Metal abundances of RR Lyrae variables in selected galactic star fields. II. The Lick astrograph fields near the North Galactic Pole

Journal Article · Sun Jul 01 00:00:00 EDT 1979 · Astron. J.; (United States)

DOI:https://doi.org/10.1086/112503· OSTI ID:6143443

Butler, D; Kinman, T D; Kraft, R P

Revised periods, light curves, and metal abundances (Preston ..delta..s's and corresponding (Fe/H) values) are given for nearly 40 RR Lyrae variables of the Lick North Galactic Pole survey. The most distant stars lie at a height z above the galactic plane of 20--25 kpc. The data give no evidence for composition gradients in the RR Lyraes apart from the composition difference between the variables in the halo (<..delta..s>=7.7, <(Fe/H)>=-1.5) and the disk (<..delta..s>=5.0, <(Fe/H)>=-1.0). We show from a statistical argument that the sample of stars is too small to detect an abundance gradient over the 20-kpc interval in z unless the space density of RR Lyraes in Oosterhoff group I falls off about four times faster than the RR Lyraes of group II. Difficulties in inferring the halo abundance gradient for common subdwarfs, based on studies of halo RR Lyraes, are cited. It is not clear whether the paucity of RR Lyraes with (Fe/H)< or approx. =-2.2 is related to a corresponding lack of extremely metal-poor subdwarfs or due to an effect of stellar evolution.

• Research Organization: Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz, California 95064
• OSTI ID: 6143443
• Journal Information: Astron. J.; (United States), Vol. 84:7
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
VARIABLE STARS
CHEMICAL COMPOSITION
ABUNDANCE
DENSITY
IRON
PHOTOMETRY
SPATIAL DISTRIBUTION
DISTRIBUTION
ELEMENTS
METALS
PHYSICAL PROPERTIES
STARS
TRANSITION ELEMENTS
640102* - Astrophysics &amp; Cosmology- Stars &amp; Quasi-Stellar
Radio &amp; X-Ray Sources