The age of 47Tuc from self-consistent isochrone fits to colour-magnitude
  diagrams and the eclipsing member V69
  Our aim is to derive a self-consistent age, distance and composition for the
globular cluster $47\,$Tucanae ($47\,$Tuc; NGC104). First, we reevaluate the
reddening towards the cluster resulting in a nominal $E(B-V)=0.03\pm0.01$ as
the best estimate. The $T_{\rm eff}$ of the components of the eclipsing binary
member V69 is found to be $5900\pm72$ K from both photometric and spectroscopic
evidence. This yields a true distance modulus $(m-M)_0=13.21\pm0.06$(random)$
\pm0.03 $(systematic) to $47\,$Tuc when combined with existing measurements of
V69 radii and luminosity ratio. We then present a new completely
self-consistent isochrone fitting method to ground based and $\textit{HST}$
cluster colour-magnitude diagrams and the eclipsing binary member V69. The
analysis suggests that the composition of V69, and by extension one of the
populations of $47\,$Tuc, is given by [Fe/H]$\sim-0.70$, [O/Fe]$\sim+0.60$, and
$Y\sim0.250$ on the solar abundance scale of Asplund, Grevesse & Sauval.
However, this depends on the accuracy of the model $T_{\rm eff}$ scale which is
50-75 K cooler than our best estimate but within measurement uncertainties. Our
best estimate of the age of $47\,$Tuc is 11.8 Gyr, with firm ($3 \sigma$) lower
and upper limits of 10.4 and 13.4 Gyr, respectively, in satisfactory agreement
with the age derived from the white dwarf cooling sequence if our determination
of the distance modulus is adopted.
