To see the source lightcurve, you should plot the column RATE with error ERROR versus column TIME, whereas to see the background lightcurve, you should plot column BACKV with error BACKE versus TIME. To display the resulting lightcurve it is convenient to use the lcurve program from the FTOOLS package:
lcurve
Number of time series for this task[] 1
Ser. 1 filename +options (or @file of filenames +options)[] crab_lc.fits[2]
Name of the window file ('-' for default window)[] -
Newbin Time or negative rebinning[] 100
Number of Newbins/Interval[] 46 (take this number from the line above:
Maximum Newbin No. 46)
Name of output file[default]
Do you want to plot your results?[] yes
Enter PGPLOT device[] /XW
hardcopy crab_lc.ps/PS
quit
As a result, the crab_lc.ps file was produced and is shown in Figure 21.