The Proper Motion of PSR J0205+6449 in 3C 58

TL;DR

This study uses advanced VLBI radio observations to precisely measure the position and proper motion of pulsar PSR J0205+6449, revealing a very low velocity inconsistent with typical pulsar speeds and refining its optical counterpart.

Contribution

Introduces a novel VLBI technique combining single-dish and correlated data to accurately measure pulsar proper motion and refutes previous optical identification.

Findings

Proper motion of (2.3 +- 0.3) mas/yr measured

Projected velocity of (35 +- 6) km/s determined

Optical counterpart identified at R~24 magnitude

Abstract

We report on sensitive phase-referenced and gated 1.4-GHz VLBI radio observations of the pulsar PSR J0205+6449 in the young pulsar-wind nebula 3C 58, made in 2007 and 2010. We employed a novel technique where the ~105-m Green Bank telescope is used simultaneously to obtain single-dish data used to determine the pulsar's period as well as to obtain the VLBI data, allowing the VLBI correlation to be gated synchronously with the pulse to increase the signal-to-noise. The high timing noise of this young pulsar precludes the determination of the proper motion from the pulsar timing. We derive the position of the pulsar accurate at the milliarcsecond level, which is consistent with a re-determined position from the Chandra X-ray observations. We reject the original tentative optical identification of the pulsar by Shearer and Neustroev (2008), but rather identify a different optical counterpart on their images, with R-band magnitude ~24. We also determine an accurate proper motion for PSR J0205+6449 of (2.3 +- 0.3) mas/yr, corresponding to a projected velocity of only (35 +- 6) km/s for a distance of 3.2 kpc, at p.a. -38 deg. This projected velocity is quite low compared to the velocity dispersion of known pulsars of ~200 km/s. Our measured proper motion does not suggest any particular kinematic age for the pulsar.