Unified Interacting Quark Matter and its Astrophysical Implications
We investigate interacting quark matter (IQM), including the perturbative QCD
correction and color superconductivity, for both up-down quark matter ($ud$QM)
and strange quark matter (SQM). We first derive an equation of state (EOS)
unifying all cases by a simple reparametrization and rescaling, through which
we manage to maximally reduce the number of degrees of freedom. We find, in
contrast to the conventional EOS $p=1/3(\rho-4B_{\rm eff})$ for non-interacting
quark matter, that taking the extreme strongly interacting limit on the unified
IQM EOS gives $p=\rho-2B_{\rm eff}$, where $B_{\rm eff}$ is the effective bag
constant. We employ the unified EOS to explore the properties of pure
interacting quark stars (IQSs) composed of IQM. We describe how recent
astrophysical observations, such as the pulsar-mass measurements, the NICER
analysis, and the binary merger gravitational-wave events GW170817, GW190425,
and GW190814, further constrain the parameter space. An upper bound for the
maximum allowed mass of IQSs is found to be $M_{\rm TOV}\lesssim 3.23
M_{\odot}$. Our analysis indicates a new possibility that the currently
observed compact stars, including the recently reported GW190814's secondary
component ($M=2.59^{+0.08}_{-0.09}\, M_{\odot}$), can be quark stars composed
of interacting quark matter.
Chen Zhang Robert B. Mann