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XMM-Newton Science Analysis System


emchain (emchain-11.15) [xmmsas_20070708_1801-7.1.0]

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Generalities

By default all events flagged for rejection during the chain are physically removed from the output file (to save space) except those OUT_OF_FOV (useful for cosmic-ray background subtraction) and REJECTED_BY_GATTI (used for proton flare rejection). To keep all events in output set rejectbadevents=N. To use a different mask on FLAG set rejectionflag to another hexadecimal value (binary flags are described in evatt, and in the header of the EVENTS table of the event lists).

For later imaging analysis selecting with #XMMEA_EM is advised. For accurate spectral analysis, selecting with #XMMEA_SM is advised. This removes all flagged events except those flagged only as CLOSE_TO_DEADPIX. Using the stricter selection 'FLAG == 0' is in theory even better in terms of spectral reliability, but in practise it makes little difference and can reject a sizable fraction of events (several entire columns per CCD are declared as DEAD).

All text output is sent to standard error, and may be redirected to a file (very useful to investigate problems). It is good practice to look at the warnings sent by the tasks and emchain itself. If the SAS_VERBOSITY environment variable is set to 1, emchain will tell which tasks it called. If SAS_VERBOSITY is set to 4 (suggested value), its constituent tasks will provide useful information. Larger values of SAS_VERBOSITY may result in large output files. If SAS_VERBOSITY=0, emchain will be mute, except for warnings and error messages.

All files are recognized by their name. Input files are looked for in the directory entered via the odf parameter or the SAS_ODF environment variable, which must also contain the general ODF files (attitude, time, summary file). Output files are created in the current directory. Intermediate files are removed at the end, unless keepintermediate=Y or an error occurred. Intermediate and output files are overwritten unless clobber=Y.

If one constituent task ends in error, emchain will continue anyway with the next CCD, exposure or instrument unless stoponerror=Y.