Giant Outbursts of the Eta Carinae - P Cygni Type

Abstract

I discuss the role of short-duration eruptive mass loss in the evolutionof very massive stars. Giant eruptions of Luminous Blue Variables (LBVs)like the 19th century event of {η} Carinae can remove large quantitiesof mass almost instantaneously, making them significant in stellarevolution. They can potentially remove more mass from the star thanline-driven winds, especially if winds are clumped such that O starmass-loss rates need to be revised downward. When seen in other galaxiesas ``supernova impostors'', these eruptions typically last for less thana decade, and they can remove of order 10 M_{&sun;} asindicated by massive nebulae around LBVs. Such extreme mass-loss ratescannot be driven by radiation pressure on spectral lines. Instead, theseoutbursts must either be continuum-driven super-Eddington winds oroutright hydrodynamic explosions, both of which are insensitive tometallicity. As such, this eruptive mode of mass loss could play apivotal role for massive metal-poor stars in the early universe.