XMM-Newton Science Analysis System


evselect (evselect-3.62) [xmmsas_20141104_1833-14.0.0]

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Filtering stage (selector)

The filtering process is carried out on an event-by-event basis controlled by user-specified selection criteria which take the form of a single boolean expression. The expression can contain symbolic names of ``intrinsic'' event attributes, and numeric constants combined with logical and arithmetic operators and functions. Events for which the expression does not evaluate to true will be marked as invalid or discarded from the data set and shall not be considered in the product extraction.

evselect supports selections based on intrinsic event attributes. These attributes are present in the input event list table as corresponding columns, the names of which are to be used in the selection expression. This group further falls into the following sub-categories:

1. spatial selections in raw pixel (RAWX/RAWY), physical detector (DETX/DETY) or sky pixel (X/Y) space, or indeed in any spatial coordinate system (e.g. TELX/TELY). Special pre-defined region shapes exists such as CIRCLE, ELLIPSE, ANNULUS, BOX, POLYGON. Spatial filtering with mask images is possible as well.

2. energy selections in the form of one or more interval specifications in either PHA or PI space.

3. time selections in the form of
   1. one or more interval specifications
   2. one or more Good Time Interval (GTI) files created with tabgtigen or any other SAS tasks which creates GTI files as output
4. any other event attributes which are present (e.g. PATTERNID, or CCDID, or WAVELENGTH in case of RGS)