The BBXRT Observation of Centaurus X-3
Session 69 -- Cataclysmic Variables and Pulsars
Oral presentation, Thursday, 10:30-12:00, Dwinelle 155 Room

## [69.07] The BBXRT Observation of Centaurus X-3

M. D. Audley, R. L. Kelley (NASA/GSFC)

The binary X-ray pulsar Cen X-3 was observed for about 1600 sec with the Broad Band X-Ray Telescope (BBXRT) in December 1990. This instrument consisted of a conical X-ray telescope and a Si/Li detector covering the range 0.3 - 12 keV with an energy resolution of 150 eV at 6 keV. This energy resolution was some four times better than previously attained. During the observation Cen X-3 was in the post-egress state with an orbital phase of about 0.27 measured from mid-eclipse. The unabsorbed luminosity of the source in the 2-10 keV band was found to be $3.7\times 10^{37}$ erg/sec, assuming a distance of 8.5 kpc. The spectrum in this energy range is best fit by a power law with interstellar absorption and line emission at 6.7 keV from H- and He-like Fe. The power law index and absorption column vary with pulse phase, which suggests that the spectrum is actually more complex than a simple power law. The Fe line has a width of about 280 eV and an amplitude that may vary with the pulse phase. This indicates that emission by H- and He-like Fe is responsible for the previously observed pulsation of the iron line (Day et al., 1992). There is also evidence for an iron fluorescence line at 6.4 keV.