Blue straggler stars beyond the Milky Way. II. A binary origin for blue straggler stars in Magellanic Cloud clusters

Weijia Sun, Chengyuan Li, Richard de Grijs, Licai Deng

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    We have analyzed populations of blue straggler stars (BSSs) in 24 Magellanic Cloud (MC) star clusters using multi-passband Hubble Space Telescope images. We compiled a homogeneous BSS database, containing both traditional and evolved BSSs. We uncovered a sublinear correlation between the number of BSSs in the cluster cores and the clusters' core masses, characterized by a power-law index of 0.51 0.07. For low stellar collision rates, the mass-normalized number of BSSs depends only weakly (or perhaps not at all) on the collision rate, implying that the binary-driven BSS formation channel dominates. Comparison with simulations suggests that stellar collisions contribute less than 20% to the total number of BSSs formed. Further tests, including the analysis of the BSS-specific frequencies and their population numbers at larger cluster radii, suggest that binary interactions may be their main formation channel, hinting at an anti-correlation between a cluster's binary fraction and its core mass.

    Original languageEnglish
    Article number133
    Pages (from-to)1-11
    Number of pages11
    JournalAstrophysical Journal
    Issue number2
    Publication statusPublished - 1 Aug 2018

    Bibliographical note

    Copyright 2018 The American Astronomical Society. First published in the Astrophysical journal, 862(2), 133, 2018, published by IOP Publishing. The original publication is available at 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: general
    • Magellanic Clouds


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