ApJ to be submitted: Dynamics of Repeating Partial Tidal Disruption Event. I. Long-term Orbital Evolution with Dynamical Tides and Loss-cone Scattering

Abstract: A star passing a supermassive black hole (SMBH) with a pericenter distance smaller than its tidal radius can be fully disrupted, producing a nuclear transient. However, on an elliptical orbit with a pericenter distance of $\sim 1-2$ tidal radii, the star may survive and undergo repeating partial tidal disruption events (rpTDEs) at intervals set by its orbital period. Here we develop an iterative map for the dynamical formation of rpTDEs through coupled loss-cone scattering and dynamical tides in single stars from nuclear star clusters, and simulate ensembles spanning different initial orbital parameters. We find that without stellar structural responses, orbits with initial periods longer than a few hundred years reach rpTDEs rapidly, whereas those with periods shorter than a few tens of years will become extreme mass ratio inspirals (EMRIs). Across the full parameter range, the median semimajor-axis shrinkage factor for rpTDEs is $\sim 2$. Including tides does not substantially increase the rpTDE formation rate relative to the pure loss-cone estimate. When stellar expansion due to accumulated dynamical tidal heating is included, systems initially expected to become EMRIs will reach rpTDEs earlier through high-eccentricity Roche-lobe overflow (HERLO). According to our results, the stellar initial conditions adopted in future simulations of short-period rpTDEs should account for the structural response to accumulated heating by dynamical tides over the preceding long-term evolution.

Paper Link: (coming soon…)