In a recent communication1 an account was given of the discovery of a new class of radio source characterized by the emission of short pulses of radiation having an extremely constant repetition frequency. The records on which the source was first detected were taken during a survey for the investigation of compact radio sources using the method of interplanetary scintillation. Following the recognition of the first pulsed source the survey records, which covered the region - 08° < δ < 44°, were examined for evidence of further similar sources. Where these records indicated that the intensity fluctuations of a particular source were more impulsive than those caused by interplanetary scintillation, further observations were made. These led to the discovery of three additional pulsed sources. Even though each area of sky was observed on about twenty separate occasions during this survey, the large day-to-day variations of flux density from the known sources indicate that this programme should not be regarded as an exhaustive search of the entire region, and observations are continuing.
Unable to display preview. Download preview PDF.