A Spectroscopic Survey of Field Red Horizontal-branch Stars


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AFŞAR M. , BOZKURT Z. , TOPCU G. B. , CASETTI-DINESCU D., Sneden C., SEHITOGLU G.

ASTRONOMICAL JOURNAL, cilt.155, 2018 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 155 Konu: 6
  • Basım Tarihi: 2018
  • Doi Numarası: 10.3847/1538-3881/aabe86
  • Dergi Adı: ASTRONOMICAL JOURNAL

Özet

A metallicity, chemical composition, and kinematic survey has been conducted for a sample of 340 candidate field red horizontal-branch (RHB) stars. Spectra with high resolution and high signal-to-noise ratio were gathered with the McDonald Observatory 2.7m Tull and the Hobby-Eberly Telescope echelle spectrographs, and were used to determine effective temperatures, surface gravities, microturbulent velocities, [Fe/H] metallicities, and abundance ratios [X/Fe] for seven a and Fe-group species. The derived temperatures and gravities confirm that at least half of the candidates are true RHB stars, with (average) parameters T-eff similar to 5000K and log g similar to 2.5. From the a abundances alone, the thin and thick Galactic populations are apparent in our sample. Space motions for 90% of the program stars were computed from Hipparcos and Gaia parallaxes and proper motions. Correlations between chemical compositions and Galactic kinematics clearly indicate the existence of both thin-disk and thick-disk RHB stars.