Duplicity in HST Guide Stars - FGS Serendipitous Survey Results

Glenn Schneider, John L. Hershey and Michael T. Wenz

Publication of the Astronomical Society of the Pacific (Accepted, In Press)

ABSTRACT: Data from the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) interferometers covering twenty two months of guide-star acquisition operations have been analysed for evidence of of stellar duplicity. The data comprise a survey of observed guide stars, all of which are taken from the HST Guide Star Catalog, ranging in magnitude from 9 to 14. The survey 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 from 13,979 acquisitions on 4882 stars have been processed. The FGS guidance data can reveal duplicity with separations ranging from approximately 30 mas, for the brighter stars, with small magnitude differences, up to the neighborhood of 500 mas, and in some cases to 1000 mas. The fraction of guide stars indicating duplicity is a function of the statistical criteria used, but is over 5% at a very high level of confidence. It is possible that if some some of the brighter and closer pairs could be identified as nearby, that their orbital motions would be rapid enough to allow mass and distance determination on the time scale of a decade 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 of large numbers of stars with lesser, but nevertheless strong, probabilities of duplicity and also for the solutions for duplicity from all acquisitions is provided.

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Table 1
Table 2 (the catalog of doubles)