No abstract

We present new radial velocity measurements for the massive binary 15 Monocerotis which indicate that the system is now very close to periastron (1996.9) in its 24 yr orbit. The velocity separation in the coming year may be large enough to permit an accurate estimate of mass ratio. We also present our first astrometric measurement of 15 Mon made with the Hubble Space Telescope Fine Guidance Sensors (FGS). The FGS transfer functions are consistent with an advanced orbital position close to periastron, and we present preliminary orbital elements for the combined spectroscopic and astrometric orbit.

We present radial velocity measurements and a single-lined spectroscopic orbit for the bright Otype star, HD 193322A, which we show to be a 311 day binary system that has a distant third companion (detected by speckle interferometry) in a 31 yr orbit. We suggest that the speckle companion appears in the spectrum as a broad-lined component of early B type. We also present a spectrum of the visual companion, HD 193322B, which appears to be an unresolved, double-lined spectroscopic binary. Thus, HD 193322, the central object in the open cluster Collinder 419, is a multiple system that contains at least five stars (possibly seven if the C and D components are physical). Such systems may play a key role in the dynamical ejection of runaway stars from young clusters.