Luminous Blue Variable Stars
Examples include etaCar, PCyg, SDor.
Luminous Blue Variable (LBV) Stars are very massive, hot supergiants. They are unstable
and variable, with irregular mass ejections. A mass loss episode increases the brightness.
A cool (8000-9000K) shell forms around the star, with optical spectra showing an A-type
supergiant with shell. In quiescence, the hot (20,000-25,000K) stellar photosphere is
revealed, yielding a spectra of an O-B supergiant, with H, He, Fe, and [Fe] emission.