subsection 8.1Summary of tasks in this section144 subsection 8.2An example of a typical timing analysis145 subsection 8.3*timsort*148 subsection 8.4*timfilter* -- List start & stop times of good data intervals149 subsection 8.5Counting rate vs. time149 subsection 8.6*timprint* -- Inspect tables on screen150 subsection 8.7*calc_bary, apply_bary* -- Barycentric Time Corrections151 subsection 8.8*fft* -- Period search using Fast Fourier Transform155 subsection 8.9*period* -- Period search using epoch folding158 subsection 8.10*fold* -- Make a folded light curve159 subsection 8.11*vartst* -- Test for Source Variability160 subsection 8.12*qpphase* -- Append phase to events in QPOE file161
Photons
detected with the Einstein IPC and HRI were time-tagged to a precision
of 63 
sec and 8 
sec, respectively. Photons detected with
the ROSAT PSPC and HRI are time tagged to precision of 61 
sec.
The xtiming
package contains tasks which make light curves and search for periodicity.
The input for most timing tasks is a time-sorted .qp file, which is made from a QPOE file by the task timsort. Region masking is usually applied to select only portions of the image, in which case, sorting will occur faster. Outputs of the other tasks are typically ST tables. A one line description of available tasks is given below and can be obtained by typing `help xtiming'.
Trial data sets can be found in the files xdata$snr.qp and
rp110590n00.qp, and examples using these are
given below. The file rp110590n00.qp is the ROSAT calibration image of the RS CVn star
AR Lac. Although not a periodic source, the spacecraft wobble causes
the image of the source to be periodically eclipsed by the detector
window-support mesh and there is a period of 
100 sec in the
resultant signal.