Related papers: Is the additional increase of the star luminosity …
Convection in the cores of massive stars becomes anisotropic when they rotate. This anisotropy leads to a misalignment of the thermal gradient and the thermal flux, which in turn results in baroclinicity and circulation currents in the…
The increase in luminosity as a star evolves on the red-giant branch is interrupted briefly when the hydrogen-burning shell reaches the vicinity of the composition discontinuity left behind from the first convective dredge-up. The…
Stellar conditions leading to a possible semi-convective mixing are discussed in three relevant cases: (1) low mass MS stars in which the CNO cycle takes progressively the lead over the PP chain due to the increase in temperature as core…
Stellar rotation produces an internal mixing of the elements due to shear instability and meridional circulation. This leads to observable $N/C$ enhancements in massive stars above about 7--9 $M_{\odot}$. Rotation also favours mass loss by…
Measurements of lithium abundances in solar-type stars have shown that standard models of stellar evolution are incapable of explaining the observed depletion as a function of stellar age. Beryllium is one of the lightest elements that can…
(Abridged) Eclipsing, spectroscopic double-lined binary star systems (SB2) are excellent laboratories for calibrating theories of stellar interior structure and evolution. We aim to investigate the mass discrepancy in binary stars. We study…
A few percent of red giants are enriched in Lithium with $A(\mathrm{Li}) > 1.5$. Their evolutionary status has remained uncertain because these Li-rich giants can be placed both on the red-giant branch (RGB) near the bump luminosity and in…
Context: Internal chemical mixing in intermediate- and high-mass stars represents an immense uncertainty in stellar evolution models.In addition to extending the main-sequence lifetime, chemical mixing also appreciably increases the mass of…
Stars with very large mass loss on the red-giant branch can undergo the helium flash while descending the white-dwarf cooling curve. Under these conditions the flash convection zone will mix the hydrogen envelope with the hot helium-…
We study the origin and properties of 'extra' or 'excess' central light in the surface brightness profiles of gas-rich merger remnants. Combining a large set of hydrodynamical simulations with data on observed mergers (spanning a broad…
Observations demonstrate that the surface abundance of $^7{\rm Li}$ in low-mass stars changes dramatically between the tip of the red giant branch and the red clump. This naturally suggests an association with the helium core flash, which…
During the post-main sequence evolution massive stars pass through several short-lived phases, in which they experience enhanced mass loss in the form of clumped winds and mass ejection events of unclear origin. The discovery that stars…
One possible scenario for the formation of carbon-enhanced metal-poor stars is the accretion of carbon-rich material from a binary companion which may no longer visible. It is generally assumed that the accreted material remains on the…
The efficiency of convection in stars affects many aspects of their evolution and remains one of the key-open questions in stellar modelling. In particular, the size of the mixed core in core-He-burning low-mass stars is still uncertain and…
The early evolution of planetary systems is expected to depend on various periods of disk matter accretion onto the central star, which may include the accretion of metal-rich matter after the star settles on the main sequence. When this…
Thanks to their usefulness in various fields of astrophysics (e.g. mixing processes in stars, chemical evolution of galaxies), the last few years have witnessed a large increase in the amount of abundance data for early-type stars. Two…
The impact of new stellar evolution models with rotation on the predictions of population synthesis models is discussed. Massive rotating stars have larger convective cores than their non-rotating counterparts, and their outer layers are…
Globular clusters contain many stars with surface abundance patterns indicating contributions from hydrogen burning products, as seen in the anti-correlated elemental abundances of e.g. sodium and oxygen, and magnesium and aluminium.…
Galaxy mergers lead to the formation of massive black hole binaries which can accelerate background stars close to the speed of light. We estimate the comoving density of ejected stars with a peculiar velocity in excess of $0.1c$ or $0.5c$…
Many observational results seem to indicate more efficient mixing processes in intermediate mass stars (5-20 M$_{\odot}$) than the expected by the standard models. These processes are usually thought to be caused by stellar rotation. Our…