Accretion Disk Structure and Orientation in the Lensed and Microlensed Q0957+561 Quasar

Because quasars are unresolved in optical imaging, their structures must currently be inferred. Gravitational microlensing offers the possibility of producing information about the luminous structure provided that the Einstein ring diameter of the microlensing particle is comparable to or smaller than the radiating quasar components. Particularly interesting is the case of multiple-image gravitational lenses, where differences in the brightness histories of the multiple images can reveal the presence of the microlensing particles and allow inferences about the quasar's structure. The long brightness history measured for the Q0957 quasar has been analyzed previously for information about the microlensing particles, and evidence for the existence of a cosmologically significant population of planetary-mass particles has been reported. The microlensing results have also directly determined the sizes of the ultraviolet light emitting surfaces in the quasar. Autocorrelation analysis of the same brightness record has produced evidence for complex structure in the quasar; if the quasar suddenly brightens today, it is probable that it will brighten again after 129, 190, 540, and 620 days. We interpret these lags as the result of luminous structure around the quasar, and in particular we interpret them in the context of the Elvis model of the quasar's structure. We find that the autocorrelation peaks imply that beyond the luminous inner edge of the accretion disk, the biconic structures of the Elvis model must lie at a radial distance of 2 × 10 17 cm from the black hole, and 2 × 10 16 cm above and below the plane of the accretion disk. The quasar is apparently inclined 55° to the line of sight. A second possible solution with lower inclination and larger structure is also indicated but statistically less probable.