Q-LET - quick lensing estimation tool: an application to SN2003es

Q-LET is a FORTRAN 77 code that enables a quick estimate of the gravitational lensing effects on a point- or an extended source. The user-provided input consists of redshifts, angular positions relative to the source, mass or velocity dispersion estimates and halo types for the lens galaxies. The considered halo types are the Navarro-Frenk-White and the singular isothermal sphere. The code uses the so-called multiple lens-plane method to find the magnification and intrinsic shape of the source. This method takes into account the multiple deflections that may arise when several mass accumulations are situated at different redshifts close to the line-of-sight. The Q-LET code is applied to the recently discovered supernova, SN2003es, which is likely to be of type Ia as its host galaxy is classified as an elliptical. We find that SN2003es is likely to have been significantly magnified by gravitational lensing, and that this should be considered in high-z studies if this SN is to be used to determine cosmological parameters. Q-LET was motivated by the supernova searches, where lensing can be a problem, but it can also be applied to any simple lens system where a quick estimate is wanted, e. g. the single lens case.