Integrated pulse profiles at 8.6 GHz obtained with the Shanghai Tian Ma Radio Telescope (TMRT) are presented for a sample of 26 pulsars. Mean flux densities and pulse width parameters of these pulsars are estimated. For eleven pulsars these are the first high-frequency observations and for a further four, our observations have a better signal-to-noise ratio than previous observations. For one (PSRs J0742−2822) the 8.6 GHz profiles differs from previously observed profiles. A comparison of 19 profiles with those at other frequencies shows that in nine cases the separation between the outmost leading and trailing components decreases with frequency, roughly in agreement with radius-to-frequency mapping, whereas in the other ten the separation is nearly constant. Different
The pulse profile of PSR B1133+16 is usually regarded as a conal double structure. However, its multifrequency profiles cannot simply be fitted with two Gaussian functions, and a third component is always needed to fit the bridge region (between two peaks). This would introduce additional, redundant parameters. In this paper, through a comparison of five fitting functions (Gaussian, von Mises, hyperbolic secant, square hyperbolic secant, and Lorentz), it is found that the square hyperbolic secant function can best reproduce the profile, yielding an improved fit. Moreover, a symmetric 2D radiation beam function, instead of a simple 1D Gaussian function, is used to fit the profile. Each profile with either well-resolved or not-so-well-resolved peaks could be fitted adequately using this beam function, and the bridge emission between the two peaks does not need to be a new component. Adopting inclination and impact angles based on polarization measurements, the opening angle (θ µ0 ) of the radiation beam in a certain frequency band is derived from beam-function fitting. The corresponding radiation altitudes are then calculated. Based on multi-frequency profiles, we also computed the Lorentz factors of the particles and their dispersion at those locations in both the curvature-radiation and inverse-Compton-scattering models. We found that the Lorentz factors of the particles decrease rapidly as the radiation altitude increases. Besides, the radiation prefers to be generated in an annular region rather than the core region, and this needs further validation.
The emission geometries, e.g. the emission region height, the beam shape, and radiusto-frequency mapping, are important predictions of pulsar radiation model. The multiband radio observations carry such valuable information. In this paper, we study two bright pulsars, (PSRs B0329+54 and B1642−03) and observe them in high frequency (2.5 GHz, 5 GHz, and 8 GHz). The newly acquired data together with historical archive provide an atlas of multi-frequency profiles spanning from 100 MHz to 10 GHz. We study the frequency evolution of pulse profiles and the radiation regions with the these data. We firstly fit the pulse profiles with Gaussian functions to determine the phase of each component, and then calculate the radiation altitudes of different emission components and the radiation regions. We find that the inverse Compton scattering (ICS) model can reproduce the radiation geometry of these two pulsars. But for PSR B0329+54 the radiation can be generated in either annular gap (AG) or core gap (CG), while the radiation of PSR B1642−03 can only be generated in the CG. This difference is caused by the inclination angle and the impact angle of these two pulsars. The relation of beaming angle (the angle between the radiation direction and the magnetic axis) and the radiation altitudes versus frequency is also presented by modelling the beam-frequency evolution in the ICS model. The multi-band pulse profiles of these two pulsars can be described well by the ICS model combined with the CG and AG.
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