BATSE OBSERVATIONS OF HARD X-RAY-EMISSION FROM X-RAY BURSTERS - PRESENTATION OF A CGRO BATSE INVESTIGATION AND FIRST RESULTS/

We present an on-going BATSE/CGRO investigation devoted to search for hard X-ray emission from Xray bursters with the earth occultation and occultation transform imaging techniques. This is a collaboration betw een the BATSE team at the NASA/Marshall Space Flight Center, Columbia University and the Harvard Smithsonian Center for Astrophysics. In thi s paper, we first outline the scientific objectives of our investigati on and briefly overview some results obtained within our collaboration . We present preliminary results on two Galactic center X-ray bursters Terzan 2 and GX354-0 for which simultaneous SIGMA data exist and we r eport on the possible BATSE detection of a hard X-ray outburst from 4U 1705-44. Finally, we discuss on the hard X-ray emission from neutron stars and review the different criteria that have been proposed for di stinguishing them from black hole systems on the basis of the properti es of their hard X-ray emission.