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eSASS task: evtool



This document provides a description of the algorithm and instructions for the correct usage of the EVTOOL task, which is part of eSASS (the eROSITA Science Analysis Software System).


The task EVTOOL provides three capabilities:
  1. Merging several event lists. All canonical extensions are merged. Note that each input event list must cover a different range of telescope modules (TMs) — it is not permitted to merge 2 or more event lists that deal with the same TM(s).
  2. Filtering the events on a subset of the columns. Filter modes available are:
    • FLAG column (via bit mask, either exclusive or inclusive).
    • PAT_TYP column (effectively via bit mask).
    • TM_NR column (via a list of desired numbers).
    • PI column (via a list of energy bounds).
    • TIME column (via a GTI specification).
    • RA, DEC columns (via a region specification).
  3. Creation of FITS images. The pixel sizes on the sky, the image dimensions in pixels, and the image centre location, are all specifiable. Some auto-sizing options are also available. Most of the extensions in the input event list(s) are optionally discardable for image output.
The input eROSITA Event FITS file is expected to include the following extension types: EVENTS, GTI, BADPIX, CORRATT, and DEADCOR. In addition EVTOOL can handle the following extension types in the file as well: QUALGTI, FLAREGTI, HK, and OFFSET. NOTE: in merging the individual files, columns which were not produced/specified in the eROSITA manual will be ignored.

Input Parameters

Known Issues: