Multifrequency Radio Properties of the Crab Pulsar

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Session 21 -- Pulsars
Oral presentation, Monday, 30, 1994, 2:00-3:30

[21.03] Multifrequency Radio Properties of the Crab Pulsar

D. A. Moffett, T. H. Hankins (NMIMT)

We report phased array VLA and Arecibo observations of the Crab pulsar at multiple frequencies and high time resolution. Average profiles were recorded at 0.33, 1.4, 4.8, and 8.4 GHz, as well as high time resolution data from the ``giant'' pulses. Coherent dedispersion of the giant pulse data reveals significant intensity structure on a 30 -- 50 ns time scale.

Some giant pulses rise very fast, then decay exponentially. Exponential time constants and autocorrelation widths of these pulses have been computed for each of the observed frequencies. At low frequencies, the pulses exhibit known interstellar scattering pulse broadening. But at high frequencies, the pulse shapes suggest another form of scattering is occurring, perhaps associated with the nebula or the magnetosphere of the pulsar itself.

The morphology of the average profiles also changes with frequency. At low frequency, 0.33 GHz, a known steep-spectrum precursor of the main pulse exists which does not appear at 1.4 GHz. At 4.8 and 8.4 GHz, two more components appear after the interpulse. The separation between the main and interpulse decreases above 1.4 GHz. In addition, the relative amplitudes of the main and interpulse change with frequency, implying either an effect of the emission geometry or a difference in spectral index.

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