English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

A considerable fraction of the central stars of planetary nebulae (CSPNe) arehydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition ofhelium, carbon, and oxygen with the majority showing Wolf-Rayet-like emissionline spectra. These stars are classified as CSPNe of a spectral type [WC]. Weperform a spectral analysis of CSPN PB 8 with the Potsdam Wolf-Rayet (PoWR)models for expanding atmospheres. The source PB 8 displays wind-broadenedemission lines from strong mass loss. Most strikingly, we find that its surfacecomposition is hydrogen-deficient, but not carbon-rich. With mass fractions of55% helium, 40% hydrogen, 1.3% carbon, 2% nitrogen, and 1.3% oxygen, it differsgreatly from the 30-50% of carbon which are typically seen in [WC]-type centralstars. The atmospheric mixture in PB 8 has an analogy in the WN/WC transitiontype among the massive Wolf-Rayet stars. Therefore we suggest to introduce anew spectral type [WN/WC] for CSPNe, with PB 8 as its first member. The centralstar of PB 8 has a relatively low temperature of T=52kK, as expected forcentral stars in their early evolutionary stages. Its surrounding nebula isless than 3000 years old, i.e. relatively young. Existing calculations for thepost-AGB evolution can produce hydrogen-deficient stars of the [WC] type, butdo not predict the composition found in PB 8. We discuss various scenarios thatmight explain the origin of this unique object.

The central star of the planetary nebula PB 8: a Wolf-Rayet-type wind of an unusual WN/WC chemical composition