E.E. Becklin 1, Murray Silverstone 1, J. Hare 1, B. Zuckerman 1, C. Spangler 2, A. Sargent 2, & P. Goldreich 2
1 University of California, Los Angeles
2 California Institute of Technology
The DEBRIS project is primarily a survey of infrared excess radiation around nearby solar-like stars, to establish how many of these stars might have associated circumstellar material that could be the debris of planet formation.
This survey used the ISOPHOT C-100 detector and the 60 and 90 micron filters to measure the far-infrared emission around a variety of stellar targets to explore the relationships of the incidence of, as well as the amount of, excess to the stellar physical parameters of mass, age, and multiplicity.
The targets discussed here fall into three categories:
1. IRAS selected F and G main-sequence stars. The sample included 39 stars which were known to have excess emission at 60 microns, but had only upper limits to the 100 micron fluxes.
2. Members of relatively nearby open clusters with ages spanning 50 to 700 Myrs. The sample included 19 stars in Alpha Perseus, 26 in Coma Berenices, 9 in the Hyades, 14 in the Pleiades, and 17 in the Ursa Majoris nucleus and stream.
3. A selection of 41 classical and weak-line T Tauri stars in the Taurus, Chamaeleon, and Scorpius star forming clouds. As in category 1 above, some were discovered by IRAS but only upper limits to the fluxes beyond 60 microns were available.
The results are presented and implications for the incidences and properties of debris disks are discussed. In particular, the preliminary description of a drop of infrared excess as a function of age reported earlier (Becklin et al, 1998) will be re-examined with a larger data set, better reduced data, and new age estimates. Several main sequence stars with newly discovered excesses are also discussed.