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Interpreting the Results

Now that you have a good fit of the data, you need to step back and figure out what those results mean. Recall that your goal was to determine some of the elements in a supernova explosion. Armed with the best-fit models for those three emission lines, you are ready to connect your model to the physical realm.

Your first task is to write down the energy where the central peaks occur for each of your three lines. Recall that this information can be found in the Xspec command window – look for the three "LineE" values in the results table. You may need to either scroll up in the command window or enlarge the window to see all of the values.

The table below lists some of the line transitions that will produce photons in the 0.2 to 5.0 keV energy range. The transitions are from ions of different elements. Try to find the ions that produced the three lines that you modeled. (In one case it might be a toss-up between two, just pick the one that's closest in energy to the best-fit line energy.)

Element Line Energy Element Line Energy
C5+ 0.37 keV C4+ 0.30 keV
N6+ 0.50 keV N5+ 0.42 keV
O7+ 0.65 keV O6+ 0.55 keV
F8+ 0.83 keV F7+ 0.77 keV
Ne9+ 1.02 keV Ne8+ 0.91 keV
Na10+ 1.23 keV Na9+ 1.11 keV
Mg11+ 1.47 keV Mg10+ 1.33 keV
Al12+ 1.72 keV Al11+ 1.57 keV
Si13+ 2.00 keV Si12+ 1.84 keV
S15+ 2.61 keV S14+ 2.43 keV
Ar17+ 3.30 keV Ar16+ 3.10 keV
Ca19+ 4.08 keV Ca18+ 3.86 keV

Answer these questions about your results:

You may need to consult a periodic table of the elements – here is an online periodic table if you need it: (

  • What elements are present in the supernova spectrum?
  • What is the atomic number for each element in your spectrum? (The atomic number is equal to the number of protons in the nucleus of the element.)
  • Recall that the numbers in the superscripts of the ion names (i.e., "5+", "9+", "14+", etc.) indicate how many electrons the ion has lost. Using the atomic weight and number of electrons lost, how many electrons do your elements have left?

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