Absence of Pulsar Characteristics in Several X-ray Sources

Abstract

VERY condensed stars have been suggested as sources of celestial X-rays^1,2 and pulsar radio emission³. The fact that the pulsar CP 0950 (ref. 4) falls within the uncertainty in the position of the X-ray source Leo XR-1 (ref. 5) could be significant and the discovery of a pulsar in the centre of the Crab nebula, a strong X-ray source, is particularly interesting although the X-rays have been shown⁶ to arise from a somewhat extended region. The distribution of pulsars and X-ray sources in galactic latitude, however, is very dissimilar. This lack of correlation could occur if the dense stars, which we assume hypothetically to be responsible for both types of object, were very common, and were confined to the galactic plane. If the pulsar phenomenon were much more prevalent than the X-ray phenomenon then, on the average, more-distant stars would be seen as X-ray objects and their distribution would appear to be much more closely confined to the galactic plane. This argument would also depend on the distance to which we are capable of detecting each type of object. The distances that have commonly been deduced for pulsars are sufficiently small that if a bremsstrahlung source similar to currently observed X-ray stars were present, it should be seen as an optical object, which is not the case.