luminous blue variables
luminous blue variables(LBVs) A class of very massive luminous blue stars known for sporadic mass ejections (eruptions); subclasses include P Cygni stars and Hubble–Sandage variables. They are generally found near the upper luminosity limit in the observed Hertzsprung–Russell diagram, and most are thought to have evolved from stars with initial masses exceeding 40 solar masses. The mass ejections are most likely due to instabilities in their stellar envelopes caused by radiation pressure. LBVs show different types of variations occurring on a wide range of timescales. The largest variations are associated with sudden brightenings by more than 3 magnitudes lasting for several hundred to several thousand years. The smallest variations (< 0.5 mag) last from several months to several years. Examples of LBVs are Eta Carinae, AG Carinae, P Cygni, and S Doradus.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006