The following document lists the file abstract/TONAKA_VARSPC.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
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==> In this proposal, more time is being requested for TONAKA.TIMVAR_1
==> This proposal requests an upgrade from Priority 3 for TONAKA.TIMVAR_1
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Mass loss of AGB stars is an important process for the evolution of matter in
the Galaxy. However, there are a number of unknowns involved in it. The largest
uncertainties reside in the formation process and optical properties of the dust
grains. Model analysis of infrared observations often suggests a low
temperature of silicate dust formation compared to theoretical predictions,
indicating a reconsideration of dust formation and mass loss process. The
interpretation of observations requires the photon absorption efficiency of
silicate dust to be much higher than that of any known silicate existing on the
earth ("dirty silicate model"). The amount of increase of the absorptivity is
arbitrarily assumed. Both problems interrelate with each other and are
difficult to be investigated separately by analyses solely based on an IR
spectrum of the dust shell. We propose to elucidate these problems by observing
spectra of optically thin dust shell around two oxygen-rich Mira variables
periodically by ISO. Periodic spectroscopic observations from near to far
infrared will provide the information of the reaction of dust shell to different
incident radiations from the photosphere. These results and the energy balance
consideration enable us to derive the absorptivity of silicate dust
quantitatively and identify the dust forming region. ISO will provide a unique
opportunity to make such periodic observations of the wide IR region with stable
accuracy, which are essential for this kind of study. The results will lead to
a better understanding of the late stellar evolution and the circulation of the
matter in the Galaxy. We have been given the observing time in the first call
and this proposal is to extend the variability coverage as well as to upgrade
the far-infrared observations.