Abstract

Received 2001 January 21, accepted 2001 May 5

Recently, the OGLE team have reported a clear quasar microlensing signal in Q2237+0305. I have analyzed the microlens event of ‘image C’ by using their finely and densely sampled light curves. From light curve fitting, I unambiguously set the source size of ≤0.98 Einstein-Ring radius as a conservative limit. This limit corresponds to 2000 AU, if I adopt M_lens ~ 0.1M obtained by a recent statistical study of the mean mass of the lens object. This gives clear evidence for the existence of an accretion disk in the central region of the quasar.