Abundances in G. Dwarfs.VI. a Survey of Field Stars.

Journal Article · Mon Jan 01 04:00:00 EST 1962 · Astrophysical Journal, Supplement Series

DOI:https://doi.org/10.1086/190067· OSTI ID:4709821

Wallerstein, George

Data are presented for deriving the abundances of the elements in 21 field stars of very nearly solar type. Ironto-hydrogen ratios are obtained from curves of growth for which the ionization temperatures are determined by considering both the excitation temperatures and the effective temperatures. The effective temperatures are derived both from the B-V colors (corrected for line blanketing) and the G-R colors of the six-color photometry system. The abundance ratios of ten other elements to iron are then derived. This material is combined with results for 13 other G dwarfs and is discussed from the point of view both of the nuclear reactions responsible for element building and of problems of galactic structure and stellar populations. There seems to be a correlation between a star's metal abundances and the velocity parameter derived from the curve of growth, in that stars with low metal content have less turbulence. The correlation between a G dwarf's ultraviolet excess and its metal deficiency is confirmed and strengthened. The relative abundances of the metals do not remain constant. Trigonometric parallaxes show that 7 stars definitely lie above the main sequence. Six of these must be very old, about 15 x 10/sup 9/ years, and 4 of these 6 are slightly metal-rich. A discussion of the motions of these stars in the galactic plane shows that both metal-rich and metal-poor stars are found with nearly circular orbits, but all the stars with large velocities with respect to the local standard of rest are metal-poor. When the stars are plotted in the HaasBottlinger diagram with the ratio of the alpha elements Mg, Si, Ca, and Ti to iron as the parameter, a clear division is seen, in that all the alpha -rich stars are high-velocity stars whose perigalactic distances are about 1/2 or less than the distance from the sun to the galactic center. All metalpoor stars with velocities near the circular velocity have normal ratios of the alpha -elements to iron. Such a separation is taken to indicate that the high-velocity stars were formed in their present orbits rather than having been scattered out of circular orbits. An analysis of the motions perpendicular to the galactic plane shows that the velocity dispersion increases steadily for stars of increasing metal deficiency.

• Research Organization: Univ. of California, Berkeley
• Sponsoring Organization: USDOE
• NSA Number: NSA-17-024199
• OSTI ID: 4709821
• Journal Information: Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Vol. 6; ISSN 0067-0049
• Publisher: American Astronomical Society
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ASTROPHYSICS
CALCIUM
COLOR
ELEMENTS
EXCITATION
HYDROGEN
IONIZATION
IRON
MAGNESIUM
METALS
MOTION
ORBITS
PHOTOMETRY
PHYSICS
QUANTITY RATIO
SILICON
STARS
TEMPERATURE
THERMONUCLEAR REACTIONS
TITANIUM
TURBULENCE
ULTRAVIOLET RADIATION
VELOCITY