Non-geodesic corrections required for a given model, spin and source. The red curves indicate the minimal corrections required in the case of GRS 1915+105. Parts of these curves with a negative sign also roughly indicate the corrections required for the other two microquasars. The blue curves indicate positive corrections for these microquasars determined by the lower limit to their M  ×  ν_U indicated by the blue dotted horizontal line in Fig. 2.