Impact of main-sequence mass loss on the appearance, structure and evolution of Wolf-Rayet stars

Stellar winds are one of the most important drivers of massive star evolution and a vital source of chemical, mechanical, and radiative feedback. Despite its significance, mass loss remains a major uncertainty in stellar evolution models. Particularly the interdependencies of different approaches with subsequent evolutionary stages and predicted observable phenomena are far from being systematically understood. In this study, we examine the impact of main sequence mass loss on the structure of massive stars throughout their evolution. A particular focus is placed on the consequences for entering the Wolf-Rayet (WR) regime and the subsequent evolution. Using the Geneva stellar evolution code, we compute grids of single, non-rotating stellar models at solar and Large Magellanic Cloud (LMC) metallicity of initial masses between 20 and 120 solar masses, with two representative prescriptions for high and low main sequence mass loss. We obtain detailed numerical predictions regarding the structure and evolution of massive stars, and infer the role of main sequence mass loss by comparison of the mass-loss rate prescriptions. We present implications for the overall evolutionary trajectory, including the evolution of WR stars, as well as the effect on stellar yields and stellar populations. Mass loss during the main sequence plays an important role due to its ability to affect the sequence and duration of all subsequent phases. We identify several distinct evolutionary paths for massive stars which are significantly influenced by the chosen main sequence mass-loss description. We also discuss the impact of uncertainties other than mass loss on the evolution, in particular those relating to convection. We further demonstrate that not just the total mass loss, but the specific mass-loss history throughout a star's life is a crucial determinant of many aspects, such as the resulting stellar yields.