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XMM-Newton Science Analysis System


embadpixfind (embadpixfind-2.1.1) [xmmsas_20050815_1803-6.5.0]

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Dark features

If finddead=Y, embadpixfind looks for too dark pixels, rows and columns too. The Li and Ma formula (Eq.1) is not used for dark pixels. The Gaussian significance is computed in the same way (but on the negative side) and the cumulative binomial probability is computed from:

$$P(k \le N_{\rm on}) \; = \; \sum_{k=0}^{N_{\rm on}} p_B(k,N_{\rm tot},q) \; = \; I_{1-q}(N_{\rm off},N_{\rm on}+1)$$ (3)

The statistics in a single observation is usually not enough to find any dark pixel, but dark rows or columns may be found. The maxratio parameter avoids detecting 'grey' pixels, rows or columns on observations with high statistics.

Whatever findbright and finddead, dark and bright columns and rows are always searched for together in order of decreasing significance (either positive or negative). This avoids finding spurious bright columns/rows next to very dark ones, and vice-versa.

If one of findbright or finddead is set to False, the corresponding bad pixels/columns/rows are not written to the output file.