The standard background 0.1-10.0 keV count rate in the central 8 radius source extraction region is s-1 keV-1 arcmin-2. The dependence of the standard background count rate on position within the FOV is shown in the left panel of Fig. 3. This image has been smoothed using a Gaussian filter with a of 4 RAW pixels. The difference in intensity between the most and least intense regions is a factor 1.8. The X-ray background appears brighter close to the center of the image due primarily to mirror vignetting. Note that the LECS mirror axis is offset by 3 from the center of the FOV due to an alignment error during integration. The two bright arcs are located radially inwards from the 55Fe calibration sources and result from 5.9 keV characteristic X-rays that are absorbed some distance from their origin.
|Figure 3: The dependence of the LECS standard background (left panel) and NXB (right panel) on RAWX, RAWY position within the FOV. Gaussian smoothing filters with a of 4 pixels have been applied|
Figure 4 illustrates the overall shape of the standard background spectrum obtained in the central 8 of the FOV. The Non X-ray background (NXB) obtained from the same region of the detector is also shown (see Sect. 5). The difference between the two is the contribution of the cosmic X-ray background (CXB), spectral fits to which are presented in a companion paper (Parmar et al. 1999).
|Figure 4: Rebinned spectrum of the standard background (filled circles) and the NXB (open circles) in the central 8 radius of the FOV|
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