Related papers: Spectroscopic and physical parameters of Galactic …
Elemental abundances of carbon, nitrogen, oxygen, magnesium, aluminum, and silicon are presented for a sample of twelve rapidly rotating OB star (v sin i > 60 km s^-1) members of the Cep OB2, Cyg OB3 and Cyg OB7 associations. The abundances…
The chemical abundance patterns of gas and stars in galaxies are powerful probes of galaxies' star formation histories and the astrophysics of galaxy assembly but are challenging to measure with confidence in distant galaxies. In this…
Evolved stars dominate galactic spectra, enrich the galactic medium, expand to change their planetary systems, eject winds of a complex nature, produce spectacular nebulae and illuminate them, and transfer material between binary…
Neutron stars are commonly considered as astronomical objects having highdensity interiors and an inner core region in which various hadronic matter phases are expected. Several studies show that the inner structures affect macroscopic…
We have determined accurate values of the product of the mass-loss rate and the ion fraction of P^{4+}, Mdot q(P^{4+}), for a sample of 40 Galactic O-type stars by fitting stellar-wind profiles to observations of the P V resonance doublet…
Low-mass stars are element factories that efficiently release their products in the final stages of their evolution by means of stellar winds. Since they are large in number, they contribute significantly to the cosmic matter cycle. To…
Mass-loss from massive stars is fundamental to stellar and galactic evolution and enrichment of the interstellar medium. Reliable determination of mass-loss rate is dependent upon unravelling details of massive star outflows, including…
The chemical evolution of the Galaxy is largely guided by the yields from massive stars. Their evolution is heavily influenced by their internal mixing, allowing the stars to live longer and yield a more massive helium core at the end of…
Although the theoretical study of very low metallicity (Z) and metal-free stars is not new, their importance has recently greatly increased since two related fields have been developing rapidly. The first is cosmological simulations of the…
Many observational results seem to indicate more efficient mixing processes in intermediate mass stars (5-20 M$_{\odot}$) than the expected by the standard models. These processes are usually thought to be caused by stellar rotation. Our…
We compute chemical evolution models to constrain the mode and the history of star formation in starburst galaxies as a whole, i.e. over a large range of mass and metallicity. To this end, we investigate the origin of the dispersion…
We derive the effective temperatures and gravities of 461 OB stars in 19 young clusters by fitting the H-gamma profile in their spectra. We use synthetic model profiles for rotating stars to develop a method to estimate the polar gravity…
We have studied four complex organic molecules (COMs), methyl formate ($CH_3OCHO$), dimethyl ether ($CH_3OCH_3$), formamide ($NH_2CHO$), and ethyl cyanide ($C_2H_5CN$), towards a large sample of 39 high-mass star-forming regions…
The GES survey using FLAMES at the VLT has obtained high-resolution UVES spectra for a large number of giant stars, allowing a determination of the abundances of the key chemical elements C and N at their surface. The surface abundances of…
We present the EUV fluxes derived from the recent "combined stellar structure and atmosphere models" (CoStar models). The atmosphere models in particular account for the stellar wind and include non-LTE effects and line blanketing. We…
In an attempt of clarifying the connection between the photospheric abundance anomalies and the stellar rotation as well as of exploring the nature of "normal A" stars, the abundances of seven elements (C, O, Si, Ca, Ti, Fe, and Ba) and the…
Hot star wind mass-loss rates depend on the abundance of individual elements. This dependence is usually accounted for assuming scaled solar chemical composition. However, this approach may not be justified in evolved rotating stars. The…
We study the evolution of nitrogen resulting from a set of spiral and irregular galaxy models computed for a large number of input mass radial distributions and with various star formation efficiencies. We show that our models produce a…
Utilizing the observational data of 55,318 star-forming galaxies (SFGs) selected from the catalog of MPA-JHU emission-line measurements for the SDSS DR8, we investigate the galaxy downsizing effect of their O and N enrichments, and the…
Magnetic field is playing an important role at all stages of star evolution from star formation to the endpoints. The main effects are briefly reviewed. We also show that O-type stars have large convective envelopes, where convective dynamo…