On the relative importance of shocks and self-gravity in modifying tidal disruption event debris streams

TL;DR

This study uses high-resolution hydrodynamical simulations to demonstrate that self-gravity, rather than shocks, predominantly influences the evolution and structure of debris streams in tidal disruption events, affecting their observational signatures.

Contribution

It reveals that self-gravity is the main factor modifying debris streams in TDEs, challenging previous assumptions that shocks were primary.

Findings

Self-gravity dominates debris stream modifications.

Specific length scales influence mass distribution changes.

Enhanced Fourier modes indicate self-gravity effects.

Abstract

In a tidal disruption event (TDE), a star is destroyed by the gravitational field of a supermassive black hole (SMBH) to produce a stream of debris, some of which accretes onto the SMBH and creates a luminous flare. The distribution of mass along the stream has a direct impact on the accretion rate, and thus modeling the time-dependent evolution of this distribution provides insight into the relevant physical processes that drive the observable properties of TDEs. Analytic models that only account for the ballistic evolution of the debris do not capture salient and time-dependent features of the mass distribution, suggesting that fluid dynamical effects significantly modify the debris dynamics. Previous investigations have claimed that shocks are primarily responsible for these modifications, but here we show -- with high-resolution hydrodynamical simulations -- that self-gravity is the dominant physical mechanism responsible for the anomalous (i.e., not predicted by ballistic models) debris stream features and its time dependence. These high-resolution simulations also show that there is a specific length scale on which self-gravity modifies the debris mass distribution, and as such there is enhanced power in specific Fourier modes. Our results have implications for the stability of the debris stream under the influence of self-gravity, particularly at late times and the corresponding observational signatures of TDEs.