INFRARED SPACE-OBSERVATORY MAPPING OF 60 MICRON DUST EMISSION AROUND VEGA-TYPE SYSTEMS

We mapped 60 mu m emission around five Vega-type systems. We utilized the PHOT-C100 far-infrared array camera on board the Infrared Space Ob servatory. The spatial resolution of the maps is similar to 30 ''. The maps of three sources (alpha CrB, sigma Her, and alpha Cen) do not sh ow any evidence of extended emission. The map of gamma Oph shows margi nal hints of extended emission similar to 30 '' (800 AU) from the star . The map of alpha PsA shows extended emission -30 ''-80 '' (similar t o 210-560 AU) from the star. This location, together with alpha PsA's characteristic IRAS temperature of 58-75 K, suggest the observed dust grains around a PsA are up to similar to 10 mu m in size. We estimate the mass of dust grains emitting the IRAS 60 Ccm excess of a! PsA to b e similar to(2-6) x 10(-3) M+.