The lithium abundances of planet-harbouring stars have been compared with those of open clusters and field stars. Young (chromospherically active) and subgiant stars have been eliminated from the comparison because they are at different stages of evolution and Li processing to the planet-harbouring stars, and hence have systematically higher Li abundances. The analysis showed that the Li abunda...

Abundance analyses of stars with planets have revealed that their metallicities are enhanced relative to field stars. Such a trend was originally suggested to be due to accretion of iron-rich planetary material. Based on this assumption, we have developed a stellar evolution code to model stars with non-uniform metallicity distributions. We have calculated “polluted” stellar evolution tracks fo...

We calculate the evolution of zero-metallicity Population III (Pop III) stars whose mass grows from the initial mass of ∼ 1M⊙ by accreting the surrounding gases. Our calculations cover a whole evolutionary stages from the pre-main sequence, via various nuclear burning stages, through the final core collapse or pair-creation instability phases. We adopt the following stellar massdependent accret...

We have compared the kinematics and metallicity of the main-sequence binary and single uvby F stars from the Hipparcos catalog to see if the populations of these stars originate from the same statistical ensemble. The velocity dispersions of the known unresolved binary F stars have been found to be dramatically smaller than those of the single F stars. This suggests that the population of these...

The evolution of young compact star clusters is studied using N -body simulations in which both stellar evolution and physical collisions between stars are taken into account. The initial conditions are chosen to represent R 136, a compact star cluster in the 30Doradus region of the Large Magellanic Cloud. The present runs do not include the effects of primordial binaries. We find that physical...