The Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT): An Open-Source Tool for Efficient Fitting of Astrometric and Radial Velocity Data

TL;DR

ExoSOFT is an open-source Python-based toolbox designed for efficient fitting of exoplanet and stellar companion orbits using combined radial velocity and astrometric data, aiding in mass estimation and orbital analysis.

Contribution

It introduces a versatile, open-source software suite that integrates multi-data fitting, multi-stage sampling, and post-processing tools for orbital analysis of exoplanets and stellar companions.

Findings

Successfully verified with artificial data

Supports combined radial velocity and astrometric data fitting

Facilitates dynamical mass estimation for substellar companions

Abstract

We present the Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT), a new, open-source suite to fit the orbital elements of planetary or stellar mass companions to any combination of radial velocity and astrometric data. To explore the parameter space of Keplerian models, ExoSOFT may be operated with its own multi-stage sampling approach, or interfaced with third-party tools such as emcee. In addition, ExoSOFT is packaged with a collection of post-processing tools to analyze and summarize the results. Although only a few systems have been observed with both the radial velocity and direct imaging techniques, this number will increase thanks to upcoming spacecraft and ground based surveys. Providing both forms of data enables simultaneous fitting that can help break degeneracies in the orbital elements that arise when only one data type is available. The dynamical mass estimates this approach can produce are important when investigating the formation mechanisms and subsequent evolution of substellar companions. ExoSOFT was verified through fitting to artificial data and was implemented using the Python and Cython programming languages; available for public download at https://github.com/kylemede/ExoSOFT under the GNU General Public License v3.