Published online by Cambridge University Press: 14 August 2015
Fully ten percent of the Wolf-Rayet stars known in our galaxy are central stars of planetary nebulae. These stars are highly-evolved stars of approximately one solar mass. The existence of WR characteristics in the spectra of central stars as well as in massive, younger stars proves conclusively that WR spectra are a phenomenon that occurs in hot stars of widely different masses and evolutionary histories. Just what this phenomenon is — the nature of the instability that drives the wind — is not known, but the phenomenon is associated with a prior event in the star's evolutionary history. The common event that links Wolf-Rayet stars is loss of most, if not all of the outer, hydrogen-rich envelope just prior to the onset of WR characteristics. As Tutakov (this volume) and others have emphasized, there are many ways for a star to lose its H-rich envelope. These ways include mixing, ejection via a wind, or, in the case of a close binary, ejection via Roche-lobe overflow. The existence of WR-type central stars implies simply that we should include one more path leading to the Wolf-Rayet phenomenon, and that is, ejection to form a planetary nebulae.
To send this article to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about sending to your Kindle. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save this article to your Dropbox account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your Dropbox account. Find out more about saving content to Dropbox.
To save this article to your Google Drive account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your Google Drive account. Find out more about saving content to Google Drive.