2008MNRAS.387.1583R

An algorithm of the ensemble pulsar time based on the optimal Wiener filtration method has been constructed. This algorithm allows the separation of the contributions to the post-fit pulsar timing residuals of the atomic clock and the pulsar itself. Filters were designed using the cross- and auto-covariance functions of the timing residuals. The method has been applied to the timing data of millisecond pulsars PSR B1855+09 and B1937+21 and allowed the filtering out of the atomic-scale component from the pulsar data. Direct comparison of the terrestrial time TT(BIPM06) and the ensemble pulsar time PT_ensrevealed that the fractional instability of TT(BIPM06)-PT_ens is equal to σ_z_= (0.8±1.9)x10^–15. Based on the σ_z statistics of TT(BIPM06)-PT_ens, a new limit of the energy density of the gravitational wave background was calculated to be equal to Ω_gh² ∼ 3 x10^–9.