Preliminary Results on Pulsating Radio Sources

Abstract

A PROGRAMME of observations of the pulsating sources recently discovered by the Cambridge group has been started at 408 MHz with the N.–S. arm of the “Northern Cross” radio telescope. At present only this arm of the Cross can be used because the E.–W. arm is being reconditioned. Some of the results obtained, however, show that even these incomplete observations may be useful, because of the long transit time (4 min) in the antenna fan beam which allows the observation of hundreds of pulses at each transit and because of the multi-beam arrangement which enables a rapid and precise determination of the declination of a source to be made. Indeed, by observing the source with the five beams of the instrument simultaneously—at these declinations each beam is 9 min of arc wide and spaced 4 min of arc from the next—it is possible, in principle, to obtain a value of δ even for a single recorded pulse. Because of the very great intensity variations of pulsating sources, this technique is advantageous as compared with the conventional technique of scanning across the source.