Hybrid stars with reactive interfaces: analysis within the Nambu-Jona-Lasinio model

Abstract

It has been shown recently that quark-hadron conversions at the interface of a hybrid star may have a key role on the dynamic stability of the compact object. In this work we perform a systematic study of hybrid stars with reactive interfaces using a model-agnostic piecewise-polytropic hadronic equation of state and the Nambu-Jona-Lasinio model for three-flavor quark matter. For the hadronic phase we use a soft, an intermediate and a stiff parametrization that match at $1.1n_0$ {with predictions} based on chiral effective field theory (cEFT) interactions. In the NJL Lagrangian we include scalar, vector and 't Hooft interactions. The vector coupling constant $g_v$ is treated as a free parameter. We also consider that there is a split between the deconfinement and the chiral phase transitions which is controlled by changing the conventional value of the vacuum pressure $-{\Omega }_0$ in the NJL thermodynamic potential by $-\left({\Omega }_0+\delta {\Omega }_0\right)$, being $\delta {\Omega }_0$ a free parameter. We analyze the mass-radius ($M$-$R$) relation in the case of rapid ($\tau \ll 1\mathrm{ms}$) and slow ($\tau \gg 1\mathrm{ms}$) conversions, being $\tau$ the reaction timescale. In the case of slow interface reactions we find $M$-$R$ curves with a cusp at the maximum mass point where a pure hadronic branch and a slow-stable hybrid star (SSHS) branch coincide. We find that the length of the slow-stable branch grows with the increase of the transition density and the energy density jump at the hadron-quark interface. We calculate the tidal deformabilities of SSHSs and analyse them in the light of the GW170817 event.

12 pages, 4 figures, to be published in Physical Review D

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Cited by in corpus (1)

• Quark confinement in an equiparticle quark model: application to stellar matter