We present a new set of radial-velocity measurements of the spectroscopic binary HD 165052 obtained by disentangling of high-resolution optical spectra. The longitude of the periastron (60 +- 2 degrees) shows a variation with respect to previous studies. We have determined the apsidal motion rate of the system (12.1 +- 0.3 degree/yr), which was used to calculate the absolute masses of the binary components: M_1 = 22.5 +- 1.0 and M_2 = 20.5 +- 0.9 solar masses. Analysing the separated spectra we have re-classified the components as O7Vz and O7.5Vz stars.
@article{arxiv.1305.1911,
title = {Apsidal motion in massive close binary systems. I. HD 165052 an extreme case?},
author = {G. Ferrero and R. Gamen and O. G. Benvenuto and E. Fernández-Lajús},
journal= {arXiv preprint arXiv:1305.1911},
year = {2015}
}