Bayesian inference of strange star equation of state using the GW170817 and GW190425 data

Abstract

The observations of compact star inspirals from LIGO/Virgo provide a valuable tool to study the highly uncertain equation of state (EOS) of dense matter at the densities in which the compact stars reside. It is not clear whether the merging stars are neutron stars or quark stars containing self-bound quark matter. In this work, we explore the allowed bag-model-like EOSs by assuming the merging stars are strange quark stars (SQSs) from a Bayesian analysis employing the tidal deformability observational data of the GW170817 and GW190425 binary mergers. We consider two extreme states of strange quark matter, either in nonsuperfluid or color-flavor locked (CFL) and find the results in these two cases essentially reconcile. In particular, our results indicate that the sound speed in the SQS matter is approximately a constant close to the conformal limit of $c/\sqrt{3}$. The universal relations between the mass, the tidal deformability and the compactness are provided for the SQSs. The most probable values of the maximum mass are found to be $M_{\mathrm{TOV}}=2.10_{-0.12}^{+0.12}(2.15_{-0.14}^{+0.16})M_{\odot }$ for normal (CFL) SQSs at a $90\%$ confidence level. The corresponding radius and tidal deformability for a $1.4M_{\odot }$ star are $R_{1.4}=11.50_{-0.55}^{+0.52}({11.42}_{-0.44}^{+0.52})\mathrm{km}$ and ${\Lambda }_{1.4}={650}_{-190}^{+230}({630}_{-150}^{+220})$, respectively. We also investigate the possibility of GW190814's secondary component $m_2$ of mass $2.59_{-0.09}^{+0.08}{M}_{\odot }$ being an SQS, and find that it could be a CFL SQS with the pairing gap $\Delta$ larger than $244\mathrm{MeV}$ and the effective bag parameter $B_{\mathrm{eff}}^{1/4}$ in the range of $170$ to $192$ MeV, at a $90\%$ confidence level.

6 pages, 3 figures, 1 table; accepted for publication in ApJL.The analyses of quark star equation of state using the NICER data are reported in arXiv:2009.12571 (to appear in MNRAS)

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• Constraints on Density Dependent MIT Bag Model Parameters for Quark and Hybrid Stars
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• Structure of magnetized strange quark star in perturbative QCD
• Properties of First-Order Hadron-Quark Phase Transition from Inverting Neutron Star Observables
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• Rotating Hybrid Stars with Color-Flavor-Locked Quark Matter
• Fully general relativistic simulations of rapidly rotating quark stars: Oscillation modes and universal relations
• Hybrid stars may have an inverted structure
• Diquark and chiral condensate in a self-consistent NJL-type model
• Effects of dark boson mediated feeble interaction between dark matter (DM) and quark matter on $f$-mode oscillation of DM admixed quark stars
• Constraint on the equation of state of strange quark star: Perturbative QCD along with a density-dependent bag constant
• Vetting quark-star models with gravitational waves in the hierarchical Bayesian framework
• Study of hybrid stars with nonstrange quark matter cores
• Strange Matter
• Equation of State of Decompressed Quark Matter, and Observational Signatures of Quark-Star Mergers
• Primordial black holes versus their impersonators at gravitational wave observatories
• Phase structures of neutral dense quark matter and application to strange stars