Mid-infrared Spectral Evolution of Post-AGB Stars. Kevin Volk, Gemini Observatory. NGC7027. Image from Ciardullo et al. (1999; AJ, 118, 488). O-rich. C-rich. Late AGB. PN phase: low , new features. PPN phase: something in between. Late AGB: high dust shells. PPN Stage.
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Kevin Volk, Gemini Observatory
Image from Ciardullo et al. (1999; AJ, 118, 488)
PN phase: low , new
Late AGB: high dust
High and T
lower and T
the dust grains
the situation seems simple
New Spitzer results are starting to appear:
Garcia-Hernandez talk this afternoon
Corrigone talk this afternoon
The SMC survey has been approved in the latest round of Spitzer proposals (Karl Gordon, PI), but not yet executed. These small galaxies probe a range of sub-solar metallicity.
Various famous post-AGB objects [the Egg Nebula, the Red Rectangle] are atypical and will not be discussed here.
One has to worry about confusion with massive evolved stars. Abundance analysis is the only sure way to identify post-AGB objects, although most carbon-rich candidates are likely to be post-AGB objects. The C-rich 21 m feature candidates all seem to be post-AGB objects. For O-rich candidate objects the situation is often unclear.