  The invariant mass spectrum and the elliptic flow of lepton pairs produced in
relativistic heavy-ion collisions at RHIC are studied with viscous
hydrodynamics. The effects of viscous corrections on dilepton observables are
explored. The lepton pairs originating from charm quarks evolving in the
viscous background are seen to be a good probe of quark energy loss and gain,
as quantified by the dilepton spectrum and by the dilepton elliptic flow.
