a) The mass distribution of all X-ray emitting stars (open histogram), and X-ray emitting stars with well determined spectral types (filled histogram). The filled circles show the Trapezium IMF, scaled to match the open histogram. The dash line shows the completeness limit of the X-ray observations (~0.4 M_⊙). b) The age distribution of all X-ray emitting stars (line-filled histograms) and X-ray sources with well determined spectral types (filled histograms). Both distributions yield a similar median age of  ~1 Myr. The solid-line histograms show the coeval model. The dashed-line histograms represent the model with an age distribution of 0.9  ±  0.9 Myr.