Fig. 5: Projected limits on scalars and vectors.

Solid blue and red lines: number of TDE events expected to be observed by the Vera Rubin's LSST in the mass bin \(8\le \log {M}_{{{{{{{{\rm{BH}}}}}}}}}/{M}_{\odot }\le 9\) for SMBHs that have been spun down by ULBs, as a function of the ULB mass μ, for scalars (a) and vectors (b). The number of events is obtained under two assumptions for the unknown maximal spins that SMBHs can attain. In the “large spin'' scenario (blue), we consider SMBHs with the maximal spin allowed by thin-disk spin-up (a = 0.998) and superradiant spin-down. In the “medium-spin'' scenario (red) we take the spins to be the maximal allowed by a spin limit of a = 0.6 and superradiant spin-down. Dotted blue and red lines: exclusion thresholds assuming that LSST TDE rate measurements are consistent with SMBHs having “large'' (a = 0.998) or “medium'' (a = 0.6) spins. These thresholds are obtained by calculating the number of TDEs that LSST would observe in the mass bin \(8\le \log {M}_{{{{{{{{\rm{BH}}}}}}}}}/{M}_{\odot }\le 9\) in the absence of superradiant effects, and accounting for a 2σ statistical and a 50% systematic uncertainty (downward fluctuation) on the measurement. Blue and red regions: projected limits on the masses of ULBs for the two spin assumptions.