Determine the conditions for formation of the circumbinary-disk lump

Determine the range of physical conditions in which the azimuthal m=1 overdensity known as the lump forms in a supermassive-black-hole circumbinary disk.

Background

The circumbinary disk surrounding a supermassive-black-hole binary can develop an m=1 azimuthal overdensity, commonly called the lump. The lump is important because it can break azimuthal symmetry and influence the predicted thermal and X-ray variability of the system.

The paper notes that existing simulations have not yet established robustly which disk, binary, or accretion conditions produce this structure. Characterizing those conditions is necessary for determining whether the lump and its associated spectroscopic modulations are generic features of supermassive-black-hole binaries or specific to particular simulations.

References

However, the range of conditions in which this lump forms is known only tentatively.

— Thermal and non-thermal emission from supermassive black hole circumbinary disks: Disks, Coronae, Streams, and Cavities  (2609.03140 - Nagele et al., 2 Sep 2026) in Section 1, Introduction