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

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Abstract

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-mainsequence 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
Volume502
Issue number3
DOIs
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, https://doi.org/10.1093/mnras/stab347. Copyright 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

Keywords

  • techniques: spectroscopic
  • galaxies: star clusters: general

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