ISO-SWS observations of planetary nebulae with [WR] central stars.
Szczerba R., Gorny S.K. & Tylenda R.
1998, ISO's view on stellar evolution,
Waters, Waelkens & van der Hucht (eds.), Ap&SS 255, 515
Abstract:
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By means of the ISO SWS observations, we have discovered the PAH emission
from planetary the nebula He 2-142 - another [WR] PN with the confirmed
PAH presence. Remarkably, about 30% of all known PN with the detected PAH
emission belong to the [WR] type. This suggests that the PAH formation in
the case of [WR] PN is very effective.
We have suggested that for a few cases (late type [WR] central stars with
low density nebulae) the late helium shell flash scenario is perhaps a good
explanation for their origin. One of such cases is He 2-459 for which we
have not detected any PAH emission with the ISO. This is compatible with the
late helium shell flash. However, the lack of PAH can be explained within
the other hypothesis. Namely, that He 2-459 has a low mass, slowly evolving
central star which have produced no carbon enrichment and thus no PAH has
been formed on the AGB.
PostScript version of the paper is accessible via anonymous ftp:
iso-sgt.ps.gz
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