Low-Mass Quark Stars or Quark White Dwarfs
  An equation of state is considered that, in superdense nuclear matter, results in a phase transition of the first kind from the nucleon state to the quark state with a transition parameter Lambda> 3/2. A calculation of the integrated parameters of superdense stars on the basis of this equation of state shows that on the stable branch of the dependence of stellar mass on central pressure (dM/dPc> 0), in the low-mass range, following the formation of a tooth-shaped break (M = 0.08Msun, R = 200 km) due to quark formation, a new local maximum with Mmax = 0.082Msun and R = 1251 km is also formed. The mass and radius of the quark core of such a star turn out to be Mcore = 0.005Msun and Rcore = 1.7 km, respectively. Mass accretion in this model can result in two successive transitions to a neutron star with a quark core, with energy release like supernova outbursts. 
G.B.Alaverdyan, A.R.Harutyunyan, and Yu.L.Vartanyan