Rapster

Rapster (Rapid cluster) is a semi-analytic population-synthesis code for evolving star clusters, the dynamical formation of compact-object mergers, and tidal disruption events. It runs thousands of cluster simulations in minutes on a laptop, and is used by research groups worldwide.

Getting started

Installation

First, create an environment called .rapsterenv in the root directory of the repository Rapster/, and hidden from view:

python3 -m venv .rapsterenv

If you use a different name, please add the environment name as a new row in .gitignore, since the environment folder should never be pushed to the repository.

To activate this environment:

source .rapsterenv/bin/activate

To install rapster and all requirements, run:

pip install -e .

Verify the installation (along with dependencies) and package version:

pip list

Finally, include the virtual environment in the kernel:

python -m ipykernel install --user --name=rapsterenv --display-name "Python (.rapsterenv)"

To install Rapster with the optional gwModel_kick_prec_flow recoil kick dependency (-RK 1), run this from the repository root:

pip install -e '.[gwkick]'

Basic usage

For a description of all input parameters, run the following command in the command line interface:

python -m rapster.run_cluster --help

Run with default parameters:

python -m rapster.run_cluster

Run with analysis summary printed at the end:

python -m rapster.run_cluster -analyze 1

Run with both analysis summary and diagnostic plots:

python -m rapster.run_cluster -analyze 1 -plot 1

Run silently (no screen output, all output saved to Results/log.txt):

python -m rapster.run_cluster -P 0

Run with beta spin distribution and random mass pairing:

python -m rapster.run_cluster -SD 2 -s 1.0 -RMP 1

Run with bimodal NS masses and NS formation times correlated with NS mass:

python -m rapster.run_cluster -NS 2 -NSt 2

The numbers of NSs formed and retained are printed at the end of log.txt.

Source: the Rapster README on GitHub.

How to cite

If you use Rapster, please cite Kritos, Strokov, Baibhav & Berti (2024), Phys. Rev. D 110, 043023.

If you use the intermediate-mass black hole formation or micro-tidal disruption event features, please also cite:

• K. Kritos, D. Wadekar & E. Berti (2026)

• K. Kritos, F. Iacovelli, R. Perna & E. Berti (2026)