The resolved size and structure of hot dust in the immediate vicinity of
  AGN
  We use VLTI/GRAVITY near-infrared interferometry measurements of 8 bright,
Type 1 AGN to study the size and structure of hot dust heated by the central
engine. We partially resolve each source, and report Gaussian FWHM sizes in the
range 0.3-0.8 milliarcseconds. In all but one object, we find no evidence for
significant elongation or asymmetry (closure phases < 1 deg). The effective
physical radius increases with bolometric luminosity as found from past
reverberation and interferometry measurements. The measured sizes for Seyfert
galaxies are systematically larger than for the two quasars in our sample when
measured relative to the previously reported R ~ L^1/2 relationship explained
by emission at the sublimation radius. This could be evidence of evolving
near-infrared emission region structure as a function of central luminosity.
