Quark matter influence on observational properties of compact stars

Densities in compact stars may be such that quarks are no longer confined in hadrons, but instead behave as weakly interacting particles. In this regime perturbative calculations are possible. Yet, due to high pressures and an attractive channel in the strong force, condensation of quarks in a superfluid state is likely. This can have interesting consequences for magnetic fields, especially in relation to the discovery of slow-period free precession in a compact star. In this proceedings there will be a discussion of the mass-radius relations of compact stars made from quark matter and magnetic field behaviour in compact stars with a quark matter core.