Angular size measurements of 18 Mira variable stars at 2.2 mu m

We present angular size measurements of 18 oxygen-rich Mira variable stars. These data are part of a long term observational program using the Infrared Optical Telescope Array (IOTA) to characterize the observable behavior of these stars. Complementing the infrared angular size measurements, values for variable star phase, spectral type, bolometric flux, and distance were established for stars in the sample; flux and distance led to values for effective temperature (T-EFF), and linear radius, respectively. We are able to define an effective temperature versus spectral type scale for Mira variables that we compare to the temperature scales for K and M giants and supergiants. T-EFF's and linear radii for these stars are shown to lie between approximately 2100 and 3200 K, and 200 and 600 R(.), respectively. Relationships among the Mira variable parameters are explored for significant trends. Notably, the phase dependence of T-EFF is shown to follow simple expectations, and examination of the radius-T-EFF relationship yields a plausible description of the V and K band light curves of these stars. A simple examination of the oscillation mode of the stars in the sample does not strongly suggest either fundamental or first-overtone oscillation as the primary mode of oscillation. This conclusion differs from that recently presented by Haniff et al. (1995), who argue that Mira variables are all first-overtone pulsators. We discuss some possible reasons for the different conclusions between the two studies. (C) 1996 American Astronomical Society.