We present single-epoch multi-wavelength optical-NIR observations of the “ anomalous ” lensed quasar SDSSÂ J0924+0219 , made using the Magellan 6.5-metre Baade telescope at Las Campanas Observatory , Chile .
The data clearly resolve the anomalous bright image pair in the lensed system , and exhibit a strong decrease in the anomalous flux ratio with decreasing wavelength .
This is interpreted as a result of microlensing of a source of decreasing size in the core of the lensed quasar .
We model the radius of the continuum emission region , \sigma , as a power-law in wavelength , \sigma \propto \lambda ^ { \zeta } .
We place an upper limit on the Gaussian radius of the u ^ { \prime } -band emission region of 3.04 \times 10 ^ { 16 } h _ { 70 } ^ { -1 / 2 } ( \langle M \rangle / M _ { \odot } ) ^ { 1 / 2 } Â cm , and constrain the size-wavelength power-law index to \zeta < 1.34 at 95 % confidence .
These observations rule out an alpha-disc prescription for the accretion disc in SDSSÂ J0924+0219 with 94 % confidence .