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Blue straggler stars in open clusters using Gaia: Dependence on cluster parameters and possible formation pathways

Jadhav, VV and Subramaniam, A (2021) Blue straggler stars in open clusters using Gaia: Dependence on cluster parameters and possible formation pathways. In: Monthly Notices of the Royal Astronomical Society, 507 (2). pp. 1699-1709.

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Official URL: https://doi.org/10.1093/mnras/stab2264


Blue straggler stars (BSSs) are the most massive stars in a cluster formed via binary or higher order stellar interactions. Though the exact nature of such formation scenarios is difficult to pin down, we provide observational constraints on the different possible mechanism. In this quest, we first produce a catalogue of BSSs using Gaia DR2 data. Among the 670 clusters older than 300 Myr, we identified 868 BSSs in 228 clusters and 500 BSS candidates in 208 clusters. In general, all clusters older than 1 Gyr and massive than 1000 M⊙ have BSSs. The average number of BSSs increases with cluster age and mass, and there is a power-law relation between the cluster mass and the maximum number of BSSs in the cluster. We introduce the term fractional mass excess ($\mathcal {M}_{e}$) for BSSs. We find that at least 54 per cent of BSSs have $\mathcal {M}_{e}$ < 0.5 (likely to have gained mass through a binary mass transfer (MT)), 30 per cent in the 1.0 < $\mathcal {M}_{e}$ [removed] 1.0 (likely from multiple mergers/MT). We also find that the percentage of low $\mathcal {M}_{e}$ BSSs increases with age, beyond 1-2 Gyr, suggesting an increase in formation through MT in older clusters. The BSSs are radially segregated, and the extent of segregation depends on the dynamical relaxation of the cluster. The statistics and trends presented here are expected to constrain the BSS formation models in open clusters.

Item Type: Journal Article
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: Oxford University Press
Additional Information: The copyright for this article belongs to the Oxford University Press.
Keywords: blue stragglers; open clusters and associations: general
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 09 Nov 2023 05:45
Last Modified: 09 Nov 2023 05:45
URI: https://eprints.iisc.ac.in/id/eprint/82817

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