Appendix J: Glossary
- Component - A part of a model.
- Additive - A component which produces a theoretical spectrum.
- Multiplicative - A component which produces
multiplicative factors to apply to the current theoretical spectrum.
- Convolution - A component which modifies the current
- Mixing - If there are multiple datasets with
separately calculated theoretical models this component modifies
all of them simultaneously.
- Datagroup - A set of observed spectra which will all be
fit using the same model and parameter values.
- Dataset - The observed spectrum and its associated information.
- Fit statistic - The statistic used to determine the
best fit value. The options are based on maximizing the likelihood.
- Model - The parameterized theoretical model for the
source spectrum. There is a default unnamed model but additional
named models can be defined.
- Plotgroup - A set of spectra which are summed together
for plotting purposes only.
- Response Model - A model which modifies the
response. At the moment this is limited to the gain.
- Source - In some observations several objects can
contribute to the same spectrum. In this case XSPEC refers to them as
different sources and each source can have its own model and response.
- Table Model - A model component stored as a FITS file
containing model spectra tabulated on a grid of parameter values.
- Test Statistic - The statistic to provide the
goodness-of-fit criterion after the parameters have been optimized
based on the fit statistic