We report on our analysis of a large sample of energy dependent pulse
profiles of the X-ray binary pulsar Hercules X-1. We find that all data are
compatible with the assumption of a slightly distorted magnetic dipole field as
sole cause of the asymmetry of the observed pulse profiles. Further the
analysis provides evidence that the emission from both poles is equal. We
determine an angle of 20 deg between the rotation axis and the local magnetic
axis. One pole has an offset of 5 deg from the antipodal position of the other
pole. The beam pattern shows structures that can be interpreted as pencil- and
fan-beam configurations. Since no assumptions on the polar emission are made,
the results can be compared with various emission models. A comparison of
results obtained from pulse profiles of different phases of the 35-day cycle
indicates different attenuation of the radiation from the poles being
responsible for the change of the pulse shape during the main-on state. These
results also suggest the resolution of an ambiguity within a previous analysis
of pulse profiles of Cen X-3, leading to a unique result for the beam pattern
of this pulsar as well. The analysis of pulse profiles of the short-on state
indicates that a large fraction of the radiation cannot be attributed to the
direct emission from the poles. We give a consistent explanation of both the
evolution of the pulse profile and the spectral changes with the 35-day cycle
in terms of a warped precessing accretion disk.Comment: 24 pages, 12 figures. To appear in ApJ 529 #2, 1 Feb 200