Repeating Nuclear Transients from Repeating Partial Tidal Disruption Events

Abstract

Extragalactic nuclear transients that exhibit repeating outbursts can be modeled as the repeated dynamical interaction between bound stars and supermassive black holes (SMBHs). A subset of these transients, with recurrence timescales of months-to-years, have been explained as accretion flares from the repeated tidal stripping of a star by an SMBH, in a repeating partial tidal disruption event (rpTDE). We outline the scope of the rpTDE model and discuss hydrodynamical simulations and analytical predictions for the stability of stars undergoing repeated mass loss, and the long-term evolution of these flares as a function of stellar type and orbital parameters. Our findings demonstrate that high-mass and centrally concentrated stars undergo negligible changes in structure in response to small amounts ($\sim 1-10\%M_{\star }$) of mass loss, and can survive many mass-stripping encounters with an SMBH. Contrarily, low-mass and less evolved stars are unstable to mass loss, and would be destroyed within a few orbits. We discuss the implications of these results for constraining the stellar type and orbital parameters of observed sources, such as ASASSN-14ko, for which $\gtrsim 20$ flares have been observed, and AT2020vdq, which exhibits a second flare that is brighter than its primary outburst.

19 pages, 15 figures, Proceedings of "X-ray Quasi-Periodic Eruptions and Repeating Nuclear Transients", 16-19 June 2025, ESAC, Madrid. Published in Astronomische Nachrichten

References in corpus (11)

• Phantom: A smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics
• An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz
• GSN 069 -- A Tidal Disruption Near-Miss
• Nonlinear Damping of Oscillations in Tidal-Capture Binaries
• Quasi-periodic eruptions from mildly eccentric unstable mass transfer in galactic nuclei
• A self-lensing binary massive black hole interpretation of quasi-periodic eruptions
• The Internal Structural Adjustment due to Tidal Heating of Short-Period Inflated Giant Planets
• A simple and accurate prescription for the tidal disruption radius of a star and the peak accretion rate in tidal disruption events
• Period Evolution of Repeating Transients in Galactic Nuclei
• Adiabatic Evolution of Mass-losing Stars
• Tidal capture of stars by supermassive black holes: implications for periodic nuclear transients and quasi-periodic eruptions