Figure 11.

Cartoon shows possible origins of dippers and UXors, and why Sun-like stars may only rarely show analogous behaviour. In each case the star, magnetic dipole and rotation axis are shown at the left (the stellar magnetic field is not necessarily always tilted with respect to the disc). Possible disc structures viewed edge-on to the right. (a) Low-mass stars (dippers) are occulted by co-rotating material that is accreting onto the star, and the dust sublimation radius is interior to co-rotation [34]. (b) Sun-like stars are rarely seen as dippers or UXors because (i) dust sublimates outside co-rotation (represented by the grey accretion column in the upper half [34]) or (ii) material lifted by turbulence is shadowed by the outer disc (spiral in the lower half). (c) Herbig Ae/Be stars (UXors) are occulted by turbulence that appears above self-shadowed discs [33].