Wyman's solution, self-similarity and critical behaviour

We show that the Wyman’s solution may be obtained from the four-dimensional Einstein’s equations for a spherically symmetric, minimally coupled, massless scalar field by using the continuous self-similarity of those equations. The Wyman’s solution depends on two parameters, the mass $M$ and the scalar charge $\mathrm{\Sigma }$. If one fixes $M$ to a positive value, say $M_0$, and let ${\mathrm{\Sigma }}^2$ take values along the real line we show that this solution exhibits critical behaviour. For ${\mathrm{\Sigma }}^2>0$ the space-times have eternal naked singularities, for ${\mathrm{\Sigma }}^2=0$ one has a Schwarzschild black hole of mass $M_0$ and finally for $-M_0^2\le {\mathrm{\Sigma }}^2<0$ one has eternal bouncing solutions.