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NGC 1866: First Spectroscopic Detection of Fast-rotating Stars in a Young LMC ClusterDupree, A. K., Dotter, A., Johnson, C. I., Marino, A. F., Milone, A. P., Bailey, J. I., Crane, J. D., Mateo, M., Olszewski, E. W. 23 August 2017 (has links)
High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (similar to 200 Myr) Large Magellanic Cloud (LMC) cluster, NGC 1866, using the Michigan/Magellan Fiber System and MSpec spectrograph on the Magellan-Clay 6.5 m telescope. These spectra reveal the first direct detection of rapidly rotating stars whose presence has only been inferred from photometric studies. The eMSTO stars exhibit Ha emission (indicative of Be-star decretion disks), others have shallow broad H alpha absorption (consistent with rotation. greater than or similar to 150 km s(-1)), or deep Ha core absorption signaling lower rotation velocities (less than or similar to 150 km s(-1)). The spectra appear consistent with two populations of stars-one rapidly rotating, and the other, younger and slowly rotating.
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