Study on anisotropic strange stars in Rastall gravity

I. G. Salako ; D. R. Boko ; G. F. Pomalegni ; M. Z. Arouko

Teoretičeskaâ i matematičeskaâ fizika, Tome 208 (2021) no. 3, pp. 522-543

Résumé

The strange quark matter (SQM) whose distribution is governed by the simplified MIT bag model equation of state has been the subject of a series of investigations within the framework of Rastall's theory. We obtain an exact solution of the modified form of the Tolman–Oppenheimer–Volkoff (TOV) equation in the Rastall gravity theory and study the dependence of different physical properties (the total mass, radius, energy density, and pressure) for the chosen values of the Rastall parameter $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}$. To examine physical acceptability of the proposed stellar model, we conduct different tests in detail: the energy conditions, the the mass–radius relation, the Compactification factor, the redshift, the system stability, the modified TOV equation, the causality condition, and the adiabatic index in terms of $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}$. We precisely explain the effects arising due to the Rastall parameter and geometry on the compact stellar system. We find that as the factor $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}$ decreases, the strange star candidates become gradually massive and larger in size with a less dense stellar configuration. But when $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}$ increases, the stars shrink gradually and become less massive, turning into a more compact stellar system. For $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}>0$, our proposed model is therefore suitable for explaining the ultradense compact stars well within the observational limits; for $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}0$, it allows representing the recent massive pulsars and super-Chandrasekhar stars. For $\lambda_{\scriptscriptstyle{\mathrm{Ras}}}=1$, we retrieve the standard results of general relativity.

Détail

Keywords: dark energy theory, Rastall gravity, massive star.