Hidden Companions to Intermediate-mass Stars. IX. Discovery of a 1.5 M ⊙, 1 au Companion to the Primary within the Multiple HIP 57606* *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.

Abstract

HIP 57606 is an intermediate-mass a ∼ 88 au visual binary (A+B) that also has 680 au (C) and a 120,000 au (D) companions. Here we report on a VLTI/GRAVITY interferometric observation that revealed that the primary star A is itself a close binary with a 83% K band flux ratio companion at a projected separation ρ = 14.8 mas ↔ 1.0 au. Through isochrone fitting we find masses M Aa = 1.58M ⊙, M Ab = 1.49M ⊙ and M B = 1.15M ⊙ and an age 1 Gyr for the inner triple. The latter will evolve to become a double or triple white dwarf system within about 6 Gyr and which will be under the dynamical influence of the outer companion C.