|
Blue straggler stars (BSS) have been identified in star clusters and in field populations in our own Milky Way galaxy and in its satellite galaxies. They manifest as stars bluer and more luminous than the dominant old population, and usually have a spatial distribution that follows the old population. Their progenitors are likely to have been close binaries. We investigate trends of the BSS population in dwarf spheroidal galaxies (dSph) and in the bulge of the Milky Way and find an anti-correlation between the relative frequency of BSS and the mean metallicity of the parent population. This trend mirrors that found for the close-binary fraction in the field populations of the Milky Way. We argue that the dominant mode of BSS formation in low-density populations is likely to be mass transfer in primordial close binary systems and thus that the similarity between the results for BSS in the dSph and field stars in our Galaxy supports the proposal that the small-scale fragmentation during star formation is driven by the same dominant physical process, despite the diversity in environment. |
|