1996A&A...312..160Q

The diameter of Arcturus has been measured with the MkIII Optical Interferometer at 5 wavelengths between 450 and 800nm. The wavelength dependence of the uniform disk diameter agrees quantitatively with predictions from limb-darkening coefficients for a grid of model atmospheres tabulated by Manduca et al. (1977) and Manduca (1979). The true limb-darkened diameter of Arcturus is 21.0±0.2mas. By combination of this value with the bolometric flux of (5.04±0.20)x10^–8W/m² from the literature, the effective temperature is determined to be 4303±47K. It is also shown that the visibility function (i.e., visibility as a function of baseline length) cannot be fitted with uniform disk models close to and beyond the first null. The measured shape of the visibility function agrees well, however, with the Manduca et al. limb-darkened disk models.