## Abstract

The tidal destruction of a star by a massive black hole, known as a tidal disruption event (TDE), is commonly modelled using the 'frozen-in' approximation. Under this approximation, the star maintains exact hydrostatic balance prior to entering the tidal sphere (radius r_{t}), after which point its internal pressure and self-gravity become instantaneously negligible and the debris undergoes ballistic free fall. We present a suite of hydrodynamical simulations of TDEs with high penetration factors β r_{t}/r_{p} = 5-7, where r_{p} is the pericentre of the stellar centre of mass, calculated using a Voronoi-based moving-mesh technique. We show that basic assumptions of the frozen-in model, such as the neglect of self-gravity inside r_{t}, are violated. Indeed, roughly equal fractions of the final energy spread accumulate exiting and entering the tidal sphere, though the frozen-in prediction is correct at the order-of-magnitude level. We also show that an $\mathcal {O}(1)$ fraction of the debris mass remains transversely confined by self-gravity even for large β which has implications for the radio emission from the unbound debris and, potentially, for the circularization efficiency of the bound streams.

Original language | English |
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Pages (from-to) | L146-L150 |

Journal | Monthly Notices of the Royal Astronomical Society: Letters |

Volume | 485 |

Issue number | 1 |

DOIs | |

State | Published - 1 May 2019 |

Externally published | Yes |

### Bibliographical note

Publisher Copyright:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

## Keywords

- black hole physics
- galaxies: nuclei
- hydrodynamics
- methods: numerical
- stars: kinematics and dynamics