DUPLICITY IN HUBBLE-SPACE-TELESCOPE GUIDE STARS - FINE GUIDANCE SENSOR SERENDIPITOUS SURVEY RESULTS

Data from the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) interferometers, covering 22 months of guide-star acquisition operatio ns, have been analyzed for evidence of stellar duplicity. The data com prise a survey of observed guide stars, all of which are taken from th e HST Guide Star Catalog, ranging in magnitude from 9 to 14. The surve y results cover a parameter space for the newly found doubles, for the fainter stars, which are of smaller limiting angular separations than in any previous surveys. The normal HST engineering telemetry data fr om 13,979 acquisitions on 4882 stars have been processed. The FGS guid ance data call reveal duplicity with separations ranging from approxim ately 30 mas; for the brighter stars, with small magnitude differences , up to the neighborhood of 500 mas, and in some cases to 1000 mas. Th e fraction of guide stars indicating duplicity is a function of the st atistical criteria used but is over 5% at a very high level of confide nce. It is possible that if some of the brighter and closer pairs coul d be identified as nearby, then their orbital motions would be rapid e nough to allow a mass and distance determination on a timescale of a d ecade if followed With ground-based interferometric and spectroscopic instruments. A brief catalog of doubles is given, nearly all of which are of certain duplicity. Information for accessing on-line catalogs o f large numbers of stars with lesser, but nevertheless strong, probabi lities of duplicity and also for the solutions for duplicity from all acquisitions is provided.