csspec
Computes spectrum for a given source.
Synopsis
This script computes the source spectrum by fitting a model in a given set of spectral bins. The model fit per spectral bin is performed using :doc:`ctlike` and the script provides the possibility to fix sources other than the source of interest (hidden parameter fix_srcs) or to fix the background model component(s) (hidden parameter fix_bkg). The script computes the source flux and its uncertainty in each spectral bin, as well as the significance of the source detection. Optionally, it also computes an upper flux limit that is particularly useful in case that the source is not significantly detected within a spectral bin (hidden parameter calc_ulim).
There are two fundamental methods to run the script depending on the value of the method parameter. If method=SLICE the energy interval defined by the emin and emax parameters is divided into a number of energy bins and an independent maximum likelihood fit is performed in each of the energy bins, while if method=NODES the spectral model will be replaced by a node function that will be fit to all data. The latter is particularly useful if non-CTA data should be fitted such as data from Fermi/LAT or COMPTEL. By default, method is set to AUTO which will automatically select the method based on the input data. For CTA-only observations SLICE will be used, otherwise NODES will be used.
The spectral binning is either defined by a FITS file containing the energy boundaries of each bin (option ebinalg=FILE) or as enumbins bins spread linearly (option ebinalg=LIN) or logarithmically (option ebinalg=LOG) from a minimum energy, given by emin, to a maximum energy, given by emax.
For binned, stacked or On/Off CTA data, all energy bins that overlap with the energy range spanned by emin and emax are considered. The number of spectral bins is only approximately determined by the enumbins parameter. Naturally, :ref:`csspec` cannot create more spectral bins than the number of energy bins that are available in the data. In case that there are more energy bins in the data than the number of spectral bins that are requested, :ref:`csspec` will fit the data in all energy bins that overlap with a given spectral bin simultaneously.
On output, the script will provide a FITS file with the fitted source spectrum in form of a binary table. Each row corresponds to a spectral bin. The columns are the mean as well as the boundaries of the spectral bin, the fitted flux and flux error, the Test Statistics value (option calc_ts=yes), the upper flux limit (option calc_ulim=yes) and the predicted number of events (only for unbinned data).
Warning
The upper limit computation is not yet implemented for the NODES method.
General parameters
- inobs [file]
- Input event list, counts cube or observation definition XML file.
- inmodel [file]
- Input model XML file.
- srcname [string]
- Name of the source in the source model XML file which should be used for spectrum generation.
- expcube [file]
- Input exposure cube file.
- psfcube [file]
- Input PSF cube file.
- edispcube [file]
- Input energy dispersion cube file.
- bkgcube [file]
- Input background cube file.
- caldb [string]
- Calibration database.
- irf [string]
- Instrumental response function.
- (edisp = no) [boolean]
- Apply energy dispersion to response computation?
- outfile [file]
- Output spectrum FITS file.
- method <SLICE|NODES|AUTO> [string]
- Spectrum generation method. SLICE will slice energy interval into enumbins independent bins, NODES will replace spectral model by node function with enumbins nodes, and AUTO will automatically select the method based on the input data. For CTA-only observations SLICE will be used, otherwise NODES will be used.
- emin [real]
- Lower energy limit of events (in TeV).
- emax [real]
- Upper energy limit of events (in TeV).
- enumbins [integer]
- Number of energy bins.
- ebinalg <FILE|LIN|LOG> [string]
- Algorithm for defining energy bins.
- ebinfile [file]
- Name of the file containing the energy bin definition.
- (statistic = DEFAULT) <DEFAULT|CSTAT|WSTAT|CHI2> [string]
- Optimization statistic. DEFAULT uses the default statistic for all observations, which is CSTAT or the statistic specified in the observation definition XML file. CSTAT uses the C statistic for all observations, WSTAT uses the W statistic for all On/Off observations, and CHI2 uses the Chi squared statistic for all binned or stacked observations.
- (calc_ts = yes) [boolean]
- Compute TS for each spectral point?
- (calc_ulim = yes) [boolean]
- Compute upper limit for each spectral point?
- (fix_srcs = yes) [boolean]
- Fix other sky model parameters?
- (fix_bkg = no) [boolean]
- Fix background model parameters?
Standard parameters
- (publish = no) [boolean]
- Specifies whether the spectrum should be published on VO Hub.
- (chatter = 2) [integer]
- Verbosity of the executable:
chatter = 0: no information will be logged
chatter = 1: only errors will be logged
chatter = 2: errors and actions will be logged
chatter = 3: report about the task execution
chatter = 4: detailed report about the task execution
- (clobber = yes) [boolean]
- Specifies whether an existing source spectrum output file should be overwritten.
- (debug = no) [boolean]
- Enables debug mode. In debug mode the executable will dump any log file output to the console.
- (mode = ql) [string]
- Mode of automatic parameters (default is ql, i.e. "query and learn").
- (logfile = csspec.log) [filename]
- Log filename.