New neighbours: II. An M9 dwarf at

We present the discovery of a previously unknown member of the immediate solar neighbourhood, DENIS-P J104814.7-395606.1 (hereafter DENIS 1048-39), identified while mining the DENIS database for new nearby stars. A HIRES echelle spectrum obtained with the 10-m Keck telescope shows that it is an M9 dwarf. DENIS 1048-39 has a very bright apparent magnitude ($I=12.67$) for its spectral type and colour ($I-J=3.07$), and is therefore very nearby. If it is single its distance is only $4.1 \pm 0.6$ pc, ranking it as between our 12th and 40th closest neighbour. It is also the closest star or brown dwarf with a spectral type later than M7V. Its proper motion was determined through comparison of Sky atlas Schmidt plates, scanned by the MAMA microdensitometer, with the DENIS images. At 1.52´´yr-1 it primarily attests the closeness of DENIS 1048-39 and hence its dwarf status. These characteristics make it an obvious target for further detailed studies