  We carried out a spectroscopic and photometric analysis of the binary V4089
Sgr with the aim to obtain absolute masses and radii of the components and to
compare these parameters with stellar evolution theoretical models. We took
high-resolution spectra and measured radial velocity using standard
cross-correlations and a technique of spectral disentangling. Absolute
parameters of the components were determined through the simultaneous fitting
of measured radial velocities and Geneva photometric data available in the
literature. In this way we obtained Ma=2.584+-0.008 Msun, Mb=1.607+-0.007 Msun,
Ra=3.959+-0.013 Rsun, and Rb=1.605+-0.016 Rsun. The comparison of these
parameters with two grids of theoretical models led to estimate narrow ranges
of possible values for system metallicity and age. According to circularization
theory it was not expected that the binary had achieved a circular orbit as a
result of tidal friction, so the null eccentricity found is an interesting
fact. On the other hand, we measured the projected rotational velocity of both
components and we conclude that the primary is not synchronized with orbital
motion.
