WR 20a: A massive cornerstone binary system comprising two extreme early-type stars

Abstract

We analyse spectroscopic observations of WR 20a revealing that this star is a massive early-type binary system with a most probable orbital period of ~3.675 days. Our spectra indicate that both components are most likely of WN6ha or O3If*/WN6ha spectral type. The orbital solution for a period of 3.675 days yields extremely large minimum masses of and for the two stars. These properties make WR 20a a cornerstone system for the study of massive star evolution.