Personal website of Simon Birrer


I am actively developing and supporting software solutions to help collaborators and the community in general to advance in science. All software I am developing are publicly available, primary on my GitHub repository. I make a big effort in facilitating the distribution and use of the software through packaging, modular built up, documentation and example use cases.

Below you can find a list of packages I have developed or of which I am part of the developing team with a short description thereof. If you have further questions, do not hesitate to get in touch with me! I am happy to support you, hand out analysis scripts and add features, if requested.


lenstronomy is a multi-purpose package to model strong gravitational lenses. The software package is presented in Birrer & Amara 2018 and is based on Birrer et al 2015. lenstronomy finds application for e.g. time-delay cosmography and measuring the expansion rate of the universe and for quantifying lensing substructure to infer dark matter properties. lenstronomy is an astropy affiliated package. The package has a large and growing users community and multiple wrappers and packages are built on top of lenstronomy.


Hierarchical analysis of strong lenses to measure the Hubble constant and galaxy density profiles. HierArc found its first application in Birrer et al 2020. and has been extended to incorporate lensed supernovae by Birrer et al. 2021.

Strong lensing lecture notes

A set of interactive lecture notes about strong gravitational lensing.


Open source software development project to forward model the sky. I am a development team member.


deeplenstronomy is a tool for simulating large datasets for applying deep learning to strong gravitational lensing. It works by wrapping the functionalities of lenstronomy in a convenient yaml-style interface, allowing users to embrace the astronomer part of their brain rather than their programmer part when generating training datasets..


Python Wrapper of the FASTELL fortran code by Rennan Barkana. It performs fast numerical integrals to compute deflection angle and lensing potential for smoothed elliptical power-law lens models.


This is a modification of the pysex package, a python wrapper of SExtractor. Original pysex package: Nicolas Cantale