ctfindvar

Searches for source variability.

Synopsis

This tool searches for source variability by applying the On/Off method in the time domain. The variability of sky map pixels is computed by binning the events as function of the photon arrival time and applying the On/Off method to each time bin, integrating the background over all the other time bins. Only bins with a variability significance below a given threshold, defined by the hidden threshold parameter, are included in the background estimate. Furthermore, only time bins that exceed a minimum number of events, specified by the hidden minoff parameter, are considered for the background estimate. The significance of each time bin is computed using Li & Ma formula.

ctfindvar will search a grid of sky map pixels for source variability. Using the hidden smooth_kernel and smooth_rad parameters, the sky map may be smoothed before the variability search. The tool will compute sky maps for a number of time bins. The duration of each time bin is specified by the tinterval parameter, the start and stop time are defined by the tmin and tmax parameters. If the start and stop time are NONE, the start and stop times will be extracted from the input event list(s). Note that tinterval specifies the time scale over which the variability will be searched.

The tool will determine the sky map pixel with the maximum variability and store the variability histogram and pixel position as MAXSIGPIXEL in the output file, specified using the outmap parameter. In addition, the tool will determine the variability for a number of source positions. If an input model is specified using the inmodel parameter, the source positions will be defined by the centre positions of all gamma-ray source components in the input model. If no input model is specified, the tool will use the xsrc and ysrc parameters to allow the specification of a source position. The results will be stored in the output file using either the source names found in the model definition file, or the name SOURCE if the source position was specified by the xsrc and ysrc parameters.

All sky map pixels with a variability above the value specified by the threshold will also added be as a point source model to the outmodel file. Each source will have a power law as the spectral component with a total flux that corresponds to 1% of the Crab nebula flux.

General parameters

inobs [file]

Input event list or observation definition XML file.

(inmodel = NONE) [file]

Input model definition file for extracting source positions.

(outcube = NONE) [file]

Filename for saving counts cube, NONE will result in no cube being saved.

outmap [file]

Filename for output sky map containing the maximum significance for each spatial pixel. The file also contains the variability significance as function of time for each source of interest, and the pixel with the maximum significance. Furthermore, it contains the Right Ascension and Declination of each source of interest and the pixel with the maximum significance.

outmodel [file]

Output model definition file containing sources for significant pixels.

caldb [string]

Calibration database (only required for IRF background subtraction if no response information is provided by inobs).

irf [string]

Instrument response function (only required for IRF background subtraction if no response information is provided by inobs).

Variability search parameters

coordsys <CEL|GAL> [string]

Coordinate system (CEL - celestial, GAL - galactic).

xsrc [real]

Right Ascension / Galactic longitude of source of interest (J2000, in degrees)

ysrc [real]

Declination / Galactic latitude of source of interest (J2000, in degrees)

emin [real]

Minimum energy (TeV) for extracting events.

emax [real]

Maximum energy (TeV) for extracting events.

(threshold = 4.5) [real]

Significance threshold for variability detection.

(minoff = 0) [real]

Minimum number of off counts to compute the significance.

(smooth_kernel = NONE) <GAUSSIAN|DISK|NONE> [string]

Kernel to be used in smoothing the counts maps before computing significances.

(smooth_rad = 0.05) [real]

Radius of smoothing kernel in degrees. This is either the sigma of the GAUSSIAN or the radius of the DISK.

Time binning parameters

tinterval [real]

Interval in seconds for each time step.

tmin [time]

Start time for interval determination (UTC string, JD, MJD or MET in seconds). Start times given in MET seconds are counted with respect to the time reference of the input observation(s). If INDEF, NONE, UNDEF or UNDEFINED is passed as value, the start time will be derived from the earliest observing time.

tmax [time]

Stop time for interval determination (UTC string, JD, MJD or MET in seconds). Stop times given in MET seconds are counted with respect to the time reference of the input observation(s). If INDEF, NONE, UNDEF or UNDEFINED is passed as value, the stop time will be derived from the latest observing time.

Spatial binning parameters

(usepnt = no) [boolean]

Use CTA pointing direction for sky map centre instead of xref/yref parameters?

nxpix [integer]

Number of cube bins in Right Ascension or Galactic longitude.

nypix [integer]

Number of cube bins in Declination or Galactic latitude.

binsz [real]

Sky map pixel size (in degrees/pixel).

proj <AIT|AZP|CAR|GLS|MER|MOL|SFL|SIN|STG|TAN> [string]

Projection method.

xref [real]

Right Ascension / Galactic longitude of sky map centre (J2000, in degrees).

yref [real]

Declination / Galactic latitude of sky map centre (J2000, in degrees).

Standard parameters

(nthreads = 0) [integer]

Number of parallel processes (0=use all available CPUs).

(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 = ctfindvar.log) [string]

Name of log file.