An Etymological Dictionary of Astronomy and Astrophysics
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A → Wolf-Rayet star whose spectrum is dominated by emission lines of ionized carbon: C III 5696 Å, C III / C IV 4650 Å, C IV 5801-12 Å. This type is divided in sub-types WC4 to WC9.
For theoretical models, a Wolf-Rayet star whose carbon abundance at surface is larger than nitrogen abundance and has the abundance ratio (C + O) / He < 1 (in number).

W short for Wolf-Rayet star, C for → carbon.