The Constant-Sound-Speed parameterization for NJL models of quark matter in hybrid stars

IGNACIO F. RANEA-SANDOVAL; SOPHIA HAN; MILVA G. ORSARIA; GUSTAVO A. CONTRERA; FRIDOLIN WEBER; MARK G. ALFORD

PHYS. REV. - C

AMER PHYSICAL SOC

Lugar: New York; Año: 2016 vol. 93 p. 4581201 - 4581212

0556-2813

The discovery of pulsars as heavy as 2 solar masses has led astrophysicists to rethink the core compositions of neutron stars, ruling out many models for the nuclear equations of state (EoS). We explore the hybrid stars that occur when hadronic matter is treated in a relativistic mean field approximation and quark matter is modeled by three flavor local and non-local Nambu􀀀Jona-Lasinio (NJL) models with repulsive vector interactions. The NJL models typically yield equations of state that feature a first-order transition to quark matter. Assuming that the quark-hadron surface tension is high enough to disfavour mixed phases, and restricting to EoSs that allow starts to reach 2 solar masses, we nd that the appearance of the quark matter core either destabilizes the star immediately (this is typical for non-local NJL models) or leads to a very short hybrid star branch in the mass-radius relation (this is typical for local NJL models). Using the Constant-Sound-Speed parametrization we can see that the reason for the near-absence of hybrid stars is that the transition pressure is fairly high and the transition is strongly first-order.