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XMM-Newton Science Analysis System


evselect (evselect-3.60.2) [xmmsas_20080701_1801-8.0.0]

Meta Index / Home Page / Description / Extraction Stage (extractor)

Products creation

The selection stage yields a modified event list in which the events which do not satisfy the selection expression are removed or appropriately flagged. From this list the extraction stage creates images, spectra, and rates files. These products are aimed to adhere to OGIP standards as closely as possible. Please note, however, that it is likewise possible to create data sets which do not map onto any standard OGIP file type, e.g. PHA-versus-wavelength image for RGS. Evselect also provides for extracting a histogram from a column of an event list. This product is for general use and does not conform to any OGIP standard.

The product creation process can be controlled via various command line parameters such as binning factors, cut-off boundaries, etc. Only one product file of each kind can be constructed per evselect run. If more than one file is required, e.g. time series files in different energy bands, evselect has to be run repeatedly. The parameters blockstocopy and attributestocopy can be used to copy selected blocks and attributes from the input file to the output product files. See the following subsections for a more detailed description of the production of the individual data product types.

For binned products, binning of a given column is in general controlled by a minimum value, a binning factor, and a maximum value. For integer-valued columns, these 3 parameters are all required to be integer-valued. In this case, any event with a value equal to the minimum value will be put into the first bin, and any event with a value equal to the maximum value will be put in the last bin. Thus for example, if the minimum value is 4, and the binning factor 3, then events with values of 3, 4 and 5 will be put into the first bin.

Information about the filtering criteria used to produce the product files will be stored in data blocks and attributes of the files using a data subspace model as described in [1]. See also documentation on the dsslib package.