HYDROGEN-DEFICIENT BINARIES - PHOTOMETRY AND ORBITS

Photometric and spectroscopic observations of the extremely hydrogen-d eficient binaries v Sgr, LSS 4300 and CPD-58 degrees 2721 have been ob tained at Mt John University Observatory (MJUO) to examine the nature of these systems. The photometric data do not confirm that v Sgr is an eclipsing system. These data are also used to examine long-term light and colour variations in the star, which show some longer-term period s of brightness variations which may be indicative of stellar activity in the primary star of this system. The spectroscopic data yield sets of orbital parameters for v Sgr and LSS 4300. For v Sgr, these are co nsistent with the orbital parameters obtained earlier this century. Co mparisons are also made between the H alpha profiles of the three syst ems and phase-related Ha profile variations in v Sgr discussed. All th e observational data provide confirmation for a model involving supers onic mass exchange between the components of the binary system.