On the binary nature of Van Biesbroeck 8

Abstract

The authors report observations by infrared speckle interferometry at 2.2 and 3.6 μm of the nearby M dwarf Van Biesbroeck 8. This low-luminosity star has raised much interest since the 1985 discovery by McCarthy and colleagues of a close cool companion (VB 8B) at 1arcsec, presented as the first observational evidence of the existence of brown dwarfs. At the time of the observations reported here, no companion could be detected at a distance greater than 0arcsec.4 (2.5 AU). Constraints on the dynamics of the system are deduced; the nature of VB 8B is discussed and its existence is questioned.