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We use photometric and spectroscopic observations of the eclipsing binaryV69-47 Tuc to derive the masses, radii, and luminosities of the componentstars. Based on measured systemic velocity, distance, and proper motion, thesystem is a member of the globular cluster 47 Tuc. The system has an orbitalperiod of 29.5 d and the orbit is slightly eccentric with e=0.056. We obtainMp=0.8762 +- 0.0048 M(Sun), Rp=1.3148 +-0.0051 R(Sun), Lp=1.94 +- 0.21 L(Sun)for the primary and Ms=0.8588 +- 0.0060 M(Sun), Rs=1.1616 +- 0.0062 R(Sun),Ls=1.53 +- 0.17 L(Sun) for the secondary. These components of V69 are the firstPopulation II stars with masses and radii derived directly and with an accuracyof better than 1%. We measure an apparent distance modulus of (m-M)v=13.35 +-0.08 to V69. We compare the absolute parameters of V69 with five sets ofstellar evolution models and estimate the age of V69 using mass-luminosity-age,mass-radius-age, and turnoff mass - age relations. The masses, radii, andluminosities of the component stars are determined well enough that themeasurement of ages is dominated by systematic differences between theevolutionary models, in particular, the adopted helium abundance. By comparingthe observations to Dartmouth model isochrones we estimate the age of V69 to be11.25 +- 0.21(random) +- 0.85(systematic) Gyr assuming [Fe/H]=-0.70,[alpha/Fe]=0.4, and Y=0.255. The determination of the distance to V69, andhence to 47Tuc, can be further improved when infrared eclipse photometry isobtained for the variable.

The Clusters AgeS Experiment (CASE). IV. Analysis of the Eclipsing Binary V69 in the Globular Cluster 47 Tuc