LBV Nebulae: The Mass Lost from the Most Massive Stars

The most massive stars, with initial masses above ~50M_sun, encounter a phase of extreme mass loss - sometimes accompanied by so-called giant eruptions - in which the stars' evolution is reversed from a redward to a blueward motion in the HRD. In this phase the stars are known as Luminous Blue Variable (LBVs).Neither the reason for the onset of the strong mass loss nor the cause for the giant eruptions is really understood, nor is their implications for the evolution of these most massive stars. I will present a study of the LBV nebulae which are formed in this phase as a consequence of the strong mass loss and draw conclusions from the morphology and kinematics of these nebulae on possible eruption mechanisms and stellar parameters of the LBV stars. The analysis contains a large collection of LBV nebulae which form an evolutionary sequence of LBV nebulae. A special concern will be the frequently observed bipolar nature of the LBV nebulae which seems to be a general feature and presents strong constraints on further models of the LBV phase and especially on the formation mechanism of the nebulae.