About Chandra Archive Proposer Instruments & Calibration Newsletters Data Analysis HelpDesk Calibration Database NASA Archives & Centers Chandra Science Links

Skip the navigation links
Last modified: 21 November 2006

URL: http://cxc.harvard.edu/ciao3.4/bugs/lightcurve.html
Hardcopy (PDF): A4 | Letter

Bugs: lightcurve


This tool has been deprecated as of CIAO 3.0; use dmextract instead.


Bugs

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

  2. lightcurve can only properly deal with unrotated, rectangular regions.


Bugs

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

  2. 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:

    1. Obtain count rates with any region, using the tool dmextract.

    2. 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.

Hardcopy (PDF): A4 | Letter
Last modified: 21 November 2006


The Chandra X-Ray Center (CXC) is operated for NASA by the Smithsonian Astrophysical Observatory.
60 Garden Street, Cambridge, MA 02138 USA.    Email: cxcweb@head.cfa.harvard.edu
Smithsonian Institution, Copyright © 1998-2004. All rights reserved.