1. The pulse profile

The pulse profile observed with BBXRT is single-peaked with a weak secondary pulse. The secondary pulse appears slightly weaker at low energies. The pulse profile is similar to that seen in previous observations of Cen X-3 most of the time (e.g. White et al. (1983)). However, the pulse profile observed during the Ginga observation had two peaks of comparable amplitude. This double-peaked pulse profile is seen only rarely (e.g. Long et al. (1975); Nagase et al. (1992); Tuohy (1976)).

The unabsorbed luminosity observed with BBXRT was 3.29 x 10³⁷ erg s^-1 in the 2-10 keV band assuming a distance of 8 kpc. This value was derived using the relaxed data quality filter described in Section 2.2 in order to minimize the effect of rejected events. In the high post-egress phase of the Ginga observation the 1-37 keV luminosity was 5 x 10³⁷ erg s^-1 which corresponds to a luminosity in the 2-10 keV band of 2.4 x 10³⁷ erg s^-1. This indicates that the differences in the pulse profile of Cen X-3 observed with Ginga and BBXRT may be due to luminosity induced changes in the structure of the accretion column as observed in EXO 2030+375 (Parmar et al. (1989)). Precession of the neutron star or variable obscuration might also be involved.