Alejandra Rosellini Calderon (UCSC)

Most stars in the field are part of binary, triple, or higher-order systems, which we primarily observe in hierarchical configurations that allow long-term stability. Over long timescales, hierarchical triple systems interact primarily through gravitational dynamics, but more complex interactions arise when stellar evolution drives mass transfer. In our latest paper, we study tertiary mass transfer in hierarchical triple systems using three-dimensional hydrodynamic simulations. We find that the finite separation of the inner binary produces oscillations in the Roche potential that critically alter both the donor star’s variability and mean mass-loss rate. For compact inner binaries, the mass-loss rate approaches that of a single accretor, while at larger separations the orbit-averaged mass-loss rate increases steeply, approximately as . This scaling is consistent with the nonlinear response of Roche-lobe overflow to the leading quadrupolar perturbation of the inner-binary potential, which scales as . We also examine the donor’s response to periodic forcing from the inner binary and find a transition between individual and collaborative accretion that determines whether the transferred material can form and sustain a circumbinary disk. Our results show that the finite separation of the inner binary can strongly regulate both the rate and fate of tertiary mass transfer, constraining a poorly understood phase of hierarchical triple evolution.