Fractional X-ray luminosity as a function of mass for Collinder 69 members within the field-of-view of the two XMM-Newton observations. X-ray detections are represented as solid circles (blue and cyan for probable and possible members, respectively). Cluster members without X-ray detection appear as solid – dark gray – triangles. Class II and Class III sources with thick or thin/transition disks, as defined by IRAC photometry, are highlighted with large solid and dotted open circles, respectively. The vertical dotted and long-dashed – magenta – line locates the completeness limit (in mass) of the X-ray observations.