Multiplicity of the Orion Trapezium stars

Abstract: Preliminary results on the ongoing spectroscopic study of the six brightest Orion Trapezium stars is presented here. The main purpose of this work is to better understand the multiplicity and stability of each of these subsystems and the dynamical future of the group. So far the most interesting results reached are: 1) The orbit of the secondary star of the eclipsing Component A (V1016 Ori) is highly inclined with respect to the equatorial plane of its primary star. 2) The also eclipsing binary BM Ori (Trapezium Component B) does have a tertiary member with period about 3.5 years, as proposed by Vitrichenko & Klochkova (2004), and is the same as the companion recently found by the GRAVITY collaboration et al. (2018}. 3) Component D is indeed a spectroscopic and interferometric double star with a relatively high-mass companion ($q=M_2/M_1=0.5$) and period $52.90\pm0.05\,d$. 4) Component F, is a CP star (B7.5 p Si); its radial velocity, $23.2\pm4.2\,km\,s^{-1}$, is smaller than that of all other Trapezium members and, possibly, the evolutionary stage of the star is more advanced than that of members with similar mass. Consequently, Component F is probably not physically related to the Trapezium. Several evidences point to the extreme youth of this stellar group; its further study, most likely, will shed light on the formation processes of massive stars.