Effective Area of the AXAF X-Ray Telescope: Dependence upon Dielectric Constants of Coating Materials

This study examines the dependence of the effective area of the AXAF x-ray telescope, upon the complex dielectric constants of possible mirror coatings, over the energy range 0.1–10 keV. At energies near and above the astrophysically important iron-line complex near 6.7 keV, the effective area is very sensitive to the coating density on the three innermost of the telescope's six mirror pairs. Thus, it is desirable to achieve as high a density as feasible. The telescope's spectral response exhibits sharp features at absorption edges of the coating materials. In view of the exceptional energy resolution of the AXAF spectrometers and uncertainties in reflectivities (especially near absorption edges), the AXAF goal of 1% accuracy requires both precise x-ray calibration of the telescope and improved modeling of the telescope and calibration sources. Presented here in the form of plots, the results are also available (on floppy disks) in tabular form.