Abstract Understanding the origins of massive, widely separated planetary-mass companions has been an ongoing effort in the field. A subset of these objects has been found around binary stars, which can provide additional constraints on their formation histories. In this paper, we use two decades of astrometric monitoring to obtain an orbital solution for one such system, ROXs 42B, which consists of a young, ∼6−14 M J companion orbiting a moderate (∼10 au) separation binary. We find two degenerate solutions for the mutual inclination between the binary and companion, corresponding to either a prograde or retrograde orbit, of 51° − 14 + 24 and 130° − 22 + 16 , respectively. Importantly, we are able to rule out scenarios in which the orbits are well aligned. We use numerical modeling to test if planet–planet scattering by multiple giant companions can reproduce the observed configuration of this system. Our observations are equally well matched by scenarios in which the companion formed in a large misaligned disk near its current semimajor axis, and those in which it was scattered outward from a smaller orbital semimajor axis via dynamical interactions with either the host binary or other planetary-mass companions. We find that capture is insufficient to explain this system given the observed stellar densities in the cluster and the age of the system. We conclude that the companion, ROXs 42B b, likely formed in the circumbinary disk.
Inglis et al. (Fri,) studied this question.