Related papers: From the atmosphere to the circumstellar environme…
The late evolutionary stages of stellar evolution are a key ingredient for our understanding in many fields of astrophysics, including stellar evolution and the enrichment of the interstellar medium (ISM) via stellar yields. Already the…
Red supergiants (RSGs) are evolved massive stars in a stage preceding core-collapse supernova. Understanding evolved-phases of these cool stars is key to understanding the cosmic matter cycle of our Universe, since they enrich the cosmos…
Optical interferometry is a powerful tool to investigate the close environment of AGB stars. With a spatial resolution of a few milli-arcseconds, it is even possible to image directly the surface of angularly large objects. This is of…
Cool giant stars are highly dynamical objects, and complex micro-physical processes play an important role in their extended atmospheres and winds. The interpretation of observations, and in particular of high-resolution IR spectra,…
We have written a 3D radiative transfer code that computes emerging spectra and intensity maps. We derive from radiative hydrodynamic (RHD) simulations of RSG stars carried out with CO5BOLD (Freytag et al. 2002) observables expected for red…
Cool, evolved stars are the main source of chemical enrichment of the interstellar medium (ISM), and understanding their mass loss and structure offers a unique opportunity to study the cycle of matter in the Universe. Pulsation,…
The recent progress in high-spatial-resolution techniques, spanning wavelengths from the visual to the radio regime, is leading to new valuable insights into the complex dynamical atmospheres of Asymptotic Giant Branch (AGB) stars and their…
We review recent advances in our understanding of massive stars through the analysis of their spectra. Improvements in model atmospheres and analysis methods are briefly discussed. Results obtained for stars in the Local Group are compared…
This brief review describes some of the observed properties of the populations of massive asymptotic giant branch (AGB) stars and red supergiants (RSGs) found in nearby galaxies, with a focus on their luminosity functions, mass-loss rates…
Long-baseline interferometry at optical and near-infrared wavelengths is an emerging technology which is quickly becoming a useful tool to investigate stellar atmospheres and to compare observations with models. Stellar atmosphere models…
Cool evolved stars are the main source of chemical enrichment of the interstellar medium. Understanding their mass loss offers a unique opportunity to study the cycle of matter. We discuss interferometric studies and their comparison to…
In this paper, I review how optical spectro-interferometry has become a particularly well suited technique to study the close environment of young stars, by spatially resolving both their IR continuum and line emission regions. I summarize…
The physical structures of the outer atmospheres of red giants are not known. They are certainly complex and a range of recent observations are showing that we need to embrace to non-classical atmosphere models to interpret these regions.…
Optical interferometry provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Through direct observation of rotationally distorted photospheres at sub-milliarcsecond scales, we are now able to…
The importance of understanding the current and historical galactic environments of cool stars is discussed. The penetration of interstellar gas into a stellar astrosphere is a function of the interaction of the star with the interstellar…
Red supergiant stars represent a late stage of the evolution of stars more massive than about nine solar masses, in which they develop complex, multi-component atmospheres. Bright spots have been detected in the atmosphere of red…
The late stellar evolutionary phases of low and intermediate-mass stars are strongly constrained by their mass-loss rates. The wind surrounding cool evolved stars frequently shows non-spherical features, thought to be due to an unseen…
Red supergiants (RSGs) are an evolved He-burning phase in the lifetimes of moderately high mass (10 - 25 solar mass) stars. The physical properties of these stars mark them as an important and extreme stage of massive stellar evolution, but…
Cool luminous giants, in particular asymptotic giant branch stars, are among the most important sources of cosmic dust. Their extended dynamical atmospheres are places where grains form and initiate outflows driven by radiation pressure,…
Emission and absorption line observations of molecules in late-type stars are a vital component in our understanding of stellar evolution, dust formation and mass loss in these objects. The molecular composition of the gas in the…