Post-main sequence stars of initial mass larger than 8-10 Mo. They are hydrogen-shell burning. Their spectral type is O/B(/A), their luminosity type is I. They are losing mass at high rates, and can become Luminous Blue Variables. Stars above about 40 Mo evolve into Wolf Rayet stars; they will never go through the yellow and red supergiant phases.

-- CecileLoup - 2014-02-20