XMM-Newton Science Analysis System: User Guide

7.1.2 Output

Three log files are stored in the current working directory from where the tool is launched:

• xmmextractor.err: Containing errors
• xmmextractor.warn: Containing warnings
• xmmextractor.info: Containing runtime information

The output is stored in different subdirectories that are created in the current working directory from where the tool is launched. The output is organised in the following subdirectories:

• pn, mos, rgs, and om: output of epchain, emchain, rgsproc, and omichain. If OM fast mode and/or grisms were used, the respective output of omfchain and omgchain will also be stored in the subdirectory om. In particular, the fully calibrated events files for all EPIC cameras, RGS and OM fast mode (if used) can be found in these directories.
• lcurve: EPIC and RGS source and background plus background-subtracted light curves. For EPIC the source and background region files as well as a single region file containing both region definitions are also stored in this directory.
• spectra: Spectra and response matrices for all EPIC instrument (RGS spectra are in rgs directory). Source and background region files as well as a single region file containing both region definitions are also stored for MOS1, MOS2, and pn in this directory.
• epatplot: diagnosis plot for pile up in EPIC instruments
• images: images of source regions for each sources found by edetect
• gti: Good Time Intervals used for time filtering (fits format)
• results: log files containing extraction parameters and science results

By default, all data from all instruments are analysed for the proposal coordinates. Other (sky) coordinates can be provided in decimal degrees using the parameters ra and dec in the configuration file. Seven analysis options are available, producing all products (default), only evens files, only doing gti correction (see below), only run edetectchain, produce only EPIC spectra and/or light curves, and only produce RGS light curves. These options are specified by setting the parameter analysisoption to 0:all, 1:events, 2:gti, 3:edetectchain, 4:epic_spectra, 5:epic_lightcurve, or 6:rgs_lightcurve. Analysis options 1-6 can only be used if events files are already present. For details, see the package description of xmmextractor.

An important step is to filter out intervals of high background in order to increase the signal to noise in EPIC spectra. This is described in § 4.4. Time intervals of high particle background are automatically excluded by xmmextractor using the criteria defined by the parameters defined in the $<$TASK purpose="gti_creation" name="tabgtigen"$>$ corresponding subsections in the configuration file for each instrument.

The default parameters follow the recommendations in the documentation, but the flare background light curves stored in the subdirectory gti/ should be checked to see if the standard parameters are appropriate for the specific observation. The gti correction is only done for EPIC spectra but not for light curves, because low signal-to-noise data are still better than gaps in a light curve.

For EPIC spectra and light curves, it is important to check for the presence of pile up. In § 4.5, a procedure is described how to assess the extent of pile up and how to correct for it. The first step is already done by xmmextractor. The diagnostics plots created by epatplot can be found in the subdirectory epatplot. If pile up is diagnosed, an annular source extraction has to be used. A user-defined format source extraction region can be communicated to xmmextractor by manipulating the corresponding expressions, $<$PARAM id="srcexp" default="expr"$>$, for each instrument where expr can be any region expression. The default is an annular extraction region with an inner radius of zero pixels, thus a circular region. The inner radius determined from following the pile-up thread can be modified by hand before rerunning the tool.

In addition to pipeline processing of all products, interactivity modes are currently being developed. These will allow the user to define individual source- and background extraction regions on a displayed ds9 image of the events file, define observation-specific good time intervals by looking at the particle background light curve, and perform pile up correction in an interactive iteration procedure.