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Last modified: 1 April 2024


Bugs: dmcopy

Table of Contents



Incorrect GTIs when time-filtering grating data with dmcopy opt=all

The CIAO team has identified a bug which affects all ACIS and HRC grating data analysis.

When a time filter is applied to a level=1.5 (evt1a.fits) or level=2 (evt2.fits) grating file and the dmcopy opt=all option is used, the GTI block in the output file is not updated to reflect the correct time range.

Time-related header keyword values - such as ontime, livetime, and exposure - will be incorrect because they are calculated from the time ranges in the GTI block.


Run dmcopy without "opt=all" when applying any time filters. Then run dmappend to copy the grating REGION block to the filtered output file, e.g.

unix% dmcopy "evt1a.fits[EVENTS][@flt1.fits]" evt2.fits
unix% dmappend "evt1a.fits[region][subspace -time]"  evt2.fits

The subspace filter is necessary so that the GTIs aren't reapplied to the output file, as explained in the dmappend caveat.

Rebinning an image with different values for the two axes causes the coordinate information to be lost

For example:

unix% dmcopy acis.img"[bin x=::5,y=::6]" acis5x6.img

Using the same value for both axes works correctly:

unix% dmcopy acis.img"[bin (x,y)=::5]" acis5.img