Relative evolution of warp radius and outer disk radius

Determine whether the warp radius in a cooling tidal-disruption-event accretion disk generically grows faster than the disk outer radius, thereby causing the inner disk to become progressively visible and producing delayed X-ray brightenings without delayed disk formation.

Background

The visibility of the inner, X-ray-emitting disk is governed by competition between the outer disk radius, which increases the capacity for occultation, and the warp radius, whose growth makes the disk more nearly aligned with the black-hole equatorial plane. The paper explores illustrative self-similar prescriptions for these quantities, including a model in which the disk aspect ratio tracks the accretion rate, but does not derive their evolution from a self-consistent warp-evolution theory.

The unresolved issue is whether the warp radius generically outpaces the expanding outer edge in real TDE disks. If it does, the inner disk should be progressively revealed and delayed X-ray brightenings could arise geometrically rather than from delayed disk formation.

References

The question then becomes whether $r_{\rm warp}$ generically grows faster than $R_{\rm out}$ as the disk cools. If it does, then the typical outcome is that the inner disk is progressively unveiled with time --- a natural, purely geometric explanation for the delayed X-ray brightenings now seen in a growing number of TDEs, one that requires no delay in the formation of the disk itself.

— Observational signatures of warped accretion flows in tidal disruption events  (2609.29787 - Mummery et al., 24 Sep 2026) in Section 7, Conclusions