Multiplicity of Herbig Ae/Be Stars

One of the most interesting constraints on the formation models comes from the study of multiplicity of young stars as a function of mass. While multiplicity studies of low mass T Tauri stars have been quite exhaustive, an unbiased and systematic investigation of multiplicity among Herbig Ae/Be stars is still lacking. We are therefore conducting a photometric and spectroscopic study of multiple systems among Herbig Ae/Be (HAEBE) stars, in order to first detect companions and then investigate their properties. The frequency and degree of multiplicity of HAEBE systems will provide new constraints on their formation mechanism. Our program consists of: 1. high resolution AO imaging to detect close companions. We have data from about 80 stars obtained mainly with NIRI/Altair at Gemini but also with NACO at the VLT; 2. differential JHKL photometry of detected binaries to derive spectral energy distributions of the components of the systems; 3. near-infrared (NIR) spectroscopy to determine the spectral type of the companions.Our program has already measured NIR spectra of all southern candidates currently known and accessible with GNIRS (21). 4. BVRIJHK imaging (FOV=2.5' & res. 0.8''), to study clustering around HAEBE stars. The spectral information combined with the photometrically calibrated SEDs will allow us to determine the distance and extinction (thereby establishing physical association of companion) and, investigate the nature of the infrared excess in the secondary stars.