Figure: CO (J=1-0 and 2-1) maps of TT Cyg averaged over the interval . The star and about a quarter of the shell have been covered. The intensity unit is Jy beam .
Interferometric CO(J=1-0 and 2-1) observations reveal a remarkably
thin shell of molecular gas around the carbon star TT Cyg,
width/radius (Fig. 1).
It expands at 13 , and contains of gas
provided the CO abundance with respect to H is 10 and the
distance is 1 kpc. The overall geometry is spherically symmetric,
but clear deviations, at the per cent level, exist. The radial
structure of the shell is barely resolved at the arc second level,
but there exists weak emission extending a few arc seconds inwards
from the peak. A drastic change in mass loss properties, possibly
combined with the effects of interacting winds, provides the most
likely explanation to the origin of the shell.