Compute FFT from the input QPOE file.
input file: rp90_sti.qp
output files: rp90_ftp.tab, rp90_pwr.tab
In searching for short periods using a long data interval many bins are
necessary [(no. of bins) = 
] and generation of a _ltc.tab file may prove
impractical. In such cases, the QPOE file may be input.
Only the largest Fourier coefficients, but not the complete
list of ( e.g., 
) coefficients should be used, so we set
power_thresh to exclude all but the largest from the table [root]_pwr.tab.
The normalization has been adjusted so the value of the power
coefficient, normpower, does not depend strongly on number of bins or number of
counts. A significant signal will have a value of 
for a
bin transform and a value of 
for 
bins.
Time required for a 
bin transform is 2--3 minutes.
xt> fft.fftcoeff=no # don't generate a long list of coefficients xt> fft.power_thresh=7 # set the significance threshold xt> fft input source file (table or time-sorted qpoe file): rp90_sti.qp root name for output files [rrot_fft(ftp,pwr).tab]: rp90lng background qpoe file: <cr> input table column heading: src number of bins 2048 # The task uses the closest power of 2 to the input valueFFT done with 2048 bins!
creating histogram output file rp90_ftp.tab creating fft power output file rp90_pwr.tab