  In this paper we present a spectroscopic study of six double-lined binaries,
five of which were recently discovered in a high-resolution spectroscopic
survey of optical counterparts of stellar X-ray sources. Thanks to
high-resolution spectra acquired with CAOS spectropolarimeter during seven
years, we were able to measure the radial velocities of their components and
determine their orbital elements. We have applied our code COMPO2 to determine
the spectral types and atmospheric parameters of the components of these
spectroscopic binaries and found that two of these systems are composed of main
sequence stars, while the other four contain at least one evolved (giant or
subgiant) component, similar to other well-known RS CVn systems. The
subtraction of a photospheric template built up with spectra of non-active
stars of the same spectral type as those of the components of each system has
allowed us to investigate the chromospheric emission that fills in the
H$\alpha$ cores. We found that the colder component is normally the one with
the largest H$\alpha$ emission. None of the systems show a detectable
LiI$\lambda$6708 line, with the exception of TYC 4279-1821-1, which exhibits
high photospheric abundances in both components. Photometric time series from
the literature allowed us to assess that the five systems with a nearly
circular orbit have also photometric periods close or equal to the orbital
ones, indicating spin-orbit synchronization. For the system with a highly
eccentric orbit, a possible pseudo-synchronization with the periastron velocity
is suggested.
