Search results for "O-type main-sequence star"
showing 4 items of 4 documents
Lithium in metal-poor red giants
2009
AbstractThe lithium abundance was calculated for five metal-poor red giant stars from Li i doublet at 6707 Å by fitting the observed high-resolution spectra with synthetic spectra. The lithium abundance was found to be low in all stars, logϵ(Li) ≤ 1.8, confirming lithium depletion on the red giant and asymptotic giant branch.
HD 50975: a yellow supergiant in a spectroscopic binary system
2014
Context. Recent detection of a yellow supergiant star as a possible progenitor of a supernova has posed serious questions about our understanding of the evolution of massive stars. Aims. The spectroscopic binary star HD 50975 with an unseen hot secondary was studied in detail with the main goal of estimating fundamental parameters of both components and the binary system. Methods. A comprehensive analysis and modeling of collected long-term radial velocity measurements, photometric data, and spectra was performed to calculate orbital elements, atmospheric parameters, abundances, and luminosities. The spectrum in an ultraviolet region was studied to clarify the nature of an unseen companion …
High-resolution spectroscopy of two metal-poor red giants: HD 232078 and HD 218732
2010
An abundance analysis for 35 chemical elements based on a high-resolution (R = 67 000) optical spectra of two metal-poor ([Fe/H] ≈ - 1.50) halo red giants, HD 232078 and HD 218732, is presented. Abundances of 10 chemical elements were derived for the first time. Both red giants are chromospherically active and optically variable, located close to the red giant branch tip. Abundances of both stars generally follow typical halo star abundance distribution, while HD 218732 should have experienced a deep mixing episode and could be a first ascent asymptotic giant branch star.
The chemical composition of extremely metal-poor and carbon-rich star HD 112869
2005
The preliminary results of abundance analysis are presented for extremely metal-poor carbon star HD 112869 = TT CVn = CGCS 3319. The radial velocity was found to be −137.7 km s −1 . Our LTE abundance analysis supports an extremely low metallicity for TT CVn, [Fe/H] = −3.2, and a significant overabundance of carbon and neutron-capture elements. The 12 C/ 13 C ratio in the atmosphere of HD 112869 is high.