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A new SAS background task

A new SAS background task. Why a SAS background task?. Point sources in FF modes: Source and background regions could be well defined. Background subtraction possible. MOS SW mode: No background region in central CCD, but in peripheric CCDs. Background subtraction possible.

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A new SAS background task

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  1. A new SAS background task

  2. Why a SAS background task? • Point sources in FF modes: Source and background regions could be well defined. Background subtraction possible. • MOS SW mode: No background region in central CCD, but in peripheric CCDs. Background subtraction possible. • PN SW: Could be very difficult to define background region. For very bright sources no background in SW area. • Extended sources: If diameter of the source > FOV definition of background region impossible.  background model needed. Martin Stuhlinger, ESAC

  3. Examples Martin Stuhlinger, ESAC

  4. Working scheme for PN FF/MOS • Get particle+electronic background from out-FOV regions. (Sufficient statistics for short observations?) • Scale particle background region to user defined background region. • Subtract particle bkg from user defined bkg to get photon background. • Correct photon background for vignetting effects. • Add corrected photon bkg and particle bkg to total background. • Scale total background to the user defined source region.  Implementation as SAS task. Martin Stuhlinger, ESAC

  5. PN SW / Extended sources • No out-FOV area: Template for particle background needed. • Investigate rules when local background is available: - Source brightness: Possible count rate limit. - Position of the source inside the small window area. • No local background available: background template needed. - Template for particle background. - Template for photon background.  “Background button” Martin Stuhlinger, ESAC

  6. Problems of background templates • Templates could be extracted using XMM data archive. • Background is a composite of various components: • Electronic noise, proton flares, cosmic particles, CCD fluorescence, cosmic photon background • Each component can show different spectral, temporal and spatial variability (see results of former background workshops).  Good understanding of each background component is needed to understand how successful these templates can be used and how these templates can be used successfully. Martin Stuhlinger, ESAC

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