Previous abstract Next abstract
The HST Astrometry Science Team is using the Fine Guidance Sensors (FGS) in the Transfer Function Scan mode to search for binaries among faint members of the Hyades cluster. Analysis of 31 scan-sets obtained prior to the servicing mission for 18 of the 40 stars on the search list has yielded five new binaries. Only one binary was found among eleven additional stars selected for parallax determination with HST-FGS. Note that duplicity-search stars were chosen only by cluster-membership probability based on proper motions and by apparent magnitude; selection of parallax candidates involved efforts to exclude binaries by examining each candidate's position in the color-magnitude diagram. \vskip 0.1 truein The newly detected Hyades binaries lie in the magnitude range V=10 to V=14 for the primary star; they have component magnitude differences as large as 3.5 mag and angular separations as small as 0.1 arcsec. The faintest companion discovered is of nearly 16th mag at a separation of 0.13 arsec from its primary of V=14. \vskip 0.1 truein This work is supported by NASA under grant NAG5-1603 to UTexas.
Wednesday program listing