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Unraveling eMSTO in NGC 2355: Stellar Rotation and Binaries
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- Journal:
- Proceedings of the International Astronomical Union / Volume 21 / Issue S398 / September 2025
- Published online by Cambridge University Press:
- 15 October 2026, pp. 25-28
- Print publication:
- September 2025
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- Article
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The extended Main Sequence Turn-off (eMSTO) in the open cluster NGC 2355 is investigated using precise astrometry and photometry from Gaia DR3 and spectroscopic data from the Gaia-ESO Survey. We find a clear positive correlation between the rotational velocity (
$v \sin i$) and color of eMSTO stars, supporting the role of stellar rotation and gravity darkening in causing the observed color spread. Contrary to predictions from binary tidal-locking scenarios, spatial distribution analysis reveals that fast-rotating stars are preferentially concentrated in the cluster’s central regions. This finding provides the observational evidence favoring star-disk interactions during the pre-main-sequence phase, rather than tidal locking in binaries, as the primary mechanism responsible for the origin of rotational spread in eMSTO stars.
