FGS Observations of Two High-Velocity Stars

Abstract

The Hubble Space Telescope Fine Guidance System has been used to obtain precise astrometry in the fields of two stars of large space velocity: R 50 = G 166-37 and W 624 = G 16-25. The measures indicate a relative trigonometric parallax for R 50 of 4.0 mas, which implies a space velocity in the galactocentric rest frame of 467 km/sec. The derived parallax for W 624 is probably about 3.0 mas but there is a large uncertainty.