July 11-15, 2011
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New Spectroscopic Categories of Young O Stars from the VLT-FLAMES Tarantula Survey

Nolan R. Walborn (Space Telescope Science Institute)

Spectral classification of nearly 200 constant-velocity O stars in the VFTS reveals six morphological main-sequence categories: 1) Extremely rapid rotators (Vn/nn/nnn) including likely the fastest massive rotator known. 2) A large number of spectra with He II 4686 stronger than other He lines (Vz). 3) Spectra with C III 4650 emission stronger than N III 4634-40-42 [V((fc))]. 4) Spectra with the N III emission much stronger than the C III [V((f))]. 5) Spectra with very high S/N and no trace of either N III or C III emission lines. 6) Spectra with He II 4541 Stark wings much stronger than those of He I 4471 or He II 4686. Some spectra combine more than one of these (logically compatible) properties. Several of the categories are newly recognized as significant components of the main-sequence population in a rich cluster of this age range; some of them may be very young. Elucidation of their physical origins and relationships will likely improve understanding of massive star formation and early evolution.
(to be confirmed by the SOC)