  Transition-metal dichalcogenide heterostructures exhibit moir\'e patterns
that spatially modulate the electronic structure across the material's plane.
For certain material pairs, this modulation acts as a potential landscape with
deep, trigonally symmetric wells capable of localizing interlayer excitons,
forming periodic arrays of quantum emitters. Here, we study these moir\'e
localized exciton states and their optical properties. By numerically solving
the two-body problem for an interacting electron-hole pair confined by a
trigonal potential, we compute the localized exciton spectra for different
pairs of materials. We derive optical selection rules for the different
families of localized states, each belonging to one of the irreducible
representations of the potential's symmetry group $C_{3v}$, and numerically
estimate their polarization-resolved absorption spectra. We find that the
optical response of localized moir\'e interlayer excitons is dominated by
states belonging to the doubly-degenerate $E$ irreducible representation. Our
results provide new insights into the optical properties of artificially
confined excitons in two-dimensional semiconductors.
