Orsola De Marco

Current Work

Blue Straggler Stars

Background
Blue Straggler stars are stars that appear brighter and bluer than cluster turn-off mass in the color-magnitude diagram of open and globular clustars and the halo. They are thought to be main-sequence stars which are too young to belong to the old co-eval population found in these clusters. Formation scenarios for these stars involve stellar rejuvanation mechanisms, whereby stellar collisions or merger bring together enough mass to form a star more massive than the cluster's turn-off mass, which then evolves normally.

My role

We have analyzed the largest spectroscopic sample of Globular Cluster Blue Stragglers yet. Initial results reveal high masses (as expected from merger scenarios) in all 4 of the analyzed clusters as well as a possibility that these stars have disks (also consistent with merger scenarios). The lack of correlation between the mass of the Stragglers and their brightness is however counter to their being straight forward main-sequences stars. This work is ongoing, but the first results are going to be submitted in February 2004.

Publicatons

  • First Evidence of Circumstellar Disks around Blue Straggler Stars
    De Marco, O., Lanz, T., Ouellette, J.A., Zurek, D., & Shara, M.M.
    2004, ApJ Letters, accepted and under revision 

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    Last Update: 15 January 2004