Variation of dispersion measure: evidence of geodetic precession of binary pulsars

Variations of dispersion measure (DM) have been observed in some binary pulsars, which can not be well explained by the propagation effects, such as turbulence of the interstellar media (ISM) between the Earth and the pulsar. This paper provides an alternative interpretation of the phenomena, the geodetic precession of the orbit plane of a binary pulsar system. The dynamic model can naturally avoid the difficulties of propagation explanations. Moreover the additional time delay represented by the DM variation of two binary pulsars can be fitted numerically, through which some interesting parameters of the binary pulsar system, i.e., the moment of inertia of pulsars can be obtained, $I_1=(2.0\pm0.6)\times 10^{45}$g cm$^{2}$. The elimination of the additional time delay by the dynamic effect means that ISM between the these pulsars and the Earth might also be stable, like some other binary pulsars.