Image Flux Ratios of Gravitationally Lensed HS 0810+2554 with High
  Resolution Infrared Imaging
  We report near simultaneous imaging using LMIRCam on the LBTI of the
quadruply imaged lensed quasar HS 0810+2554 at wavelengths of 2.16, 3.7 and
$4.78~\mu$m with a Full Width Half Max (FWHM) spatial resolution of
$0^{\prime\prime}\!\!.13$, $0^{\prime\prime}\!\!.12$ and
$0^{\prime\prime}\!\!.15$ respectively, comparable to HST optical imaging. In
the $\rm{z} = 1.5$ rest frame of the quasar, the observed wavelengths
correspond to 0.86, 1.48, and $1.91~\mu$m respectively. The two brightest
images in the quad, A and B, are clearly resolved from each other with a
separation of $0.187^{\prime\prime}$. The flux ratio of these two images (A/B)
trends from 1.79 to 1.23 from 2.16 to $4.78~\mu$m. The trend in flux ratio is
consistent with the $2.16~\mu$m flux originating from a small sized accretion
disk in the quasar that experiences only microlensing. The excess flux above
the contribution from the accretion disk at the two longer wavelengths
originates from a larger sized region that experiences no microlensing. A
simple model employing multiplicative factors for image B due to stellar
microlensing $(m)$ and sub-structure millilensing $(M)$ is presented. The
result is tightly constrained to the product $m\times M=1.79$. Given the
observational errors, the 60\% probability contour for this product stretches
from $m= 2.6$, $M = 0.69$ to $m= 1.79$, $M = 1.0$, where the later is
consistent with microlensing only.
