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The nozzle shock in tidal disruption events

Bonnerot, Clément and Lu, Wenbin (2022) The nozzle shock in tidal disruption events. Monthly Notices of the Royal Astronomical Society, 511 (2). pp. 2147-2169. ISSN 0035-8711. doi:10.1093/mnras/stac146.

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Tidal disruption events (TDEs) occur when a star gets torn apart by the strong tidal forces of a supermassive black hole, which results in the formation of a debris stream that partly falls back towards the compact object. This gas moves along inclined orbital planes that intersect near pericentre, resulting in a so-called ‘nozzle shock’. We perform the first dedicated study of this interaction, making use of a two-dimensional simulation that follows the transverse gas evolution inside a given section of stream. This numerical approach circumvents the lack of resolution encountered near pericentre passage in global three-dimensional simulations using particle-based methods. As it moves inward, we find that the gas motion is purely ballistic, which near pericentre causes strong vertical compression that squeezes the stream into a thin sheet. Dissipation takes place at the resulting nozzle shock, inducing a rise in pressure that causes the collapsing gas to bounce back, although without imparting significant net expansion. As it recedes to larger distances, this matter continues to expand while remaining thin despite the influence of pressure forces. This gas evolution specifies the strength of the subsequent self-crossing shock, which we find to be more affected by black hole spin than previously estimated. We also evaluate the impact of general relativistic effects, viscous dissipation, magnetic fields, and radiative processes on the nozzle shock. This study represents an important step forward in the theoretical understanding of TDEs, bridging the gap between our robust knowledge of the fallback rate and the more complex following stages, during which most of the emission occurs.

Item Type:Article
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URLURL TypeDescription Paper ItemMovie
Bonnerot, Clément0000-0001-9970-2843
Lu, Wenbin0000-0002-1568-7461
Additional Information:© 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 December 28. Received 2021 November 29; in original form 2021 June 3. Published: 28 January 2022. We thank Roseanne Cheng, Phil Hopkins, Chris Matzner, Ramesh Narayan, Martin Pessah, Sterl Phinney, and Tony Piro for useful discussions. We acknowledge the use of SPLASH (Price 2007) for producing most of the figures in this paper. This research benefited from interactions at the ZTF Theory Network Meeting, partly funded by the National Science Foundation under Grant No. NSF PHY-1748958. The research of CB was funded by the Gordon and Betty Moore Foundation through Grant GBMF5076. This project has received funding from the European Union’s Horizon 2020 Framework Programme under the Marie Sklodowska-Curie grant agreement no. 836751. WL was supported by the David and Ellen Lee Fellowship at Caltech and the Lyman Spitzer, Jr Postdoctoral Fellowship at Princeton University. The authors thank the Yukawa Institute for Theoretical Physics at Kyoto University, where this work was initiated during the YITP-T-19-07 International Molecule-type Workshop ‘Tidal Disruption Events: General Relativistic Transients’. CB is particularly grateful to Richard D. Saxton for recognizing the knotty problem of the nozzle shock at this conference. Data Availability: The data underlying this paper will be shared on reasonable request to the corresponding author. A public version of the GIZMO code is available at
Funding AgencyGrant Number
Gordon and Betty Moore FoundationGBMF5076
Marie Curie Fellowship836751
David and Ellen Lee Postdoctoral ScholarshipUNSPECIFIED
Princeton UniversityUNSPECIFIED
Subject Keywords:black hole physics –hydrodynamics –galaxies: nuclei
Issue or Number:2
Record Number:CaltechAUTHORS:20211217-233241331
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Official Citation:Clément Bonnerot, Wenbin Lu, The nozzle shock in tidal disruption events, Monthly Notices of the Royal Astronomical Society, Volume 511, Issue 2, April 2022, Pages 2147–2169,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112546
Deposited By: George Porter
Deposited On:20 Dec 2021 16:18
Last Modified:18 Mar 2022 22:13

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