Parsec-scale jet properties of the gamma-ray quasar 3C 286
  The quasar 3C~286 is one of two compact steep spectrum sources detected by
the {\it Fermi}/LAT. Here, we investigate the radio properties of the
parsec(pc)-scale jet and its (possible) association with the $\gamma$-ray
emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at
various frequencies reveal a one-sided core--jet structure extending to the
southwest at a projected distance of $\sim$1 kpc. The component at the jet base
showing an inverted spectrum is identified as the core, with a mean brightness
temperature of $2.8\times 10^{9}$~K. The jet bends at about 600 pc (in
projection) away from the core, from a position angle of $-135^\circ$ to
$-115^\circ$. Based on the available VLBI data, we inferred the proper motion
speed of the inner jet as $0.013 \pm 0.011$ mas yr$^{-1}$ ($\beta_{\rm app} =
0.6 \pm 0.5$), corresponding to a jet speed of about $0.5\,c$ at an inclination
angle of $48^\circ$ between the jet and the line of sight of the observer. The
brightness temperature, jet speed and Lorentz factor are much lower than those
of $\gamma$-ray-emitting blazars, implying that the pc-scale jet in 3C~286 is
mildly relativistic. Unlike blazars in which $\gamma$-ray emission is in
general thought to originate from the beamed innermost jet, the location and
mechanism of $\gamma$-ray emission in 3C~286 may be different as indicated by
the current radio data. Multi-band spectrum fitting may offer a complementary
diagnostic clue of the $\gamma$-ray production mechanism in this source.
