Absolute dimensions and apsidal motion of the eccentric binary PT Velorum

High-resolution (λ/dλ∼ 41 000) echelle spectra of the eccentric binary system PT Vel were analysed. Precise spectroscopic orbital elements of the system were obtained by means of cross-correlation technique. According to the solution of radial velocities with Hipparcos and All Sky Automated Survey-3 (ASAS-3) light curves, PT Vel consists of two main-sequence stars with masses M₁= 2.198 ± 0.016 M_⊙, M₂= 1.626 ± 0.009 M_⊙, radii R₁= 2.094 ± 0.020 R_⊙, R₂= 1.559 ± 0.020 R_⊙ and temperatures T_eff1= 9250 ± 150 K, T_eff2= 7650 ± 200 K separated from each other by A= 9.74 ± 0.02 R_⊙ in an orbit inclined . The projected rotational velocities of component stars were found to be (v sin i)₁= 63 ± 2 and (v sin i)₂= 40 ± 3 km s⁻¹ from the comparison of observed spectra with synthetic spectra which were calculated using model atmospheres. Our measurements of the projected rotational velocities indicate that both stars rotate synchronously. Analysis of longitude of periastron values obtained from light-curve analysis from different photometric sets of this moderately eccentric system (e= 0.127 ± 0.006) has revealed a significant motion of the line of apsides of corresponding to an apsidal motion period of U= 182.2 ± 8.4 yr. The contribution from general relativity effects is moderate (∼9 per cent). A comparison with predictions from interior structure models shows the real stars to be more concentrated in mass than expected. Comparison of absolute dimensions with theoretical isochrones yielded an age of the system of 400 ± 40 Myr.