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Last modified: 23 Dec 2014

URL: http://cxc.harvard.edu/ciao/threads/xspec_note/

A Note on Responses for XSpec Users

CIAO 4.9 Science Threads


The energy grid of the ARF and RMF files must be the same for use in XSpec.

Sherpa allows you to use different energy grids for your ARF and RMF files, but XSpec does not. Note that XSpec will still run if the grids do not match, but it issues a warning and sets all values in the ARF to unity (1).

  1. Create the RMF first

    Since mkacisrmf can change the requested grid to match the calibration data, create the RMF first and then use it to define the energy grid when creating the ARF. This will work for both mkarf and mkwarf:

    unix% pset mkarf \
          engrid="grid(sources_ciao.rmf[cols ENERG_LO,ENERG_HI])"
    
    or
    
    unix% pset mkwarf \
          egridspec="grid(sources_ciao.rmf[cols ENERG_LO,ENERG_HI])"
    
  2. Match an existing ARF

    If the specextract script was used, you already have an ARF file for the data. Rather than remake both the RMF and ARF, get the grid information from the history in the ARF file:

    unix% dmhistory acis_src1.arf tool=all
    # dmhistory (CIAO): WARNING: Found "pixlib" library parameters
    
    # dmhistory (CIAO): WARNING: Found "ardlib" library parameters
    
    mkwarf infile="acis_src1.[WMAP]" outfile="acis_src1.arf" weightfile="acis_src1.wfef" 
    spectrumfile="" egridspec="0.3:9.5:0.01" threshold="0" feffile="CALDB" 
    mskfile="" mirror="HRMA" detsubsysmod="" ardlibpar="ardlib" geompar="geom" 
    clobber="no" verbose="2"  
    

    Your file may have been created with mkarf instead of mkwarf; the dmhistory tool=all will show the tool used in either case.

    Use the egridspec value (or engrid in the mkarf case) as input for the energy parameter in mkacisrmf:

    unix% pset mkacisrmf energy="0.3:9.5:0.01"
    

The mkacisrmf why topic has more information on matching the RMF and ARF grids.


History

09 Mar 2010 new for CIAO 4.2: information moved from CIAO bugs pages
15 Dec 2010 reviewed for CIAO 4.3: no changes
09 Jan 2012 reviewed for CIAO 4.4: removed reference to psextract, which is no longer in CIAO
13 Dec 2013 Review for CIAO 4.6; minor edits.
23 Dec 2014 Review for CIAO 4.7, no changes.


Last modified: 23 Dec 2014
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