Pulsar Scintillation And Timing Studies

Pulsar is a fast-rotating neutron star with physical properties of ultra-high pressure,ultra-high temperature,ultra-strong magnetic field and radiation intensity.It is a space physical laboratory that cannot find on the earth,so the pulsar is known as probe that is used to research interstellar medium,Milky Way magnetic field,solar system ephemeris and gravitational waves.This paper uses the Kunming 40-meter radio telescope(KM40M)of the Yunnan Ob-servatory to study pulsar scintillation and timing studies.Scintillation is phenomenon due to influence of the interstellar medium during the propagation of the pulsar signal.The amplitude of pulsar is variable,because the effect of interstellar medium.we observed the scintillation of PSR B0355+54 at a center frequency 2256MHz with span 60-day,we de-tected 15 15 dynamic spectral and found scintillation arc at S band,we found that the curvature of the scintillation arc ? changes on the order of day.The theory of scintillation hold that the scintillation arc ? is constant,we propose that scintillation are dominated by different scintillation screen at different observation epoch.we calculated the position of the scintillation screen between 0.01-0.lkpc,and the size of the interstellar medium mass is 0.1au.we builded the pulsar timing system using Pulsar Digital Filterbank 4(PDFB4),Now we monitor more than 90 pulsars,there are more 3 years timing data.Millisecond pulsar arrival time accuracy of PSR J0437-4715 is<800ns,it is the highest precision pulsar in China;We have observed the Vela pulsar at frequency of 2256 MHz last for two years using the S band receiver on the Kunming 40 m radio telescope.In this paper,we report the glitch event in the Vela pulsar which occurred on 2016 December 12,using the timing data from 2016 January 30 to 2018 February 1.The timing solutions for pre-and post-glitch are presented.By fitting the glitch model to the timing data,we found that the post-glitch recovery exhibits two terms of exponential decay with timescales of 1 d and 6 d.The glitch parameters are obtained with ??g/?=1.431(2)×10-6 and ??/?=73.354×10-3.The degree of glitch recovery(Q)is determined with Q?0.0085(4).The post-glitch behavior is dominated by a linear decrease in slow-down rate |?|.It was shown that,for the exponential decays in the Vela pulsar glitches with high degree of recovery,the time-scales are most-ly longer.In this paper,we also discussed the distribution of glitch sizes,the cumulative probability of waiting time.