Bugs: lightcurve - CIAO 3.4

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Matching CIAO and CALDB Versions

CIAO 3.4 requires CALDB 3.3.0 or higher to operate properly.

CALDB 3.4.0 and higher should not be used unless you are running CIAO 3.4 or CIAO 4.0.

Are your versions mismatched? Time to update CIAO and CALDB!

News Previous Items

11 Nov 2008

These are the webpages relative to the CIAO 3.4 release (18 December 2006). They are no longer actively updated, however the CXC will continue limited support of CIAO 3.4 for the near future.

CIAO 3.4 users should check the CALDB 3 website for compatible calibration updates.

15 Dec 2008

The newest version of the Chandra Interactive Analysis of Observations software, is CIAO 4.1, released on 15 December 2008. Read the release notes for detailed information. This release requires that CALDB 4.1.0 be installed for the software to work correctly.

Bugs

The background GTI is taken to be the same as the input GTI.

lightcurve can only properly deal with unrotated, rectangular regions.

If a circle (or any complex region) is given, the area calculated will be the area of a rectangle which completely includes this region (called the "bounding box"). This principally affects background-subtracted lightcurves by overestimating the contribution of the background. The final effect is to give artificially high count rates.

Workarounds:

Obtain count rates with any region, using the tool dmextract.
If you insist on using lightcurve, one could obtain background subtracted lightcurves by extracting lightcurves for source and background individually. Then use dmtcalc to scale and subtract the background lightcurve from the source. Note that the scaling would need to account for the original error of casting a circle into a square.