Related papers: Improving 1D stellar atmosphere models with insigh…
We compare current 1D and multi-dimensional atmosphere modelling approaches for massive stars to understand their strengths and shortcomings. We calculate averaged stratifications from selected 2D calculations for O stars -- corresponding…
With their emission-line dominated spectra, the appearance of Wolf-Rayet stars is shaped by their strong stellar winds. Yet, the physical mechanisms behind their high mass loss have long remained enigmatic. While we know nowadays that…
Massive and luminous O-star atmospheres with winds have been studied primarily using one-dimensional (1D), spherically symmetric, and stationary models. However, observations and theory rather suggest that O-star atmospheres are highly…
Classical Wolf Rayet (WR) stars are direct supernova progenitors undergoing vigorous mass-loss. Understanding the dense and fast outflows of such WR stars is thus crucial for understanding advanced stages of stellar evolution, the dynamical…
Massive stars shape their surrounding medium through the force of their stellar winds, which collide with the circumstellar medium. Because the characteristics of these stellar winds vary over the course of the evolution of the star, the…
Vigorous mass loss in the classical Wolf-Rayet (WR) phase is important for the late evolution and final fate of massive stars. We develop spherically symmetric time-dependent and steady-state hydrodynamical models of the radiation-driven…
During the recent years significant progress has been made in the modeling of red giant atmospheres with the aid of 3D hydrodynamical model atmosphere codes. In this contribution we provide an overview of selected results obtained in this…
We review our current understanding on the outer envelope structures of massive stars based on three dimensional (3D) radiation hydrodynamic simulations. We briefly summarize the fundamental issues to construct hydrostatic one dimensional…
Mass loss from massive stars located in the part of the Hertzsprung-Russell diagram (HRD) where we find luminous blue variables (LBVs) is profoundly important for stellar evolution yet poorly understood. We use time-dependent…
Line-driven stellar winds are ubiquitous among hot massive stars. In some cases they can become so strong, that the whole star is cloaked by an optically thick wind. The strong outflow gives rise to large emission lines, defining the class…
Stellar winds are a major source of uncertainty in understanding the life and deaths of massive stars. Across studies in the field, prescriptions for stellar winds differ substantially in both their physical assumptions and implementation,…
Towards the end of their evolution hot massive stars develop strong stellar winds and appear as emission line stars, such as WR stars or LBVs. The quantitative description of the mass loss in these important pre-SN phases is hampered by…
Many Wolf-Rayet (WR) stars have optically thick winds that cloak the hydrostatic layers of the underlying star. In these cases, traditional spectral analysis methods are plagued by degeneracies that make it difficult to constrain parameters…
Our understanding of stellar structure and evolution coming from one-dimensional (1D) stellar models is limited by uncertainties related to multi-dimensional processes taking place in stellar interiors. 1D models, however, can now be tested…
The chemical enrichment of the Universe; the mass spectrum of planetary nebulae, white dwarfs and gravitational wave progenitors; the frequency distribution of Type I and II supernovae; the fate of exoplanets ... a multitude of phenomena…
Spectroscopic studies of massive and luminous O-type stellar atmospheres and winds have primarily been done by using 1D, spherically symmetric and stationary models. Both observations and modern theoretical models show that such stars have…
In this paper we present Complete Stellar models (CoStar) for massive stars, which treat the stellar interior and atmosphere, including its wind. Particular emphasis is given to Wolf-Rayet stars. We address the question of the effective…
We present a simple analytical method to describe the structure of a spherically expanding envelope with strong mass outflow. The structure is consistently connected to the hydrostatic stellar interior and provides an adequate description…
CONTEXT: For more than two decades, stellar atmosphere codes have been used to derive the stellar and wind parameters of massive stars. Although they have become a powerful tool and sufficiently reproduce the observed spectral appearance,…
Standard 1D stellar evolution models do not correctly reproduce the structure of the outermost layers of stars with convective envelopes. This has been a long-standing problem in stellar modelling affecting both the predicted evolutionary…