The Impact of Stellar Rotations and Binaries on the Shape of Upper Main Sequence near Turnoff in Open Cluster NGC6067

Maurya, J, Zhang, Y, Kamann, S ORCID: 0000-0001-6604-0505, Niu, H, Frémat, Y, Lang, K, Joshi, YC, Samal, MR, De Cat, P and Esamdin, A (2025) The Impact of Stellar Rotations and Binaries on the Shape of Upper Main Sequence near Turnoff in Open Cluster NGC6067. The Astrophysical Journal, 989 (1).

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Abstract

We present the analysis of the extended main-sequence turnoff (eMSTO) in the open cluster NGC 6067. We derive the projected rotational velocity, vsini, of the stars belonging to the eMSTO region of the main sequence (MS) utilizing Gaia-ESO spectra. Our results reveal a positive correlation between vsini and the color of eMSTO stars, where fast-rotating stars predominantly occupy the red part of the MS while slow-rotating ones prefer a bluer side of the MS. The gravity-darkening effect might be a reason for this correlation. We find that most of the close binaries present in the eMSTO population would be slow-rotating due to the tidal-locking phenomenon. We identify four double-lined spectroscopic binaries (SB2) featuring slow-rotating companions, further supporting this tidal-locking hypothesis. However, the spatial distribution and the cumulative radial distribution indicate a higher concentration of red eMSTO stars in the cluster’s central region than their bluer counterparts. This suggests that tidal locking is less likely to be the cause of the observed spread in rotation rates among eMSTO stars. Instead, we propose that star–disk interactions during the pre-main-sequence phase might have played a crucial role in spreading the rotation rates of stars, leading to the eMSTO phenomenon in NGC 6067.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); 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:	American Astronomical Society
Date of acceptance:	10 July 2025
Date of first compliant Open Access:	13 August 2025
Date Deposited:	13 Aug 2025 10:15
Last Modified:	13 Aug 2025 10:30
DOI or ID number:	10.3847/1538-4357/adef40
URI:	https://researchonline.ljmu.ac.uk/id/eprint/26930

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