Astronomy And Astrophysics

. We report the discovery of two L dwarfs (the new spectral class defined for dwarfs cooler than the M type) in a two-epoch CCD proper motion survey of 413 square degrees, complemented by infrared photometry from DENIS. One of them has a strong lithium line and is therefore a brown dwarf. The other is a common proper motion companion to the mid-M dwarf LHS 102 (GJ 1001), which has a well determined trigonometric parallax. LHS 102B is thus the coolest L dwarf of known distance and luminosity. Key words: : Galaxy: kinematics and dynamics --- dark matter --- stars: low-mass, brown dwarfs 1. Introduction Two years ago, several very cold dwarfs were identified by DENIS (Delfosse et al., 1997) and Kelu 1 was found through its high proper motion (Ruiz, Leggett and Allard, 1997). Follow-up observations immediately showed that Send offprint requests to: Bertrand.Goldman@cea.fr ? Based on observations made at the European Southern Observatory, La Silla, Chile. their optical spectra bear li..