On Jan 29, 3:44*pm, (Steve Willner) wrote:

Any star that's losing mass will likely have dust condense in the
outflow. *

Our Sun is losing mass. Obviously the rate matters!

There are plenty of "extreme carbon stars" with luminosities around
10^5 solar.

No, there aren't. According to the paper you cite, there are only
about 30 known - also it seems none are near that luminosity.

A paper I found, http://arxiv.org/PS_cache/arxiv/pdf/...908.3087v1.pdf
, says that no carbon stars exceed about 35,000 Lsun; therefore there
is an upper as well as a lower limit to the mass at which AGBs become
C stars.
It also gives one super-AGB candidate (Mbol = -8.0); it is dust-
enshrouded.

*One recent paper is by Speck et al. (2009 ApJ 691,
1202). *References in it will probably lead you to the extensive
literature on the subject, or you could just put the phrase quoted
above into ADS and see what appears.

That paper says that the 'extreme carbon star' phase is very short-
lived. Anyway, I think I've found it; the models of Poelarends (http://
http://www.iop.org/EJ/article/0004-6...3-54fa94eb3701)
show that the superwind phase (where the star will be obscured), which
is still fairly short at 5 Msun compared to the whole TP-AGB, grows to
encompass almost all of it by the limit. So optically visible late-
SAGB stars should indeed be rare - but not unknown.

Andrew Usher