HENIX Measurements of Higher-order Flow Harmonics for Identified Charged Hadrons in Au+Au Collisions at $\sqrt {{s_{NN}}} $ = 39 - 200 GeV

Collective flow measurements continue to play an important role in ongoing efforts to map out the temperature dependence of the transport coefficient $\frac{\eta}{s}(T)$, for the strongly interacting matter produced in heavy ion collisions at RHIC. Recently, the PHENIX experiment has performed a detailed set of measurements of the higher-order flow coefficients ($v_{n}$ for n=2,3,4), for both inclusive and identified charged hadrons at mid-rapidity. The results from these new measurements will be presented, as a function of $p_T$, centrality and beam collision energy, along with several scaling properties observed for these data. The role of these results as additional constraints for $\frac{\eta}{s}(T)$ will also be discussed.