New insights into the formation of the blue main sequence in NGC 1850

Abstract

Recent discoveries of bimodal main sequences (MSs) associated with young clusters (with ages $\lesssim 1$ Gyr) in the Magellanic Clouds have drawn a lot of attention. One of the prevailing formation scenarios attributes these split MSs to a bimodal distribution in stellar rotation rates, with most stars belonging to a rapidly rotating population. In this scenario, only a small fraction of stars populating a secondary blue sequence are slowly or non-rotating stars. Here, we focus on the blue MS in the young cluster NGC 1850. We compare the cumulative number fraction of the observed blue-MS stars to that of the high-mass-ratio binary systems at different radii. The cumulative distributions of both populations exhibit a clear anti-correlation, characterized by a highly significant Pearson coefficient of $-0.97$. Our observations are consistent with the possibility that blue-MS stars are low-mass-ratio binaries, and therefore their dynamical disruption is still ongoing. High-mass-ratio binaries, on the other hand, are more centrally concentrated.

arXiv comment8 pages, 6 figures, accepted to ApJ

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Cited by in corpus (6)

• The effects of stellar rotation along the main sequence of the 100 Myr old massive cluster NGC 1850
• Isochrone-cloud fitting of the extended Main-Sequence Turn-Off of young clusters
• The spatial distributions of blue main-sequence stars in Magellanic Cloud star clusters
• Extended Main Sequences in Star Clusters
• NGC 1850 BH1 is another stripped-star binary masquerading as a black hole
• Hubble Space Telescope proper motions of Large Magellanic Cloud star clusters -- II. Kinematic structure of young and intermediate-age clusters