New photometry and astrometry of the isolated neutron star RX J0720-3125
  using recent VLT/FORS observations
  Since the first optical detection of RXJ0720.4-3125 various observations have
been performed to determine astrometric and photometric data. We present the
first detection of the isolated neutron star in the V Bessel filter to study
the spectral energy distribution and derive a new astrometric position. At ESO
Paranal we obtained very deep images with FORS 1 (three hours exposure time) of
RXJ0720.4-3125 in V Bessel filter in January 2008. We derive the visual
magnitude by standard star aperture photometry.Using sophisticated resampling
software we correct the images for field distortions. Then we derive an updated
position and proper motion value by comparing its position with FORS 1
observations of December 2000. We calculate a visual magnitude of V = 26.81 +-
0.09mag, which is seven times in excess of what is expected from X-ray data,
but consistent with the extant U, B and R data. Over about a seven year epoch
difference we measured a proper motion of mu = 105.1 +- 7.4mas/yr towards theta
= 296.951 deg +- 0.0063 deg (NW), consistent with previous data.
