Fallback-to-accretion mapping in tidal disruption events

Develop a complete theory relating the mass fallback rate of stellar debris to the accretion rate onto the supermassive black hole, including the effects of circularisation efficiency and mass loss through outflows.

Background

The simulations use the debris fallback rate as their primary diagnostic, but the fallback rate is not identical to the rate at which material is promptly accreted by the black hole. The relationship depends on how efficiently the debris circularises into an accretion disc and how much material is lost in outflows.

Because this mapping is unresolved, luminosities estimated by directly scaling the fallback rate should be interpreted only as order-of-magnitude indicators rather than predictions of observed light curves.

References

We stress that this is not the accretion rate $\dot{M}_{\rm acc}$ onto the BH, and that a complete theory relating the two is still lacking: the mapping depends on the efficiency of circularisation and on mass lost to outflows.

— Tidal disruption of stellar binaries as a pathway to exotic transients  (2608.22735 - González-Servín et al., 24 Aug 2026) in Section 2.1, 'Classical tidal disruptions'

First, the conversion efficiency of disrupted stellar mass into black hole growth remains uncertain.

— Rapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar DisruptionsRapid Growth of Intermediate-Mass Black Holes through Disk-induced Stellar Disruptions  (2609.03701 - Wang et al., 3 Sep 2026) in Section 5, Limitations and future work

The efficiency and timescale of debris circularisation remain highly uncertain, with simulations suggesting that relativistic apsidal precession and black hole spin can influence this process.

— Aarmed with Data: Bumps, Outflows, and Disk-like Emission in TDE 2025aarm  (2609.09725 - Aamer et al., 9 Sep 2026) in Introduction, Section 1

The origin of this variability remains uncertain, but proposed explanations include changes in reprocessing efficiency, episodic accretion, evolving obscuration, or additional shocks within the debris streams.

— Aarmed with Data: Bumps, Outflows, and Disk-like Emission in TDE 2025aarm  (2609.09725 - Aamer et al., 9 Sep 2026) in Introduction, Section 1