2025PASP..137k4102R

JWST/MIRI observations can place photometric limits on the presence of an intermediate-mass black hole (IMBH) near the Galactic Centre. The stellar complex IRS 13E, a co-moving conglomerate of young and massive stars, is a prime location to study because it has been speculated to be bound by an IMBH. Assuming a standard radiatively inefficient accretion flow (RIAF) and a minimum fractional variability of 10% of the intrinsic luminosity, the wavelength of peak emission in the spectral energy distribution for an IMBH would lie in the mid-infrared (∼5-25 μm), and the variability would be detectable in MIRI time-series observations. Monitoring fails to detect such variable emission (other than from Sgr A*) in and around the IRS 13E complex, and upper limits on a putative IMBH's intrinsic variability on timescales of minutes to ∼1 hr are ≲ 1 mJy at 12 μm and ≲2 mJy at 19 μm. These translate to luminosities ≲ 25 × 10³² erg s^–1. The resulting limits on the IMBH mass and accretion rate rule out any IMBH with mass ≳10³M_⊙ accreting at ≳10^–6 times Eddington rate at the location of IRS 13E. Further, the observations rule out an IMBH anywhere in the central 6″ × 6″ region that is more massive than ≈ 2 × 10³M_⊙ and accreting at ≥10^–6 of the Eddington rate. Assuming Bondi accretion scaled to typical RIAF-accretion efficiencies, albeit somewhat uncertain, also allows us to rule out IMBHs moving with typical velocities ∼200 km s^–1 and masses ≳ 2 × 10³M_⊙. These methods showcase the effectiveness of photometric variability measurements in constraining the presence of accreting black holes in Galactic centre-like environments.