The origin of blue straggler stars in star clusters

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The blue stragglers (hereafter BS) of a stellar population are classified as those main-sequence members which are bluer than the primary main-sequence population and appear as an extension of the main sequence in the colour-magnitude diagram beyond the main sequence turn-off. BSs are found in significant numbers in a wide range of stellar environments beginning from low-mass open clusters to massive globular clusters and as well in galactic fields. They are believed to be stars rejuvenated via stellar collisions, mergers or binary evolution. BSs in star clusters are interesting due to the correlations of their population with different cluster parameters and their remarkable multiplicity properties, as obtained through high-resolution imaging and measurements of proper motions. These properties have prompted detailed studies on their origin. Theoretical work involves semi-analytic methods to understand the correlations with cluster parameters and also using direct N-body computations to study the population and multiplicity properties of BSs in specific open clusters. In this proposed study, the dependencies of the BS population and of their various formation channels on cluster parameters are to be investigated through direct N-body integrations of model clusters in order to understand the observed correlations. In addition to this general study, two very remarkable BS populations will be focused on, viz., that of the open cluster NGC 188 and of the globular cluster M30.