Related papers: Microscopic diffusion and subdwarfs
We present here results of stellar evolution calculations that include the latest advances in radiative opacities and neutrino cooling, and discuss on the basis of these models how the internal stellar structure responds to mass-loss from…
We show that element diffusion can produce large fluctuations in the initial helium abundance of the star-forming clouds. Diffusion time-scale, which in stars is much larger than the Hubble time, can fall below 10^8 years in the neutral gas…
Their ubiquity and extreme densities make star clusters probes of prime importance of galaxy evolution. Old globular clusters keep imprints of the physical conditions of their assembly in the early Universe, and younger stellar objects,…
Stellar parameters are not easily derived from M dwarf spectra, which are dominated by complex bands of diatomic and triatomic molecules and not well described at the line by line level by atmospheric models. M dwarf metallicities are…
The effects of the orbital diffusion of stars and clusters on the galactic abundance gradient have been modelled. For a single generation of field stars, the results confirm previous analyses based upon the assumption of a linear gradient…
Dissimilarities in the spatial distribution of small (micron-size) and large (millimeter-size) dust grains at the cavity edge of transition disks have been recently pointed out and are now under debate. We obtained VLT-NACO near-IR…
We aim to understand the influence of evolutionary modified surface abundances on the strength of the stellar wind in the helium-dominated subdwarfs CD-46 8926 and CD-51 11879. We used our own optical spectroscopy combined with archival…
Context. M-type subdwarfs are metal-poor low-mass stars and probe for the old populations in our Galaxy. Accurate knowledge of their atmospheric parameters and especially the composition is essential for understanding the chemical history…
I review the uncertainties in two observational constraints of the Galactic disc chemical evolution: the metallicity distribution (MD) of long-lived dwarfs and the age-metallicity relation (AMR). It is shown first that the observed MD,…
Recently, Jao et al. (2018) discovered a gap in the mid-M dwarfs main sequence revealed by the analysis of Gaia data Release 2. They suggested the feature is linked to the onset of full convection in M dwarfs. Following the announcement of…
We present a study of the hypothesis that white dwarfs undergo a spectral change from hydrogen- to helium-dominated atmospheres using a volume-limited photometric sample drawn from the $Gaia$ DR2 catalogue, the Sloan Digital Sky Survey…
During plastic deformation, metals change shape while continuously becoming stronger. The microscopic origin of these processes lies in the proliferation and movement of line defects, dislocations, and the subsequent self-organisation and…
White dwarfs can be used as galactic chronometers and, therefore, provide important information about galactic evolution if good theoretical models of their cooling are available. Consequently, it is natural to wonder if all the sources or…
A series of recent theoretical atomic diffusion studies has address the challenging problem of predicting inhomogeneous vertical and horizontal chemical element distributions in the atmospheres of magnetic ApBp stars. Here we critically…
In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to develop a physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material is…
Context. M subdwarfs are metal poor and cool stars. They are important probes of the old galactic populations. However, they remain elusive due to their low luminosity. Observational and modeling efforts are required to fully understand…
The Magellanic Clouds are a local laboratory for understanding the evolution and properties of dwarf irregular galaxies. To reveal the extended structure and interaction history of the Magellanic Clouds we have undertaken a large-scale…
We investigate the evolution of cooling helium atmosphere white dwarfs using a full evolutionary code, specifically developed for following the effects of element diffusion and gravitational settling on white dwarf cooling. The major…
In order to recognize environmental effects on the evolution of dwarf galaxies in clusters of galaxies, it is first necessary to quantify the properties of objects which have evolved in relative isolation. With oxygen abundance as the gauge…
A candidate diffuse stellar substructure was previously reported in the halo of the nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination of deep integrated-light images…