See gtlike:

Help | Examples

Also see:

• gtexpmap
• gtltcube
• gtmodel
• gtsrcmaps
• Model Editor
  (modeleditor)
• pyLikelihood Attributes and Methods

Instrument response functions.

The instrument response (PSF, effective area, energy resolution) is currently a function of energy, inclination angle (the angle between the source and the LAT normal), and photon category. Since the LAT usually surveys the sky, a source is observed at different inclination angles. Each count is therefore characterized by a different instrument response function (IRF).

Exposure hypercube file.

FITS file containing livetime as a function of sky position and off-axis angle. This file can be generated by gtltcube or obtained from SLAC's Data Portal. See gtltcube Help for further explanation.

XML file containing the source model definitions.

The source model can be generated by the Model Editor (modeleditor) utility, or by following source model templates.

Choice of Objective Function and Optimizer

Statistic to use.

The options are binned or unbinned likelihood analysis. (See the Procedure for Likelihood Analysis.)

Optimizer package to use.

The options are: DRMNFB, NEWMINUIT, MINUIT, DRMNGB, LBFGS.
(See Model Fitting.)

Re-optimize for TS fits?

Whether to refit in the null hypothesis in evaluating the test statistic values for each point source. This is a hidden parameter. (default: no)

Write output files: counts_spectra.fits and results.dat?

These files have a summary of the results of the likelihood analysis with the TS values, the predicted number of counts and the values of the fit for the free parameters in the source model file.

This is a hidden parameter. (default: yes) The results are also printed in the Standard OUTPUT if chatter is set to 2 (the default value).

Allow for refitting?

Whether to prompt to refit, re-reading the source model XML file before refitting. This is a hidden parameter. (default: no)

Unbinned

Input event file. This is the file containing the event data. If several events files have to be input, an ASCII file with the complete list of all of them should be entered here with an "@" sign before the name.

For example, if the name of that ASCII file is "events", then its parameter should be entered: evfile=@events.

Spacecraft file.

Spacecraft data file containing information such as the spacecraft pointing as a function of time. This file could be generated by gtorbsim for simulated observations (see gtorbsim and gtorbsim Help for further explanation), or more commonly it can be obtained from the SLAC Data Portal.

Unbinned exposure map.

Exposure map file used in an unbinned likelihood analysis and created by gtexpmap. See gtexpmap and gtexpmap Help for further explanation.

Plot unbinned counts spectra.

This parameter allows to plot (or not) the counts spectrum for data and model. This is a hidden parameter. (default: no)

Binned

Counts map file.

Optionally includes the convolved maps of the sources in the model as image extensions. Only for binned likelihood analysis.

Binned exposure map.

The geometry of the map must match the geometry of the counts map.
Only for binned likelihood analysis.

Hidden Parameters

Activate debugging mode. (default: no)

When debug is "no", all exceptions that are not caught and handled by individual tool-specific code are caught by a top-level exception handler that
displays information about the exception and then exits. When debug is "yes", such exceptions are not caught by the top-level code. Instead the tool produces a segmentation violation, which is more useful for debugging. When debugging mode is enabled, the tool produces more verbose output describing any errors or exceptions that are encountered.