SIMBAD references

Monitoring of the flux-densities near 30GHz are reported for four pulsars. Statistically significant variations apparently random in nature are found over 10 to 20 minutes, with rms amplitudes 20% to 100% of the mean flux. These fluctuations are substantially above the predictions for interstellar scintillation at these high frequencies. The observations presented here comprise the first attempt towards understanding the effects of the ISM on pulsar signals at such high frequencies, a spectral region where very little is known about the behaviour of pulsars or the ISM. When extrapolated from observations at lower frequencies, the four pulsars should exhibit very weak interstellar scintillation, with rms modulation indices from 2% to 14%. The fluctuations therefore are attributed rather to intrinsic variation of the pulsar emission at these frequencies.