2004MNRAS.349..303J

We present interferometric visibility measurements of the nearby Mira-like star R Doradus and the Mira R Leo taken over a wide range of wavelengths (650-990 nm). These are the first simultaneous observations of visibility as a function of wavelength over such a wide wavelength range for a Mira. The observations were made using MAPPIT (Masked APerture-Plane Interference Telescope), an interferometer operating at the 3.9-m Anglo-Australian Telescope. We used a slit to mask the telescope aperture and a prism to disperse the interference pattern in wavelength. We observed in both stars strong decreases in visibility within the TiO absorption bands across the observed wavelength range. Comparison of our results with theoretical models shows general agreement but differences in detail, suggesting that further work is needed to refine the theoretical models. We find that models for stars pulsating in the fundamental mode best fit our observations.