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Molecules with hyperfine splitting of their rotational line spectra are useful probes of optical depth, via the relative line strengths of their hyperfine components.The hyperfine splitting is particularly advantageous in interpreting the…
Recent WMAP observations indicate that the primordial abundance of lithium should have been 2-4 times higher than the value measured in low-metallicity stars. We show that this discrepancy can be explained by the process of ambipolar…
Among stars in Galactic globular clusters the carbon abundance tends to decrease with increasing luminosity on the upper red giant branch, particularly within the lowest metallicity clusters. While such a phenomena is not predicted by…
The effect of a newly born star cluster inside a giant molecular cloud (GMC) is to produce a hot bubble and a thin, dense shell of interstellar gas and dust swept up by the H II expansion, strong stellar winds, and repeated supernova…
It is generally believed that O stars, confined near the galactic midplane, are somehow able to photoionize a significant fraction of what is termed the "diffuse ionized gas" (DIG) of spiral galaxies, which can extend up to 1-2 kpc above…
We investigate the elemental and isotopic stratification in the atmospheres of selected chemically peculiar (CP) stars of the upper main sequence. Reconfiguration of the UVES spectrograph in 2004 has made it possible to examine all three…
Ap/Bp stars are magnetic chemically peculiar early A and late B type stars of the main sequence. They exhibit peculiar surface abundance anomalies that are thought to be the result of gravitational settling and radiative levitation. The…
A possible explanation for the central abundance dips found from spatially-resolved X-ray spectroscopy of several groups and clusters of galaxies is resonance scattering. A number of the prominent iron emission lines are resonance lines. We…
Strongly magnetic, rapidly rotating B-type stars with relatively weak winds form centrifugal magnetospheres (CMs), as the stellar wind becomes magnetically confined above the Kepler co-rotation radius. Approximating the magnetic field as a…
Chiral magnetic effect (CME) is a macroscopic transport phenomenon induced by quantum anomaly in the presence of chiral imbalance and an external magnetic field. Relativistic heavy ion collisions provide the unique opportunity to look for…
Low energy cosmic-rays (CRs) are responsible for gas heating and ionization of interstellar clouds, which in turn introduces coupling to Galactic magnetic fields. So far the CR ionization rate (CRIR) has been estimated using indirect…
We calculate the uvby light curves of the helium-strong chemically peculiar (CP) star HD 37776. Assuming that the chemical peculiarity influences the monochromatic radiative flux due to mainly the bound-free processes and using the model of…
Heavy metal subdwarfs are a class of hot subdwarfs with very high abundances of heavy elements, typically around 10 000 times solar. They include stars which are strongly enhanced in either lead or zirconium, as well as other elements.…
We study the hypothesis of high metallicity clumps being responsible for the abundance discrepancy found in planetary nebulae between the values obtained from recombination and collisionaly excited lines. We generate grids of…
By using self-consistent dynamic model atmospheres which simulate pulsation-enhanced dust-driven winds of AGB stars we studied in detail the influence of (i) pulsations of the stellar interiors, and (ii) the development of dusty stellar…
The collisions between high-energy ions and solids can result in significant physical and chemical changes to the material. These effects are potentially important for better understanding the chemistry of interstellar and planetary bodies,…
HD~63401 is known magnetic chemically peculiar (mCP) star that shows a slow rotation and probably possesses a hydrodynamically stable stellar atmosphere. In the latter case the atomic diffusion mechanism enforced by the magnetic field can…
We study broad red-shifted emission in chromospheric and transition region lines that appears to correspond to a form of post-flare coronal rain. Profiles of Mg II, C II and Si IV lines were obtained using the IRIS instrument before, during…
The ability to observe extrasolar planets transiting their stars has profoundly changed our understanding of these planetary systems. However, these measurements depend on how well we understand the properties of the host star, such as…
Massive star winds are structured both stochastically ("clumps") and often coherently (Co-rotation Interaction Regions, or CIRs). Evidence for CIRs threading the winds of Wolf-Rayet (WR) stars arises from multiple diagnostics including…