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Session 16 - Radio Pulsars.
Display session, Monday, January 15
North Banquet Hall, Convention Center
The frequency dependence of pulsar radiation is of substantial interest as its investigation can lead to a better understanding of pulsar emission mechanisms. Due to the steep emissiom spectra that pulsars often exhibit observations at high frequencies are rare; due to technical difficulties, multifrequency studies are even more scarce. We have conducted simultaneous observations of 19 pulsars using the dual frequency 11 cm and 3.8 cm (2.3 GHz and 8.5 GHz) receiver at the secondary focus of the Effelsberg 100 m radiotelescope. The experiment was repeated at 5 different epochs.
Average profiles were used to derive Dispersion Measures and compare these with the previously available measures, calculated from low frequency data. Our instumental set up is such that the time stamp which accompanies the two frequencies is identical, and therefore it is not necessary to postulate any timing model to derive Disperion Measures. The avegage profiles at the two frequencies were simply correlated and Dispersion Measures were derived from the lag at maximum correlation.
At high frequencies the average profiles tend to be stable and longitude reference points are conserved, resulting in a confirmation of the f^-2 cold plasma dispersion relation in the observed time of arrival delays. In the cases where some anomalies were detected they were usually attributed to profile distortions between the two frequencies; implying that systematic errors could be contained in earlier low-frequency Dispersion Measure calculations where parts of the profiles have no analogy at high frequencies.
