ctbutterfly

Computes butterfly diagram for a given spectral model.

Synopsis

This tool calculates a butterfly diagram for a specific source according to its spectral model. The butterfly diagram is the envelope of all spectral models that are within a given confidence limit compatible with the data. The default method used for the calculation is Gaussian error propagation using the covariance matrix from a maximum likelihood fit. By default a confidence level of 68% is used, but the level can be adjusted using the hidden confidence parameter. For power law models, an alternative calculation method can be specified by setting the hidden parameter method=ENVELOPE. By using this method, the envelope is computed by evaluating for each energy the minimum and maximum intensity of all power law models that fall within the error ellipse of the prefactor and index parameters. The error ellipse is derived from the covariance matrix of a maximum likelihood fit.

ctbutterfly assumes that the input model (parameter inmodel) has been adjusted using ctlike to the data, but if this is not the case you can request a maximum likelihood fit by setting the hidden parameter fit=yes.

ctbutterfly writes the butterfly diagram into a FITS file with a binary table extension.

The butterfly diagram can be displayed using the show_butterfly.py script in the example folder.

General parameters

inobs [file]

Input event list, counts cube or observation definition XML file.

inmodel [file]

Input model XML file.

srcname [string]

Name of source model for which the butterfly diagram should be computed.

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]

Applies energy dispersion to response computation.

outfile [file]

Output butterfly FITS file.

(fit = no) [boolean]

Performs maximum likelihood fitting of input model ignoring any provided covariance matrix.

(method = "GAUSSIAN") <GAUSSIAN|ENVELOPE> [string]

Computation method.

(confidence = 0.68) [real]

Confidence level for error computation.

(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.

(like_accuracy = 0.005) [real]

Absolute accuracy of maximum likelihood value. Reducing this value will increase the number of iterations and provide a more accurate maximum log likelihood value. Converserly, decreasing the value will result in less iterations at the expense of a less accurate maximum likelihood value.

(max_iter = 50) [integer]

Maximum number of fit iterations.

(matrix = "NONE") [file]

Input covariance matrix file (not used)

(ebinalg = LOG) <FILE|LIN|LOG> [string]

Algorithm for defining energy bins. For FILE, the energy bins are defined in a FITS file that is specified by the ebinfile parameter, for LIN and LOG there will be enumbins energy bins spaced linearly or logarithmically between emin and emax, respectively.

emin [real]

Lower energy value for first energy bin (in TeV) if LIN or LOG energy binning algorithms are used.

emax [real]

Upper energy value for last energy bin (in TeV) if LIN or LOG energy binning algorithms are used.

(enumbins = 100) [integer]

Number of energy bins if LIN or LOG energy binning algorithms are used.

ebinfile [file]

Name of the file containing the energy binning definition if ebinalg=FILE. You may use csebins to generate a file with appropriate energy binning.

Standard parameters

(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 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 = ctbutterfly.log) [string]

Name of log file.