HYBRID STAR MODELS IN THE LIGHT OF NEW MULTI-MESSENGER DATA

HYBRID STAR MODELS IN THE LIGHT OF NEW MULTI-MESSENGER DATA

Draft version May 21, 2024 | Jia Jie Li1, Armen Sedrakian2,3, Mark Alford4
This paper examines the consistency of hybrid star models with recent astrophysical and laboratory data, focusing on the mass inferences of compact stars HESS J1731-347 and PSR J0952-0607, as well as the measurement of the neutron skin of Ca in the CREX experiment. Hybrid stars, which contain a quark core surrounded by a nucleonic envelope, are explored as potential models for these new data. The authors use a family of 81 nucleonic equations of state (EoSs) with variable skewness and slope of symmetry energy at saturation density, combined with a constant speed-of-sound EoS for quark matter. These models are tested against data from GW170817 and J1731-347, which favor low-density soft EoSs, and PSR J0592-0607 and J0740+6620, which require high-density stiff EoSs. The addition of J0592-0607's mass measurement does not significantly impact the parameter space of admissible EoSs but allows for the exploration of potential effects of more massive pulsars. The study also investigates twin configurations, where two stars have the same mass but different radii, and quantifies the ranges of masses and radii they can possess. The results show that including J1731-347 data favors EoSs that predict low-mass twins with masses up to 1.3 solar masses, and allow for maximum masses of hybrid stars in the range of 2.0 to 2.6 solar masses, depending on the speed of sound in quark matter. The paper concludes that current astrophysical and nuclear physics data do not rule out hybrid stars and leave room for hybrid-nucleonic mass twins if a strong first-order phase transition occurs in dense matter.This paper examines the consistency of hybrid star models with recent astrophysical and laboratory data, focusing on the mass inferences of compact stars HESS J1731-347 and PSR J0952-0607, as well as the measurement of the neutron skin of Ca in the CREX experiment. Hybrid stars, which contain a quark core surrounded by a nucleonic envelope, are explored as potential models for these new data. The authors use a family of 81 nucleonic equations of state (EoSs) with variable skewness and slope of symmetry energy at saturation density, combined with a constant speed-of-sound EoS for quark matter. These models are tested against data from GW170817 and J1731-347, which favor low-density soft EoSs, and PSR J0592-0607 and J0740+6620, which require high-density stiff EoSs. The addition of J0592-0607's mass measurement does not significantly impact the parameter space of admissible EoSs but allows for the exploration of potential effects of more massive pulsars. The study also investigates twin configurations, where two stars have the same mass but different radii, and quantifies the ranges of masses and radii they can possess. The results show that including J1731-347 data favors EoSs that predict low-mass twins with masses up to 1.3 solar masses, and allow for maximum masses of hybrid stars in the range of 2.0 to 2.6 solar masses, depending on the speed of sound in quark matter. The paper concludes that current astrophysical and nuclear physics data do not rule out hybrid stars and leave room for hybrid-nucleonic mass twins if a strong first-order phase transition occurs in dense matter.
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