1999ApJ...527...46N

We present and discuss near-infrared broadband and spectrophotometric images (λ/Δλ=60) of the gravitationally lensed quadruple image of Q2237+0305 obtained with the MONICA camera at the Canada-France-Hawaii Telescope in 1991, 1992, 1993, and 1994. The spectrophotometric observations cover the wavelength range 1700<λ (nm)<2400, which includes the Hα emission redshifted to 1770 nm. Our results show that microamplification was achromatic from 1992 to 1994 and had similar amplitudes in the Hα and continuum emission. On the other hand, a comparison of our near-infrared continuum data with visible data from the literature shows a striking wavelength dependence of the relative amplification of components A and B at epoch 1991 September. This provides strong support to the thermal accretion disk model as a source of the UV-visible continuum emission of quasars. The Hα line profile changed between 1992 and 1994 but, at each epoch, differences in line profile between components are not significant (<5%). Since the time delays between images is less than one day, this sets a limit of <3% per day for profile evolution.