The Radio Parallax of the Crab Pulsar: A First VLBI Measurement Calibrated with Giant Pulses

Abstract

We use four observations with the European very long baseline interferometry (VLBI) network to measure the first precise radio parallax of the Crab Pulsar. We found two in-beam extragalactic sources just outside the Crab Nebula, with one bright enough to use as a background reference source in our data. We use the Crab Pulsar’s giant pulses to determine fringe and bandpass calibration solutions, which greatly improved the sensitivity and reliability of our images and allowed us to determine precise positional offsets between the pulsar and the background source. From those offsets, we determine a parallax of π = 0.53 ± 0.06 mas and proper motion of ( μ _α , μ _δ ) = (−11.34 ± 0.06, 2.65 ± 0.14) mas yr ^−1 , yielding a distance of $d={1.90}_{-0.18}^{+0.22}\,\mathrm{kpc}$ and transverse velocity of ${v}_{\perp }={104}_{-11}^{+13}\,\mathrm{km}\,{{\rm{s}}}^{-1}$ . These results are consistent with the Gaia 3 measurements, and open up the possibility of far more accurate astrometry with further VLBI observations.

Keywords

• Very long baseline interferometry
• Supernova remnants
• Radio bursts
• Radio astrometry
• Pulsars
• Parallax