Quataert, EliotDi Matteo, TizianaNarayan, RameshHo, Luis C.2019-09-221999Quataert, Eliot, Tiziana Di Matteo, Ramesh Narayan, and Luis C. Ho. 1999. “Possible Evidence for Truncated Thin Disks in the Low-Luminosity Active Galactic Nuclei M81 and NGC 4579.” The Astrophysical Journal 525 (2): L89–92. https://doi.org/10.1086/312353.0004-637X1538-4357http://nrs.harvard.edu/urn-3:HUL.InstRepos:41384919M81 and NGC 4579 are two of the few low-luminosity active galactic nuclei that have an estimated mass for the central black hole, detected hard X-ray emission, and detected optical/UV emission. In contrast to the canonical "big blue bump," both have optical/UV spectra that decrease with increasing frequency in a vL(v) plot. Barring significant reddening by dust and/or large errors in the black hole mass estimates, the optical/UV spectra of these systems require that the inner edge of a geometrically thin, optically thick accretion disk lies at similar to 100 Schwarzschild radii. The observed X-ray radiation can be explained by an optically thin, two-temperature, advection-dominated accretion flow at smaller radii.en-USJournal Article2019-09-2210.1086/312353