Asymptotic formulas for the magnification of a gravitational lens system near a fold caustic

• Published in: Astronomy letters Vol. 36; no. 5; pp. 329 - 337
• Main Authors: Alexandrov, A. N., Zhdanov, V. I., Fedorova, E. V.
• Format: Journal Article
• Language: English
• Published: Dordrecht SP MAIK Nauka/Interperiodica 01.05.2010; Pleiades; Springer Nature B.V
• Subjects: Astronomy; Astrophysics; Astrophysics and Astroparticles; Earth, ocean, space; Exact sciences and technology; Gravity; Observations and Techniques; Physics; Physics and Astronomy; Quasars; Einstein Cross; microlensing; Q2237+0305; gravitational lenses; Gravitational system; Gravitational lenses
• ISSN: 1063-7737; 1562-6873
• DOI: 10.1134/S1063773710050038

An approximate formula for the magnification of a point source near a fold caustic obtained in the first linear caustic approximation is widely used in the theory of gravitational lens systems. Here, this formula is refined to include the post-linear terms that have been found both for a point source and for an extended Gaussian source in the absence of continuous matter on the line of sight. The formulas are reduced to a form containing three additional parameters; the derivation of nontrivial corrections requires including the expansion terms in the lens equation up to the fourth order. The modified formula for an extended source is used to analyze strong microlensing events in the gravitational lens system Q2237+0305 (the Einstein Cross). For such an event on the light curve of image C (1999, OGLE data), the corrections found are statistically significant.