Research On Pulsar Timing Model And Stability Of Spin Behaviors

Pulsar timing has turned millisecond pulsars into powerful tools for the study of time keeping, neutron star physics, the interstellar medium and binary systems. Pulsar-timing observations have produced some of the most exciting results in pulsar astronomy and indeed in all of astronomy, but detecting gravitational radiation has put the higher demands on the precision of the pulsar timing model. The spin stability of millisecond pulsar can reach to 10 ?1 9 ~10?2 1 s/s, may be used as the most stable natural frequency standards in fundamental metrology. This paper has studied mainly the pulsar timing model and pulsar spin stability, including relativistic modeling of pulsar timing,the fitting of these TOAs to a model and the analysis of pulsar spin stability.Main conclusions of the paper are:1. The newtonian and relativistic theoretical foundations of pulsar timing are compared and analyzed. The relativistic modeling of pulsar timing is discussed.2. The second order relativistic effects of the sun and the earth in deriving high precision transformation equation between the proper time on the earth and the coordinate time in solar system are considered. The arrival time formula of pulsar signal is obtained from the null geodesic equation; meanwhile, the different kinds of relativistic effects are discussed. The difference between the pulsar timing equation and VLBI delay model is discussed in detail3. The various effects must be confronted in the program which pulsars signal spreaded from the pulsar to the receiver. An analytical model of the TOA with 1ns precision is designed. And the timing observations of PSR J0437-4715 are processed by using the Tempo2 software, the parameters of the timing model are confirmed, the different kinds of relativistic effects are established. The timing model errors are mainly from the analytical model errors of the TOA, the error on the interstellar dispersive time delay, the instability of pulsar spin.4. A measurement model for precision pulsar timing is established, a method is discusses which characterizing pulsar timing noise. The detection of TOA perturbations, which caused by the gravitational wave background, is affected by the levels of the millisecond pulsar timing noise. The influences of the different timing effects in TOA perturbations are summarized. The effects of the four canonical pulsars timing noise that contributed to the white-noise term are analyzed. The method to mitigate the timing noise from non-dispersive chromatic effects is summarized.5. The conclusion that the stability of pulsar spin is a guarantee of pulsar navigation and time-keeping is gained. The spatial region of navigation is enhanced using pulsars to define space-time coordinates. Through the analysis of pulsar time-scale forecast, the prediction precision of pulsar pulse model is high at the time near the reference epochs; also, the precision would decline at the time away from the reference epochs. The suggestion is concluded that the latest pulsar timing model should be applied in the pulsar navigation.6. The stability of the atomic time and pulsar time is compared and analyzed. The stability of atomic clock are affected mainly by its internal noise, while, the biggest noise of pulsar time is the instability of pulsar spin. The stability of pulsar time is charactered by ? z method. The results of research have shown: the stability of atomic time is better than pulsar time in the short time span, whereas, the stability of pulsar time is better than atomic time in the long time span(e.g.: 1y). The ensemble pulsar time, which is assembled by multi pulsar time, can well remove the common errors to rise up the precision of pulsar time.