The immediate environment of the Class 0 protostar VLA1623, on scales of
  ~50-100 AU, observed at millimetre and centimetre wavelengths
  We present high angular resolution observations, taken with the Very Large
Array (VLA) and Multiple Element Radio Linked Interferometer Network (MERLIN)
radio telescopes, at 7mm and 4.4cm respectively, of the prototype Class 0
protostar VLA1623. At 7mm we detect two sources (VLA1623A & B) coincident with
the two previously detected components at the centre of this system. The
separation between the two is 1.2arcsec, or ~170AU at an assumed distance of
139pc. The upper limit to the size of the source coincident with each component
of VLA1623 is ~0.7arcsec, in agreement with previous findings. This corresponds
to a diameter of ~100AU at an assumed distance of 139pc. Both components show
the same general trend in their broadband continuum spectra, of a steeper dust
continuum spectrum shortward of 7mm and a flatter spectrum longward of this.
  We estimate an upper limit to the VLA1623A disc mass of <0.13Msol and an
upper limit to its radius of ~50AU. The longer wavelength data have a spectral
index of \alpha~0.6+/-0.3. This is too steep to be explained by optically thin
free-free emission. It is most likely due to optically thick free-free
emission. Alternatively, we speculate that it might be due to the formation of
larger grains or planetesimals in the circumstellar disc. We estimate the mass
of VLA1623B to be <0.15M$sol. We can place a lower limit to its size of ~30x7
AU, and an upper limit to its diameter of ~100AU. The longer wavelength data of
VLA1623B also have a spectral index of \alpha~0.6+/-0.3. The nature of VLA1623B
remains a matter of debate. It could be a binary companion to the protostar, or
a knot in the radio jet from VLA1623A.
