A new radial velocity curve for the RS CVn star <i>σ</i> Gem

Abstract

26 high quality radial velocity measurements of the RS CVn star σ Gem taken in 1993, 1994, and 1995 are used in combination with older measurements to fit a new radial velocity curve. Essentially, the orbital parameters given by Bopp & Dempsey (1989) are confirmed. However, the orbit turns out to be circular. σ Gem is known as a single–lined binary, and also in the new spectra no trace of the secondary is found. However, combining the orbital with rotational parameters, constraints on the fundamental parameters can be found: the inclination, the radius and the two masses. The inclination is high; the mass of the primary seems to be normal for a K1 giant, its radius, however, seems to be too small.