  We study cold dense quark matter and hybrid neutron stars with a
Dyson-Schwinger quark model and various choices of the quark-gluon vertex. We
obtain the equation of state of quark matter in beta equilibrium and
investigate the hadron-quark phase transition in combination with a hadronic
equation of state derived within the Brueckner-Hartree-Fock many-body theory.
Comparing with the results for quark matter with the rainbow approximation, the
Ball-Chiu ansatz and the 1BC ansatz for the quark-gluon vertex lead to a
reduction of the effective interaction at finite chemical potential,
qualitatively similar to the effect of our gluon propagator. We find that the
phase transition and the equation of state of the quark or mixed phase and
consequently the resulting hybrid star mass and radius depend mainly on a
global reduction of the effective interaction due to effects of both the
quark-gluon vertex and gluon propagator, but are not sensitive to the vertex
ansatz.
