2002 Chandra Calibration Workshop

Cygnus X-1

This example concerns the HETGS observation (obsid_107) of Cygnus X-1 by Claude Canizares in October of 1999.

The first figure shows the result of flux-correcting using the standard technique. In this figure the dashed black line indicates the best guess of the correct flux based upon the use of the pileup model.

Figure showing result of standard technique

Here is the result of the pileup model:

Figure showing result of the pileup
model

Although there is better agreement between the four dispersed orders for wavelengths greater than 11 angstroms, the pileup model has performed poorly elsewhere. The sudden apparant increase in flux in the MEG orders below 11 angstroms is a manifestation of the nonlinearity of the pileup model. This point will be discussed in more detail in the next section.

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This page was last updated Dec 16, 2002 by John E. Davis. To comment on it or the material presented here, send email to davis (at) space.mit.edu.