The Detection Of Strong Pulses From PSR B1237+25 At 1540 MHz Using Nanshan 25-m Radio Telescope

The main content of this paper is focused on the research work of single pulse radiation characteristics of pulsars.The observations and investigations of single pulse is very important because it can reflect the pulsar radiation processes.The research work related to the characteristics of single pulse radiation can help us to further understand the pulsar radiation mechanism and geometry.In this paper,we investigated the distribution of the residuals of TOA of the strong pulse radiation detected from PSR B1237+25,so as to confirm the radiation mechanism of the strong pulse of pulsars.Secondly,in order to distinguish the radiation mechanism of giant pulse,strong pulse and normal pulse,we studied the statistical distributions of signalto-noise ratio,pulse width and peak flux density ratio of strong pulses.The shape of integrated pulse profiles of strong pulses and geometry of radiation region are also being studied.It is of great scientific significance to study the strong pulse radiation of PSR B1237 + 25.Firstly,the energy of strong pulse and giant pulse are very high,which can be observed by telescopes with small radius.PSR B 1237 + 25 has many strange phenomena,such as pulse nulling,mode changing and giant pulse emission and so on.IT is helpful to understand the geometry of pulsars to studying the radiation geometry of PSR B1237 + 25In this paper we intended to study the strong pulse emission from PSR B1237+25(J name is PSR J1239+2453)in detail to investigate its radiation mechanism and structure.The observation were carried out with the Nanshan 25-m radio telescope at a central frequency of 1540 MHz,the sampling interval is 0.5 ms.A total of 793 strong pulses with signal-to-noise ratio above 5 threshold and peak flux density above 10 were detected in nearly 7-hour observational data.A five-band distribution of arrival time residuals is confirmed by timing analysis of single pulses,and the strong pulses are all distributed in five emission components in the pulse profile.This leads us to believe that there is no difference in the basic emission mechanism of the five components,and confirms that the strong pulses are emitted from the same region of the magnetosphere as the average pulse.The strong pulses in the central component,including the brightest and widest bursts,are extremely complicated.We determine the statistical properties of signal-to-noise ratios,W50 and peak flux densities of bursts at high values with power-law indices of5.10,4.93,3.25 respectively.The strong pulses are narrower than average pulse profiles by a factor of nearly 11.The peak flux densities are from 10.2 to 80.2 times that of average pulse profile.The structures of strong pulses can be divided into five types of uni-modal burst and four types of bi-modal burst.PSR B1237+25 as well as the previously detected in PSR B0031-07?PSR B1112+50?PSR J1752+2359?PSR B0656+14?PSR B1133+16 and PSR B0950+08 belong to the group of pulsars which emit strong pulses without strong magnetic fields at the light cylinder and whose power-law indices of peak flux densities are all larger than 2.Furthermore,a weak innermost cone around the core is firstly discovered at 1540 MHz,and the detailed analysis of the structures of three cones are carried out.