Physical Properties
LBVs are unstable supergiant (or hypergiant) stars. In their "quiescent" state they are B-type stars with unusual emission lines, lying in a zone of the HR diagram where the least luminous have a temperature around 10,000K and a luminosity about 250,000 times the sun, while the most luminous have a temperature around 25,000K and a luminosity over a million times the sun making them some of the most luminous of all stars. During a normal "outburst" phase the temperature decreases to around 8,500K for all stars, while the bolometric luminosity remains constant (meaning visual luminosity increases somewhat). The outbursts mean there are usually nebulae around such stars; Eta Carinae is the nearest and best-studied example.
Read more about this topic: Luminous Blue Variable Star
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