Spectra of Southern Pulsars

Abstract

We compare the spectral properties of the millisecond and slow pulsars detected in the Parkes 70 cm survey. The mean spectral index for the millisecond pulsars (MSPs) is -1.9 +/- 0.1 whereas the mean spectral index for the slow pulsars is a surprisingly steep -1.72 +/- 0.04. A Kolmogorov-Smirnov test indicates that there is only a 72% probability that the two distributions differ. As a class, MSPs are therefore only fractionally steeper-spectrum objects than slow pulsars, as recent literature would suggest. We then model the expected distribution of millisecond pulsars in the Galaxy and find that high-frequency surveys, with sensitivities similar to the current Parkes multibeam survey, are likely to detect MSPs in large numbers. The observed distribution of MSPs will be much less isotropic than that resulting from low-frequency surveys, with 50% of detectable MSPs residing within 11 degrees of the Galactic plane in an all-sky survey.