  We present sub-milliarcseond resolution imaging and modeling of two nearby
rapid rotators Alpha Cephei and Alpha Ophiuchi, obtained with the CHARA array -
the largest optical/IR interferometer in the world. Incorporating a gravity
darkening model, we are able to determine the inclination, the polar and
equatorial radius and temperature, as well as the fractional rotation speed of
the two stars with unprecedented precision. The polar and equatorial regions of
the two stars have ~2000K temperature gradient, causing their apparent
temperatures and luminosities to be dependent on their viewing angles. Our
modeling allow us to determine the true effective temperatures and luminosities
of Alpha Cep and Alpha Oph, permitting us to investigate their true locations
on the H-R diagram. These properties in turn give us estimates of the masses
and ages of the two stars within a few percent of error using stellar evolution
models. Also, based on our gravity darkening modeling, we propose a new method
to estimate the masses of single stars in a more direct way through Vsin(i)
measurements and precise geometrical constraint. Lastly, we investigate the
degeneracy between the inclination and the gravity darkening coefficient, which
especially affects the modeling of Alpha Oph. Although incorporating Vsin(i)
has lifted the degeneracy to some extent, higher resolution observations are
still needed to further constrain the parameters independently.
