* Astronomy

Title: Apsidal motion in massive close binary systems. I. HD 165052 an extreme case?
Authors: G. Ferrero, R. Gamen, O. G. Benvenuto, E. Fernández-Lajús

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.

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