Interferometric Observations of Irc ]10011 and Irc ]10420 in the Mid-infrared

The 11 km fringe visibilities of IRC ]10011 (\ CIT3) and IRC ]10420 have been measured at baselines ranging from 2 to 14 m with a two-telescope interferometer. The visibility data provide onedimensional proÐles of these two stars and their immediate surroundings with higher resolution in this spectral range than is presently possible with a single-aperture telescope. Spherically symmetric radiative transfer models suggest that IRC ]10011 is surrounded by a dust shell with an inner radius subtending which falls o† in density as r~1.5, slightly slower than the r~2 expected for constant dust outÑow. 0A.033, IRC ]10420 appears to have a dust shell of inner radius the density of which drops very slowly 0A.12, compared with that in a constant outÑow. This implies decreasing outÑow or a signiÐcant emission in the past. Subject headings : circumstellar matter È infrared : stars È stars : AGB and post-AGB È stars : individual (IRC ]10011, IRC ]10420) È techniques : interferometric