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Globular clusters were thought to be simple stellar populations, but recent photometric and spectroscopic evidence suggests that the clusters' early formation history was more complicated. In particular, clusters show star-to-star abundance…
The possibility of the phenomenon of Bose condensation having a part to play in the discussion of neutron stars has been around for some time. Here the sorts of temperatures and densities that might be involved are discussed. Also, an…
B[e] stars are among the most peculiar objects in the sky. This spectral type, characterised by allowed and forbidden emission lines, and a large infrared excess, does not represent an homogenous class of objects, but instead, a mix of…
Hundreds of brown dwarfs (BDs) have been discovered in the last few years in stellar clusters and among field stars. BDs are almost as numerous as hydrogen burning stars and so a theory of star formation should also explain their origin.…
Interstellar bubbles are structures in the interstellar medium with diameters of a few to tens of parsecs. Their progenitors are stellar winds, intense radiation of massive stars, or supernova explosions. Star formation and young stellar…
The physical origin of enhanced star formation activity in interacting galaxies remains an open question. Knowing whether starbursts are triggered by an increase of the quantity of dense gas or an increase of the star formation efficiency…
The expansion of interstellar bubbles is suggested to be an important mechanism of triggering material accumulation and star formation. In this work, we study the gaseous environment of a large sample of bubbles, aiming to explore the…
(Abridged) High dispersion spectrographs on large aperture telescopes have recently allowed observers to study the stellar and accretion properties of deeply embedded young stars, commonly referred to as Class I stars. We summarize these…
The increase in luminosity as a star evolves on the red-giant branch is interrupted briefly when the hydrogen-burning shell reaches the vicinity of the composition discontinuity left behind from the first convective dredge-up. The…
Globular Cluster (GC) formation seems to be a widespread mode of star formation in extreme starbursts triggered by strong interactions and mergers of massive gas-rich galaxies. We use our detailed chemically consistent evolutionary…
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…
Numerous stars exhibit surprisingly large variations in their refractory element abundances, often interpreted as signatures of planetary ingestion events. In this study, we propose that differences in the dust-to-gas ratio near stars…
Growing evidence suggests that protoplanetary discs may be influenced by late stage infall from the interstellar medium (ISM). It remains unclear the degree to which infall shapes disc populations at ages $\gtrsim 1$~Myr. We explore…
Star formation is intimately linked to the dynamical evolution of molecular clouds. Turbulent fragmentation determines where and when protostellar cores form, and how they contract and grow in mass via accretion from the surrounding cloud…
Metal-poor stars in the Galactic halo often show strong enhancements in carbon and/or neutron-capture elements. However, the Galactic bulge is notable for its paucity of carbon-enhanced metal-poor (CEMP) and/or CH-stars, with only two such…
Brown dwarfs constitute a missing link between low-mass stars and giant planets. Their atmospheres display chemical species typical of planets, and one could wonder whether they also have weather-like patterns. While brown dwarf surface…
The distribution of stellar masses that form in one star-formation event in a given volume of space is called the initial mass function (IMF). The IMF has been estimated from low-mass brown dwarfs to very massive stars. Combining IMF…
The observed increase in star formation efficiency with average cloud density, from several percent in whole giant molecular clouds to ~30 or more in cluster-forming cores, can be understood as the result of hierarchical cloud structure if…
We summarize recent studies of the predominantly neutral gas in the Magellanic Clouds (MC), based on combinations of high-resolution optical spectra and UV spectra obtained with IUE, HST, and FUSE. Similarities in relative gas-phase…
Clouds of metal-bearing condensates play a critical role in shaping the emergent spectral energy distributions of the coolest classes of low-mass stars and brown dwarfs, L and T dwarfs. Because condensate clouds in planetary atmospheres…