  Based on the density-dependent relativistic Hartree-Fock theory (DDRHF) for
hadronic matter, the properties of neutron stars have been studied and compared
with the results from the density-dependent relativistic mean field theory
(DDRMF). Though similar equations of state are obtained, DDRHF calculations
give larger fractions of proton, electron and muon at high baryon density for
neutron star matter than the ones from DDRMF. The maximum masses of neutron
stars lie between 2.3 M$_\odot$ and 2.5 M$_\odot$, and the corresponding radii
between 11.7 km and 12.5 km. In addition, the phase transition from hadronic
matter to quark matter in neutron stars is studied by using the MIT bag model
for the quark phase. The transition is studied in both Gibbs and Maxwell
constructions.
