NAME gtbkg - Creates a background spectrum file (PHA1 format). USAGE gtbkg phafile outfile scfile expcube expmap irfs srcmdl target DESCRIPTION To produce a background spectrum file (PHA1), gtbkg uses as input several files that are created with other tools: The input spectrum file (PHA1) by gtbin; The live-time file, by gtltcube; The exposure map by gtexpmap; The source xml file by ModelEditor. The exposure map is the same as the one created for the unbinned likelihood analysis. The background spectrum file contains total counts based on a gtlike source model and covers the same energy bands and region-of-interest as the input PHA1 file. The model will typically contain interstellar and extragalactic diffuse components as well as nearby point sources. PARAMETERS phafile [filename] Name of input spectrum file (PHA1). This file should be produced with gtbin (option PHA1). Type "fhelp gtbin" for further explanation. outfile [filename] Output spectrum file (PHA1). scfile [filename] 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 help for further explanation) or more commonly it can be obtained from the FSSC website. (sctable) [string] Spacecraft data extension. Default is "SC_DATA". expcube [filename] FITS file containing livetime as a function of sky position and off-axis angle. This file can be generated by gtltcube or obtained from the FSSC website. See the gtltcube help for further explanation. Default is "none". expmap [filename] Exposure map file used in an unbinned likelihood analysis and created by gtexpmap. Do not use an exposure map that is appropriate for binned analysis (i.e. from gtexpcube2). See gtexpmap help for further explanation. Default is "none". irfs [string] 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 will usually survey the sky, a source will be observed at different inclination angles. Each count will therefore be characterized by a different instrument response function (IRF). The default value is “CALDB”. evtype [integer] The evtype to be used in generating the background data. The default is INDEF which will use the default in the PHA file. This can be overridden by entering the desired event type e.g. 3 for FRONT + BACK events. srcmdl [filename] XML file containing the source model definitions. The source model can be generated by the ModelEditor utility or by following source model templates. See the ModelEditor help for further explanation. This model file can be the output of a likelihood fit (either binned or unbinned) as well. target [string] The name of the target source as it appears in the source model file. Its contribution will be excluded from the background calculation. If there are no sources to exclude, this field may be left blank or set to "none" (default). (chatter) [integer] This parameter fixes the output verbosity: no screen output (0), nominal screen output (2), maximum verbosity (4). Default is "2". (clobber) [boolean] If true, an existing file of the same name will be overwritten. Default is "yes". (debug) [boolean] Activate debugging mode. Default is "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. (gui) [boolean] Graphical User Interface (GUI) mode is activated if set to "yes". Default is "no". (mode) [string] Mode of automatic parameters: "h" for batch, "ql" for interactive. Default is "ql". EXAMPLES Parameters are passed following the FTOOLs model: They could be passed answering from a prompt, as a list in a command line, or by editing the parameter file. To run gtbkg simply type in the command line: >gtbkg This will prompt for parameter values. Not all parameter are prompted: some of them are "hidden". To change one of the "hidden" parameter, the user should specify the values in the command line or modify its mode by editing the parameter file. For example to prevent overwriting an existing output file, the following command line as to be typed:: >gtbkg clobber=no An example of how to run the tool is given below: The file 3C279_3C273_back_filtered_pha1.fits was created using gtbin (option PHA1) from an original event file. The expMap.fits and the expCube.fits file were created with gtexpmap and gtltcube respectively. 3C279 is the source excluded from the background model. The name "3C279" is the same as the one in the source model file. > gtbkg pha file[] 3C279_3C273_back_filtered_pha1.fits output file[] pha1.fits Spacecraft file[] spacecraft_data_file.fits Exposure hypercube file[] expCube.fits Exposure file[none] expMap.fits Response functions to use[CALDB] CALDB Source model file[] src_model.xml Target source name (excluded from background estimate)[none] 3C279 Excluding source 3C279 from background model. To run the same example in the command line type: >gtbkg phafile=3C279_3C273_back_filtered_pha1.fits outfile=pha1.fits \ scfile=spacecraft_data_file.fits expcube=expCube.fits expmap=expMap.fits \ irfs=CALDB srcmdl=src_model.xml target=3C279 SEE ALSO gtbin gtltcube gtexpmap gtlike gtorbsim gtexposure2 ModelEditor