2002MNRAS.333..202A

We present a new optical spectroscopic study of the O-type binary HD 165052 based on high- and intermediate-resolution CCD observations. We re-investigated the spectral classification of the binary components, obtaining spectral types of O6.5V and O7.5V for the primary and secondary, respectively, finding that both stars display weak Ciiiλ 5696 emission in their spectra. We also determined a radial-velocity orbit for HD 165052 with a period of 2.95510±0.00001d, and semi-amplitudes of 94.8 and 104.7±0.5km.s^–1, resulting in a mass ratio Q =0.9. From a comparison with previous radial-velocity determinations, we found evidence of apsidal motion in the system. Several signatures of wind-wind collision, such as phase-locked variability of the X-ray flux and the Struve-Sahade effect, are also considered. It was also found that the reddening in the region should be normal, in contrast with previous determinations.