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tokens: mass vs. period of h Per members, including detected and non-detected X-ray sources. For MS stars the separation between saturated and non-saturated regimes occurs at fixed values, regardless of stellar mass. When is computed as , this threshold occurs at ( Wright et al. 2011 ), which turns into when it is taken into account that . Therefore, assuming that the same applies to intermediate-age PMS stars and considering the internal structures of 13 Myr old stars of different masses, it is possible to compute rotational periods corresponding to this value. We report in Fig. 7 this expected separation between non-saturated and saturated regimes (blue dashed line). We also computed where the supersaturated regime is expected to occur. However, the paucity of observational constraints of supersaturation makes this prediction more uncertain. Hence we considered the two physical mechanisms suggested to explain the supersaturation: centrifugal stripping ( Jardine Unruh 1999 ) and polar updraft migration ( Stȩpień et al. 2001 ). The centrifugal stripping mechanism predicts that coronal emission might be reduced when rotational velocity increases because the largest coronal structures might be disrupted by the centrifugal force. This mechanism takes place when the largest coronal structures extend beyond the co-rotation radius 4 . Assuming therefore that centrifugal stripping becomes effective when the co-rotation radius is smaller than (i.e., assuming that coronal structures extending up to above the photosphere), as suggested by Wright et al. (2011) , we obtained the dash-dotted red line shown in Fig. 7 . The polar updraft effect instead predicts that when the rotational velocity increases, then the magnetic flux emergence becomes more efficient near stellar poles, leaving the equatorial regions free of magnetic flux tubes and hence without coronal structures. Wright et al. (2011) quantified the efficiency of this mechanism by defining the parameter where and are the mass and radius of the radiative core, is its rotational angular velocity, and is the colatitude on stellar surface. Considering MS stars, they suggested that supersaturation occurs where . Considering again the internal structures of 13 Myr old stars, assuming that the core rotates with the same period as the convective envelope and averaging over the stellar surface, we computed the locus corresponding to and report this threshold with a red dashed line in Fig. 7 . A more detailed discussion on centrifugal stripping and poleward migration is reported in Sect. 5 . Fig. 7 Mass vs. period of X-ray selected h Per members detected (black) and undetected (gray) in X-rays. Filled and open symbols indicate single and binary stars, respectively. Red lines separate the loci corresponding to supersaturation and saturation, assuming centrifugal stripping (dash-dotted line) or polar updraft (dashed line) theories. The blue dashed line marks the expected separation between non-saturation and