  We investigate analytically and numerically the synchronization dynamics of
dipolarly coupled vortex based Spin-Torque Nano Oscillators (STNO) with
different pillar diameters. We identify the critical interpillar distances on
which synchronization occurs as a function of their diameter mismatch. We
obtain numerically a phase diagram showing the transition between
unsynchronized and synchronized states and compare it to analytical predictions
we make using Thiele approach. Our study demonstrates that for relatively small
diameters differences the synchronization dynamics can be described
qualitatively using Adler equation. However when the diameters difference
increases significantly, the system becomes strongly non-Adlerian.
