Blue Straggler Star Populations in Globular Clusters
“Blue Straggler Star Populations in Globular Clusters”
In the recent literature, Blue Straggler Stars (BSSs) have gained much notoriety as a powerful diagnostic tool to track the dynamical state of their parent globular clusters, as their relatively high stellar masses makes them the perfect test particles to estimate the relaxation level of a stellar system, and additionally, because of their ability to set constraints on their formation conditions as inferred from their photometric properties. In particular, the formation of double BSS sequences – as seen in a color-magnitude diagram – has been successfully linked to a core-collapse event in the globular cluster M 30 and, more recently, in NGC 362. This kind of observation provides valuable verification tests on stellar collision models, as one expects that BSS formation through collisions will be enhanced in the cluster’s core during a core-collapse event. In this talk, I will present the discovery of a new double BSS sequence in the globular cluster NGC 1261, as well as the remarkable discovery of a third, yet less populated, younger component. Moreover, their photometric properties, obtained from HST/ACS public catalogs, seem to show an excellent agreement with stellar collisional models. I will discuss interpretations for the multiple sequence formation scenarios, as well as its relation with the dynamical history of NGC 1261. The study of these processes will provide an extremely valuable laboratory for stellar collision and BSS formation theory as well as the dynamical evolution of GC in general.
Seminar Room Institute of Astronomy
Thursday October 30th 2014