  Using MESA code (Modules for Experiments in Stellar Astrophysics, version
9575), an evaluation was made of the evolutionary state of the epsilon Aurigae
binary system (HD 31964, F0Iap + disk). We sought to satisfy several
observational constraints: 1) requiring evolutionary tracks to pass close to
the current temperature and luminosity of the primary star; 2) obtaining a
period near the observed value of 27.1 years; 3) matching a mass function of
3.0; 4) concurrent Roche lobe overflow and mass transfer; 5) an isotopic ratio
12 C/ 13 C = 5 and, (6) matching the interferometrically determined angular
diameter. A MESA model starting with binary masses of 9.85 + 4.5 Msun , with a
100 day initial period, produces a 1.2 + 10.6 Msun result having a 547 day
period, and a single digit 12 C/ 13 C ratio. These values were reached near an
age of 20 Myr, when the donor star comes close to the observed luminosity and
temperature for epsilon Aurigae A, as a post-RGB/pre-AGB star.
Contemporaneously, the accretor then appears as an upper main sequence, early
B-type star. This benchmark model can provide a basis for further exploration
of this interacting binary, and other long period binary stars.
