We report new and archival K-band interferometric uniform disk diametersobtained with the Palomar Testbed Interferometer for the eclipsing binary star$\epsilon$ Aurigae, in advance of the start of its eclipse in 2009. Theobservations were inteded to test whether low amplitude variations in thesystem are connected with the F supergiant star (primary), or with theintersystem material connecting the star with the enormous dark disk(secondary) inferred to cause the eclipses. Cepheid-like radial pulsations ofthe F star are not detected, nor do we find evidence for proposed 6% per decadeshrinkage of the F star. The measured 2.27 +/- 0.11 milli-arcsecond K banddiameter is consistent with a 300 times solar radius F supergiant star at theHipparcos distance of 625 pc. These results provide an improved context forobservations during the 2009-2011 eclipse.
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