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We propose a redirection and extension of our ISO program JSTAUFFE.ASTARS.
That program has been gathering photometry at 25, 60, and 100 microns of
'A' main sequence stars in open clusters with ages corresponding to the
era of planet formation in our solar system.  This new proposal is for
observations just at 16 and 25 microns of 40 stars in 4 clusters to search
for "hot" (terrestrial planet temperature) dust.  We wish to:  a) observe at
16-25 microns stars that were targeted in our 1st-call proposal for
photometry only at 60 microns, and b) add new targets in clusters reachable
in the extended ISO mission.
The optically thin dust responsible for far-IR excesses discovered by IRAS
around many field main sequence stars is most likely produced by collisions of
planetesimals or cometary activity in these systems. In some cases the star
ages are consistent with the epoch of "heavy bombardment" when the planets in
our solar system were completed.  ISO flux density and color temperature
measurements can be related to planetesimal population densities and locations
for comparison with models of the planet formation process.  A good way to
understand this process is via study of stars in a series of open clusters
with a range of ages and for which we have good information on properties of
the primary stars.  This project is especially focused on measuring the
timescale for evolution of material in inner disks.
Our team includes members who manage the two main cluster membership
databases.  We have selected a sample in each cluster that includes single
and binary stars and stars with a range of other stellar parameters within
spectral class 'A'.  In the Pleiades we have additionally selected stars to
avoid as much as possible the bright IR-emitting nebulosity.