Physics
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........8s&link_type=abstract
Ph.D. Thesis Washington Univ., Seattle.
Physics
1
Chemical Analysis, Chemical Composition, Dwarf Stars, Stellar Mass, Stellar Spectra, Astronomical Spectroscopy, K Stars, Metallicity, Solar Neighborhood, Stellar Atmospheres
Scientific paper
In this study we perform a chemical analysis of the most abundant stars of our galaxy, the low mass dwarfs. Little of the chemistry and physics that operate in low mass stars has been measured directly, and most of what we do know about them is based on theory or inferred from higher mass stars. Here we take a first close look at these unwieldy stars using high dispersion spectroscopy, modern stellar atmospheres, and synthetic spectrum techniques. Low mass dwarfs are particularly difficult to study. They are intrinsically faint, so even with modern detectors and large telescopes, we can study only those dwarfs that are very near the sun. Their cool atmospheres are incredibly complex with many molecules contributing to the opacity, and with deep, highly efficient convection. Their spectra are line rich, and since the surface gravities are so high, molecular and atomic lines are almost hopelessly broadened and blended. Despite the difficulties with analyzing these stars, the fact that the evolutionary status of all low mass dwarfs places them unambiguously on the main sequence (or the pre-main sequence) makes knowledge of their chemical content indispensable. Since their convective masses are large, results based on analyses of low mass stars are less susceptible to contamination by impurities which might be added to stellar atmospheres through accretion after star formation. We demonstrate that the temperature scale for the cool dwarfs must be shifted upwards towards warmer temperatures. We present abundance results for a sample of metal-poor and metal-rich K dwarfs showing that the trends of abundance ratios with metallicity seen in giants and in the warmer dwarfs also apply to the lower main sequence. We determine (O/Fe) for the first time from the TiO molecule, with results which are similar to those from atomic lines. Our abundance results for oxygen show that (O/Fe) does not rise above +0.5 for metal poor stars, even at low metallicities. We find that the correlation of sodium abundance with nitrogen that is seen in globular cluster giants also appears in Halo dwarfs. The abundance results for these unevolved stars are interpreted as consequences of the prestellar material from which these stars formed.
No associations
LandOfFree
A chemical analysis of solar neighborhood dwarfs does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A chemical analysis of solar neighborhood dwarfs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A chemical analysis of solar neighborhood dwarfs will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1264146