High velocity structures in, and the X-ray emission from the LBV nebula around η Carinae

Abstract

The Luminous Blue Variable star eta Carinae is one of the most massive stars known. It underwent a giant eruption in 1843 in which the Homunculus nebula was created. ROSAT and ASCA data indicate the existence of a hard and a soft X-ray component which appear to be spatially distinct: a softer diffuse shell of the nebula around eta Carinae and a harder point-like source centered on the star eta Car. Astonishingly the morphology of the X-ray emission is very different from the optical appearance of the nebula. We present a comparative analysis of optical morphology, the kinematics, and the diffuse soft X-ray structure of the nebula around eta Carinae. Our kinematic analysis of the nebula shows extremely high expansion velocities. We find a strong correlation between the X-ray emission and the knots in the nebula and the largest velocities, i.e. the X-ray morphology of the nebula around eta Carinae is determined by the interaction between material streaming away from eta Car and the ambient medium.