Can interaction alone explain AT2024wpp’s post-peak evolution?

Ascertain whether shock interaction between the fast ejecta and pre-existing circumstellar material, by itself, can account for the post-peak ultraviolet/optical evolution of AT2024wpp, specifically the sustained hot, featureless thermal spectrum and the contracting blackbody radius despite contemporaneous luminous X-ray emission.

Background

The paper models AT2024wpp’s early light curve as consistent with fast, optically thick ejecta that could be powered by shock interaction with dense circumstellar material. However, after peak the inferred photospheric radius contracts while the temperature remains high, and strong X-ray radiation is present—behavior atypical for standard interaction-powered supernovae where a geometrically thin, expanding shell dominates the emission.

This raises a key uncertainty about whether interaction-only models can reproduce the observed post-peak properties. Resolving this question is central to distinguishing between shock-powered versus central-engine-powered scenarios for AT2024wpp and similar LFBOTs.

References

While ejecta-CSM interaction can thus provide a satisfactory explanation for the initial rise to peak, it is unclear whether interaction alone can explain the post-peak behaviour.

— AT2024wpp: An Extremely Luminous Fast Ultraviolet Transient Powered by Accretion onto a Black Hole  (2601.03337 - Perley et al., 6 Jan 2026) in Section 4.1 (Ejecta mass constraints and inner pre-explosion material)

This may be relevant to the final epoch of AT2024wpp, where the final inferred radius is smaller than that of the previous epoch, which seems difficult to realize physically (i.e., while the reverse shock or contact could conceivably move to smaller radii in the rest frame of the ambient medium, how the forward shock could do so is unclear).

— Outflows in steep density gradients: diversity of behavior and implications for tidal disruption events and luminous fast blue optical transients  (2608.19512 - Amend et al., 20 Aug 2026) in Section 4.4, “Caveats in Radio Inferred Shock Dynamics” (discussion of AT2024wpp)