The rate of caustic crossing microlensing events for Q2237 0305

Abstract

Spectrophotometric observations of the gravitationally microlensed quasar Q2237+0305 made during a high magnification event (HME) potentially provide a very powerful tool for probing the structure of the accretion discs of quasars, on scales of ∼10-8 arcsec. In cases where the HME is produced by a single caustic (SHME), microlensing induced changes in the spectrum during the event may be used to directly infer the source intensity profile. Several groups are actively monitoring Q2237+0305 with this goal in mind. How often we can expect to observe an HME is dependent on the lens system parameters of galactic transverse velocity, mean microlens mass and the size of the magnified continuum sour..