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Last modified: 18 May 2010

URL: http://cxc-newtest.cfa.harvard.edu/ciao4.2/bugs/dmextract.html

Bugs: dmextract


Bugs

  1. dmextract does not ignore pixels in an image with a value equal to the BLANK keyword.

  2. dmextract does not correctly parse binning region strings when multiple shapes are used and the first is an annulus. (02 Mar 2010)


Bugs

  1. dmextract does not ignore pixels in an image with a value equal to the BLANK keyword.

  2. dmextract does not correctly parse binning region strings when multiple shapes are used and the first is an annulus. (02 Mar 2010)

    If the region specified in the bin command begins with an annulus(), the rest of the string is ignored. The counts, area, and all derived quantities (net_counts, rates, surface brightness) for the source and background region only use the annulus() part of the region expression.

    Since the bug occurs when binning with these regions, it only affects users making radial profiles (spatial mode, opt=generic).

    Regions containing an annulus stored as external files and read in using the region() or @ syntax are not affected by this bug.

    In this example, a circle is subtracted from the annulus:

    unix% dmextract infile="evt2.fits[bin sky=annulus(4074.4322,4064.3644,30,70)-circle(4100.5638,4107.5213,5)]" \
          outfile=out.fits opt=generic
    
    unix% dmlist out.fits"[cols area]" data,clean
    #  AREA
          12566.371093750
    

    The area should be pi*(70^2-30^2) - pi*(5^2) = 12487.8 .

    Workaround:

    Put the region definition in a file, e.g.

    infile="evt2.fits[bin sky=region(source.reg)]"
    

    where

    unix% cat source.reg
    annulus(4074.4322,4064.3644,30,70)-circle(4100.5638,4107.5213,5)
    

    Repeating the example command with this syntax results in an accurate background area:

    unix% dmextract infile="evt2.fits[bin sky=region(source.reg)]" \
          outfile=out_reg.fits opt=generic
    
    unix% dmlist out_reg.fits"[cols area]" data,clean
    #  AREA
             12485.8750
    

Last modified: 18 May 2010