Charged gravastar model in Rastall theory of gravity

Abstract

Gravastars are considered as one of the prime exotic type compact objects which may be found at the end state of gravitational collapse of massive stars with a view to resolve the complexities that are pertinent in case of a black hole \cite{Mazur}-\cite{Mazur2}. In this paper, we analyse the role of charge on the possible formation of isotropic spherically symmetric gravastar configuration in the framework of Rastall gravity. Gravastar contains three distinct layers {\it viz.} i) Interior region, ii) Thin shell and iii) Exterior region. The interior region is characterised by the equation of state $p=-ρ$ that defines the repulsive outward pressure in radial direction at all points on the thin shell. The thin shell, contains ultra-relativistic stiff fluid which is denoted by the equation of state $p=ρ$ following Zel'dovich's criteria \cite{Zeldovich,Zeldovich1} for cold baryonic universe, can withstand the repulsive pressure exerted by the interior region. The exterior region is the vacuum space-time represented by the Reissner-Nordstr$\ddot{o}$m solution. In view of the above specifications, we construct and analyse a charged gravastar model in Rastall theory of gravity which represents several salient features. The basic physical attributes, {\it viz.} proper length, energy, entropy and equation of state parameter of the shell are investigated. In this model, it is interesting to note that for large value of the radius of hyper-surface (R) the EoS parameter of the thin shell corresponds to dark energy EoS with $\mathcal{W}(R)\rightarrow-1$. However, for small value of $R$ the EoS parameter $\mathcal{W}(R)\rightarrow0$, defines a dust shell. The stability of the model is ensured through the study of gravitational surface redshift and maximisation of shell entropy within the framework of Rastall theory of gravity.