Large Circumbinary Dust Grains around Evolved Giants?

Abstract

We have detected continuum emission at 450 microns, 850 microns and 1.35 millimeters from SS Lep (or 17 Lep), 3 Pup and probably BM Gem, likely or confirmed binary systems consisting of at least one evolved giant. The observed submillimeter fluxes are probably emitted by grains rather than ionized gas. The dust temperature is greater than 70 K within 6 arcseconds of each source. To explain why grains are so cold near the star, we suggest that the emission at wavelengths greater than 450 microns is produced by particles as large as 0.1 millimeter in radius, and that these large particles probably have grown by coagulation in circumbinary orbiting disks.