The infrared angular diameter of omicron Ceti near maximum light

IR angular diameter measurements of Omicron Ceti obtained near maximum light with the Infrared Michelson Array are presented. Visibilities obtained with telescope separations of 8.0 and 12.0 m are reported. The data were fit with both uniform disk and limb darkened models. For the time of the observations, the uniform disk angular diameter of Omicron Ceti at 2.2 microns was found to be 36.1 +/- 1.7 milliarcsec. The limb darkening models of Scholz & Takeda (1987) and the present angular diameter measurement are used to derive a stellar physical angular diameter of 43.3 +/- 1.7 milliarcsec. From this angular diameter and contemporaneous photometry, the effective temperature of Omicron Ceti during the observations was determined to be 2270 +/- 140 K. This value agrees well with the IR color temperature for Mira, but is considerably lower than T(eff) indicated by molecular excitation temperatures. (P.D.)