Stable Gravastars: Guilfoyle's electrically charged solutions

Abstract

Compelling alternatives to black holes, namely, gravitational vacuum star ({\it gravastar}) models, the multilayered structure compact objects, have been proposed to avoid a number of theoretical problems associated with event horizons and singularities. In this work, we construct a spherically symmetric thin-shell charged gravastar model where the vacuum phase transition between the de Sitter interior and the external Reissner--Nordstr$\ddot{\text{o}}$m spacetime (RN) are matched at a junction surface, by using the cut-and-paste procedure. Gravastar solutions are found among the Guilfoyle exact solutions where the gravitational potential $W^2$ and the electric potential field $\phi$ obey a particularly relation in a simple form $ a\left(b-\epsilon \phi \right)^2 +b_1$, where $a$, $b$ and $b_1$ being arbitrary constants. The simplest ansatz of Guilfoyle's solution is implemented by the following assumption: that the total energy density $8\pi \rho_m+\frac{Q^2}{ r^4}$ = constant, where $Q(r)$ is the electric charge up to a certain radius $r$. We show that, for certain ranges of the parameters, we can avoid the horizon formation, which allows us to study the linearized spherically symmetric radial perturbations around static equilibrium solutions. To lend our solution theoretical support, we also analyze the physical and geometrical properties of gravastar configurations.