Testing the role of merging binaries in the formation of the split main sequence in young clusters

Bastian, N, Kamann, S orcid iconORCID: 0000-0001-6604-0505, Niederhofer, F and Saracino, S (2025) Testing the role of merging binaries in the formation of the split main sequence in young clusters. Astronomy & Astrophysics. ISSN 0004-6361

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Abstract

A number of theories have been put forward to explain the bimodal stellar rotational distribution observed in young massive clusters. These include stellar mergers and interactions induced in binary systems, and the role of angular momentum transfer between a star and its circumstellar disk in its early evolution. Each theory predicts unique rotation distributions in various locations of the color-magnitude diagram. Specifically, the stellar merger hypothesis posits that the upper end of the main sequence will host a significant number of slowly rotating merger products, i.e., the blue straggler stars are an extension of the blue main sequence. We used observations, a combination of HST photometry and VLT/MUSE spectroscopy, of three massive (∼10^5 young ($100-300$ Myr) clusters in the Large Magellanic Cloud. We show that in all three clusters, these bright blue stars have stellar rotational distributions that differ significantly from that measured on the blue main sequence. We conclude that stellar mergers do not play a significant role in the formation of the split main sequence or the bimodal rotational distribution. As a corollary, we show that blue straggler stars in these young massive clusters display a wide range of rotational velocities.

Item Type: Article
Uncontrolled Keywords: 5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: EDP Sciences
Date of acceptance: 4 July 2025
Date of first compliant Open Access: 27 August 2025
Date Deposited: 27 Aug 2025 15:53
Last Modified: 27 Aug 2025 16:00
DOI or ID number: 10.1051/0004-6361/202555369
URI: https://researchonline.ljmu.ac.uk/id/eprint/27003
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