Related papers: Dusty Blue Supergiants: News from High-Angular Res…
Stellar evolution theory is most uncertain for massive stars. For reliable predictions of the evolution of massive stars and their final fate, solid constraints on the physical parameters, and their changes along the evolution and in…
Blue supergiant stars of B and A spectral types are amongst the visually brightest non-transient astronomical objects. Their intrinsic brightness makes it possible to obtain high quality optical spectra of these objects in distant galaxies,…
Thanks to the high spatial resolution provided by long baseline interferometry, it is possible to understand the complex circumstellar geometry around stars with the B[e] phenomenon. These stars are composed by objects in different…
The B[e] phenomenon discovered nearly 50 years ago features the presence of forbidden emission lines due to extended and dense circumstellar gas and large IR excesses due to the radiation from circumstellar dust in a wide variety of objects…
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…
B[e] supergiants are evolved massive stars with a complex circumstellar environment. A number of important emission features probe the structure and the kinematics of the circumstellar material. In our survey of Magellanic Cloud B[e]…
It is surprising to find dust around B type stars, as in the case of B[e] stars. These stars exhibit a dense, dusty environment witnessed by their infrared-excess and many emission lines from permitted and forbidden transitions. Given the…
In this paper, we investigate the evolutionary status of B[e]~stars from the point of view of stellar evolution theory. We try to answer to the question of how massive hot supergiants --- i.e. evolved stars --- can be capable of producing a…
Blue supergiant stars can be exceptionally bright objects in the optical, making them prime targets for the determination of extragalactic distances. I describe how their photometric and spectroscopic properties can be calibrated to provide…
The present generation of large telescopes facilitates spectroscopy of blue supergiants in galaxies out to distances beyond the Local Group. Recent developments in NLTE spectrum synthesis techniques allow for an accurate determination of…
Mass loss is one of the key parameters that determine stellar evolution. Despite the progress we have achieved over the last decades we still cannot match the observational derived values with theoretical predictions. Even worse, there are…
B[e] supergiants (B[e]SGs) are emission-line objects, presumably in a short-lived phase in the post-main sequence evolution of massive stars. Their intense infrared excess emission indicates large amounts of warm circumstellar dust, and the…
I review multiwavelength observations of material seen around different types of evolved massive stars (i.e. red supergiants, yellow hypergiants, luminous blue variables, B[e] supergiants, and Wolf-Rayet stars), concentrating on diagnostics…
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…
Observational manifestations of far evolved stars at the asymptotic giants branch and their nearest descendants are briefly considered. Main results of their chemical composition determinations based on long term high resolution…
Despite major progress in our understanding of massive stars, concerning discrepancies still remain between observations and theory. Most notable are the numerous stars observed beyond the theoretical main sequence, an evolutionary phase…
B[e] Supergiants are a phase in the evolution of some massive stars for which we have observational evidence but no predictions by any stellar evolution model. The mass-loss during this phase creates a complex circumstellar environment with…
Blue supergiants of spectral types B and A are the visually brightest stars in spiral and irregular galaxies, with their most luminous members (at M_V=-10) outshining entire dwarf galaxies. This characteristic allows us to use them as…
The direct images of giant extrasolar planets recently obtained around several main sequence stars represent a major step in the study of planetary systems. These high-dynamic range images are among the most striking results obtained by the…
We have examined the ratio of blue to red (B/R) supergiants in the dwarf irregular galaxy Sextans A. The supergiants were identified in previously published stellar photometry measured from Hubble Space Telescope imaging. The high…