Presentation #403.04 in the session Resonant Dynamics and Consequences, Plus Disks!.
A leading theoretical expectation for the final stages of planet formation is that disk migration should naturally drive orbits into chains of mean motion resonances (MMRs). In order to explain the dearth of MMR chains observed at Gyr ages (<1%), this picture requires such configurations to destabilize and scramble period ratios following disk dispersal. Strikingly, the only two known stars with three or more planets younger than 100 Myrs, HR 8799 and V1298 Tau, have been suggested to be in such MMR chains, given the orbits’ near-integer period ratios. We incorporate recent transit and radial velocity observations of the V1298 Tau system, and investigate constraints on the system’s orbital architecture imposed by requiring dynamical stability on timescales much shorter than the system’s age. We show that the recent radial-velocity mass measurement of V1298 Tau b places it within a factor of two of the instability limit, and this allows us to set significantly lower limits on the eccentricity (eb ≤ 0.18 at 99.7% confidence). Additionally, we rule out a resonant chain configuration for V1298 Tau at >99% confidence. Thus, if the 23 Myr-old V1298 Tau system formed as a resonant chain, it must have undergone an instability and rearrangement shortly after disk dispersal. We expect that similar stability constrained characterization of future young multi-planet systems will help inform planet formation models.