Fermi Gamma-ray Space Telescope

Model Creation

The model of the sky used by gtobssim is stored as an XML file. The format of this XML file differs from that used by gtlike. All the source models used by gtlike can be expressed as gtobssim source models, but the gtobssim XML format does not include parameter uncertainties. In the next section we provide a simple example of XML for a point source.

Although the gtobssim XML format differs from the gtlike XML format, the same Model Editor tool (see the likelihood section) can create and edit the files from both formats. This tool can also convert between formats, within the capabilities of these formats. Thus the parameter uncertainties in a gtlike XML model will be lost in creating a gtobssim XML file, and conversely, the time dependence of a gtobssim XML file will not carry over to the gtlike model. Use of this GUI-driven tool is fairly intuitive.

Note that you can create a model with more sources than you intend to use in gtobssim simulation.

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