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We present radial-velocity (RV) measurements for the K giant $\nu$ Oph (=HIP88048, HD163917, HR6698), which reveal two brown dwarf companions with aperiod ratio close to 6:1. For our orbital analysis we use 150 precise RVmeasurements taken at Lick Observatory between 2000 and 2011, and we combinethem with RV data for this star available in the literature. Using a stellarmass of $M = 2.7\,M_\odot$ for $\nu$ Oph and applying a self-consistent N-bodymodel we estimate the minimum dynamical companion masses to be $m_1\sin i\approx 22.2\,M_{\mathrm{Jup}}$ and $m_2\sin i \approx 24.7\,M_{\mathrm{Jup}}$,with orbital periods $P_1 \approx 530$ d and $P_2 \approx 3185$ d. We study alarge set of potential orbital configurations for this system, employing abootstrap analysis and a systematic $\chi_{\nu}^2$ grid-search coupled with ourdynamical fitting model, and we examine their long-term stability. We find thatthe system is indeed locked in a 6:1 mean motion resonance (MMR), with $\Delta\omega$ and all six resonance angles $\theta_{1}, \ldots, \theta_{6}$ libratingaround 0$^\circ$. We also test a large set of coplanar inclined configurations,and we find that the system will remain in a stable resonance for most of theseconfigurations. The $\nu$ Oph system is important for probing planetaryformation and evolution scenarios. It seems very likely that the two browndwarf companions of $\nu$ Oph formed like planets in a circumstellar diskaround the star and have been trapped in a MMR by smooth migration capture.

Precise radial velocities of giant stars. XI. Two brown dwarfs in 6:1 mean motion resonance around the K giant star $\nu$ Ophiuchi