NGC 1866: First Spectroscopic Detection of Fast Rotating Stars in a
  Young LMC Cluster
  High-resolution spectroscopic observations were taken of 29 extended main
sequence turn-off (eMSTO) stars in the young ($\sim$200 Myr) 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 H-alpha emission (indicative of
Be-star decretion disks), others have shallow broad H-alpha absorption
(consistent with rotation $\gtrsim $150 km s$^{-1}$), or deep H-alpha core
absorption signaling lower rotation velocities ($ \lesssim $150 km s$^{-1}$ ).
The spectra appear consistent with two populations of stars - one rapidly
rotating, and the other, younger and slowly rotating.
