http://arxiv.org/abs/2108.13071
We explored the implications of the recent radius determination of PSR J0740+6620 by the NICER experiment combined with the neutron skin measurement by PREX-II experiment for the structure of hybrid stars with a strong first-order phase transition from nucleonic to quark matter. We combine a covariant density-functional nucleonic equation of state (EoS) with a constant speed of sound EoS for quark matter. We show that the radius and tidal deformability ranges obtained from GW170817 can be reconciled with the PREX-II results if there is a phase transition to quark matter in the low-mass compact star. In the high-mass segment, the EoS needs to be stiff to comply with the large-radius inference for PSR J0740+6620 and J0030+0451 with a masses $M\simeq 2M_{\odot}$ and $M\simeq 1.4M_{\odot}$. We show that twin stars are not excluded, but the mass and radius ranges (with $M \geq M_\odot$) are restricted to narrow domains $\Delta M_{\rm twin} \lesssim 0.05 M_\odot$ and $\Delta R_{\rm twin} \sim 1.0$~km. We also show that the existence of twin configurations is compatible with the light companion in GW190814 event being a hybrid star in the case of values of the sound-speed square $s \simeq 0.6$.
J. Li, A. Sedrakian and M. Alford
Tue, 31 Aug 21
56/73
Comments: 5 pages and 4 figures