A Model of Low-Mass Neutron Stars with a Quark Core.

We consider an equation of state that leads to a first-order phase transition from the nucleon state to the quark state with a transition parameter λ > 3/2 (λ = ρ[sub Q]/(ρ[sub N] + P[sub 0]/c²)) in superdense nuclear matter. Our calculations of integrated parameters for superdense stars using this equation of state show that on the stable branch of the dependence of stellar mass on central pressure (dM/dP[sub c] > 0) in the range of low masses, a new local maximum with M[sub max] = 0.082[sub ⊙] and R = 1251 km appears after the formation of a toothlike kink (M = 0.08M[sub ⊙], R = 205 km) attributable to quark production. For such a star, the mass and radius of the quark core are M[sub core] = 0.005M[sub ⊙] and R[sub core] = 1.73 km, respectively. In the model under consideration, mass accretion can result in two successive transitions to a quark-core neutron star with energy release similar to a supernova explosion: initially, a low-mass star with a quark core is formed; the subsequent accretion leads to configurations with a radius of ∼ 1000 km; and, finally, the second catastrophic restructuring gives rise to a star with a radius of ∼ 100 km. [ABSTRACT FROM AUTHOR]