Power spectra, with application to EXOSAT data.

Abstract

It is shown how an instrumental effect, coupled with the on-board computer sampling, affects the pulse-height analysis data obtained from Exosat, and analytic expressions are developed to remove these effects from the data for the case of small source variability. In the method, the expectation of the power spectrum is the Fourier transform of the derived autocovariance function. The present analytic expressions have been tested on Exosat data on Cir X-1 obtained for days 56-57 of 1986. Some problems with the estimation parameter values from power spectra are also considered. It is noted that the present method can be extended to other applications and to other instruments.