Supplement to the Published Duplicity Catalog

The complete electronic catalog of HST/FGS Acquisition Double Stars referred to in:

"Duplicity in HST Guide Stars: FGS Serendipitous Survey Results"
      by G. Schneider, J. L. Hershey, and M.T. Wenz
published in P.A.S.P, 110, #751, pp. 1012-1025 (1998), may be found here.

Queries should be addressed to: Glenn Schneider at

This web site currently provides information on ALL of the 4882 stars and 13,979 acquisitions examined for evidence of duplicity in our serendipitous survey under HST Archival Research program AR/5811.  Most of these show no indication of harboring close companions within our detection limits.  The published catalog of 269 FGS doubles contains only those detections of very high confidence as discussed in the above referenced paper.  The statistical certainty of detection declines sharply for companions with separations less than approximately 30mas (also as a function of delta-magnitude).  Undoubtedly a significant number of these (as well as some more widely spaced systems of larger delta-magnitude) are actually double.  The files available on this server will allow individuals to assess for themselves the likelihood of duplicity for all of the stars in our survey.

Under HST Archival Research program AR/8370 we anticipate tripling the size of the current supplemental catalog with the addition of information on 9,168 new stars from 26,279 acquisitions not previously studied.  Part II of the catalog, which should be released later this year will span 1,766 days and contain data extracted from all acquisitions from 1995 day 1, though 1999 day 316.


Observation and duplicity information for the survey stars are keyed by observation date/time, cross-referenced by HST Guide Star Catalog ID number.  The complete list of candidate stars analyzed in this study is given in the Cross-Reference List of Observed HST Guide Stars.  Consult this list to find the "root name" of the data files associated with the candidate guide star of interest.  The "root name" contains the date of the first acquisition of the star.  The Source (Input) Catalog has been broken up into nine files (due to it's large size), organized by date.  To find information about a Guide Star of interest find its data "root name" in the Cross-Reference List and search the appropriate Source Catalog File for the file name or guide star ID.  Records C-F (for each acquisition) will provide information on the likelihood of duplicity.  Tabular (ASCII) listings of observed FGS S-Curves with their acquisition parameters, as well as parametric fits to double-star S-Curves may be downloaded as keyed by the data root name.  We also provide PostScript plots of the fringe visibility functions for the detections of high confidence reported in our published catalog.

Cross-Reference List of Observed HST Guide Stars

Source (Input) Catalog Files

Organized by date of acquisition

FORMAT of the Source Catalog Files

  • 1996: Day 041-219
  • 1996: Day 220-318
  • 1996  Day 318 - 1997 Day 073
  • 1997: Day 074-145
  • 1997: Day 145_215
  • 1997: Day 215-270
  • 1997: Day 271-328
  • 1997: Day 328-365
  • 1998: Day 001-046

  • Observed FGS S-Curves and Acquisition Parameters

    Headers: FGS Number, GSC Magnitude, X/Y Walkdown length, # lines of data, U.T., FGS/FGE parameters, S/C Attitude and Sun Angle.
    Content by Column: X-Coordinate, Y-Coordinate, X S-Curve, Y S-Curve
  • Possible Double-Star Determined from Successful Walkdowns to FineLock
  • Possible Double-Star Determined from Fine-Lock Failures
  • All Observed S-Curves (including those with no evidence of duplicity) [not yet loaded on server]

  • Parametric Fits to Double Star S-Curves

    Headers: FGS Number, GSC Magnitude, Separation (MAS), Magnitude Difference, FGS-Axis, Guide Star ID, Error Ratios.
    Content by Column: Coordinate, Observed Fringe Amplitude, Mode Fringe Amplitude, Component Fringe Amplitudes
    Note: The published double star catalog contains only those solutions with very high confidence of duplicity (>~95%). For smaller separations (typically <~30mas) the statistical certainty of duplicity is diminished. The error ratios for both the candidate primary and secondary star fringe visibility curves were used to establish the confidence level of duplicity for those stars which were published in the catalog (see the referenced paper for details).
  • Determined from Successful Walkdowns to FineLock
  • Determined from Fine-Lock Failures

  • PostScript Plots of Catalog Double Star S-Curves

  • Determined from Successful Walkdowns to FineLock
  • Determined from Fine-Lock Failures

  • This work is based upon observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

    This study is supported under Archive Proposals 5811 and 8370 to the University of Arizona and Computer Sciences Corportion, with additional resources from STScI's Science and Enginnering Support Division.