Static circularly symmetric perfect fluid solutions with an exterior BTZ   metric
  In this work we study static perfect fluid stars in 2+1 dimensions with an exterior BTZ spacetime. We found the general expression for the metric coefficients as a function of the density and pressure of the fluid. We found the conditions to have regularity at the origin throughout the analysis of a set of linearly independent invariants. We also obtain an exact solution of the Einstein equations, with the corresponding equation of state $p=p(\rho)$, which is regular at the origin. 
Norman Cruz, Marco Olivares and Jose Villanueva