Pulsars with the masses 2.14M⊙ and 2.27M⊙ as strange star candidates

Abstract

Strange stars with maximal masses, more than the values of recently precisely measured masses of two radio pulsars: $SRJ0740+6620$, with the mass $2.14{М}_{\odot }$, and $PSRJ2215+5135$, with the mass $2.27{М}_{\odot }$, have been studied. For the examination of strange quark matter $\left(SQM\right)$, the bag model, developed in Massachusetts Technological Institute was chosen. The observed bag model depends on vacuum pressure $B$, quark-gluon interaction constant ${\alpha }_c$, and strange quark mass $m_s$. Since the transition to $SQM$ state takes place at the energy density, not exceeding double density in atomic nuclei, neutron stars with small mass and configuration, consisting of $SQM$, form one family in the dependence curve of the mass $M$, of the equilibrium super-dense configurations, on the energy central density ${\rho }_c$ (curve $M\left({\rho }_c\right)$). The state equation of strange quark matter was studied when the vacuum pressure was constant. Groups of the values of these parameters were determined; their application in the state equation of $SQM$ leads to the maximal mass of the equilibrium quark configurations $M_{max}$, which are heavier than the aforementioned radio pulsars. For such configurations, the values of mass, radius, the entire number of baryons, red shift from the strange star surface were calculated, depending on the energy central density ${\rho }_c$. For each series with $M_{max}>2.14M_{\odot }$ and $M_{max}>2.27M_{\odot }$ the values of the mentioned integral parameters were calculated as well for super-dense configurations with $2.27\text{and}2.14$ solar masses that were precisely determined from observations. According to the obtained state equations, these two radio pulsars can be the possible candidates for the strange stars.