Hidden Companions to Intermediate-mass Stars. V. Discovery of a 1.6 M ⊙, 0.3 au Companion to Marfik within the 48 au Visual Binary HIP 80883 = λ Ophiuchi*

Abstract

Abstract λ Ophiuchi is a nearby 48 au intermediate-mass visual binary with a hierarchical, 6400 au wide companion. We report on the discovery of a close companion to the primary star (Marfik) with a K band flux ratio of 33% at a projected separation ρ = 6.1 mas ↔ 0.32 au based on a VLTI/GRAVITY observation. Isochrone fitting yields masses M Aa  = 2.39M ⊙, M Ab  = 1.62M ⊙ and M B  = 1.82M ⊙. λ Oph therefore joins a growing number of intermediate-mass binaries with 10–60 au separation in which the primary is found to be a close binary and which suggest that many white dwarfs with a main sequence companion at such separations (such as Sirius B) ultimately descended from merger products. In fact, λ Oph is a potential progenitor for a system resembling Sirius.