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XMM-Newton Science Analysis System


omdetect (omdetect-5.14.2) [???]

Meta Index / Home Page / Source Flagging Algorithms

Source lies near to a bright source - bit 6

Any source either having a raw count-rate >= 80, or with quality flag bit 4 set (mod-8 pattern) is checked for "close" neighbours, which may be flagged.

The algorithm is as follows

Check each source in the vicinity of the bright source

1. Ignore any neighbour with quality bits 4 or 6 set or has a greater count rate.
2. Compute the maximum distance for flagging the source from maxRad = max(exclusionradius, min(70.0, 35.0 * countTable(i) // 80.0) ) If the flagging is done by omdetect, the exclusion radius is determined from the algorithm at the end

3. If the neighbour lies within this radius, flag the star.

Exclusion radius algorithm (omdetect)

The algorithm is as follows:

1) Determine the mean pixel value around the centre of the source, for a series of increasing radii from the centre.

2) Fit a polynomial to these values.

3) Compute the radius at which the profile reaches the background value, and set the exclusionradius equal to this value.