Carbon And Oxygen Abundances Across The Hertzsprung Gap
Abstract
We derived atmospheric parameters and spectroscopic abundances for C and O for a large sample of stars located in the Hertzsprung gap in the Hertzsprung-Russell diagram in order to detect chemical peculiarities and get a comprehensive overview of the population of stars in this evolutionary state. We have observed and analyzed high-resolution spectra (R = 60,000) of 188 stars in the mass range 2-5M(circle dot) with the 2.7 m Harlan J. Smith Telescope at the McDonald Observatory including 28 stars previously identified as Am/Ap stars. We find that the C and O abundances of the majority of stars in the Hertzsprung gap are in accordance with abundances derived for local lower-mass dwarfs but detect expected peculiarities for the Am/Ap stars. The C and O abundances of stars with T-eff < 6500 K are slightly lower than for the hotter objects but the C/O ratio is constant in the analyzed temperature domain. No indication of an alteration of the C and O abundances of the stars by mixing during the evolution across the Hertzsprung gap could be found before the homogenization of their atmospheres by the first dredge-up.
Department
Subject
stars: abundances
stars: atmospheres
stars: chemically peculiar
stars: evolution
a-type stars
effective temperature scale
chemically peculiar stars
planet-harboring stars
upper main-sequence
lte line-formation
delta-scuti stars
solar-type stars
fundamental parameters
atmospheric
parameters
astronomy & astrophysics
stars: atmospheres
stars: chemically peculiar
stars: evolution
a-type stars
effective temperature scale
chemically peculiar stars
planet-harboring stars
upper main-sequence
lte line-formation
delta-scuti stars
solar-type stars
fundamental parameters
atmospheric
parameters
astronomy & astrophysics