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PSRCHIVE user documentation: paz
1.0 PurposeThe Pulsar Archive Zapper paz combines a number of manual and automatic modes of interference excision. Lists and/or ranges of frequency channels and/or sub-integrations to be excised can be specified on the command line. Automatic interference excision algorithms are described in section 3 below.
2.0 UsageFor a full list of options, use:
paz -hNote that there are three kinds of zapping:
3.1 Median Smoothed Difference Channel ZappingUse paz -r to enable an automatic channel zapping algorithm based on tolerance to differences between the bandpass and a median smoothed version of the bandpass.
By default, a median smoothing window 21 channels wide is applied, and all frequency channels with total flux greater than 4 standard deviations away from the median will have their weight set to zero.
Note: standard deviation is defined recursively. That is, the algorithm works as follows
#!/usr/bin/env psrsh zap median window=13 zap median cutoff=6 zap median unload ext=zz
3.2 Profile Lawn MowingUse paz -L to enable an algorithm that replaces spikey phase bins with the local median plus noise.
For each sub-integration, the zero-DM total integrated profile is formed and median smoothed with a duty cycle of 0.02 turns. The difference between the profile and its median smoothed self is searched for spikes greater than 4 standard deviations, where the standard deviation is computed using a recursive algorithm that discards both spikes and zeroes (a large number of phase bins tend to equal the local median).
If spikes are found then, for each frequency channel, the off-pulse baseline in the total intensity profile is found and, for each polarization:
4.0 Testing and examples
For example, to zero-weight the first three subints:
paz -w "0 1 2" *.arNote: Frequency channel and sub-integration indeces start at zero.
5.0 Known bugs and features that require implementation