First results on the optical campaign devoted to the gamma-ray binary candidate HD259440

Quite recently, a very high-energy gamma-ray source has been detected in the Monoceros region. This source belongs to the category of TeV emitters with no identified counterpart at other wavelengths, even though it may be coincident with other high-energy sources detected with other observatories (ROSAT, CGRO). However, it is interesting to note that the error box of this TeV source admits the possibility that the Be star HD259440 is at the origin of the high-energy emission. This may be possible only if that Be star is member of a still undetected binary system including a compact (neutron star or black hole) companion, therefore belonging to the very scarce category of gamma-ray binaries. We describe here the first results of the optical campaign devoted to HD 259440, with emphasis on the investigation of its multiplicity, using spectra obtained at the Observatoire de Haute-Provence (OHP) and at the Kitt Peak National Observatory (KPNO).