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| Paper: |
Imaging the Circumstellar Dust Distribution around AGB Stars
with the NOT/PolCor Instrument |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
367 |
| Authors: |
Ramstedt, S.; Maercker, M.; Olofsson, G.; Olofsson, H.; Schöier, F. L. |
| Abstract: |
Stellar light from an AGB star is scattered by circumstellar dust
and polarized in the direction perpendicular to the source.
Therefore, images of circumstellar envelopes around AGB stars in
polarized light trace the dust distribution and can be used to
search for asymmetries, and to achieve a better understanding of
the mechanisms at play when AGB stars are transformed into planetary
nebulae. The PolCor instrument is a combined imager, polarimeter,
and coronograph providing images with an angular resolution down
to 0.2″. We have used it to map the dust distribution around
three AGB stars: the S star W Aql, and the detached shell carbon
stars DR Ser, and U Cam. W Aql is a binary and we find indications
of a bi-polar dust distribution around the star. The observations of
the latter two sources clearly reveal the detached shells, likely
the result of a brief, strongly enhanced mass-loss rate during the
late evolution of these stars. Mapping the detached shells gives us
clues to the symmetry of the mass loss and important evolutionary
processes. |
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