
ctulimit
========

Computes upper flux limit for a source model.


Synopsis
--------

This tool computes the upper flux limit for a specific source model. Except
of the node function, all spectral models are supported. Starting from the
maximum likelihood model parameters, the tool finds the model flux that leads
to a decrease of the likelihood that corresponds to a given confidence level.
By default a confidence level of 95% is used, but this level can be adjusted
using the hidden confidence parameter.

ctulimit writes the differential upper flux limit at a given reference
energy (specified by the hidden parameter eref) and the integrated 
upper flux limit (specified by the hidden parameters emin and emax)
into the log file. This information can also be accessed using the diff_ulimit(),
flux_ulimit(), and eflux_ulimit() methods.


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 upper flux limit 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.

(confidence = 0.95) [real]
    Confidence level of upper limit.

(sigma_min = 0.0) [real]
    Minimum boundary to start searching for upper limit value.
    Number of standard deviations above best fit value

(sigma_max = 10.0) [real]
    Maximum boundary to start searching for upper limit value.
    Number of standard deviations above best fit value  

(eref = 1.0) [real])
    Reference energy for differential limit (in TeV).

(emin = 1.0) [real])
    Minimum energy for integral flux limit (in TeV).

(emax = 100) [real]
    Maximum energy for integral flux limit (in TeV).

(tol = 1e-5) [real]
    Computation tolerance.

(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 iterations before stopping the upper
    limit computations.


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 = ctulimit.log) [string]
    Name of log file.


Related tools
-------------

ctlike
cterror
ctbutterfly
