Modeling the data

What you will learn

You will learn how to generate a model definition file for the analysis of COMPTEL data.

As next step you need to create a model to describe the COMPTEL data. This step is accomplished using the comobsmodel script. The example below shows how you can generate a model for a point source at the position of the Crab.

$ comobsmodel
Input observation definition file [obs.xml] obs_binned.xml
Right Ascension of point source (deg) [NONE] 83.6331
Declination of point source (deg) [NONE] 22.0145
Name of point source [NONE] Crab
Bremsstrahlung component (NONE|MAP|CUBE) [NONE]
Inverse Compton component (NONE|MAP|CUBE) [NONE]
Isotropic component (NONE|CONST|CONSTFIX) [NONE]
Output model definition file [models.xml]

comobsmodel produces on output a model definition file which in the example is named models.xml. The content of this file is shown below. The model comprises a point source with power law spectrum at the position of the Crab and a background model component for each of the four energy bins. By default the background model is of type DRBPhibarBins which defines a free scaling factor for each of the \(\bar{\varphi}\) layers of the COMPTEL data space.

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<source_library title="source library">
  <source name="Crab" type="PointSource" tscalc="1">
    <spectrum type="PowerLaw">
      <parameter name="Prefactor" value="1" error="0" scale="0.002" min="5e-23" free="1" />
      <parameter name="Index" value="1" error="-0" scale="-2" min="-5" max="5" free="1" />
      <parameter name="PivotEnergy" value="1" scale="1" free="0" />
    </spectrum>
    <spatialModel type="PointSource">
      <parameter name="RA" value="83.6331" error="0" scale="1" free="1" />
      <parameter name="DEC" value="22.0145" error="0" scale="1" free="1" />
    </spatialModel>
  </source>
  <source name="Background_vp0001_0_000750-001886keV" type="DRBPhibarBins" instrument="COM" id="vp0001_0_000750-001886keV">
    <parameter name="Normalization" value="1" scale="1" min="0" max="1000" free="0" />
    <parameter name="Normalization" value="1" scale="1" min="0" max="1000" free="0" />
    <parameter name="Normalization" value="1" scale="1" min="0" max="1000" free="0" />
    <parameter name="Normalization" value="1" scale="1" min="0" max="1000" free="0" />
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
    ...
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
  </source>
  <source name="Background_vp0001_0_001886-004743keV" type="DRBPhibarBins" instrument="COM" id="vp0001_0_001886-004743keV">
    <parameter name="Normalization" value="1" scale="1" min="0" max="1000" free="0" />
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
    ...
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
  </source>
  <source name="Background_vp0001_0_004743-011929keV" type="DRBPhibarBins" instrument="COM" id="vp0001_0_004743-011929keV">
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
    ...
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
  </source>
  <source name="Background_vp0001_0_011929-029999keV" type="DRBPhibarBins" instrument="COM" id="vp0001_0_011929-029999keV">
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
    ...
    <parameter name="Normalization" value="1" error="0" scale="1" min="0" max="1000" free="1" />
  </source>
</source_library>

Note

To shorten the display, identical lines were replaced by three dots.