Shocked CO and 13CO around Wolf-Rayet ring nebulae

Symposium - International Astronomical Union ◽

10.1017/s0074180900213302 ◽

2003 ◽

Vol 212 ◽

pp. 740-741 ◽

Cited By ~ 2

Author(s):

J. Ricardo Rizzo ◽

Jesús Martín-Pintado ◽

Jean-François Desmurs

Keyword(s):

Molecule Formation ◽

Evolved Stars ◽

Probable Origin ◽

Wr Nebulae ◽

Global Parameters ◽

Ring Nebulae

We show CO and 13CO maps toward the WR nebulae NGC 2359, NGC 6888 and Anon (WR 134). We determine global parameters and discuss the probable origin of this gas. Nowadays it is becoming clear that molecule formation and survival is be possible around massive evolved stars.

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Molecular gas around the Wolf-Rayet star WR 18 (WN4)

Symposium - International Astronomical Union ◽

10.1017/s0074180900213260 ◽

2003 ◽

Vol 212 ◽

pp. 732-733

Author(s):

Anthony P. Marston

Keyword(s):

Mass Loss ◽

Optical Emission ◽

Emission Lines ◽

Molecular Gas ◽

Evolved Stars ◽

Ring Nebula ◽

History Of ◽

Optical Ring ◽

Ring Nebulae ◽

Rayet Star

Optically observed ring nebulae and H i cavities around Wolf-Rayet stars have enabled us to obtain information on the history of mass-loss associated with these massive evolved stars. However, such studies have left a number of unanswered questions regarding the amount of mass-loss and the conditions of the stars during a sequence of mass-loss phases. Here we discuss the molecular gas environments of the WR star WR 18, which has an associated optical ring nebula NGC 3199. Our observations show that significant amounts of molecular gas appear close to and associated with the star. Mapping of molecular CO near the star shows that molecular materials appear to substantially avoid areas of optical emission and, instead, form a distorted clumpy shell interior to NGC 3199. Molecular emission lines are broader than lines seen in the interstellar medium and suggest the shell is composed of ejecta. This is further corroborated by the enhanced abundances of molecules containing C, N and O. Implications of the observations for the evolution of WR 18 are discussed.

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Properties of hot massive stars from studies of their ring nebulae

Symposium - International Astronomical Union ◽

10.1017/s0074180900201526 ◽

1995 ◽

Vol 163 ◽

pp. 24-33

Author(s):

Linda J. Smith

Keyword(s):

Flux Distribution ◽

Chemical Processes ◽

Emission Lines ◽

Luminous Blue Variables ◽

The Past ◽

Effective Temperatures ◽

Wr Nebulae ◽

Emission Studies ◽

Ring Nebulae ◽

Central Stars

Wolf-Rayet (WR) stars and their possible precursors, the Luminous Blue Variables (LBVs), are often surrounded by ring nebulae. It is believed that these nebulae are formed by the action of the stellar wind, matter being ejected from the star in the past, or a combination of these two processes. The various research applications of LBV and WR nebulae are reviewed with regard to the information they provide on the properties of the central stars. They are very useful probes of stellar evolution since the details of the previous evolutionary phases of the central stars are contained in the nebulae. In particular, abundance studies can provide insights into the chemical processes operating during the precursor phases. The nebulae can also be used as probes of the far-UV ionizing flux distribution of the central WR stars by comparing the observed levels of nebular ionization with those produced with non-LTE WR model flux distributions. Comparisons of stellar effective temperatures and luminosities derived using this technique with those determined by modelling stellar emission lines can identify deficiencies such as the lack of line-blanketing in WR model atmospheres. Very hot WR stars can also be identified by searching for nebular HeII emission. Studies of bipolar structures in LBV and WR nebulae provide valuable clues on wind asymmetries in the central stars.

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Open discussion

Symposium - International Astronomical Union ◽

10.1017/s0074180900029533 ◽

1982 ◽

Vol 99 ◽

pp. 605-613

Author(s):

P. S. Conti

Keyword(s):

Buenos Aires ◽

Large Mass ◽

List Type ◽

Common Phenomenon ◽

Open Discussion ◽

The Stability ◽

Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

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