Run XSPEC: Part 2

This is a continuation of Run XSPEC: Part 1, and it is assumed that you are still in the same session in which you ran Part 1.

Note: When performing spectral fitting with XSPEC, issues to consider are:

• The number of photons in the spectrum.

• The number of counts per bin
  (and therefore the number of bins).

• The energy range that should be fit.

• The fitting statistic.

Procedure

Note: It is recommended that you use the search function of the XSPEC User's Guide for a more detailed explanation of the following examples.

1. To rebin the plot, enter:

XSPEC12>setplot rebin 1 10 XSPEC12>plot

Tip: To see setplot options enter: setplot?
to see plot options, enter; plot?

2. Enter:

XSPEC12>setplot rebin 1 2
XSPEC12>plot

3. Enter:

XSPEC12>setplot rebin 2 10
XSPEC12>plot

4. Enter:

XSPEC12>setplot rebin 2 5
XSPEC12>plot

5. Enter:

XSPEC12>setplot rebin 5 5
XSPEC12>plot

6. Enter:

XSPEC12>setplot rebin 5 10
XSPEC12>plot

7. Enter:

XSPEC12>setplot rebin 5 5
XSPEC12>plot

8. To perform a fit, enter:

XSPEC12>fit

See Example: Fit 2.

9. Since we have a small number of counts, we will use the C-statistic, enter:

XSPEC12>statistic cstat

See Example of cstat result. For more information, refer to the XSPEC User's Guide.

10. Enter:

XSPEC12>plot

11. To view the Theoretical Model, enter:

XSPEC12>plot mod

12. To plot energy² unfolded, enter:

XSPEC12>plot eeuf

13. To plot the unfolded model, enter:

XSPEC12>plot uf

14. To plot data and folded model, enter:

XSPEC12>plot ldata

15. Enter:

XSPEC12>plot uf

16. Enter:

XSPEC12>plot euf

17. Enter:

XSPEC12>plot eeuf

18. To calculate the flux, enter:

XSPEC12>flux 1 100

The result will be displayed:

No overlap between matrix range ( 100000, 3e+08 ) and the requested range ( 1, 100 )

19. Enter:

XSPEC12>flux 100e3 100e6

Model Flux 0.0001555 photons (1.1255e-07 ergs)/cm^2/s range (1.0000e+05 - 1.0000e+08 keV)