## Abstract

The tidal disruption of a star by a supermassive black hole, and the subsequent accretion of the disrupted debris by that black hole, offers a direct means to study the inner regions of otherwise-quiescent galaxies. These tidal disruption events (TDEs) are being discovered at an ever-increasing rate. We present a model for the evolution of the tidally disrupted debris from a partial TDE, in which a stellar core survives the initial tidal encounter and continues to exert a gravitational influence on the expanding stream of tidally stripped debris. We use this model to show that the asymptotic fallback rate of material to the black hole in a partial TDE scales as ∝ t ^{-2.26±0.01}, and is effectively independent of the mass of the core that survives the encounter; we also estimate the rate at which TDEs approach this asymptotic scaling as a function of the core mass. These findings suggest that the late-time accretion rate onto a black hole from a TDE either declines as t ^{-5/3} if the star is completely disrupted or t ^{-9/4} if a core is left behind. We emphasize that previous investigations have not recovered this result due to the assumption of a Keplerian energy-period relationship for the debris orbits, which is no longer valid when a surviving core generates a time-dependent, gravitational potential. This dichotomy of fallback rates has important implications for the characteristic signatures of TDEs in the current era of wide-field surveys.

Original language | English (US) |
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Article number | L17 |

Journal | Astrophysical Journal Letters |

Volume | 883 |

Issue number | 1 |

DOIs | |

State | Published - Sep 20 2019 |

Externally published | Yes |

## Keywords

- black hole physics
- galaxies: nuclei
- hydrodynamics
- methods: analytical

## ASJC Scopus subject areas

- Astronomy and Astrophysics
- Space and Planetary Science