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Last modified: 27 August 2013


Source Fluxes

Source fluxes are determined by aperture photometry in each science energy band. Aperture photometry measurements are obtained in the source region, and in an elliptical aperture that includes the 90% Encircled Counts Fraction of the PSF at the source location, with corrections applied for the PSF aperture fraction. The correction factor is computed from the ray-trace local PSF under the assumption that the source spatial distribution matches the local PSF.

Energy Bands

Aperture Photometry Fluxes

Aperture photometry quantities are derived from the binned image-equivalents of the Level 3 event files (while spectral fit fluxes are derived directly from event data). The image files, recorded in units of photons s-1 cm-2, are produced by subtracting the full-field background image in the appropriate science energy band from the filtered and blocked full-field event data, and dividing the result by the full-field exposure map. See the complete description of the full-field image file in the Data Products section.