Binary-driven stellar rotation evolution at the main-sequence turn-off in star clusters

Weijia Sun*, Richard de Grijs, Licai Deng, Michael D. Albrow

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
16 Downloads (Pure)


The impact of stellar rotation on the morphology of star cluster colour–magnitude diagrams is widely acknowledged. However, the physics driving the distribution of the equatorial rotation velocities of main-sequence turn-off stars is as yet poorly understood. Using Gaia Data Release 2 photometry and new Southern African Large Telescope medium-resolution spectroscopy, we analyse the intermediate-age (∼ 1-Gyr-old) Galactic open clusters NGC 3960, NGC 6134, and IC 4756 and develop a novel method to derive their stellar rotation distributions based on SYCLIST stellar rotation models. Combined with literature data for the open clusters NGC 5822 and NGC 2818, we find a tight correlation between the number ratio of slow rotators and the clusters’ binary fractions. The blue-main-sequence stars in at least two of our clusters are more centrally concentrated than their red-main-sequence counterparts. The origin of the equatorial stellar rotation distribution and its evolution remains as yet unidentified. However, the observed correlation in our open cluster sample suggests a binary-driven formation mechanism.
Original languageEnglish
Pages (from-to)4350-4358
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - Apr 2021

Bibliographical note

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 502, Issue 3, April 2021, Pages 4350–4358, Copyright 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


  • techniques: spectroscopic
  • galaxies: star clusters: general


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