Spectroscopic study of early-type multiple stellar systems II. New binary subsystems

摘要

Context. This work is part of a long-term spectroscopic study of a sample of30 multiple stars with early-type components. In this second paper we presentthe results of six multiple systems in which new stellar components have beendetected. Aims. The main aim is to increase the knowledge of stellar properties anddynamical structure of early-type multiple stellar systems. Methods. Using spectroscopic observations taken over a time baseline of morethan 5 years we measured RVs by cross-correlations and applied a spectraldisentangling method to double-lined systems. Besides the discovery of objectswith double-lined spectra, the existence of new spectroscopic subsystems havebeen inferred from the radial velocity variations of single-lined componentsand through the variation of the barycentric velocity of double-linedsubsystems. Orbital elements have been calculated when possible. Results. Seven new stellar components and two members that we expect toconfirm with new observations have been discovered in the six studiedmultiples. We present orbital parameters for two double-lined binaries andpreliminary orbits for three single-lined spectroscopic binaries. Five of thesix analysed systems are quadruples, while the remaining has five componentsdistributed in four hierarchical levels. These multiplicity orders are in factlower limits, since these systems lack high-resolution visual observations andadditional hierarchical level might exist in that separation range. Conclusions. The six analysed systems have greater multiplicity degree and amore complex hierarchical structure than previously known, which suggests thathigh-order multiple systems are significantly more frequent that it iscurrently estimated. The long term spectroscopic monitoring of multiple systemshas shown to be useful for the detection of companions in intermediatehierarchical levels.