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We have studied the long-term (1971-2005) behaviour of the 1.24 sec pulseperiod and the 35 day precession period of Her X-1 and show that both periodsvary in a highly correlated way (see also Staubert et al. 1997 and 2000). Whenthe spin-up rate decreases, the 35 day turn-on period shortens.This correlationis most evident on long time scales (~2000 days),e.g.around four extendedspin-down episodes, but also on shorter time scales (a few 100 days) on whichquasi-periodic variations are apparent. We argue that the likely common causeis variations of the mass accretion rate onto the neutron star.The data since1991 allow a continuous sampling and indicate a lag between the turn-onbehaviour and the spin behaviour, in the sense that changes are first seen inthe spin, about one cycle later in the turn-on. Both the coronal wind model(Schandl & Meyer 1994) as well as the stream-disk model (Shakura et al.999)predict this kind of behaviour.Comment: 6 pages, 4 figures, In: The transient Milky Way: a perspective for  MIRAX, AIP Conf. Proc. 840 (2006) 65-7

Long-term developments in Her X-1: Correlation between the histories of the 35 day turn-on cycle and the 1.24 sec pulse period