Molecular gas associated with the ejecta ring nebula around the Wolf-Rayet star WR 16.
MARSTON A.P., WELZMILLER J., BRANSFORD M.A., BLACK J.H. and BERGMAN P.
Abstract (from CDS):
The environments of stars have the potential of providing important clues to their evolution. The history of a changing stellar output, in the form of winds and ejecta, is written in the environments of Wolf-Rayet stars. These show that Wolf-Rayet stars are evolved massive stars that are likely to have gone through several stages of mass loss in the forms of both fast and slow winds. At present, the evolutionary path of massive stars to the Wolf-Rayet stage is not well understood. As part of a program to probe the evolution of massive stars through their environments, we have begun a study of the neutral gas around Wolf-Rayet stars. Our intent is to determine information on the mass loss and kinematics of ejected material from Wolf-Rayet stars. In this paper we show the WN 8 star WR 16 to be almost completely surrounded by a cocoon of molecular gas. Optical spectra of associated ionized gas suggest that the whole cocoon is likely to be made of nitrogen-rich, processed material probably ejected in a red supergiant phase. Some tentative evidence is also given for fast-moving components that may have come from an eruption of the star in a prior phase as a luminous blue variable. The total molecular gas mass is estimated to be in the range 5-78 M☉, depending on the degree of enrichment of heavy elements and the uncertain distance to the star.
ISM: Bubbles - ISM: Molecules - Stars: Mass Loss - Stars: Wolf-Rayet