An on-the-fly line-driven wind iterative mass-loss estimator (LIME) for hot, massive stars of arbitrary chemical compositions

Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium

^★ Corresponding author: jon.sundqvist@kuleuven.be

Received: 1 April 2025
Accepted: 2 October 2025

Abstract

Context. Mass-loss rates, Ṁ, from hot, massive stars are important for a range of astrophysical applications.

Aims. We present LIME, a fast, efficient, and easy-to-use real-time mass-loss calculator for line-driven winds from hot, massive stars with given stellar parameters and arbitrary chemical compositions. The tool is publicly available online.

Methods. We compute the line force on-the-fly from excitation and ionization balance calculations using a large atomic data base containing more than four million spectral lines. We then derive mass-loss rates from line-driven wind theory, including effects of a finite stellar disk and gas sound speed.

Results. For a given set of stellar parameters and chemical composition, we obtain predictions for Ṁ and for the three line-force parameters, Q̄, Q₀, and α, at the wind critical point. A comparison of our predicted Ṁ with a large sample of recent, state-of-the-art, homogeneously derived empirical mass-loss rates obtained from the XSHOOTU collaboration project demonstrates that the simple calculator presented here performs on average as well as, or even better than, other available mass-loss recipes based on fits to restricted model grids computed from more sophisticated but less flexible methods.

Conclusions. In addition to its speed and simplicity, a strength of our mass-loss calculator is that it avoids uncertainties related to applying fit formulae to underlying model grids calculated for more restricted parameter ranges. In particular, individual chemical abundances can be easily modified, and their effects on predicted mass-loss rates can be readily explored. This enables direct applications also to stars that are significantly chemically modified at the surface.