  We propose a continuum model for the theoretical study of hybridized moir\'e
excitons in transition metal dichalcogenides heterobilayers, and we use a
variational method to solve the exciton wavefunction and calculate the optical
absorption spectrum. The exciton continuum model is built by the charge
continuum model for electrons and holes in moir\'e superlattices, thereby
preserving the moir\'e periodicity and lattice symmetry from the charge
continuum model. The momentum-space shift of interlayer electron-hole
distribution is included, and thus the indirect nature of interlayer excitons
is described. The spin and valley degrees of freedom and related interactions
are omitted, except for the spin-orbit energy splitting of A and B excitons.
This continuum model is applied to the simulation of optical absorption by
hybridized moir\'e excitons in $\text{WSe}_2$/$\text{WS}_2$ and
$\text{MoSe}_2$/$\text{WS}_2$ heterobilayers. Twist-angle and electric-field
dependences of absorption spectra are studied. Calculated spectra are compared
with experimental observations in the literature, and correspondences of
signatures are found. The deficiency and the potential of the present model are
discussed.
