# PRECESSION 2.1: black-hole binary spin precession on eccentric orbits

## TL;DR

Precession 2.1 is an updated Python tool for simulating the dynamics of precessing black hole binaries, now including eccentric orbits and new features for orbital evolution and gravitational-wave analysis.

## Contribution

The paper introduces version 2.1 of the precession code, extending its capabilities to handle eccentric orbits and providing new equations for orbital and gravitational-wave parameters.

## Key findings

- Extended the code to handle eccentric orbits using a semi-automatic method.
- Added orbit- and precession-averaged evolution equations for eccentricity.
- Revised expressions for converting between separation and gravitational-wave frequency.

## Abstract

We present version 2.1 of the public code {\sc precession}, a Python module for studying the post-Newtonian dynamics of precessing black hole binaries. In this release, we extend the code to handle eccentric orbits. This extension leverages the existing numerical infrastructure wherever possible, introducing a semi-automatic method to adapt circular-orbit functions to the eccentric case via a Python decorator. Additional new features include orbit- and precession-averaged evolutionary equations for the eccentricity, as well as revised expressions to convert between post-Newtonian separation and gravitational-wave emission frequency.