  Background: At high density deconfinement of hadronic matter may occur
leading to quark matter. The immense densities reached in the inner core of
massive neutron stars may be sufficient to facilitate the transition. Purpose:
To investigate a crossover transition between two phenomenological models which
epitomise QCD in two different regimes, while incorporating the influence of
quark degrees of freedom in both. Method: We use the Hartree-Fock quark-meson
coupling model and the proper time regularised three flavour NJL model to
describe hadronic and quark matter, respectively. Hybrid equations of state are
obtained by interpolating the energy density as a function of total baryonic
density and calculating the pressure. Results: Equations of state for hadronic,
quark and hybrid matter and the resulting mass versus radius curves for hybrid
stars are shown, as well as other relevant physical quantities such as species
fractions and the speed of sound in matter. Conclusions: The observations of
massive neutron stars can certainly be explained within such a construction.
However, the so-called thermodynamic correction arising from an interpolation
method can have a considerable impact on the equation of state. The
interpolation dependency of and physical meaning behind such corrections
require further study.
