Core-envelope model of super dense star with distinct equation of states

Neeraj Pant,Satyanarayana Gedela,Ravindra K. Bisht,R. P. Pant

doi:10.1140/epjc/s10052-019-7098-4

Neeraj Pant, Satyanarayana Gedela

Open Access

https://doi.org/10.1140/epjc/s10052-019-7098-4

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Abstract

The aim of the present paper is to study an anisotropic spherically symmetric core-envelope model of a super dense star in which core is equipped with linear equation of state, consistent with the quark matter while the envelope is considered to be of quadratic equation of state by adopting the philosophy of Takisa et al. (Pramana J Phys 92:40, 2019). We demonstrate that all the physical parameters are realistic within the core as well as envelope of the stellar object and continuous at the junction. Our model is shown to be physically viable and substantiate with the strange stars SAX J1808.4-3658 and 4U1608-52. Further, We infer that if the mass of the star increases then central density results to higher values and core shrinks, which justifies the dominating effect of gravity for higher mass celestial objects.

Highlights

The composition of a super dense stellar material determines various macroscopic features including moment of inertia, degree of compactness, approximate values of mass and radius of a star
We infer that if the mass of the star increases central density results to higher values and core shrinks, which justifies the dominating effect of gravity for higher mass celestial objects
The demand of more input parameters, viz, central density and density at the boundary suggests employing of two different equation of state (EOS) to construct a realistic stellar model

Summary

Introduction

The composition of a super dense stellar material determines various macroscopic features including moment of inertia, degree of compactness, approximate values of mass and radius of a star. By motivation of the pioneer work of [47], we explore an anisotropic spherically symmetric core-envelope model of a super dense star in which core is equipped with linear EOS consistent with the quark matter while the envelope is considered to be of quadratic EOS with Tolman VII type metric potential (grr ) such that eλ is 1 at origin geometrically non-singular By virtue of this all physical parameters (density, pressures, red-shift, compactfication factor, anisotropic constants, causality condition, adiabatic index, energy conditions) are realistic within the core as well as the envelope of the stellar object and regular at the junction (interface). Our model is shown to be physically viable and substantiate with the strange stars SAX J1808.4-3658 and 4U1608-52 [48]

A system of the Einstein field equations

Conditions for a physically realistic core-envelope model

The core-envelope model

25 Ab2 8π

Continuity at the boundary

Density and pressures trends

Adiabatic index

Energy conditions

TOV equation of core-envelope model

Conclusion