  We obtained deep H- and K-band images of DENIS-P J104814-395606 using SofI
and the speckle camera SHARP-I at the ESO-3.5m-NTT as well as QUIRC at the
Mauna Kea 2.2m telescope between December 2000 and June 2001. The target was
recently discovered as nearby M9-dwarf among DENIS sources (Delfosse et al.
2001). We detect parallactic motion on our images and determine the distance to
be 4.6 pm 0.3 pc, more precise than previously known. From the available
colors, the distance, and the spectral type, we conclude from theoretical
models that the star has a mass of ~0.075 to 0.09 M_sun and an age of ~1 to 2
Gyrs. We also obtained H- and K-band spectra of this star with ISAAC at the
VLT. A faint companion candidate is detected 6 arc sec NNW of the star, which
is 6.4 pm 0.5 mag fainter in H. However, according to another image taken
several month later, the companion candidate is not co-moving with the
M9-dwarf. Instead, it is a non-moving background object. Limits for undetected
companion candidates are such that we can exclude any stellar companions
outside of ~0.25 arc sec (1 AU), any brown dwarf companions (above the
deuterium burning mass limit) outside of ~2 arc sec (9 AU), and also any
companion down to ~40 M_jup with \ge 0.15 arc sec (0.7 AU) separation, all
calculated for an age of 2 Gyrs. Our observations show that direct imaging of
sub-stellar companions near the deuterium burning mass limit in orbit around
nearby ultra-cool dwarfs is possible, even with separations that are smaller
than the semi-major axis of the outermost planet in our solar system, namely a
few tens of AU.
