Elliptic flow of electrons from heavy-flavor hadron decays in Au + Au collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msqrt><mml:msub><mml:mi>s</mml:mi><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:msqrt><mml:mo>=</mml:mo><mml:mn>200</mml:mn></mml:mrow></mml:math>, 62.4, and 39 GeV

We present measurements of elliptic flow (${v}_{2}$) of electrons from the decays of heavy-flavor hadrons (${e}_{\mathrm{HF}}$) by the STAR experiment. For Au+Au collisions at $\sqrt{{s}_{NN}}=200$ GeV we report ${v}_{2}$, for transverse momentum (${p}_{T}$) between 0.2 and 7 $\mathrm{GeV}/c$, using three methods: the event plane method (${v}_{2}{\mathrm{EP}}$), two-particle correlations (${v}_{2}{2}$), and four-particle correlations (${v}_{2}{4}$). For Au+Au collisions at $\sqrt{{s}_{NN}}=62.4$ and 39 GeV we report ${v}_{2}{2}$ for ${p}_{T}&lt;2\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}/c$. ${v}_{2}{2}$ and ${v}_{2}{4}$ are nonzero at low and intermediate ${p}_{T}$ at 200 GeV, and ${v}_{2}{2}$ is consistent with zero at low ${p}_{T}$ at other energies. The ${v}_{2}{2}$ at the two lower beam energies is systematically lower than at $\sqrt{{s}_{NN}}=200$ GeV for ${p}_{T}&lt;1\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$. This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to $\sqrt{{s}_{NN}}=200$ GeV.