Thawing the frozen-in approximation: implications for self-gravity in deeply plunging tidal disruption events

Abstract

The tidal destruction of a star by a massive black hole, known as a tidal disruption event (TDE), is commonly modeled using the "frozen-in" approximation. Under this approximation, the star maintains exact hydrostatic balance prior to entering the tidal sphere (radius $r_{\mathrm{t}}$), 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 $\beta \equiv r_{\mathrm{t}}/r_{\mathrm{p}}=5-7$, where $r_{\mathrm{p}}$ is the pericenter of the stellar center 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 $r_{\mathrm{t}}$, 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 $\beta$ which has implications for the radio emission from the unbound debris and, potentially, for the circularization efficiency of the bound streams.

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References in corpus (4)

• Stellar disruption by a supermassive black hole: is the light curve really proportional to $t^{-5/3}$?
• General Relativistic Hydrodynamic Simulation of Accretion Flow from a Stellar Tidal Disruption
• Tidal disruption events: the role of stellar spin
• Rich: Open Source Hydrodynamic Simulation on a Moving Voronoi Mesh

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• Elliptical accretion disk as a model for tidal disruption events
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• Ultra-deep tidal disruption events: prompt self-intersections and observables
• Simulations of Tidal Disruption Events
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• Future Simulations of Tidal Disruption Events