Published online by Cambridge University Press: 12 April 2016
Luminous Blue Variables (LBV’s) are losing mass at a rate which is higher than in normal stars of the same luminosity. This high mass loss is evident from the occurrence of P Cygni profiles in the visual spectrum, the large numbers of UV lines which are Doppler shifted or show P Cygni profiles and the large IR excess or radio free-free emission. Mass loss from LBV’s is strongly variable on a wide range of timescales from months to centuries and possibly even millenia. During these variations the mass loss may vary from values as low as 10-6 to 10-5 M⊙/yr, when the star is quiet, to outbursts of the type observed in P Cygni in AD 1600 and n Car in 1837 (for reviews see Davidson, 1987; Lamers, 1986, 1987).