5. Summary

The various X-ray observatories used in this work have different characteristics which make them useful for investigating different properties of Cen X-3. BBXRT was useful for iron line spectroscopy as it covered the iron line region with high spectral resolution and an extremely low background. Although it covered the iron line region with worse spectral resolution than BBXRT, the EXOSAT GSPC had a better high energy response which allowed the shape of the continuum spectrum to be investigated. The ASCA SIS has slightly better spectral resolution than BBXRT, allowing the iron line to be further resolved. The spectral resolution of the ASCA GIS is only slightly better than that of the EXOSAT GSPC but the imaging capabilities allow more reliable subtraction of the X-ray background. The RXTE PCA covers the energy range from 15 to 60 keV. HEXTE covers the range from 15 to 200 keV. The background subtraction in HEXTE is better than that in the PCA but it has poorer energy resolution. In Figure 5 I show the energy responses of these instruments. These are total effective area curves appropriate for the data analysed in this work. They were derived from the ARF and RMF files that were generated for the Cen X-3 data. Because of vignetting the effective areas shown here will generally be smaller than the advertised values. In Table 5 I list the X-ray observatories used in this dissertation along with the main results.

Figure 6: Comparison of the effective areas of the X-ray telescopes used in this work. The SIS effective area is not much different from that of the GIS and has been omitted for clarity.

Table 1: X-ray observatories and results used in this dissertation.

Mission	Mission Dates	Results
EXOSAT	1983 May 26-1986 April 9	Continuum Spectrum -- consistent
		with cyclotron opacity
BBXRT	1990 December 2-11	Partially resolved iron lines,
		predicted CSRF from QPO
ASCA	1993 February 20-	Resolved iron lines,
		6.4 keV line pulsed
RXTE	1995 December 30-	Detected CSRF