Quasar Microlensing Variability Studies Favor Shallow Accretion Disk Temperature Profiles

• Published in: The Astrophysical journal Vol. 895; no. 2; pp. 93 - 100
• Main Authors: Cornachione, Matthew A., Morgan, Christopher W.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01-06-2020; IOP Publishing
• Subjects: Accretion; Accretion disks; Astrophysics; Continuum radiation; Emission measurements; Gravitational lensing; Luminosity; Microlenses; Quasar microlensing; Quasars; Temperature profiles
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab8aed

We compare the microlensing-based continuum emission region size measurements in a sample of 15 gravitationally lensed quasars with estimates of luminosity-based thin disk sizes to constrain the temperature profile of the quasar continuum accretion region. If we adopt the standard thin disk model, we find a significant discrepancy between sizes estimated using the luminosity and those measured by microlensing of log(rL/r ) = −0.57 0.08 dex. If quasar continuum sources are simple, optically thick accretion disks with a generalized temperature profile T ( r ) ∝ r − β , the discrepancy between the microlensing measurements and the luminosity-based size estimates can be resolved by a temperature profile slope 0.37 < β < 0.56 at 1 confidence. This is shallower than the standard thin disk model (β = 0.75) at 3 significance. We consider alternate accretion disk models that could produce such a temperature profile and reproduce the empirical continuum size scaling with black hole mass, including disk winds or disks with nonblackbody atmospheres.