Measurement of the VELA pulsar's proper motion and detection of the optical counterpart of its compact X-ray nebula

Optical astronometry and photometry in the Vela pulsar field is presented, investigating the proper motion of the pulsar and the optical counterpart of the 2-arcmin-diameter compact nebula seen in X-rays. Fitting the relative position measurements together with previously published data yields mu(alpha) = 26 + or - 6 marcsec (1sigma) and mu(delta) = 28 + or - 6 marcsec/yr (1 sigma) as the proper motion of the pulsar. After a star-detection algorithm is used to detect and subtract the stellar contribution, a diffuse nebula centered around the pulsar is clearly distinguishable in the V and B exposures; several wisplike structures can be recognized in the images. The optical size of the compact nebula, 2-6 x 10 to the 17th cm, is comparable to that in X-rays, and the optical intensity can be connected to the X-ray points by a power-law-type emission with photon number index gamma = about 2.