Spectral Analysis

subsection 7.1Summary of Taskss in this Section116 subsection 7.2A Quick Look at Spectral Fitting116 subsection 7.3Notes on IPC and PSPC Spectral Fitting117 subsection 7.4Model Spectra for Spectral-Fitting Program119 subsection 7.5Structure of the Spectral Package122 subsection 7.6*qpspec* -- Extraction of Photon Distributions from QPOE files124 subsection 7.7*fit* -- Fit Data to a Specified Model127 subsection 7.8*counts_plot* -- Inspection of Results133 subsection 7.9*search_grid* -- Grid of - default mode133 subsection 7.10*grid_plot* -- Plot Results on Screen136 subsection 7.11*xflux, hxflux* -- Calculation of X-ray Flux136 subsection 7.12*upspecrdf, downspecrdf* -- Transform between RDF and pre-RDF spectral tables140 subsection 7.13*xspec* -- External Fitting Program141

The x-ray spectral analysis consists of a comparison between the observed pulse height spectrum and a pulse height spectrum calculated using a given spectral model. The model, chosen by the user, is convolved with the instrument and telescope responses.

To obtain the spectral parameters for an x-ray source, several steps need to be followed. For each source:

• extract counts (pulse height spectrum) from the source or region of interest
• select background region and extract counts
• obtain the distribution of the gain values -- for Einstein IPC only
• obtain the best fit parameters for a spectral model - repeated for each model of interest
• obtain a 1-D or 2-D grid of values around the best fit values - this can be done for as many models as desired
• determine the flux and luminosity of the source from the best fit model

Plots of the gain distribution, the pulse height distribution, the data compared to the model spectra, and of the grids can be generated.

• Summary of Tasks in this Section
• A Quick Look at Spectral Fitting
• Notes on IPC and PSPC Spectral Fitting
• Model Spectra for Spectral-Fitting Program
• Structure of the Spectral Package
• *qpspec* -- Extraction of Photon Distributions from QPOE files
  • Spectral Extraction of Point Sources
  • Spectral Extraction of Extended Sources
  • Charged Particle Subtraction
  • Error Determination
• *fit* -- Fit Data to a Specified Model
  • Power Law fit to a Point Source
  • Raymond Model
  • Two-Temperature Raymond Model
  • Limiting Energy Channels Input to the Fit
  • Multiple Data Sets
  • Verbose Mode
  • Fit a source with a small number of net counts
  • Inspection of results
• *counts_plot* -- Inspection of Results
• *search_grid* -- Grid of - default mode
  • *search_grid* -- Customized grid
• *grid_plot* -- Plot Results on Screen
• *xflux, hxflux* -- Calculation of X-ray Flux
• *upspecrdf, downspecrdf* -- Transform between RDF and pre-RDF spectral tables
• *xspec* -- External Fitting Program