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  • NGC 1866: First Spectroscop...
    Dupree, A. K.; Dotter, A.; Johnson, C. I.; Marino, A. F.; Milone, A. P.; Bailey, J. I.; Crane, J. D.; Mateo, M.; Olszewski, E. W.

    Astrophysical journal. Letters, 09/2017, Letnik: 846, Številka: 1
    Journal Article

    High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (∼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 H emission (indicative of Be-star decretion disks), others have shallow broad H absorption (consistent with rotation 150 km s−1), or deep H core absorption signaling lower rotation velocities ( 150 km s−1). The spectra appear consistent with two populations of stars-one rapidly rotating, and the other, younger and slowly rotating.