  We present STAR measurements of azimuthal anisotropy by means of the two- and
four-particle cumulants $v_2$ ($v_2\{2\}$ and $v_2\{4\}$) for Au+Au and Cu+Cu
collisions at center of mass energies $\sqrt{s_{_{\mathrm{NN}}}} = 62.4$ and
200 GeV. The difference between $v_2\{2\}^2$ and $v_2\{4\}^2$ is related to
$v_{2}$ fluctuations ($\sigma_{v_2}$) and nonflow $(\delta_{2})$. We present an
upper limit to $\sigma_{v_2}/v_{2}$. Following the assumption that eccentricity
fluctuations $\sigma_{\epsilon}$ dominate $v_2$ fluctuations
$\frac{\sigma_{v_2}}{v_2} \approx \frac{\sigma_{\epsilon}}{\epsilon}$ we deduce
the nonflow implied for several models of eccentricity fluctuations that would
be required for consistency with $v_2\{2\}$ and $v_2\{4\}$. We also present
results on the ratio of $v_2$ to eccentricity.
