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

¹ Institut für Theoretische Astrophysik, Tiergartenstr. 15, 69121 Heidelberg, Germany
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³ University of Illinois, Department of Astronomy, 1002 W. Green Street, Urbana, IL 61801, USA
⁴ Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum, Germany

Corresponding author: K. Weis, kweis@ita.uni-heidelberg.de

Received: 4 August 1999
Accepted: 7 December 2000

Abstract

The Luminous Blue Variable star η 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 η Carinae and a harder point-like source centered on the star η 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 η 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 η Carinae is determined by the interaction between material streaming away from η Car and the ambient medium.