Anisotropic Compact Stars Research Articles

Analysis of charged compact stars in modified gravity

Current study highlights the physical characteristics of charged anisotropic compact stars by exploring some exact solutions of modified field equations in [Formula: see text] gravity. A comprehensive analysis is performed from the obtained solutions regarding stability, energy conditions, regularity, sound velocity and compactness. These solutions can be referred to model the compact celestial entities. In particular, a compact star named, [Formula: see text] has been modeled which indicates that current solution fits and is in conformity to the observational data as well. A useful and interesting fact from this model arises that relative difference between two forces of anisotropic pressure and electromagnetic force may occur inside the aforementioned compact star. This is another mechanism which is essential for stability of the compact object and prevent stellar object to annihilate.

Anisotropic compact stars in non-conservative theory of gravity

We develop anisotropic compact stars in the scenario of non-conservative theory such as Rastall theory. We consider the Krori and Barua static spherically symmetric metrics and find their unknown constants by using the masses and radii of well-known compact stars. We investigate the anisotropic compact star through various physical quantities such as anisotropic behavior, regularity conditions, stability and surface redshift. It is found that the present compact stars are stable and are in the stellar equilibrium form.

Exact anisotropic polytropic cylindrical solutions

In this paper, we study anisotropic compact stars with static cylindrically symmetric anisotropic matter distribution satisfying polytropic equation of state. We formulate the field equations as well as the corresponding mass function for the particular form of gravitational potential $z(x)=(1+bx)^{\eta }~(\eta =1,~2,~3)$ and explore exact solutions of the field equations for different values of the polytropic index. The values of arbitrary constants are determined by taking mass and radius of compact star (Her X-1). We find that resulting solutions show viable behavior of physical parameters (density, radial as well as tangential pressure, anisotropy) and satisfy the stability condition. It is concluded that physically acceptable solutions exist only for $\eta =1,~2$ .

Effect of electric charge on anisotropic compact stars in conformally symmetric spacetime

We obtain a new class of interior solutions for charged anisotropic stars which admits non-static conformal motion. The Einstein–Maxwell field equations are solved by taking a physically reasonable choice for the grr metric co-efficient and a suitable expression for charge density. From the analysis we have shown that there is a central singularity on space–time by calculating Kretschmann scalar though the central density and central pressure are finite. The emphasis are given on the causality condition and the stability analysis of the model. The masses and radii of the compact stars PSR J16142230, PSR J1903 + 327 and LMC X-4 obtained from the model are well match with the observed values provided by Gangopadhyay et al (2013 Mon. Not. R. Astron. Soc. 431 3216)

A new class of anisotropic charged compact star

A new model of charged compact star is reported by solving the Einstein-Maxwell field equations by choosing a suitable form of radial pressure. The model parameters ρ,pr,p⊥ and E2 are in closed form and all are well behaved inside the stellar interior. A comparative study of charged and uncharged model is done with the help of graphical analysis.

Anisotropic compact star models in Karmarkar space time continuum

In the present article, we have explored some new anisotropic compact star models by using embedded class one space time metric. We proceed our calculations by assuming a particular form of $g_{rr}$ metric potential and solved for the other metric $g_{tt}$ using Karmarkar condition. The matter density, radial pressure, tangential pressure, mass function, surface red-shift, anisotropy are all well behaved inside the fluid sphere. The solution satisfies all energy conditions i.e. strong energy condition, null energy condition, dominant energy condition and weak energy condition. The solution also satisfies the causality condition and can represent stable stellar fluid system as the adiabatic index $\varGamma > 4/3$ and the stability factor $-1\leq v_{t}^{2}-v_{r}^{2}\leq 0$ holds good inside the fluid sphere. We have framed our solution for two compact stars PSR J1614-2230 and SAX J1808.4-3658, which are well-behaved in all respects. The mass and radius of the compact stars PSR J1614-2230 and SAXJ1808.4-3658, obtained from the models are very close to the observational data proposed by Gangopadhyay et al. (Mon. Not. R. Astron. Soc. 431:3216, 2013) and Bhattacharya (2001) respectively.

Analytical study of anisotropic compact star models

A simple classification is given of the anisotropic relativistic star models, resembling the one of charged isotropic solutions. On the ground of this database, and taking into account the conditions for physically realistic star models, a method is proposed for generating all such solutions. It is based on the energy density and the radial pressure as seeding functions. Numerous relations between the realistic conditions are found and the need for a graphic proof is reduced just to one pair of inequalities. This general formalism is illustrated with an example of a class of solutions with linear equation of state and simple energy density. It is found that the solutions depend on three free constants and concrete examples are given. Some other popular models are studied with the same method.

A comparative study on generalized model of anisotropic compact star satisfying the Karmarkar condition

A new solution satisfying the Karmarkar condition is presented here. We were first to have discovered a hypergeometric function metric potential representing embedding class I spacetime. This new solution yields finite values of metric potentials, density, pressure, redshift, etc. and hence a non-singular solution. The solution is well behaved with respect to the parameter n=12 to n=24 corresponding to a stable configuration of mass 2.01M_odot and radius 9.1 km. The internal properties of the solution are very different for n=12 to n=24; however, the total mass and radius is independent of the parameter n. The energy conditions are also holds good by the solution which thus can represent a physically viable matter distribution. The equilibrium condition and stability are also discussed through TOV-equation, cracking method and Gamma >4/3. The static stability criterion is also well satisfied and the turning point corresponds to 4.46M_odot for a radius of 9.1 km.

Physical attributes of anisotropic compact stars in f(R,\xa0G) gravity

Modified gravity is one of the potential candidates to explain the accelerated expansion of the universe. Current study highlights the materialization of anisotropic compact stars in the context of f(R, G) theory of gravity. In particular, to gain insight in the physical behavior of three stars namely, Her X1, SAX J 1808-3658 and 4U 1820-30, energy density, and radial and tangential pressures are calculated. The f(R, G) gravity model is split into a Starobinsky like f(R) model and a power law f(G) model. The main feature of the work is a 3-dimensional graphical analysis in which, anisotropic measurements, energy conditions and stability attributes of these stars are discussed. It is shown that all three stars behave as usual for positive values of the f(G) model parameter n.

Modeling of charged anisotropic compact stars in general relativity

A charged compact star models have been determined for anisotropic fluid distribution. We have solved the Einstein's- Maxwell field equations to construct the charged compact star models by using radial pressure, metric function $e^{\lambda}$ and electric charge function. The generic charged anisotropic solution is verified by exploring different physical conditions like, causality condition, mass-radius relation and stability of the solution (via. adiabatic index, TOV equations and Herrera cracking concept). It is observed that the present charged anisotropic compact star is compatible with the star PSR 1937+21. However we also presented the EOS $\rho=f(p)$ for present charged compact star model.

Anisotropic stellar models admitting conformal motion

We address the problem of finding static and spherically symmetric anisotropic compact stars in general relativity that admit conformal motions. The study is framed in the language of f(R) gravity theory in order to expose opportunity for further study in the more general theory. Exact solutions of compact stars are found under the assumption that spherically symmetric spacetimes which admits conformal motion with matter distribution anisotropic in nature. In this work, two cases have been studied for the existence of such solutions: first, we consider the model given by f(R) = R and then f(R) = aR+b. Finally, specific characteristics and physical properties have been explored by analytically along with graphical representations for conformally symmetric compact stars in f(R) gravity.

A new class of relativistic model of compact stars of embedding class I

In the present paper, we have constructed a new relativistic anisotropic compact star model having a spherically symmetric metric of embedding class one. Here we have assumed an arbitrary form of metric function [Formula: see text] and solved the Einstein’s relativistic field equations with the help of Karmarkar condition for an anisotropic matter distribution. The physical properties of our model such as pressure, density, mass function, surface red-shift, gravitational redshift are investigated and the stability of the stellar configuration is discussed in details. Our model is free from central singularities and satisfies all energy conditions. The model we present here satisfy the static stability criterion, i.e. [Formula: see text] for [Formula: see text][Formula: see text]g/cm3(stable region) and for [Formula: see text][Formula: see text]g/cm3, the region is unstable i.e. [Formula: see text].

A New Charged Anisotropic Compact Star Model in General Relativity

In the present article, we explore a new static, spherically symmetric charged anisotropic fluid model of compact star in curvature coordinates. We consider metric potential g44 of Durgapal’s fifth solution [1] with a specific choice of electric field intensity E and physically acceptable expression of anisotropy factor Δ , which involve parameters K (charge) and Δ (anisotropy) respectively. The solution so obtained is utilized to construct the model for superdense star like neutron star. We have analysed that corresponding to X=0.1, K=2.8, a=1.6 and by assuming surface density , the mass of the compact star comes out to be with radius 14.51 kms, which closely resembles to that of PSRJ0348 + 0432. The solution is well behaved for the values of K satisfying 1≤K5. Our model is described analytically as well as with the help of graphical representations. Our solution is well behaved and free from any central singularity. It also satisfies all the energy conditions as well as the causality condition thus reconfirming the stability of our model.

Anisotropic charged compact star of embedding class I

In this paper, we present a model of a compact relativistic anisotropic star in the presence of an electric field. In order to obtain an exact solution of the Einstein–Maxwell field equations, we assume that the stellar material inside the star obeys a Chaplygin equation of state which is a nonlinear relationship between the radial pressure and the matter density. Using Tolman’s metric potential for [Formula: see text], we obtain the other metric co-efficient by employing the Karmarkar condition which is a necessary and sufficient condition for the interior spacetime of our model to be of embedding class I. Our stellar model is free from central singularity and obeys all the conditions for a realistic stellar object.

Generalised model for anisotropic compact stars

In the present investigation an exact generalized model for anisotropic compact stars of embedding class one is sought for under general relativistic background. The generic solutions are verified by exploring different physical aspects, viz. energy conditions, mass-radius relation, stability of the models, in connection to their validity. It is observed that the model present here for compact stars is compatible with all these physical tests and thus physically acceptable as far as the compact star candidates $RXJ~1856-37$, $SAX~J~1808.4-3658~(SS1)$ and $SAX~J~1808.4-3658~(SS2)$ are concerned.

Compact Stars of Emending Class One in f(T) Gravity

In this paper, we study the spherically symmetric anisotropic compact stars of emending class one in f(T) (where T being the torsion of the spacetime) gravity. For this purpose, we have used a particular form of the metric functions to solve the modified equation of motion in f(T) gravity for static anisotropic fluid source. The constructed models represent the class of anisotropic stars like $$SAX J 1808.4-3658 (SS1)$$ , $$Her X - 1, Vela X-12, PSR J1614-2230$$ and $$Cen X -3$$ . We have calculated the physical parameters of the stars such as pressure, density, regularity and anisotropy. We have also discussed the stability of formulated models and proved that in f(T) theory of gravity (with diagonal tetrad) these models of the stars are unstable.

Well behaved anisotropic compact star models in general relativity

Anisotropic compact star models have been constructed by assuming a particular form of a metric function \(e^{\lambda}\). We solved the Einstein field equations for determining the metric function \(e^{\nu}\). For this purpose we have assumed a physically valid expression of radial pressure (\(p_{r}\)). The obtained anisotropic compact star model is representing the realistic compact objects such as PSR 1937 +21. We have done an extensive study about physical parameters for anisotropic models and found that these parameters are well behaved throughout inside the star. Along with these we have also determined the equation of state for compact star which gives the radial pressure is purely the function of density i.e. \(p_{r}=f(\rho)\).

Modelling of anisotropic compact stars of embedding class one

In the present article, we have constructed static anisotropic compact star models of Einstein field equations for the spherical symmetric metric of embedding class one. By assuming the particular form of metric function $\nu$, We have solved the Einstein field equations for anisotropic matter distribution. The anisotropic models are representing the realistic compact objects such as SAX J 1808.4-3658 (SS1), Her X - 1, Vela X-12, PSR J1614-2230 and Cen X - 3. We have reported our results in details for compact star Her X-1 on the ground of physical properties such as pressure, density, velocity of sound, energy conditions, TOV equation and red-shift etc. Along with these, we have also discussed about stability of the compact star models. Finally we made the comparison between our anisotropic stars with the realistic objects on the key aspects as central density, central pressure, compactness and surface red-shift.

Physical behavior of anisotropic compact stars in f(R, T, RμνTμν) gravity

This paper investigates the behavior of anisotropic compact stars in the background of R + αRμνTμν gravity model. For this purpose, we use Krori–Barua metric solutions where constants are calculated using masses and radii of compact stars like Her X-1, SAX J 1808.4–3658, and 4U1820–30. We analyze regular behavior of effective energy density, and radial and transverse pressures in the interior of compact stars. We also discuss energy conditions, effect of anisotropic factor, and stability criteria of these stars. It is concluded that the considered compact star models satisfy all the energy conditions and remain stable against the anisotropic effect in this gravity.

Anisotropic compact star with Tolman IV gravitational potential

In the current paper we have investigated a well-behaved new model of anisotropic compact star in (\(3+1\))-dimensional spacetime. The exterior spacetime is described by the Schwarzschild vacuum solution. The model is obtained in the background of Tolman IV \(g_{rr}\) metric potential. Our model is free from central singularities and satisfies all energy conditions. The solution is compatible with observed masses and radii of a few compact stars like Her X-1, PSR J0737-3039A, PSR B1913+16, RX J1856.5-3754, Cyg X-2 and PSR J1903+0327.