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Absolute Magnitude Calibration for the W UMa-Type Systems Based on HIPPARCOS Data

Rucinski, S. M.; Duerbeck, H. W.

Hipparcos parallax data for 40 contact binary stars of the W UMa-type (with epsilon M_V < 0.5) are used to derive a new, (B-V)-based absolute-magnitude calibration of the form M_V = M_V(log P,B-V). The calibration covers the ranges 0.26 < (B-V)_0 < 1.14, 0.24 < P < 1.15 day, and 1.4 < M_V < 6.1; it is based on a solution weigh…

Luminosities of SX Phoenicis, Large-Amplitude Delta Scuti, and RR Lyrae Stars

McNamara, D.

Strömgren _uvbyβ photometry of SX Phoenicis and large-amplitude δ Scuti variables is analyzed to determine the mean temperatures, metal abundances, and surface gravities of the stars. The mean temperatures and fundamental periods are used in conjunction with the pulsation equation and stellar models to derive masses, radii, surface gravities, and …

High S/N Echelle Spectroscopy in Young Stellar Groups. I. Observations and Data Reduction

Brown, A. G. A.; Le Poole, R. S.; David, M. +4 more

This is the first paper in a series in which we study the kinematical structure and dynamical evolution of OB associations and young stellar clusters. By means of high-resolution high-S/N spectroscopic observations, we aim at obtaining accurate stellar radial and rotational velocities and information on binarity in a selected number of such system…

Parallaxes and Proper Motions of Prototypes of Astrophysically Interesting Classes of Stars. I. R Coronae Borealis Variables

Kundu, Arunav; Trimble, V.

Hipparcos data were obtained under the 1982 announcement of opportunity for the seven brightest R CrB stars then known. None of the parallax measurements is different from zero in a statistically significant way, though most of the proper motions are. The body of the data nevertheless suggest that the stars belong to two rather different populatio…

HIPPARCOS Astrometry of Infrared-Selected Sources and the Connection Between Optical and Infrared Reference Frames

Sutton, E.

Astrometric data from the Hipparcos satellite are reported for the optical counterparts of 87 bright infrared sources. These sources may be useful in defining a reference frame for infrared observations. The data are also useful in studying the locations of circumstellar SiO masers. (SECTION: Stars)