HD 152248: Evidence for a colliding wind interaction

We present the results of a four year spectroscopic campaign on the early-type binary system HD 152248. Our analysis yields a new classification as O7.5III(f) + O7III(f), in contradiction with previous classifications of the components as supergiants. We derive improved orbital elements and the corresponding masses (M_1=29.6 M[SUB]sun[/SUB] and M_2=29.9 M[SUB]sun[/SUB]) are somewhat larger than previously reported in the literature, although they are still significantly lower than the ones expected from evolutionary tracks. Both components of the system are close to filling their Roche lobe at periastron passage. We also investigate the equivalent width variations of the lines of the two components and we discuss their relation to the Struve-Sahade effect. Finally, we show that the line profile variability of the He Iil4686 and Halpha lines is consistent with a strong wind interaction between the two stars, quite as predicted by current colliding wind models. Based on data collected at the European Southern Observatory (La Silla, Chile) and at the Cerro Tololo Inter-American Observatory (Cerro Tololo, Chile)