Related papers: Scandium: A key element for understanding Am stars
The measurement of the cosmic microwave background has strongly constrained the cosmological parameters of the Universe. When the measured density of baryons (ordinary matter) is combined with standard Big Bang nucleosynthesis calculations,…
We analyze a high-resolution spectrum of the A3m star HD27411. We compare abundances derived from ATLAS9 model atmospheres with those using the more computationally-intensive ATLAS12 code. We found very little differences in the abundances,…
Protoplanetary disks, debris disks, and disrupted or evaporating planets can all feed accretion onto stars. The photospheric abundances of such stars may then reveal the composition of the accreted material. This is especially likely in B…
Convection is ubiquitous in stars and occurs under many different conditions. Here we explore convection in main-sequence stars through two lenses: dimensionless parameters arising from stellar structure and parameters which emerge from the…
Context. The modelling of chemical transport mechanisms is crucial for accurate stellar characterizations. Atomic diffusion is one of these processes and it is commonly included in stellar models. However, it is usually neglected for F-type…
The prediction of the PLANCK-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been…
The measurement of stellar properties such as chemical compositions, masses and ages, through stellar spectra, is a fundamental problem in astrophysics. Progress in the understanding, calculation and measurement of atomic properties and…
Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution…
When modelling stars with masses larger than 1.2Msun with no observed chemical peculiarity, atomic diffusion is often neglected because, on its own, it causes unrealistic surface abundances compared with those observed. The reality is that…
We study lithium depletion in low-mass and solar-like stars as a function of time, using a new diffusion coefficient describing extra-mixing taking place at the bottom of a convective envelope. This new form is motivated by…
We present results from 2D radiation-hydrodynamical simulations of fully compressible convection for the surface layers of A-type stars with the ANTARES code. Spectroscopic indicators for photospheric convective velocity fields show a…
We have developed a radiative transfer code, CMFGEN, which allows us to model the spectra of massive stars and supernovae. Using CMFGEN we can derive fundamental parameters such as effective temperatures and surface gravities, derive…
Abundance trends in heavier elements with evolutionary phase have been shown to exist in the globular cluster NGC 6752 [Fe/H]=-1.6. These trends are a result of atomic diffusion and additional (non-convective) mixing. Studying such trends…
We developed a comprehensive model atom of Sc II-Sc III. Abundances of scandium for a sample of eight unevolved A9-B3 type stars with well-determined atmospheric parameters were determined based on the non-local thermodynamic equilibrium…
We attempt to constrain the efficiency of additional transport or mixing processes that reduce the effect of atomic diffusion in stellar atmospheres. We apply spectral synthesis methods to spectra observed with the GIRAFFE spectrograph on…
In spite of the efforts made in the latest years, still there is no comprehensive explanation for the chemical anomalies of globular cluster stars. Among these, the most striking is oxygen depletion, which reaches values down to [O/Fe]~-0.4…
Rotational velocity, lithium abundance, and the mass depth of the outer convective zone are key parameters in the study of the processes at work in the stellar interior, in particular when examining the poorly understood processes operating…
A popular self--enrichment scenario for the formation of globular clusters assumes that the abundance anomalies shown by the stars in many clusters are due to a second stage of star formation occurring from the matter lost by the winds of…
The chemistry of molecular clouds has been studied for decades, with an increasingly general and sophisticated treatment of the reactions involved. Yet the treatment of turbulent diffusion has remained extremely sketchy, assuming simple…
Context: Typical space plasmas contain spatially and temporally variable turbulent electromagnetic fields. Understanding the transport of energetic particles and the acceleration mechanisms for charged particles is an important goal of…