Using Strichartz estimates, it is possible to pass to the limit in the weakly compressible 2-D Euler system, when the Mach number tends to zero, even if the initial data are not uniformly smooth. More precisely, their norms in Sobolev spaces embedded in C 1 can be allowed to grow as small powers of −1 .This leads to results of convergence to solutions of the incompressible Euler system whose regularity is critical, such as vortex patches or Yudovich solutions.