Related papers: The lambda Bootis stars
A pedagogical overview of strange quark matter and strange stars is presented. After a historical notation of the research and an introduction to quark matter, a major part is devoted to the physics and astrophysics of strange stars, with…
The ejecta of the first probably very massive stars polluted the Big Bang primordial element mix with the first heavier elements. The resulting ultra metal-poor abundance distribution provided the initial conditions for the second stars of…
$\lambda$ Bo\"otis stars are a subset of chemically peculiar A-stars that display Solar abundances in lighter elements (C, N, O, S, etc.) but a deficiency in Iron-peak elements. This difference has been attributed to the A-stars accreting…
In A- and late B-type stars, strong magnetic fields are always associated with Ap and Bp chemical peculiarities. However, it is not clear at what point in a star's evolution those peculiarities develop. Strong magnetic fields have been…
Extremely low metallicity stars are intensely studied as they take observations the closest to the very first generations of stars in the universe. Widely assumed to be enriched by just one dying massive star, some of these very metal poor…
The theoretical work on roAp stars is reviewed, especially in relation with observational facts that still need to be understood: high frequencies of the modes observed, which can be higher than the theoretical critical cutoff frequency for…
A search for duplicity of lambda Bootis stars has been made by using the speckle camera installed at the Telescopio Nazionale Galileo. The operation mode and the reduction procedure allow one to obtain not only the separation, but also the…
A significant fraction of very metal-poor stars have unexpectedly high carbon abundances. I recap on their discovery, describe the results of high-resolution spectroscopic studies of their composition, and consider possible origins. It is…
We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Bootes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution…
The formation of hot subdwarf stars is still unclear. Both single-star and binary scenarios have been proposed to explain the properties of these evolved stars situated at the extreme blue end of the horizontal branch. The observational…
We argue that extreme metal-poor stars show a high dispersion in metallicity, because their abundances are the outcome of very few supernova events. Abundance anomalies should appear because of the discrete range of progenitor masses. There…
The selective abundance of C, N, O (almost solar) with respect to that of other elements (underabundant) in lambda Boo stars has been interpreted as a characteristic peculiarity of these objects, when considered as single stars. We show…
Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive…
Metal-poor stars provide information on the characteristics and chemical evolution of the halo population of the Galaxy, the first epoch of star formation and Galaxy formation (not just locally but with relevance to high-redshift objects),…
Ancient, long-lived stars remain present in all components of our home galaxy, the Milky Way. Born a few hundred million after the Big Bang and during a time that marked the very beginning of the chemical evolution, these stars display very…
Since Baschek & Slettebak (1988) drew attention to the similarity between the abundance pattern of lambda Boo stars and that of Vega, there has been a long debate whether Vega should be listed among the chemically peculiar stars of lambda…
It is shown that for very rapidly rotating low mass strange stars the marginally stable orbit is located above the stellar surface. This effect is explained by the very important role of the oblateness of the rotating strange star. The…
The presence of the lithium-6 isotope in some metal-poor stars is a matter of surprise because of the high values observed. Non-standard models of Big Bang nucleosynthesis and pre-Galactic cosmic ray fusion and spallation have been proposed…
With increasingly accurate data on RR Lyrae stars we find that the Blazhko effect may be a rule rather than an exception. However, we still do not know what is the cause of this mysterious amplitude and phase modulation. In my talk, I…
Among the emission-line stars, the classical Be stars known for their extreme properties are remarkable. The Be stars are B-type main sequence stars that have displayed at least once in their life emission lines in their spectrum. Beyond…