Duplicity inHubble Space TelescopeGuide Stars: Fine Guidance Sensor Serendipitous Survey Results

Abstract

Data from the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) interferometers, covering 22 months of guide-star acquisition operations, have been analyzed for evidence 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 of the brighter and closer pairs could be identified as nearby, then their orbital motions would be rapid enough to allow a mass and distance determination on a timescale 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.

X-ray and optical bursts and flares in YSOs: results from a 5-day XMM-Newton monitoring campaign of L1551

“…The primary spectral type is G8, and Schneider et al (1998) report a separation of 73 mas and a magnitude difference of 1.19 mag.…”

“…Unlike the other stars in the present study, HD 285845 (an active binary system) is not a member of the star-forming region, on the basis of its radial velocity and proper motion (Walter et al, 1988). The primary spectral type is G8, and Schneider et al (1998) report a separation of 73 mas and a magnitude difference of 1.19 mag.…”

An XMM-Newton-based X-ray survey of pre-main sequence stellar emission in the L1551 star-forming complex

“…with the ones of a main sequence star, and a projected rotational velocity of Ú × Ò ¿¼ km/s (Walter et al, 1988). Schneider et al (1998) report, using HST FGS observations, a separation for the binary companion of 73 mas and a magnitude difference among the components of 1.19 mag. The apparent magnitude Î ½ ¼ ¾ implies a photometric parallax of 90 pc, indicating that HD 285845 likely is an active binary system in the foreground of L1551.…”

Asteroids observations with the Hubble Space Telescope FGS

“…The FGS astrometer offers many observation capabilities (Nelan et al 1998) that have already been used in the past for binary stars (Franz et al 1991(Franz et al , 1992Bernacca et al 1993Bernacca et al , 1995Schneider et al 1998), extended Miras (Lattanzi et al 1994(Lattanzi et al , 1997 and AGN (Hook et al 2000). For such objects the fringe pattern or S -curve changes with respect to that of a point-like source.…”

“…which is most often used to detect binary stars (Hershey 1992;Schneider et al 1998;Schneider et al 1999). This procedure is used here to provide some first hints on the size, shape and possible duplicity of the target.…”