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Here is described the set of EXSAS commands to perform timing analysis
on data files in output from the projection.
The timing commands can be divided into five different families:
- Commands working from Binned Data Tables (BDT)
- FOLDING SEARCH: it is possible to run a folding algorithm
from binned data (Stellindgwerf method) from a BDT. It
is useful to look for periodicities in data on which some
corrections have been applied.
- Commands working from Photon Event Tables (PET)
- ARRIVAL TIME CORRECTION: it is possible to apply
barycentric corrections to a PET. The output from
this module can be either be input again for the projection
(e.g. for binning to produce a BDT), or it can be
directly input to the analysis programs.
- FOLDING SEARCH: it is possible to perform a folding
search (on period and period derivative). Different
statistical tests for the best period detection are
available.
- ACCEPTED TIMES PLOT: it is possible to produce a plot
of the accepted times applied to a PET
- Commands working both from BDTs and PETs
- SEGMENTED POWER SPECTRUM: it is possible
to produce a power spectrum (from either a list of BDTs
or a single PET) by dividing the light curve in small stretches
(maximum length 8192 points) and averaging the single power
spectra. It is optionally possible to produce a
-T
image, in which the single power spectra are reported vs.
time. This image is in a rough format and it can be handled by
means of some dedicated commands.
- LONG POWER SPECTRUM: it is possible to produce a single power
spectrum (from either a list of BDTs or a single PET), with a
maximum length of 524288 (
) points for the input time
series.
- SEGMENTED AUTOCORRELATION: as in the case of power spectrum
analysis it is possible to produce average autocovariance
(or autocorrelation) functions on short stretches of data
(maximum length 8192) starting from either a list of BDTs
or from a single PET.
Different choices for the normalization are allowed.
- SEGMENTED CROSSCORRELATION: as in the case of power spectrum
analysis it is possible to produce average crosscovariance
(or crosscorrelation) functions on short stretches of data
(maximum length 8192) starting from either a list of BDTs
or from a single PET.
Different choices for the normalization are allowed.
- KOLMOGOROV-SMIRNOV TEST: K-S test against source constancy
- Commands working on tables in output from 3.
- POWER SPECTRUM PLOT: it is possible to plot a power spectrum
either SEGMENTED or LONG. If the LONG PS is
very long, it is advisable to use the SIGNIFICANCE
DETECTION program to look for periodicities.
- AUTOCORRELATION and CROSSCORRELATION PLOT: to plot ACF and CCF tables
in output from the ACF and CCF program.
- FOLDING PLOT: to plot folding tables in output from the
period folding program.
- KOLMOGOROV-SMIRNOV PLOT: to plot K-S tables in output from the
Kolmogorov-Smirnov test program.
- SIGNIFICANCE DETECTION: with this command it is possible to
identify (in a power spectrum produced via the LONG PS
command) bins with power exceeding a given significance.
- Frequency-Time IMAGE DISPLAY: this command takes in input the
rough
-T image in output from the SEGMENTED PS
command, and produces a more displayable image.
- Frequency-Time IMAGE CONVERSION: it is a command for
the conversion to rms of the rough
-T
image in output from the SEGMENTED PS command.
- Frequency-Time IMAGE PLOT: it is possible to produce a 3-D plot
either in power or in rms from a rough
-T image in
output from the SEGMENTED PS command.
- General utilities
- CHI-SQUARE INTEGRATION: it is possible to integrate a
distribution function with a specified number of d.o.f. above
a certain 
level. This command can be used to
estimate the significance of detection for the period
folding programs.
- LIGHT CURVE PLOT: it is possible to plot light curves in
count rate units.
- SCC-JD CONVERSION: conversion from ROSAT
spacecraft clock to Julian Day and Rosat Day.
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