Open AccessEffects of a deformation of a star on the gravitational lensing
Author(s) -
Asada H.
Publication year - 2005
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08486.x
Subject(s) - physics , gravitational lens , star (game theory) , gravitation , magnetic monopole , expression (computer science) , distortion (music) , simple (philosophy) , classical mechanics , mathematical analysis , astrophysics , quantum mechanics , amplifier , philosophy , optoelectronics , redshift , cmos , epistemology , galaxy , computer science , programming language , mathematics
We study analytically a gravitational lens due to a deformed star, which is modelled by using a monopole and a quadrupole moment. Positions of the images are discussed for a source on the principal axis. We present explicit expressions for the lens equation for this gravitational lens as a single real 10th‐order algebraic equation. Furthermore, we compute an expression for the caustics as a discriminant for the polynomial. Another simple parametric representation of the caustics is also presented in a more tractable form. A simple expression for the critical curves is obtained to clarify a topological feature of the critical curves; the curves are simply connected if and only if the distortion is sufficiently large.