  In this work, we consider the consequences of phase transition in dense QCD
on the properties of compact stars and implications for the observational
program in gravitational wave and X-ray astrophysics. The key underlying
assumption of our modeling is a strong first-order phase transition past the
point where the hadronic branch of compact stars reaches the two-solar mass
limit. Our analysis predicts ultracompact stars with very small radii - in the
range of 6-9 km - living on compact star sequences that are entirely consistent
with the current multimessenger data. We show that sequences featuring
two-solar mass hadronic stars consistent with radio-pulsar observations are
also consistent with the inferences of large radii for massive neutron stars by
NICER X-ray observations of neutron stars and the small radii predicted by
gravitational waves analysis of the binary neutron star inspiral event GW170817
for our models that feature a strong first-order QCD phase transition.
