Possible Interpretation of Pulses from a Radio Source

Abstract

THE Cambridge group¹ recently announced the recording of pulses from a local object, lasting for about 0.016 s and repeating with extreme regularity with a period of 1.337 s, the accuracy being one part in 10⁷. There have been further observations from Cambridge² and from Jodrell Bank³. The amplitude of the pulses varies randomly, the pulses appearing and disappearing for periods of a few minutes. There is also a fine structure superimposed on the main pulse. Despite the regularity of the pulses, the power emitted varies significantly over all periods. Furthermore, observations indicate a frequency drift of −5 MHz s⁻¹. The absence of any proper motion of the source, and the interpretation of the frequency drift in terms of dispersion through the interstellar plasma, limit the distance of the source to the range 10³ A.U. <d<65 pc. An eighteenth magnitude blue stellar object has been found near the object, although there seems to be uncertainty about the nature of the object. From the pulse width and the rate of frequency drift the source is smaller than 5 × 10⁸ cm.