Masato Imae

Pulsar VLBI experiment with the Kashima (Japan)–Kalyazin (Russia) baseline

Abstract The position of PSR0329+54 on the International Celestial Reference Frame was measured at epochs March 1995, May 1996, and May 1998. Our observations detected the proper motion of PSR0329+54. The position and proper motion agreed well with the position determined by Bartel et al. (1985) . From combined analysis with our data and that of Bartel, the proper motion of PSR0329+54 was determined: μ α =+17.4±0.3 mas yr −1 , μ δ =−11.0±0.3 mas yr −1 . These results are consistent with the value by Harrison et al. (1993) measured with the MERLIN interferometer. We also determined the coordinates of PSR0329+54 very accurately within the ICRF: α =03 h 32 m 59 s .3761±0 s .0002, δ =54°34′43′′.5119±0′′.0015 at 1995.

Two-frequency timing of the pulsar B1937+21 in Kalyazin and Kashima in 1997-2002

We present the results from our timing of the millisecond pulsar B1937+21, performed jointly since 1997 on two radio telescopes: the RT-64 in Kalyazin (Russia) at a frequency of 0.6GHz and RT-34 in Kashima (Japan) at a frequency of 2.15 GHz. The rms value of the pulse time of arrival (TOA) residuals for the pulsar at the barycenter of the Solar system is 1.8 μs (the relative variation is ≈10−14 over the observing period). The TOA residuals are shown to be dominated by white phase noise, which allows this pulsar to be used as an independent time scale keeper. The upper limit for the gravitational background energy density Ωgh2 at frequencies ≈6.5 × 10−9 Hz is estimated to be no higher than 10−6. Based on the long-term timing of the pulsar, we have improved its parameters and accurately determined the dispersion measure and its time variation over the period 1984–2002, which was, on average, −0.00114(3) pc cm−3 yr−1.