PySME -- Spectroscopy Made Easier

TL;DR

PySME is a user-friendly, open-source Python software for high-resolution stellar spectral fitting, enhancing the original SME with updated optimization and maintaining robust parameter determination.

Contribution

PySME provides a modern, accessible Python implementation of the proven SME spectral fitting tool, with improved flexibility and performance.

Findings

PySME performs comparably to the original SME in parameter determination.

PySME is available across common platforms and free from commercial licenses.

The software successfully fits spectra from stars of different types.

Abstract

The characterization of exoplanet requires reliable determination of the fundamental parameters of their host stars. Spectral fitting plays an important role in this process. For the majority of stellar parameters matching synthetic spectra to the observations provides a robust and unique solution for fundamental parameters, such as effective temperature, surface gravity, abundances, radial and rotational velocities and others. Here we present a new software package for fitting high resolution stellar spectra that is easy to use, available for common platforms and free from commercial licenses. We call it PySME. It is based on the proven Spectroscopy Made Easy (later referred to as IDL SME or "original SME") package. The IDL part of the original SME code has been rewritten in Python, but we kept the efficient C++ and FORTRAN code responsible for molecular-ionization equilibrium, opacities and spectral synthesis. In the process we have updated some components of the optimization procedure offering more flexibility and better analysis of the convergence. The result is a more modern package with the same functionality of the original SME. We apply PySME to a few stars of different spectral types and compared the derived fundamental parameters with the results from IDL SME and other techniques. We show that PySME works at least as well as the original SME.