A young stellar quadruple with non-coplanar orbits

Stars form in clusters and associations; some of the multiple systems born in such environments will remain gravitationaly bound for their entire life. Multiplicity is thus an inherent property of stellar populations. Recent large spectroscopic surveys have harvested many spectroscopic multiple systems with two and three components but those with four components (SB4) remain comparatively very rare. Here we report on the preliminary properties of the first SB4 found within a cluster: HD 74438, located in the close-by young open cluster IC 2391. It is the youngest (43 My) SB4 discovered so far. Identified in the context of the Gaia-ESO Survey, this system benefited from HRS/SALT, HERCULES/UCMJO spectroscopic follow-up and archival observations from ESO. We show that the system consists of a 2+2 bound hierarchical stellar system, \emph{i.e.} two SB2 gravitationaly bound. We derived orbital and astrophysical parameters for the two inner pairs and found that their orbits are non-coplanar. The outer pair is characterized by a preliminary orbit of 6 y with an eccentricity of 0.5. The non-coplanarity of the two inner pairs sheds light on secular evolution of quadruple systems that can lead to merger end-points of stellar evolution in multiples.