appear bluer and brighter than a cluster turnoff mass in the color-magnitude diagram. Because of their photometric characteristics they are expected to have masses larger than the cluster's turnoff mass and hence to be much too young to shared a birthday with all the other cluster stars. Accepted formation scenarios range from stellar collisions to binary merger and mass transfer. While some evidence points to these scenarios' partial success, other evidence
uncovered by our spectroscopy does not tally with the current Blue Straggler's common wisdom.