Interferometric Studies of the extreme binary, $\epsilon$ Aurigae: Pre-eclipse Observations

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Stencel, R.
Creech-Eakman, M.
Hart, A.
Hopkins, J.
Kloppenborg, B.
Mais, D.
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We report new and archival K-band interferometric uniform disk diameters obtained with the Palomar Testbed Interferometer for the eclipsing binary star $\epsilon$ Aurigae, in advance of the start of its eclipse in 2009. The observations were inteded to test whether low amplitude variations in the system are connected with the F supergiant star (primary), or with the intersystem material connecting the star with the enormous dark disk (secondary) inferred to cause the eclipses. Cepheid-like radial pulsations of the F star are not detected, nor do we find evidence for proposed 6% per decade shrinkage of the F star. The measured 2.27 +/- 0.11 milli-arcsecond K band diameter is consistent with a 300 times solar radius F supergiant star at the Hipparcos distance of 625 pc. These results provide an improved context for observations during the 2009-2011 eclipse.
Comment: Accepted for Ap.J. Letters, Oct. 2008
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Astrophysics
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