An astronomer's dozen: spectroscopy of six double-lined binaries and constraints on detection limits*

Abstract

Out of a group of 11 previously known binaries with f(m) ≤ 0.1 M ⊙ observed at red wavelengths centred near 6430 A, seven have been found to be double-lined. Orbital elements and the mass ratio for six double-lined systems have been determined from the current and previously published radial-velocity observations. Spectrum addition was used to estimate the spectral types of the secondaries for the four solar-type systems but, because of the weakness of the secondary lines, only a limiting range of spectral types could be determined. HR 7038 appears to be metal rich relative to the spectral-type reference stars