Maximum Mass of the Hot Neutron Star with the Quark Core

We have considered a hot neutron star with a quark core, a mixed phase of quark-hadron matter, and a hadronic matter crust and have determined the equation of state of the hadronic phase and the quark phase, we have then found the equation of state of the mixed phase under the Gibbs conditions. Finally, we have computed the structure of hot neutron star with the quark core and compared our results with those of the neutron star without the quark core. For the quark matter calculations, we have used the MIT bag model in which the total energy of the system is considered as the kinetic energy of the particles plus a bag constant. For the hadronic matter calculations, we have used the lowest order constrained variational (LOCV) formalism. Our calculations show that the results for the maximum gravitational mass of the hot neutron star with the quark core are substantially different from those of without the quark core.Comment: 19 pages, 7 figures Res. Astron. Asrtophys. (2010) accepte

Calculation of the Structure Properties of a Strange Quark Star in the Presence of Strong Magnetic Field Using a Density Dependent Bag Constant

In this article we have calculated the structure properties of a strange quark star in static model in the presence of a strong magnetic field using MIT bag model with a density dependent bag constant. To parameterize the density dependence of bag constant, we have used our results for the lowest order constrained variational calculation of the asymmetric nuclear matter. By calculating the equation of state of strange quark matter, we have shown that the pressure of this system increases by increasing both density and magnetic field. Finally, we have investigated the effect of density dependence of bag constant on the structure properties of strange quark star.Comment: 23 pages, 9 figures, Res. in Astron. Astrophys. (2012) accepte

The effect of dynamical quark mass in the calculation of strange quark star structure

We have discussed dynamical behavior of strange quark matter components, in particular the effects of density dependent quark mass on the equation of state of strange quark matter. Dynamical masses of quarks have been computed within Nambu-Jona-Lasinio (NJL) model, then we have done the strange quark matter calculations employing the MIT bag model with these dynamical masses. For the sake of comparing dynamical mass interaction with QCD quark-quark interaction, we have considered the one-gluon-exchange term as the effective interaction between quarks for MIT bag model. Our dynamical approach illustrates an improvement for the obtained values of equation of state. We have also investigated the structure of strange quark star using Tolman-Oppenheimer-Volkoff (TOV) equations for all applied models. Our results show that the dynamical mass interaction leads to lower values for the gravitational mass.Comment: 18 pages, 1 table, 7 figure

Computation of the structure of magnetized strange quark star

In this work, we have calculated some properties of the spin polarized strange quark matter (SQM) in a strong magnetic field at zero temperature using the MIT bag model. We have shown that the equation of state of spin polarized SQM is stiffer than that of the unpolarized case. We have also computed the structure properties of the spin polarized strange quark star (SQS) and have found that the presence of magnetic field leads to a more stable SQS compared to the unpolarized SQS.Comment: 23 pages, 13 figures, 2 tables Res. Astron. Astrophys. (2011) in pres

Calculation of the Structure Properties of Asymmetrical Nuclear Matter

In this paper the structure properties of asymmetrical nuclear matter has been calculated employing AV18 potential for different values of proton to neutron ratio. These calculations have been also made for the case of symmetrical nuclear matter with UV14, AV14 and AV18 potentials. In our calculations, we use the lowest order constrained variational (LOCV) method to compute the correlation function of the system.Comment: 23 pages, 6 figures, 1 table Research in Astronomy and Astrophysics (2011) accepte

Anisotropic magnetized neutron star

As we know, the effect of strong magnetic field causes the anisotropy for the magnetized compact objects. Therefore, in this paper, we have studied the structure properties of anisotropic case of magnetized neutron star. We have derived the equation of state (EoS) of neutron star matter for two forms of magnetic fields, one uniform and one density dependent. We have solved the generalized Tolman–Oppenheimer–Volkoff equations to examine the maximum mass and corresponding radius, Schwarzschild radius, gravitational redshift, Kretschmann scalar, and Buchdahl theorem for this system. It was shown that the maximum mass and radius of neutron star are increasing functions of the magnetic field. Also redshift, strength of gravity, and Kretschmann scalar increase as the magnetic field increases. In addition, the dynamical stability of anisotrop neutron star has been investigated, and finally a comparison with the empirical results has been made

Influence of strong magnetic field on the structure properties of strange quark stars

We investigate the thermodynamic properties of strange quark matter under the strong magnetic field in the framework of the MIT bag model in two cases of bag constants. We consider two cases of the magnetic field, the uniform magnetic field and the density-dependent magnetic field to calculate the equation of state of strange quark matter. For the case of density-dependent magnetic field, we use a Gaussian equation with two free parameters $$\beta$$ and $$\theta$$ and use two different sets of the parameters for the magnetic field changes (a slow and a fast decrease of the magnetic field from the center to the surface). Our results show that the energy conditions based on the limitation of the energy-momentum tensor, are satisfied in the corresponding conditions. We also show that the equation of state of strange quark matter becomes stiffer by increasing the magnetic field. In this paper, we also calculate the structure parameters of a pure strange quark star using the equation of state. We investigate the compactification factor (2M/R) and the surface redshift of star in different conditions. The results show that the strange quark star is denser than the neutron star and it is more compact in the presence of the stronger magnetic field. As another result, the compactification factor increases when we use a slow increase of the magnetic field from the surface to the center. Eventually, we compare our results with the observational results for some strange star candidates, and we find that the structure of the strange star candidates is comparable to that of the star in our model