  Discrete fundamental and dipole solitons are constructed, in an exact
analytical form, in an array of linear waveguides with an embedded
$\mathcal{PT}$-symmetric dimer, which is composed of two nonlinear waveguides
carrying equal gain and loss. Fundamental solitons in tightly knit lattices, as
well as all dipole modes, exist above a finite threshold value of the total
power. However, the threshold vanishes for fundamental solitons in loosely knit
lattices. The stability of the discrete solitons is investigated analytically
by means of the Vakhitov-Kolokolov (VK) criterion, and, in the full form, via
the computation of eigenvalues for perturbation modes. Fundamental and dipole
solitons tend to be stable at smaller and larger values of the total power
(norm), respectively. The increase of the strength of the coupling between the
two defect-forming sites leads to strong expansion of the stability areas. The
scattering problem for linear lattice waves impinging upon the defect is
considered too.
