## The binary gravitational lens and its extreme cases
^{1} Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA^{2} Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands (dominik@astro.rug.nl)
The transition of the binary gravitational lens from the equal mass
case to small (planetary) mass ratios
* Work carried out at the Space Telescope Science Institute has been financed by a research grant from Deutsche Forschungsgemeinschaft (Do 629-1/1) and work carried out at the Kapteyn Astronomical Institute is financed by a Marie Curie Fellowship from the European Union (FMBICT972457). ## Contents- 1. Introduction
- 2. The lens equation
- 3. The Chang-Refsdal lens with pure shear
- 4. The quadrupole lens
- 5. The different topologies of the critical curves and caustics of the binary lens
- 6. The vicinity of the secondary object
- 6.1. Full lens equation
- 6.2. Taylor-expansion
- 6.3. Chang-Refsdal limit and caustics
- 7. The perturbative picture for small mass ratios and its limits
- 8. The central caustic
- 9. Diamond-shaped caustics
- 10. Summary
- Acknowledgements
- Appendices
- References
© European Southern Observatory (ESO) 1999 Online publication: August 25, 1999 |