  We determine the effect of rotation on the luminosity of supermassive stars.
We apply the Roche model to calculate analytically the emitted radiation from a
uniformly rotating, radiation-dominated supermassive configuration. We find
that the luminosity at maximum rotation, when mass at the equator orbits at the
Kepler period, is reduced by ~36% below the usual Eddington luminosity from the
corresponding nonrotating star. A supermassive star is believed to evolve in a
quasistationary manner along such a maximally rotating ``mass-shedding''
sequence before reaching the point of dynamical instability; hence this reduced
luminosity determines the evolutionary timescale. Our result therefore implies
that the lifetime of a supermassive star prior to dynamical collapse is ~56%
longer than the value typically estimated by employing the usual Eddington
luminosity.
