2010A&A...515A..83T


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.03CEST00:26:36

2010A&A...515A..83T - Astronomy and Astrophysics, volume 515, A83-83 (2010/6-1)

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

TODT H., PENA M., HAMANN W.-R. and GRAEFENER G.

Abstract (from CDS):

A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition of helium, carbon, and oxygen with the majority showing Wolf-Rayet-like emission line spectra. These stars are classified as CSPNe of a spectral type [WC]. We perform a spectral analysis of CSPN PB8 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. The source PB8 displays wind-broadened emission lines from strong mass loss. Most strikingly, we find that its surface composition is hydrogen-deficient, but not carbon-rich. With mass fractions of 55% helium, 40% hydrogen, 1.3% carbon, 2% nitrogen, and 1.3% oxygen, it differs greatly from the 30-50% of carbon which are typically seen in [WC]-type central stars. The atmospheric mixture in PB8 has an analogy in the WN/WC transition type among the massive Wolf-Rayet stars. Therefore we suggest to introduce a new spectral type [WN/WC] for CSPNe, with PB8 as its first member. The central star of PB8 has a relatively low temperature of T*=52kK, as expected for central stars in their early evolutionary stages. Its surrounding nebula is less than 3000 years old, i.e. relatively young. Existing calculations for the post-AGB evolution can produce hydrogen-deficient stars of the [WC] type, but do not predict the composition found in PB8. We discuss various scenarios that might explain the origin of this unique object.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: AGB and post-AGB - stars: atmospheres - stars: mass-loss - stars: individual: PN PB8 - stars: Wolf-Rayet

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14825 1
2 SMP LMC 83 PN 05 36 20.7216020344 -67 18 07.659774493 15.56 16.225 14.948   16.558 [WN4.5:] 139 0
3 PN K 1-27 PN 05 57 02.1748480138 -75 40 22.475592752     16.04 16.27 16.41 sdOHe 80 0
4 CD-45 5058 HS* 09 20 10.1321975829 -45 31 54.939916304 9.81 11.03 11.33 11.62   sdO 47 0
5 PN PB 8 PN 11 33 17.8154413787 -57 06 14.926075766     14.00     [WC5/6] 108 0
6 ESO 320-28 PN 11 52 29.231 -42 17 38.69           ~ 51 0
7 PMR 5 WR* 16 19 40.1911099790 -49 13 59.027412470           [WN6]: 31 2

    Equat.    Gal    SGal    Ecl

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2020.07.03-00:26:36

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