abrata Deb

Relativistic model for anisotropic strange stars

Abstract In this article, we attempt to find a singularity free solution of Einstein’s field equations for compact stellar objects, precisely strange (quark) stars, considering Schwarzschild metric as the exterior spacetime. To this end, we consider that the stellar object is spherically symmetric, static and anisotropic in nature and follows the density profile given by Mak and Harko (2002) , which satisfies all the physical conditions. To investigate different properties of the ultra-dense strange stars we have employed the MIT bag model for the quark matter. Our investigation displays an interesting feature that the anisotropy of compact stars increases with the radial coordinate and attains its maximum value at the surface which seems an inherent property for the singularity free anisotropic compact stellar objects. In this connection we also perform several tests for physical features of the proposed model and show that these are reasonably acceptable within certain range. Further, we find that the model is consistent with the energy conditions and the compact stellar structure is stable with the validity of the TOV equation and Herrera cracking concept. For the masses below the maximum mass point in mass vs radius curve the typical behavior achieved within the framework of general relativity. We have calculated the maximum mass and radius of the strange stars for the three finite values of bag constant B g .

Strange stars in f(R,) gravity

In this article we try to present spherically symmetric isotropic strange star model under the framework of f(R,) theory of gravity. To this end, we consider that the Lagrangian density is a linear function of the Ricci scalar R and the trace of the energy momentum tensor given as f(R,)=R+2χ . We also assume that the quark matter distribution is governed by the simplest form of the MIT bag model equation of state (EOS) as p=1/3(ρ−4B), where B is the bag constant. We have obtained an exact solution of the modified form of the Tolman-Oppenheimer-Volkoff (TOV) equation in the framework of f(R,) gravity theory and have studied the dependence of different physical properties, viz., the total mass, radius, energy density and pressure for the chosen values of χ. Further, to examine physical acceptability of the proposed stellar model, we have conducted different tests in detail, viz., the energy conditions, modified TOV equation, mass-radius relation, causality condition etc. We have precisely explained the effects arising due to the coupling of the matter and geometry on the compact stellar system. For a chosen value of the bag constant, we have predicted numerical values of the different physical parameters in tabular form for the different strange star candidates. It is found that as the factor χ decreases the strange star candidates become gradually massive and larger in size with less dense stellar configuration. However, when χ increases the stars shrink gradually and become less massive to turn into a more compact stellar system. Hence for χ>0 our proposed model is suitable to explain the ultra-dense compact stars well within the observational limits and for χ<0 case allows to represent the recent massive pulsars and super-Chandrasekhar stars. For χ=0 we retrieve as usual the standard results of the general relativity (GR).

A Model for Anisotropic Strange Stars

Assuming that the compact star is made up of anisotropic fluid and the MIT Bag model is applicable in this environment we construct a spherically symmetric, static and anisotropic stellar model. We have found several physical parameters, the stellar radius, surface redshift and anisotropic property. It can be observed that anisotropy is increasing with the radial coordinate inside the stellar system from zero at the center to it’s maximum at the surface for all the strange stars.

A new model for strange stars

In the present work, we attempt to find a new class of solutions for the spherically symmetric perfect fluid sphere by employing the homotopy perturbation method (HPM), a new tool via which the mass polynomial function facilitates to tackle the Einstein field equations. A set of interior solutions found on the basis of the simplest MIT bag model equation of state in the form

Exact Radiation Model For Perfect Fluid Under Maximum Entropy Principle

p=\frac{1}{3}(\rho -4B)

Anisotropic strange stars in the Einstein–Maxwell spacetime

p=13(ρ-4B) where B is the bag constant. The proposed interior metric for the stellar system is consistent with the exterior Schwarzschild spacetime on the boundary. In addition, we also conduct a detailed study on different tests, viz. the energy conditions, TOV equation, adiabatic index, Buchdahl limit, etc., to verify the physical validity of the proposed model. The numerical value of the used parameters are predicted for different strange star candidates, for different chosen values of the bag constant. In a nutshell, by exploiting HPM technique first time ever in the field of relativistic astrophysics, we have predicted in the present literature a singularity-free and stable stellar model which is suitable to describe ultra-dense objects, like strange (quark) stars.