Apsidal motion in massive close binary systems. I. HD 165052 an extreme case?

TL;DR

This study measures the apsidal motion of the massive binary HD 165052, determining its orbital parameters, stellar masses, and spectral classifications through high-resolution spectral analysis and radial velocity measurements.

Contribution

It provides new radial velocity data and calculates the apsidal motion rate, leading to refined stellar masses and spectral classifications for the binary components.

Findings

Apsidal motion rate of 12.1 degrees per year

Component masses: 22.5 and 20.5 solar masses

Spectral types reclassified as O7Vz and O7.5Vz

Abstract

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.