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Recent downward revision of solar heavy-element abundances using three-dimensional atmospheric model has introduced serious discrepancies between standard solar models and helioseismic inferences about solar structure. In this paper, we…
We carry out direct numerical simulations of turbulent astrophysical media that explicitly track ionizations, recombinations, and species-by-species radiative cooling. The simulations assume solar composition and follows the evolution of…
Context. It has been shown that convection in red supergiant stars gives rise to large granules causing surface inhomogeneities together with shock waves in the photosphere. The resulting motion of the photocenter (on time scales ranging…
Molecular clouds in the interstellar medium suffer gravitational instabilities that lead to the formation of one or multiple stars. A recently formed star inside a cold cloud communicates its gravitational force to the surrounding…
Context. Abundance anomalies observed in a fraction of A and B stars of both Pop I and II are apparently related to internal particle transport. Aims. Using available constraints from Sirius A, we wish to determine how well evolutionary…
Context: The surface abundances of massive stars show evidence of internal mixing, while asteroseismic data suggest that efficient angular momentum (AM) transport occurs in stellar interiors. It is of interest to find a consistent physical…
Context. Mixing by convective overshooting has long been suggested to play an important role for the amount of hydrogen available to nuclear burning in convective cores of stars. The best way to model this effect is still debated. Aims. We…
The abundances of elements in stars are a critical clue to their origins. Observed star-to-star variations in logarithmic abundance within an open cluster are typically only $\sim 0.01-0.05$ over many elements, significantly smaller than…
In stellar astrophysics, the study of the atmospheres of early-type stars plays a very special role. The atmospheres of these stars display a variety of different phenomena, such as the presence of large magnetic fields, strong surface…
Our ability to predict the structure and evolution of stars is in part limited by complex, 3D hydrodynamic processes such as convective boundary mixing. Hydrodynamic simulations help us understand the dynamics of stellar convection and…
We model the physical behaviour at the surface of a relativistic radiating star in the strong gravity limit. The spacetime in the interior is taken to be spherically symmetrical and shear-free. The heat conduction in the interior of the…
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…
The early phase of the hydrodynamic evolution following collision of two stars is analyzed. Two strong shocks propagate at a constant velocity (which is a small fraction of the velocity of the approaching stars) from the contact surface…
We study the impact of accretion from protoplanetary discs on stellar evolution of AFG-type stars. We use a simplified disc model computed using the Two-Pop-Py code that contains the growth and drift of dust particles in the protoplanetary…
The chemical evolution of protoplanetary discs is not fully understood, several factors influence the final distribution of disc material. One such factor are inward drifting and evaporating pebbles that enrich the inner disc with vapour.…
The compositions of stars are a critical diagnostic tool for many topics in astronomy such as the evolution of our Galaxy, the formation of planets, and the uniqueness of the Sun. Previous spectroscopic measurements indicate a large…
The evolution of massive stars is affected by a variety of physical processes including convection, rotation, mass loss and binary interaction. Because these processes modify the internal chemical abundance profiles in multiple ways…
Stellar convection is a non-local process responsible for the transport of heat and chemical species. It can lead to enhanced mixing through convective overshooting and excitation of internal gravity waves (IGWs) at convective boundaries.…
State-of-the-art one-dimensional (1D) stellar evolution codes rely on simplifying assumptions, such as mixing length theory, in order to describe superadiabatic convection. As a result, 1D stellar structure models do not correctly recover…
One-dimensional (1D) stellar evolution models are widely used across various astrophysical fields, however they are still dominated by important uncertainties that deeply affect their predictive power. Among those, the merging of…