See Makarov, "A Substellar Companion to van Maanen 2" (Astrophys. J., 600, L71-L73 (2004), Bibcode: 2004ApJ...600L..71M), and Farihi et al., and "Mid-infrared observations of Van Maanen 2: no substellar companion" (Astrophys. J., 608, L109-L112 (2004), Bibcode: 2004ApJ...608L.109F.)
