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Astron. Astrophys. 340, 617-625 (1998)

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6. ROSAT PSPC response to theoretical X-ray spectra

The ROSAT Position Sensitive Proportional Counter has a rather poor spectral resolution, which can be roughly approximated by


where both the true energy E of the photon incident on the PSPC and its measured energy [FORMULA] are expressed in keV. The equation gives the full width at half maximum of a profile describing the scatter of energy measurements. Eq. (6.1) has been given in the Appendix F to the NASA Research Announcements, describing the ROSAT Guest Observer Program.

Theoretical X-ray spectra of both HZ 43 A and PG 0824+289, presented in the previous Sections, can easily be transformed to the shapes as if they were observed with the PSPC detector of a limited spectral resolution. After folding of true spectra with a normalized rectangular profile of width given by Eq. (6.1), the simulated observed spectra approach those obtained with classical Thomson scattering and the flux cutoff shifts to higher energies (0.7 keV, equivalent to 18 Å). There are practically no X-ray photons of such high energies, recorded by ROSAT from both white dwarfs. Therefore one can conclude, that the ROSAT PSPC archival data cannot be analysed to look for the observational confirmation of the energy cutoff in any of the two DA white dwarfs.

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© European Southern Observatory (ESO) 1998

Online publication: November 9, 1998