clearly established [@Marconi08; @Marconi09; @Netzer10]. If radiation pressure in the BLR turns out to be important, then the black hole masses, as we discuss them here, are underestimated.

Masses of AGN black holes are computed as $$\label{eq:masseqn}
M_{\rm BH} = f \left(\frac{V^2 R}{G}\right),$$ where $V$ is the line width, $R$ is the size of the BLR from the reverberation lag, and $G$ is the gravitational constant. The quantity in parentheses is often referred to as the virial product $\mu$; it incorporates the two observables in RM, line width and time delay $\tau = R/c$, and is in units of mass. The scaling factor $f$ is a dimensionless quantity of order unity that depends on the geometry, kinematics, and inclination of the AGN. Throughout most of this work, we ignore $f$ (i.e., set it to unity) and work strictly with the virial product.

While reverberation mapping has emerged as the most effective technique for measuring the black hole masses in AGNs [@Peterson14], it is resource intensive, requiring many observations over an extended period of time at fairly high cadence. Fortunately, observational confirmation of the $R$–$L$ relationship [@Kaspi00; @Kaspi05; @Bentz06a; @Bentz09a; @Bentz13] enables “single-epoch” (SE) mass estimates because, in principle, a single 