| Interferometric measurements of late-type stars using the Infrared Spatial Interferometer (ISI) are reported. The ISI is a three-element array of movable telescopes using heterodyne detection in the mid-infrared. The mobility of the telescopes allows measurement of stars to be taken using a variety of array configurations and baseline lengths. The heterodyne detection scheme results in very narrow bandwidth measurements of about 12.6 GHz and allows measurements to be made away from obvious spectral lines. The details of the operation of the ISI are discussed along with the science targets of primary interest: late-type stars.;Measurements of stellar dust shells have been made with the ISI in a linear east-west configuration with baselines of 4, 8, and 12m. From these data, one-dimensional imaging of dust around late-type stars is discussed and demonstrated for the case of R Leonis, which shows obvious asymmetry. Various mechanisms for creating this asymmetry, including influence from the companion, are discussed. Also, in 2006 the telescopes were moved into a triangular array with longer baselines of approximately 35-40 m. Measurements at the higher resolution provided by these longer baselines show asymmetry in the stars alpha Orionis and R Leonis. The star o Ceti is found, however, to be quite symmetric and is circular to within the accuracy of these measurements. |
