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We report on measurements of dielectron ($e^+e^-$) production in Au$+$Aucollisions at a center-of-mass energy of 200 GeV per nucleon-nucleon pair usingthe STAR detector at RHIC. Systematic measurements of the dielectron yield as afunction of transverse momentum ($p_{\rm T}$) and collision centrality show anenhancement compared to a cocktail simulation of hadronic sources in the lowinvariant-mass region ($M_{ee}<$ 1 GeV/$c^2$). This enhancement cannot bereproduced by the $\rho$-meson vacuum spectral function. In minimum-biascollisions, in the invariant-mass range of 0.30 $-$ 0.76 GeV/$c^2$, integratedover the full $p_{\rm T}$ acceptance, the enhancement factor is 1.76 $\pm$ 0.06(stat.) $\pm$ 0.26 (sys.) $\pm$ 0.29 (cocktail). The enhancement factorexhibits weak centrality and $p_{\rm T}$ dependence in STAR's accessiblekinematic regions, while the excess yield in this invariant-mass region as afunction of the number of participating nucleons follows a power-law shape witha power of 1.44 $\pm$ 0.10. Models that assume an in-medium broadening of the$\rho$ meson spectral function consistently describe the observed excess inthese measurements. Additionally, we report on measurements of $\omega$ and$\phi$-meson production through their $e^+e^-$ decay channel. Thesemeasurements show good agreement with Tsallis Blast-Wave model predictions aswell as, in the case of the $\phi$-meson, results through its $K^+K^-$ decaychannel. In the intermediate invariant-mass region (1.1$<M_{ee}<$ 3 GeV/$c^2$),we investigate the spectral shapes from different collision centralities.Physics implications for possible in-medium modification of charmed hadronproduction and other physics sources are discussed.

Measurements of Dielectron Production in Au$+$Au Collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV from the STAR Experiment