Of are a sub-class of O stars, possible representing the O supergiants. The defining feature of Of stars is the presence of NIII (4630-4634Å) in emission. Of stars also have HeII (4686Å) emission, while O(f) stars have a weak HeII feature, and O((f)) stars have HeII absorption. Other features may include H emission, and CIII (5696 Å) emission.
Oe stars are the hotter extension of the Be stars. They are typically main sequence stars, variable, rapid rotators (broad lines), and show H emission that is often double-peaked. Stellar mass loss has produced a disk and/or shell of material around the star.
Click here for a catalog of selected bright O stars.
O5.5f O5.5f O5.5f