Origin of the late-time double-peaked H and He emission in AT2024wpp

Identify the physical origin of the late-time, double-peaked intermediate-width hydrogen and helium emission features in AT2024wpp—comprising a component near the systemic redshift and a blueshifted component separated by about 6600 km s−1 with individual widths of roughly 2000 km s−1—and determine the mechanism producing their simultaneous emergence around 35–55 rest-frame days post-explosion.

Background

Starting about one month after explosion, AT2024wpp develops unusual H and He emission lines with two distinct components: one near the systemic velocity and another blueshifted by ~6600 km s−1. Each is relatively narrow (full width ~2000 km s−1) and stable over several weeks, implying coherent, separate structures.

The authors discuss possibilities such as tidal streams in a TDE-like scenario or ablation of a surviving companion by the central engine/wind, but note unresolved issues, including why both components appear simultaneously if one is bound and located deeper in the wind. Pinning down the origin is crucial for understanding the geometry and progenitor system of LFBOTs.

References

The actual origin of these spectral features remains unclear.

— AT2024wpp: An Extremely Luminous Fast Ultraviolet Transient Powered by Accretion onto a Black Hole  (2601.03337 - Perley et al., 6 Jan 2026) in Section 4.7 (The origin of late-time narrow spectral features)