A gravitational lens origin for AGN-variability ? Consequences of micro- lensing.
Abstract
The work of Kayser et al. (1986) and Paczynski (1986) on microlensing is extended. The gravitational action of an ensemble of stars on the light of a compact background source is studied. Representative light curves of sources which move relative to the star field are computed along with amplification probabilities and the distribution of the amplification factor as a function of the relative source position. The numerical scheme permits considering very large optical depth or, equivalently, a large number of stars (up to about 10,000). Where for moderate optical depth a typical light-curve is characterized by rather quiet behavior most of the time, interrupted by sudden 'outbursts', sources behing dense star fields tend to show a very irregular flickering, without very dramatic changes of their apparent luminosity. The amplification probability function shows a much more complex behavior than the analytically estimated I to the -2 dependence. It is proposed that the time-dependent amplification by micro-lenses provides a reasonable explanation for variability in at least some active galactic nuclei.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1987
- Bibcode:
- 1987A&A...171...49S
- Keywords:
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- Active Galactic Nuclei;
- Astronomical Models;
- Gravitational Lenses;
- Light Curve;
- Quasars;
- Star Distribution;
- Optical Thickness;
- Radiant Flux Density;
- Wave Amplification;
- Astrophysics