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==> This proposal requests an upgrade from Priority 3 for TTSUJI.PROP_004.
==> In this proposal, more time is being requested for TTSUJI.PROP_004.
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We propose to extend spectrophotometry of M dwarf stars by CVF mode of ISOCAM
to the very late M dwarfs near the end of the main sequence. Based on this
observation we hope to determine the basic physical properties of very low mass
stars (VLMSs) with the use of model atmospheres we have developed and to clarify
the nature of such VLMSs which may even be young brown dwarfs.
The major scientific goals of our observations are:
1) The major new problem in understanding the photospheres of VLMSs is that
dust may already form in stellar photospheres. In fact, the thermodynamical
condition of dust condensation is well met in M dwarf later than about M7V and
we have recently incorporated the effect of dust formation in our modeling of
the photospheres of VLMSs (Tsuji et al., 1996a).  Our models predict that the
H2O bands at 2.7 and 6.3 micron will be much weaker in dusty models than in
dust-free models because of the heating effect of dust opacities, and we hope
to analyse these H2O bands, first observed by the ISO, to examine the effects of
dust opacities in the photospheres of VLMSs. We also look for observational
evidence of silicate (probably Al2O3) bands at 9-13 micron region.
2) The present proposal is a part of more extensive program to test the model
atmospheres of VLMSs by comparing observed infrared flux with the predictions
based on a new grid of model atmospheres of VLMSs covering the Teff range
between 800 and 4,000K, with and without dust opacities, for a wide range of
metallicities, and to determine the basic physical parameters of the atmospheres
of M (sub)dwarfs and brown dwarfs (Tsuji et al., 1996b).
By such new information to be obtained by ISO, we hope that our understanding
on the atmospheres of VLMSs can be radically innovated and that we can go to
the next step to explore the substellar object such as brown dwarf which is an
important candidate of the dark matter of the Universe.