射电天文研究组知识库

Emission geometries, including emission region heights, beam shapes and radius-to-frequency mapping, are important clues for pulsar radiation models. Multiband radio observations reveal this valuable information. In this paper, we study two bright pulsars, PSRs B0329+54 and B1642-03, and observe them at high frequencies: 2.5, 5 and 8 GHz. The newly acquired data, together with historical archives, provide an atlas of multifrequency profiles spanning from 100 MHz to 10 GHz. We study the frequency evolution of pulse profiles as well as radiation regions using these data. First, we fit the pulse profiles with Gaussian functions to determine the phase of each component, and then we calculate the radiation altitudes of different emission components and radiation regions. We find that the inverse Compton scattering (ICS) model can reproduce the radiation geometry of these two pulsars. However, for PSR B0329+54, the radiation can be generated in either an annular gap (AG) or a core gap (CG), while the radiation of PSR B1642-03 can only be generated in a CG. This difference is caused by the inclination angle and the impact angle of these two pulsars. The relationship between the beaming angle (the angle between the radiation direction and the magnetic axis) and the radiation altitude versus frequency is also presented by modelling the beam-frequency evolution in the ICS model. The multiband pulse profiles of these two pulsars can be described well by the ICS model combined with the CG and AG.