The purpose of this proposal is to obtain ISOCAM imaging observations
 of Lindroos wide binary systems at two wavelengths (6.7mu and 15mu).
 Lindroos binaries are physical systems consisting of an early-type
 Main Sequence primary and a late-type Pre-Main Sequence(PMS)secondary,
 typically a bright B-star with a faint K-star or G-star companion.
 These coeval pairs span a range of ages between 10 and 120 Myr and
 a range of projected separations of 10 to 30 arcsec (1000-6000 AU).
 The secondaries thus constitute a perfect sample of PTT stars, i.e.
 stars older than the weak-line T Tauri stars but not yet on the ZAMS.
 We have already used these systems to study the evolution of X-ray
 emission as a function of time (with the ROSAT HRI) and now intend
 to use them in order to investigate how disk properties vary in the
 age gap between the T Tauri phase and the ZAMS. We have also tried
 to detect dust emission using ground-based facilities like the SEST
 but could not detect it, since it is likely to be very weak.
 ISO observations are of the order of 100 times more sensitive to
 to detect small amounts of micron-sized dust particles than
 ground-based observations and should thus allow us to probe the
 timescale for planet formation around solar-type stars near a more
 massive hot star, i.e. in a binary environment where additional
 dynamical and radiation effects may operate on the PTT star's disk.
 We have 10/12 Lindroos systems available for each launch window,
 some of which have been detected at 12 microns in the IRAS FSC.
 For these systems ISOCAM imaging is especially rewarding, since we
 can resolve the IRAS emission and pinpoint its spatial distribution
 (is it dust emission from a remnant disk of the low-mass PMS star,
  or is it photospheric emission from the brighter higher-mass star?)
 In these cases, additional 60 and 90 mu ISOPHOT photometry will be
 carried out (PHT22_C100), in order to search for cold dust emission.
 We predict that some Lindroos primaries will show the Vega phenomenon.