Signal for the Quark-Hadron Phase Transition in Rotating Hybrid Stars

For the past 20 years it had been thought that the coexistence phase of the confined hadronic and quark matter phases, assumed to be a first order transition, was strictly excluded from neutron stars. This, however, was due to a seemingly innocuous idealization which has approximated away important physics. The reason is that neutron stars constitute multi-component bodies rather than single-component ones formerly (and incorrectly) used to describe the deconfinement phase transition in neutron stars. So, contrary to earlier claims, `neutron' stars may very well contain quark matter in their cores surrounded by a mixed-phase region of quark and hadronic matter. Such objects are called hybrid stars. The structure of such stars as well as an observable signature that could signal the existence of quark matter in their cores are discussed in this paper.