Mid‐IR Observations and a Revised Time Delay for the Gravitational Lens System Quasar HE 1104−1805

The mid-IR flux ratios FA/FB 2:84 0:06 of the two images of the gravitationally lensed quasar HE 1104 1805 show no wavelength dependence to within 3 % across 3.6Y8.0 m, show no time dependence over 6 months, and agree with the broad emission-line flux ratios. This indicates that the mid-IR emission likely comes from scales large enough to be little affected by microlensing and that there is little differential extinction between the images. Wemeasure a revised time delay between these two images of 152:2þ2:83:0 (1 ) days from R- and V-band data covering the years 1997Y2006. This time delay indicates that the lens has an approximately flat rotation curve over scales of 1Y2Re. We also observed uncorrelated variations of0.05mag yr1, which we attribute to microlensing of the optical emission from the accretion disk. The optical colors have also changed significantly in the sense that image A is now redder than image B, rather than bluer, as it was in 1993. Subject headings: gravitational lensing — quasars: general — quasars: individual (HE 11041805) Online material: machine-readable table 1.