  We present a detailed analysis of observations of the high mass X-ray binary
Cen X-3 spanning two consecutive binary orbits performed with the RXTE
satellite in early March 1997. The PCA and HEXTE light curves both show a clear
reduction in count rate after mid-orbit for both binary revolutions. We
therefore analyze two broad band spectra for each orbit, before and after
mid-orbit. Consistent with earlier observations these four joint PCA and HEXTE
spectra can be well described using a phenomenological pulsar continuum model,
including an iron emission line and a cyclotron resonance scattering feature.
While no strong spectral variations were detected, the second half of orbit 2
shows a tendency toward being softer and more strongly absorbed. In order to
follow the orbital phase-dependent evolution of the spectrum in greater detail,
we model spectra for shorter exposures, confirming that most spectral
parameters show either a gradual or sudden change for the second half of the
second orbit. A comparison with a simple wind model indicates the existence of
an accretion wake in this system. We also present and discuss high resolution
pulse profiles for several different energy bands, as well as their hardness
ratios. PCA and HEXTE spectra were created for 24 phase bins and fitted using
the same model as in the phase averaged case. Systematic pulse phase-dependent
variations of several continuum and cyclotron line parameters were detected,
most notably a significant increase of the cyclotron line energy during the
early rise of the main peak, followed by a gradual decrease. We show that
applying a simple dipole model for the magnetic field is not sufficient to
describe our data.
