The bifurcated patterns in the color-magnitude diagrams of blue straggler stars (BSSs) have attracted significant attention. This type of special (but rare) pattern of two distinct blue straggler sequences is commonly interpreted as evidence that cluster core-collapse-driven stellar collisions are an efficient formation mechanism. Here, we report the detection of a bifurcated blue straggler distribution in a young Large Magellanic Cloud cluster, NGC 2173. Because of the cluster's low central stellar number density and its young age, dynamical analysis shows that stellar collisions alone cannot explain the observed BSSs. Therefore, binary evolution is instead the most viable explanation of the origin of these BSSs. However, the reason why binary evolution would render the color-magnitude distribution of BSSs bifurcated remains unclear.
Bibliographical noteCopyright 2018 The American Astronomical Society. First published in the Astrophysical journal, 856(1), 25, 2018, published by IOP Publishing. The original publication is available at http://www.doi.org/10.3847/1538-4357/aaad65. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
- blue stragglers
- galaxies: star clusters: individual (NGC 2173)
- Hertzsprung-Russell and C-M diagrams
- Magellanic Clouds
- stars: kinematics and dynamics