Orbits of Hyades Multiple-Lined Spectroscopic Binaries. Paper 2: The Double-Lined System HD 27149

Abstract

A new determination of the orbit of the Hyades double-lined spectroscopic binary HD 27149 is presented. The well-defined orbit provides the spectroscopic basis for an extremely accurate orbital parallax for the system -- in particular, the size of the relative orbit ($a\sin i = (a_1 + a_2)\sin i = (67.075 \pm 0.045) \times 10^6$ km) is accurate to $\pm 0.07$ %. The minimum masses for the primary and secondary -- $m_1\sin ^3i = 1.096 \pm 0.002 M_\odot$ and $m_2\sin ^3i = 1.010 \pm 0.002 M_\odot$ -- are unexpectedly large for the spectral types thus suggesting the possibility of eclipses. Although the probability of eclipses is not large, the system being composed of G3V and G6V stars in a 75-day orbit, the possibility is of great interest. A rediscussion of a search for eclipses made by Jørgensen & Olsen$^1$ in 1972 shows that central eclipses can be excluded, but that shorter duration off-centre eclipses cannot be ruled out. Ephemerides for possible primary and secondary eclipses are given.