A Systematic Study Of The Frequency Evolution Of Pulsar Pulse Profiles Width

Pulsars are compact objects with high magnetic fields.Since their discovery,many models have their own advantages in explaining various observed phenomena;however,consensus on the radiation mechanism of the pulsars has not been fully achieved yet.Multiband observations are very important for understanding the emission physics of pulsars,especially the frequency dependent behaviors of pulse profiles and their evolution,and are very useful for testing and constraining pulsar radiation models.At present,the evolution of pulsar pulse width with frequency has been studied by many researchers,but the frequency range of their studies is narrow and there are few data points,which make some observed phenomena go undiscovered.The first work of this paper is to systematic study of the frequency evolution behavior of pulse width W(the full width of the pulse profile at 50% of the pulsar amplitude)of 74 pulsars combined with the latest results of EPN and ATNF databases.We find that 71 pulsars show absorption features,which indicates that the absorption is a universal phenomenon in the pulsar population.And this phenomenon appears in all types of pulsar profile,this is different from the conclusion obtained by Rankin.This paper found that the absorption features appear in the frequency range of 100 – 800 MHz.Finally,we quantify the absorption intensity and analyze the correlation between the absorption intensity and the pulsar parameters(such as the spin period,magnetic field,and age of the pulsar).It is found that there is no direct correlation between them.Therefore,in the second work of this paper,multiband observations of PSR B1737+13 will be used to test this model.Firstly,we obtain the multiband pulse profile data of the pulsar by using the observation results of FAST and combining EPN and ATNF data.Then,each profiles are separated with square hyperbolic secant function,and the radiation beam width and radiation height of each radiation component at different frequencies are calculated.Finally,the evolution of PSR B1737 +13radiation beam width and radiation height with frequency is simulated by ICS model,and the radio radiation region of PSR B1737 +13 is determined.Our study shows that the inner cone and outer cone components of the pulsar have opposite frequency dependence,and The radiation altitude of the inner cone is lower than that of the outer cone.And the radio radiation of this pulsar may be generated in the annular gap region.We find that the ICS model well explains the evolution of the pulsar profile,suggesting that the ICS process may be the radiation mechanism of pulsars.