2004ApJ...604..339C

We present the first pulsar parallaxes measured with phase-referenced pulsar VLBI observations at 5 GHz. Because of the steep spectra of pulsars, previous astrometric measurements have been at lower frequencies. However, the strongest pulsars can be observed at 5 GHz, offering the benefit of lower combined ionospheric and tropospheric phase errors, which usually limit VLBI astrometric accuracy. The pulsars B0329+54, B0355+54, and B1929+10 were observed for seven epochs spread evenly over 2 years. For B0329+54, large systematic errors led to only an upper limit on the parallax (π<1.5 mas). A new proper motion and parallax were measured for B0355+54 (π=0.91±0.16 mas), implying a distance of 1.04^+0.21_–0.16kpc and a transverse velocity of 61⁺¹²_–9km/s. The parallax and proper motion for B1929+10 were significantly improved (π=2.77±0.07 mas), yielding a distance of 361⁺¹⁰_–8pc and a transverse velocity of 177⁺⁴_–5km/s. We demonstrate that the astrometric errors are correlated with the angular separation between the phase-reference calibrator and the target source, with significantly lower errors at 5 GHz as compared to 1.6 GHz. Finally, based on our new distance determinations for B1929+10 and B0355+54, we derive or constrain the luminosities of each pulsar at high energies. We show that, for thermal emission models, the emitting area for X-rays from PSR B1929+10 is roughly consistent with the canonical size for a heated polar cap and that the conversion of spin-down power to γ-ray luminosity in B0355+54 must be low. The new proper motion for B1929+10 also implies that its progenitor is unlikely to have been the binary companion of the runaway O star ζ Ophiuchi.