  In thermal equilibrium, the fluctuation-dissipation theorem relates the
linear response and correlation functions in a model and observable independent
fashion. Out of equilibrium, these relations still hold if the equilibrium
temperature is replaced by an observable and frequency-dependent parameter
(effective temperature). When the system achieves a long time thermal state all
of these effective temperatures should be equal and constant. Following this
approach we examine the long times regime after a quantum quench in a system
with bipartite entanglement in which the asymptotic values of the observable
are compatible with the ones obtained in a Gibbs ensemble. We observe that when
the initial entanglement is large, and for a large range of (intermediate)
frequencies, the effective temperatures corresponding to the analyzed local and
non-local operators approach an approximate constant value equal to the
temperature that governs the decay of correlations. Still, the residual
frequency dependence in the effective temperature, and the differences observed
among observables discards strict thermalization.
