Abstract We present the results from performing spectral energy distribution (SED) fitting on 121 variable active galactic nuclei (AGN) candidates in the Hubble Ultra Deep Field using photometry from both the Hubble Space Telescope and the James Webb Space Telescope (JWST) covering 0.2–4.8 μ m. We designed a bespoke SED fitting code, which decomposes the total SED into its stellar and AGN contributions. Our SED fitting retrieves a significant contribution to the total SED from an AGN template for 26 of our variable sources with 0 6. This object has z phot = 6.74, and we estimate a lower limit on its black hole mass of log 10 ( M BH / M ⊙ ) > 7.36 .
Young et al. (2026) studied this question.