MULTIFREQUENCY FLUX-DENSITY MEASUREMENTS OF 280 PULSARS

We report flux density measurements of pulsars made at radio frequenci es centred around 408, 606, 925, 1408 and 1606 MHz using the 76-m Love ll telescope at Jodrell Bank. The large number of observations made ov er a period of more than 3 yr have reduced many of the effects of refr active and diffractive interstellar scintillation and have provided gr eatly 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 la w. Using this data base, together with other published data, we have s tudied the spectra of a large fraction of the known pulsar population. The mean spectral index in our sample is - 1.6, similar to that previ ously thought. There is a broad inverse correlation between spectral i ndex and characteristic age. Millisecond pulsars exhibit a strong, pos itive correlation between spectral index and period. As a by-product o f this study, we have determined pulse widths at 408 MHz for the major ity of the pulsars in our sample, many of which were not previously pu blished. The correlation between pulse duty cycle and pulse period, as noted by previous authors, is clearly seen in our data.