Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002a%26a...385.1008p&link_type=abstract
Astronomy and Astrophysics, v.385, p.1008-1013 (2002)
Astronomy and Astrophysics
Astrophysics
Ism: Planetary Nebulae: General, Ism: Jets And Outflows
Scientific paper
Bipolar planetary nebulae (BPNe) possess a broad range of shapes, ranging from narrow-waisted butterfly-like structures, through to those which are more nearly cylindrical. We point out that these morphologies appear to be correlated with radio surface brightness Tb, in the sense that higher values of Tb are associated with envelopes having narrower waists. If one interprets the variation in Tb as arising from shell evolution, as is usually assumed for other planetaries, this would then imply that shell morphology varies with time in a manner which appears not to be consistent with evolutionary models. It also remains possible, however, that different BPNe morphologies arise as a result of differing mechanisms of formation, and that the pre-collimation of high velocity central winds gives rise to narrower waists, and higher surface brightness nuclei. Our results, if this is true, may then imply that central winds possess a broad range of collimations.
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