MULTIFREQUENCY FLUX-DENSITY MEASUREMENTS OF 280 PULSARS

We report flux density measurements of pulsars made at radio frequencies centred around 408, 606, 925, 1408 and 1606 MHz using the 76-m Lovell telescope at Jodrell Bank. The large number of observations made over a period of more than 3 yr have reduced many of the effects of refractive and diffractive interstellar scintillation and have provided greatly improved flux density measurements for 280 pulsars. Our results show that, over the frequency range considered, the spectral behaviour of the majority of pulsars can be well described by a simple power law. Using this data base, together with other published data, we have studied the spectra of a large fraction of the known pulsar population. The mean spectral index in our sample is - 1.6, similar to that previously thought. There is a broad inverse correlation between spectral index and characteristic age. Millisecond pulsars exhibit a strong, positive correlation between spectral index and period. As a by-product of this study, we have determined pulse widths at 408 MHz for the majority of the pulsars in our sample, many of which were not previously published. The correlation between pulse duty cycle and pulse period, as noted by previous authors, is clearly seen in our data.