Some features of the pulsed radiation from the pulsar 1919+21 at 16.7, 20 and 25 MHz

An intense interpulse radio frequency radiation of PSR 1919+21 has been detected in the range of 16.7, 20 and 25 MHz. An integrated waveform of this radiation was investigated with time resolutions ofT/16 andT/64, and several characteristic regions of the intensity maxima and minima have been revealed. As has been shown, the maximum number of the best pronounced interpulses is about four, their location being symmetrical relative to the centre of the main pulse. The fine frequency structure of the integrated radiation was also investigated. It has been found that the shape of the signal can differ considerably with a frequency diversity of 10 to 100 kHz and only slightly with a separation of 5 to 10 MHz, the difference diminishing with an increase of the observation bandwidth and of the averaging time. Pulse broadening was studied at 16.7 and 25 MHz and has been found to agree with the interstellar scattering mechanism. The mean intensity of the main pulse and the interpulses has been evaluated and an essential difference of their spectral indices established.