9.1. PowerlawΒΆ

Before doing this exercise, we advise you to read How to run SPEX.

The spectrum in the files powerl.spo and powerl.res was recorded from a source at 6 kpc distance.

  1. Load the spectrum into SPEX and plot it.

  2. The calibration of the instrument is not very accurate for energies below 0.3 keV and above 10 keV. Ignore those parts of the spectrum.

  3. How many data bins do you have in the spectrum? Now try to apply optimal binning to the spectrum. How many bins are left?

  4. Set up an absorbed powerlaw model. Do not forget to set the distance to the source.

  5. Next step: fit the spectrum. Is it a good fit?

  6. Calculate the errors on all free parameters and save your results in a text file.

  7. It may be wise to save the commands that you entered in SPEX to a command file, so you can repeat the analysis where needed. Try to make such a command file.

Learning goals:

After having done this spectrum, you should know: