1. The pulse profile

The pulse profile of Cen X-3 has been observed as an asymmetric single peak in the high state (e.g. Audley et al. (1996), see Chapter 5) and a double peaked structure in the low state (e.g. Nagase et al. (1992)).

The mean unabsorbed 2-10 keV luminosity during the present observation was 5 x 10³⁶ erg s^-1, while it was 3.29 x 10³⁷ erg s^-1 during the BBXRT observation when the profile had a single asymmetric peak (Audley et al. (1996)). The pulse profile varies during the present observation, becoming less double-peaked during the ``flare'' at $\phi$ = 0.4. Another trend which is evident from figure 3.3 is that the two peaks in the profile appear to swap places as the intensity increases. Before the ``flare'' the peak which follows the pulse minimum dominates. After the ``flare'' the peak which precedes the minimum is more prominent. During the ``flare'' itself this latter peak is less significant and the pulse profile is in effect an asymmetric single peak, as often seen in Cen X-3's high state.

This indicates that the observed differences in the pulse profile of Cen X-3 may be due to luminosity induced changes in the structure of the accretion column as observed in EXO 2030+375 (Parmar et al. (1989)).