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

Calculation of the thermodynamic properties of the spin polarized strange quark star in the presence of strong magnetic field

Documentos apresentados no âmbito do reconhecimento de graus e diplomas estrangeirosIn this thesis, we investigated the strange quark matter (SQM) composed of the spin-up and spin-down; up, down and strange quarks at finite temperature in the presence of the strong magnetic field using the MIT bag model. We computed the total free energy of the spin polarized SQM at finite temperature in the presence of the strong magnetic field. We found that the free energy gets a minimum at a particular value of the spin polarization parameter showing a meta-stable state. The calculation shown that by increasing temperature, the equation of state of spin polarized SQM becomes stiffer. Also, using the general relativistic TOV equation, we studied the structure of the spin polarized strange quark star (SQS). We calculated the maximum mass and corresponding radius of spin polarized SQS at different temperatures and magnetic fields. We shown that the gravitational mass of spin polarized SQS rapidly increases by increasing the central energy density. We also indicated that the mass and the radius of the spin polarized SQS decreases by increasing both temperature and magnetic field

The maximum mass and deformation of rotating strange quark stars with strong magnetic fields

We study the structure and total energy of a strange quark star (SQS) endowed with a strong magnetic field with different rotational frequencies. The MIT bag model is used, with the density-dependent bag constant for the equation of state (EOS). The EOS is computed considering the Landau quantization effect regarding the strong magnetic fields (up to $5\times10^{17}$ G) in the interior of the strange quark star. Using the LORENE library, we calculate the structural parameters of SQS for different setups of magnetic field strengths and rotational frequencies. In each setup, we perform calculations for $51$ stellar configurations, with specified central enthalpy values. We investigate the configurations with the maximum gravitational mass of SQS in each setup. Our models of SQSs are compared in the maximum gravitational mass, binding energy, compactness, and deformation of the star. We show that the gravitational mass might exceed $2.3 M_\odot$ in some models, which is comparable with the mass of the recently detected ``black widow'' pulsar \emph{PSR J0952-0607} and the mass of \emph{GW190814} detected by the LIGO/Virgo collaboration. The deformation and maximum gravitational mass of SQS can be characterized by simple functions that have been fitted to account for variations in both magnetic field strength and frequency. Rapidly rotating strange stars have a minimum gravitational mass given by the equatorial mass-shedding limit.Comment: 18 pages, 10 Figures, 2 tables, submitted to PhysRev

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