  We derive the equations for calculating the high-frequency asymptotics of the
local two-particle vertex function for a multi-orbital impurity model. These
relate the asymptotics for a general local interaction to equal-time
two-particle Green's functions, which we sample using continuous-time quantum
Monte Carlo simulations with a worm algorithm. As specific examples we study
the single-orbital Hubbard model and the three $t_{2g}$ orbitals of SrVO$_3$
within dynamical mean field theory (DMFT). We demonstrate how the knowledge of
the high-frequency asymptotics reduces the statistical uncertainties of the
vertex and further eliminates finite box size effects. The proposed method
benefits the calculation of non-local susceptibilities in DMFT and diagrammatic
extensions of DMFT.
