Speckle Masking Imaging of the Spectroscopic Binaries Gliese 150.2 and 41 Draconis

Abstract

Despite a history of micrometric observations dating back more than 150 years, and many decades of astrometric and interferometric study of low-mass main sequence binary stars in the solar neighborhood, their masses and luminosities are known with much lower accuracies than for massive (1.5 ≤ M/M _⊙ ≤ 10) stars of early spectral types. The latest”conservative” list of 45 binaries with normal components, whose masses and radii are measured with an error ≤ 2%, includes only 3 objects of spectral type G, one pair of the type M, and no K-type binaries (Andersen, 1991). Only 3 systems from this list are within 50 pc from the Sun. This is explained by the observation selection effect which confines the list of stars with fundamental masses and luminosities to double-lined eclipsing binaries. The HIPPAR-COS astrometric mission will not change the situation significantly because its parallax errors will be too high to satisfy the 2% accuracy criterion even for stars within 25 pc from the Sun. Therefore, we decided to focus our attention on spectroscopic pairs recently discovered by cross-correlation spectroscopy. For nearby solar-type stars the most extensive surveys of radial velocities have been done by Duquennoy and Mayor (1991) and Tokovinin (1988). From Tokovinin’s list, a few spectroscopic binaries with fast orbital motion were first resolved by speckle interferometric observations at the 6-m telescope of the Special Astrophysical Observatory (SAO) in Zelenchuk.