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[WN] central stars of planetary nebulae

Published online by Cambridge University Press:  08 August 2017

H. Todt ,
B. Miszalski ,
J. A. Toalá  and
M. A. Guerrero
H. Todt
Affiliation:
Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany email: [email protected]
B. Miszalski
Affiliation:
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa; Southern African Large Telescope Foundation, PO Box 9, Observatory 7935, South Africa
J. A. Toalá
Affiliation:
Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), 10617 Taipei, Taiwan, Republic of China Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
M. A. Guerrero
Affiliation:
Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, E-18008 Granada, Spain
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Abstract

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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.

Keywords

Stars: abundancesStars: AGB and post-AGBStars: atmospheresStars: mass-lossStars: PN PB 8Stars: IC 4663Stars: Abell 48Stars: PMR 5Stars: Wolf-Rayet
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S323: Planetary Nebulae: Multi-Wavelength Probes of Stellar and Galactic Evolution , October 2016 , pp. 174 - 178
Copyright
Copyright © International Astronomical Union 2017 

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