Ghost Image

An artifact in data from pulsar backends due to interleaved samplers (analog-to-digital converters, or ADCs) that are not perfectly synced and have different gains. The “image” appears as the recorded signal (multiplied by a small system-dependent factor) that has been reflected around the center observing frequency prior to de-dispersion/folding, etc. The artifact is worst for very strong, low-DM pulsars. First removed from GUPPI/PUPPI data in the 12.5 year dataset.