Overview of the Analysis System
The following are the tools included in the Standard Analysis Environment (SAE), the set of Fermi-specific tools provided to analyze LAT data. Some tools, such as gtbin, can also process GBM data products. A map of the system can be found here.
| Name | Description |
|---|---|
| Utilities | |
| gtselect | Creates a new FITS file of selected rows in an input event data file based on cuts that are applied to the values in each row of the input file. This application enables more detailed selections to be made on data obtained from the data server. |
| gtsrcid | This tool creates a counterpart candidate catalogue by correlating the objects from a source catalogue (e.g., the LAT source catalogue) with the objects of a counterpart catalogue. |
| Likelihood | |
| gtcntsmap | This tool computes the counts maps for use in a binned likelihood analysis. The bins are 'cubes' in latitude, longitude, and log(energy). |
| gtexpmap | This tool computes the exposure maps for use in an unbinned likelihood analysis. |
| gtdiffresp | This tool computes the event-specific response for each diffuse source in the input source model. A column containing these data is added to the event file for each source. |
| gtlikelihood | LAT data can be analyzed with this tool using an unbinned or binned formulation of the log-likelihood. |
| gtlivetimecube | Using the spacecraft data file and the time range and GTI selections in the event file, this tool integrates the livetime as a function of sky position and off axis angle. The sky is represented using a nested HEALPix array. |
| gtmodelmap | This tool creates a model counts map by summing up convolved source maps that have been scaled by the spectral parameters given in the source model XML file. |
| gtpsf | This tool calculates the effective point spread function, as a function of energy at a given source location, averaged over an observation. |
| gtsrcmaps | This tool convolves the components of the specified source model with the instrument response for a given observation. The geometry in sky and energy coordinates of the output maps match that of the input counts map. |
| gttsmap | This tool computes a test statistic map for source localization and detection in an unbinned likelihood analysis. |
| Gamma-Ray Burst Analysis | |
| gtbin | This tool bins an event list in time, energy, or space, and results in spectra, lightcurves or a count map. |
| gtbindef | This utility reads in an ASCII file with the time or energy bin definitions, and produces the appropriately-formatted FITS file that can be used by gtbin to bin an event list. |
| gtrspgen | This tool creates a standard FITS file required to analyze a binned spectrum with a spectral analysis tool such as XSPEC. |
| gtburstfit | This tool analyzes burst light curves by applying a Bayesian algorithm to determine the optimum set of blocks to follow the burst profile shape; blocks may also be used by gtburstfit to construct a pulse model, which gtburstfit can fit to the data. |
| Pulsar Analysis | |
| gtbary | This tool performs a barycentering time correction to FITS files using Fermi orbit files. |
| gtpsearch | This tool searches for pulsation frequencies near to a known, guessed or estimated reference frequency. |
| gtpphase | This tool operates on an event file to compute the spin (pulse) phase for the time of each event, and writes this phase to the PULSE_PHASE column of the event file. |
| gtophase | This tool operates on an event file to compute the orbital phase for the time of each event, and writes this phase to the ORBITAL_PHASE column of the event file. |
| gtephcomp | This tool presents the user with the best ephemeris available in a pulsar database for a given pulsar and instant of time. |
| gtpulsardb | This tool creates, filters, and/or combines pulsar ephemerides database files. |
| Observation Simulation | |
| gtorbsim | This tool generates spacecraft orbit and attitude data for a variety of pointing strategies. |
| gtobssim | This tool generates photon events from astrophysical sources and processes those photons according to the specified instrument response functions. |