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Filtering Errors

Filtering Errors-more

April 20, 2001

These quick and dirty analysis results do not include background subtraction, and used a spectral extraction region narrower than in Automated Processing.

Long Wavelengths, HZ43

Top panel: HZ43 spectrum (+ order) with different levels of PI filtering, but no Status-Bit filtering.

Middle panel: Spectra normalized to unfiltered spectrum. Unfiltered spectrum contains about 3-6% background, which is largely removed by PI filtering (see bottom figure in Background Region), thus explaining why even the "0.5%" filtering curve falls about 3-4% below 100%. Periodic dips in the Heavy filtering curve are most apparent at long wavelengths.

Bottom panel: Effect of Status-Bit filtering, with spectra normalized to the Medium-PI-filtered spectrum. Status-Bit filtering without bit 21 removes an additional <1% of valid x-ray events, but Status Bit 21 causes large troughs. (Figures by B. Wargelin.)

Short Wavelengths (central segment), PKS2155

Same set of plots, for PKS 2155. As seen in the bottom panel, Status-Bit filtering on bit21 produces troughs in the spectrum, although not as deep as at longer wavelengths.

Middle panel details: The deep dips on either side of 0th order can be ignored--there were only a handful of counts. From -6 to +6 Angstroms, no filtering is applied (because of scattering, support structure diffraction, etc.) and the three curves are identical.

Other dips in the PI filtering curves occur at wavelengths where the spectrum has few x-ray counts, since the background (which is removed by filtering) makes up a larger fraction of the events.

Last modified: 06/14/02

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