Abstract
We present an observational analysis of the eclipsing double-lined spectroscopic binary HR 7422=V4089 Sgr. Nineteen spectra were obtained with the 2.15 m telescope and the bench echelle spectrograph EBASIM of the CASLEO observatory, while photometric observations in the Johnson V band were carried out with the 61 cm telescope at CASLEO. We measured radial velocities to a precision of 0.45 km s^-1 for both stellar components using the method of separation of composite spectra by González & Levato (2006, A&A, 448, 283). From light and radial velocity curves we derived orbital and physical parameters for the system using the Wilson & Devinney code. With this aim, our light curve was complemented with the photometry in the V band of the Geneva system published by North et al. (1997, A&A, 324, 137). We obtained masses and radii to a precision of 0.45% and 0.9%, respectively. The system V4089 Sgr is very useful to test stellar models due to the great difference between the components. The comparison with theoretical stellar models of Lejeune & Schaerer (2001, A&A, 366, 538) suggest an age of log τ = 8.695+/-0.007. Since the primary is close to the TAMS, we used this system to compare the predictions of standard and overshooting models.
