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Cosmic Helium Production

Flynn, Chris

K-dwarfs are very long lived, slowly evolving stars, so that their present day helium Y and metal content (metallicity Z) is essentially the same as when they were born. K-dwarfs thus contain a fossil record of the amount of helium and metals which has been produced in successive stellar generations over the lifetime of the Galaxy. We here estimat…

The Geneva-Copenhagen Survey of the Solar Neighbourhood

Pont, F.; Holmberg, J.; Nordström, B. +3 more

We report on a new survey of metallicities, ages, and Galactic orbits for a complete, magnitude-limited, and kinematically unbiased all-sky sample of 16682 nearby F- and G-dwarfs. Our~63000 new, accurate radial velocities for nearly 13500 of the stars, combined with Hipparcos parallaxes and Tycho-2 proper motions, complete the kinematic data for 1…

Comprehensive Analysis of RGU Photometry in the Direction to M5

Bilir, S.; Karaali, S.; Buser, R.

The RGU-photographic investigation of an intermediate latitude field in the direction to the Galactic centre is presented. 164 extra-galactic objects, identified by comparison of Minnesota and Basel charts, are excluded from the program. Also, a region with size 0.104 square-degrees, contaminated by cluster (M5) stars and affected by background li…

Solar Neighbourhood Age-Metallicity Relation Based on Hipparcos Data

Ibukiyama, Akihiko

We derive age-metallicity relations (AMRs) and orbits for the 1658 solar neighbourhood stars for which accurate distances are measured by the Hipparcos satellite. The sample comprises 1382 thin disk stars, 229 thick disk stars, and 47 halo stars according to their orbital parameters. We find a considerable scatter for thin disk AMRs along the one-…