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arXiv · 1612.03719

[WN] central stars of planetary nebulae

H. Todt·B. Miszalski·J. A. Toalá·M. A. Guerrero
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Abstract

While most of the low-mass stars stay hydrogen-rich on their surface throughout their evolution, a considerable fraction of white dwarfs as well as central stars of planetary nebulae have a hydrogen-deficient surface composition. The majority of these H-deficient central stars exhibit spectra very similar to massive Wolf-Rayet stars of the carbon sequence, i.e. with broad emission lines of carbon, helium, and oxygen. In analogy to the massive Wolf-Rayet stars, they are classified as [WC] stars. Their formation, which is relatively well understood, is thought to be the result of a (very) late thermal pulse of the helium burning shell. It is therefore surprising that some H-deficient central stars which have been found recently, e.g. IC 4663 and Abell 48, exhibit spectra that resemble those of the massive Wolf-Rayet stars of the nitrogen sequence, i.e. with strong emission lines of nitrogen instead of carbon. This new type of central stars is therefore labelled [WN]. We present spectral analyses of these objects and discuss the status of further candidates as well as the evolutionary status and origin of the [WN] stars.

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H. Todt, B. Miszalski, J. A. Toalá, M. A. Guerrero. 2016-12-12. [WN] central stars of planetary nebulae. https://doi.org/10.1017/s1743921317000540

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